Duteau 2015. Fish Silage Project Final Report

Yukon Research Centre 1 / 52
Michel Duteau, Cold Climate Innovation Centre
Yukon College | 500 College Drive, PO Box 2799, Whitehorse, Yukon Y1A 5K4
Fish Silage Project: Experimental
protocol and Annotated Bibliography
MICHEL DUTEAU
Yukon Research Centre, Yukon College, 500 College Drive, Whitehorse YT Y1A 5K4
Phone: (867) 689-8490, Fax: (867) 456-8672, email: mduteau@yukoncollege.yk.ca
Oct 27, 2015
Yukon Cold Climate Innovation Centre at Yukon College

Michel Duteau, Cold Climate Innovation Centre

Michel Duteau and Amélie Janin, NSERC Industrial Research Chair in Mine Life Cycle
PROJECT INVESTIGATORS AND PARTNERS
This project was prepared in agreement with and in partnership with:
_________________________________ _______________________________
Michel Duteau Ziad Sahid
Yukon Research Centre Yukon Research Center
_________________________________
Jonathan Lucas
Grizzly Pigs Farm
Yukon Cold Climate Innovation Centre is providing the funding for this project, through its funding
partnerships and agreements.

INTRODUCTION
Fish silage definition
Fish silage can be defined as “a liquid product made from whole fish or parts of fish that are liquefied by
the action of enzymes in the fish in the presence of an added acid (Tatterson and Windsor, 2001).”
Current situation
It is estimated that fish processing for human consumption yields around 40% of edible meat, while the
remnant 60% composed of bones, skin, head, viscera, meat scraps and scales, is fishery by-products
(Gildberg 1993 in Ramirez, 2013).
The technology required to produce fish silage is much simpler than that needed for fish meal. Fish
silage thus has a net advantage in areas where the tonnage of waste material is insufficient to justify the
production of fish meal and it is estimated that fish silage is most likely to be successful in areas where
fish offal or waste fish is regularly available, but the cost of sending it to the nearest meal plant is
prohibitive, and where there are farms, particularly pig farms, close by (Tatterson and Windsor, 2001).
According to estimates by Bimbo (2012), cold crude fish silage sold for USD 70-173/metric ton on the
Alaska market during 1998-2007. For the purpose of the present analysis, a conservative estimate would
be that farmers would have to pay CAD 200/metric ton for fish silage on the Yukon market in 2015.
Aim and objectives
The objectives of fish silage production in the Yukon are to:
- lower the cost of animal production in the Yukon (pigs, broiler chickens and laying hens),
through the production of a local feed option
- unlock the value of fish waste (Icy Waters Ltd. fish offal and casualties)
- make use of available fish resource (chum salmon)
The vision is that fish silage can be manufactured at a commercial scale and distributed as a wet mash to
animal husbandry operations in the Yukon
An introductory experiment was conducted during summer 2014 at Icy Waters Ltd., where it was
established that it is possible to transformed fish offal into fish silage using formic acid.
With this project, we intend in developing guidelines as to fish silage production in the Yukon from two
main sources: Icy Waters fish waste, and chum salmon. We also want to assess the bioequivalence of
fish silage when compared to feed stuff that is conventionally used in the Yukon i.e. we want to prove
that replacing conventional (imported) protein with locally-sourced fish silage does not have a negative
impact on animal productions. Thus, a comparative experiment is designed to test the fish silage diet on
a sample of pigs, broiler chickens and laying hens, and infer conclusions onto all such animals in Yukon
conditions.

EXPERIMENTAL PROTOCOL
Setup
The feeding trials were designed to be conducted in the fall (October-December) of 2015 at Grizzly Pigs
farm, situated North of Whitehorse Yukon, on the Mayo Road. Grizzly Pigs Farm produced pig, broiler
chickens, and eggs. Following dismantlement of Grizzly Pigs Farm in the fall of 2015, the feeding trials
can be conducted where the animals now are hosted, contingent on conditions suitability.
Grizzly Pigs Farm rears two kinds of pig, with hybrids and back crossings: English Large Black (Figure 3)
and Landrac-Durac (pink; Figure 4 ). The pigs range in outdoor wind-protected (low bush) paddocks, and
have access to sheltered wood hutches. All piglets are weaned (separated from the mother) at 1 month.
Male piglets are castrated at 4-5 days (barrows). All pigs are vaccinated for Parvovirus and Legionella
twice a year. The pigs are butchered (market weight) at 100 kg (220 lb), which is attained at
approximately 4 months of age.
In the fall (Sept-Oct) of 2015, 6 litters are expected, with 4-6 piglets each. 3 pink and 1 black sows were
bred with a same pink boar. 1 black and 1 hybrid black/pink sows were bred with a same black boar. All
in all, this is 3 litters of pure pink, 1 hybrid, 1 pure black, and 1 hybrid backcrossing to a black. Overall, 24
piglets are expected. According to the owner’s experience, these piglets in all likelihood should be
similar enough for the purpose of this experiment.
Water is provided 1-2 times a day in one bucket per paddock. Feed is provided once a day in individual
bowls for each pig (Figure 4). Pigs at Grizzly Pigs Farm are usually fed a commercial pig grower in the
form of pellets containing oat, barley, wheat, corn, protein supplement, and canola oil (manufactured by
Federated Co-operatives Ltd, Saskatoon, SK; Figure 5). This grower is certified FeedAssure®, a feed
safety management and certification program developed by the Animal Nutrition Association of Canada
(ANAC). This grower is imported from Southern Canada and is bought from C&D Feed (Whitehorse, YT).
Yukon Grain Farm (Steve Mackenzie-Grieve) also has pig grower available, which would likely not be as
standardized and slightly more expensive (approximately 6$ extra per bag).
The broiler chickens stay in a heated building (garage). In the fall of 2015, 30 chicks of a .. mix are
expected, which should all be similar enough for the purpose of this experiment. Broiler chickens are
usually fed a commercial feed also available at C&D Feed.
The laying hens are housed in two heated temporary buildings (tarp sheds). One is insulated with straw,
and the other one is insulated with foam. One is facing South, and the other one is facing North. The
individual space area is approximately 1 sq ft, which amounts to 25 animals per building. In the fall of
2015, a new hatch is expected. Water is provided once a day. The water troughs are cleaned every 2-3
days. Feed is provided ad libitum. Light is provided 6 am to 10 pm. The hens usually lay eggs for 10
weeks. They will have been laying for 2 weeks prior to the experiment. The hens are expected to start
laying mid-September. Two types of laying hens are available: Brown Hybrid Leghorn and Columbine
Rock. Typical productivity at Grizzly Pigs Farm is 2 eggs per 3 days and 1 egg per 2 days for Brown Hybrid
Leghorn and Columbine Rock, respectively. Typical overall productivity at Grizzly Pigs Farm is 5-6 eggs
per week per hen for the first 8 months. Potentially, the buildings could be inverted mid-experiment, so
as to account for the difference in living conditions. Another way to circumvent this would be to assign

the hens to cages and feed them accordingly, providing for a Complete Block Design. Laying hens are
usually fed a commercial feed also available at C&D Feed.
The animals are cared for according to guidelines of the Canadian Council on Animal Care (1993).
Experimental plan
Testing
The objective of this experiment is to test the bioequivalence of a recommended fish silage dosage (test
diet) as an alternative to conventional feed (control diet) for pigs, broiler chickens and laying hens. For
more complex trials (e.g. comparison of different levels of inclusion of fish silage), more sophisticated
experimental setup would be necessary, along with finer statistical tools.
This experiment is thus designed as a simple comparison of the means of the two diets for a series of
response variables. Bioequivalence is granted if no statistically significant difference is found between
the means. The hypothesis of there being a difference between the group means is tested with a series
of univariate t-tests, and a Bonferroni correction (Kuehl, 2001) is applied to adjust α(α’) and minimize
the experiment-wise error rate (i.e. take into account the fact that a series of statistical tests are
performed on the same individuals). The results depend on the size of the difference between the
means, divided by the standard error of the difference. Alternatively, a multivariate analysis could be
performed, considering all response variables at once.
The null hypothesis is stated as H0: d ≤ d0, where d0 is the minimum difference between the groups that
is to be detected. The alternate hypothesis is: H1: d > d0.
Experimental design
Ideally, all individuals are the same (age, sex, ancestry), and all conditions are the same (environmental
exposure -wind, sun, snow, rain, temperature-, floor space per individual, type of watering system, type
of feeding through, type of faeces management system). When such an ideal situation is unattainable,
the differences become nuisance factors, and can potentially become sources of variability.
Randomization is essential to reduce the contaminating effect of nuisance factors (e.g. sex and ancestry)
and reduce variability: subjects are randomly assigned to one treatment or the other (control diet vs.
test diet). When needed, blocking can be used to reduce the effect of a specific nuisance factor (e.g.
exposure to wind): creating homogeneous blocks in which the nuisance factors are held constant.
However, a simple t-test will not suffice in analyzing results for a Randomized Block Design; an ANOVA
would be called for and the F-test would become the initial statistic of importance.
Confidence interval
In this experiment, bioequivalence is granted with a confidence interval of 95%, i.e. the null hypothesis
of no difference between the means is rejected when p < 0.05. The probability of making a Type I error
(rejecting the null hypothesis when it should not be rejected) is thus 5%.
Power of the test
A test's power is the probability of rejecting the null hypothesis when it should be rejected. The power
of a statistical test is calculated as 1-β, where β is the probability of making a Type II error (accepting a

null hypothesis when it should be rejected). A test's power is influenced by the choice of confidence
interval (1- α), and depends on the sample size and the magnitude of the effect (the degree of departure
in the population from the null hypothesis). It is conventional to set 80% as the target value for
statistical power. This convention implies a four-to-one trade off between β-risk and α-risk. (β is the
probability of a Type II error; α is the probability of a Type I error, 0.2 and 0.05 are conventional values
for β and α).
When a test shows that a significant difference is present, then usually there is no need to further
consider the statistical power of the study. However, if no significant differences are detected, then
questions may arise as to whether detection of significant differences in the means would have been
made had there been more replications in the experiment. In a bioequivalence experiment, it is thus
paramount to make sure that the power of the test be sufficient (≥80%) and thus insure validity of the
conclusions, by using the proper minimum amount of replicates.
Number of replicates
It is tempting to declare that for a specific experiment, a critical minimum quantity of replicates (n) is
necessary to detect a statistically valid difference (assess bioequivalence); however, the interaction of
specific breed, type of feed, environmental conditions etc. makes it impossible to make concrete
declarations of sample size or levels of significance (Roush, 2004). In order to approximate the
minimum number of replicates, it is helpful to conduct an a priori power analysis. The website of R. V.
Lenth (www.stat.uiowa.edu/rlenth/Power/) provides links to several power analysis calculators.
When the coefficient of variation (CV) and the magnitude of the effect is known for a specific trait, a
table such as that presented in Roush (2004) or Reese (2010) can be used to estimate the minimum
number of replicates. A trait with a small CV needs fewer samples for detection than a trait with a large
CV. In the same way, a trait with a large magnitude of the effect (e.g. 0.8) needs fewer samples for
detection than a trait with a medium (e.g. 0.4) or small (e.g. 0.1) magnitude of the effect.
Because the total number of replicates that are required depends both on the variability of the trait
(response variable) under scrutiny and the magnitude of the effect that is expected, the number of
replicates is specific to each trait. In order for the power to reach 80% throughout all the traits for a
specific animal (pigs, broiler chickens, laying hens), it is important to calculate n using the trait that has
the highest CV, and lowest magnitude of the effect.
As a guidance, Reese (2010) determined that for two-sample diet experiments with pigs, 4 pens per diet
is necessary to detect a potential difference of 15% or higher, assuming a CV of 5% - hence a total of 8
pens is necessary. In this case, the pen (group of pigs) is the replicate (hence, 3 degrees of freedom). The
number of pigs per pen should be as high as possible (in order to have averages with minimum standard
error, and to be able to account for dead pigs), taking into account the comfort of the animals and the
total number of pigs available for the experiment. Based on Reese (2010)’s recommendations, three pigs
per pen should be used for this experiment, for a total number of 24 animals. Floor space should be
equal for every individual.
For two-sample diet experiments with broiler chickens and laying hens, MacMillan suggested that 60
individuals be used per diet. In this case, the individual is the replicate.

Time frame
For pigs, the experiment takes place over the growing-finishing cycle. During this period of
approximatively 3 months, the pigs grow from 25 kg (55 lb) to 100 kg (220 lb, market weight).
Alternatively, the experiment could take place during the growing period only (25 kg to 60 kg
liveweight). Additionally, 7 days should be allocated for adaptation to the feed, and 10 days for
adaptation to the cage.
The feeding trial on broiler chickens should be carried out through a normal production range (6-8
weeks).
For laying hens, the experiment should take place through the first half of the laying period (point of lay
to 22 weeks).
Fish silage production
Fat in the silage may increase poly-unsaturated fatty acids (PUFA) content, including the long-chain
omega-3 fatty acids C22:6 (DHA), C22:5 (DPA) and C20:5 (EPA). This may be beneficial for human
nutrition, since the consumption of long-chain omega-3 fatty acid may strength immune and nervous
systems, as well as prevention of the cardiovascular diseases and some types of cancer (Ramirez, 2013).
However, this may have an adverse effect on the sensory quality of meat, leading to the development of
a rancid or ‘’fishy’’ taste (Raa and Gildberg 1982; Krogdahl 1985). Hence, fish silage fed to pigs, broiler
chickens or laying hens needs to be defatted.
In this experiment, defatted fish silage is produced following Jangaard (1987; Figure 1 and Figure 2):
- The raw material is first minced; suitably small particles can be obtained by using a hammer mill
grinder fitted with a screen containing 10 mm diameter holes (Tatterson and Windsor, 2001).
- Immediately after mincing, formic acid is added at a level of 15–25 g kg–1 (1.5-2.5 %) wet weight
depending on the ash content in the raw. The more bone the higher rate of acid is required to
bring pH down -high calcium content will neutralize the acid and therefore the product
requirement will be higher. When making large batches, acidity should be monitored and
adjusted empirically to stay within the 3.6-4 range; if it is above 4 more acid should be added; if
it is below 3.8 less acid could probably have been used, with a saving in cost. It is important to
mix thoroughly so that all the fish comes into contact with acid, because pockets of untreated
material will putrefy.
- Ethoxyquin is added as an anti-oxidant at 200–300 ppm wet weight (200-300 mg/kg wet weight)
- The fish silage is let to cure for liquefaction to operate, and occasional stirring helps to ensure
uniformity. The rate of liquefaction highly depends on the temperature of the process. For
instance, white fish offal can take about two days to liquefy at 20°C, but takes 5-10 days at 10°C,
and much longer at lower temperatures. Thus in winter it would be necessary to heat the
mixture initially, or to keep it in a warm area until liquid (Tatterson and Windsor, 2001).
- In a subsequent step, fish silage is heated to 95°C, and passed through a decanter and a
centrifuge to separate the fat from the rest. Fish fat could potentially be valued through routes
such as energy production (e.g. biodiesel), compost, dog food, etc.

Fish silage of the correct acidity keeps at room temperature for at least two years without putrefaction.
The protein becomes more soluble, and the amount of free fatty acid increases in any fish oil present
during storage, but these changes are unlikely to be significant nutritionally (Tatterson and Windsor,
2001).
According to Tatterson and Windsor (2001), the fish silage can be blended with cereals to make a
semidry feed or “wet mash”.
Pre-experiment measurements
Variability of farm-specific production performance
Variability of production performance is measured before the experiment, in order to determine the
minimum number of replicates needed to assess bioequivalence of the test diet when compared to the
control diet. Variability is specific to the farm where the experiment takes place. Variability expresses
“chance variation” – i.e. the difference that exists between individuals, despite the best effort to feed
and treat a group alike. For instance, variability of weight gain is a measure of weight gain difference
that exists between individuals because of factors that cannot be explained or anticipated. Metrics used
to assess production performance are detailed in the “Response Variables” section. Variability should be
assessed over a whole production cycle (e.g. weaning to slaughter for pigs). Variability is expressed in
terms of Coefficient of Variation:
CV = SD/X * 100%
where CV = Coefficient of Variation
SD = Standard Deviation
X = Treatment Mean
Weight at time zero of the experiment
Weight of each individual animal used in the experiment is measured at the time of inception of the
experiment.
Pig weight is determined using heart girth as a proxy (Groesbeck et al., 2002):
Pig weight (lb) = 10.1709 × heart girth (in) - 205.7492
Quality of the feed
Quality of the feed ingredients and quality of the feed is determined prior to the experiment (Table 1).
Dry matter content should equate to the addition of Protein, Fat, and Ash content. Similar to Kjos (2001,
2000, 1999), all analyses are conducted according to standard procedures described by the Association
of Official Analytical Chemists (1990).
Protein content is calculated as the Nitrogen content (Kjedahl) multiplied by 6.25. Fat is measured as
HCl-ether extract; fatty acid composition is analyzed by GLC procedures. Metabolizable energy is
determined according to procedures described in Krogdahl (1985), following Just (1982)’s method and
using the Rostock equation described by Schiemann et al. (1971).
Quality is determined for the crude fish matter, crude fish silage, fresh de-fatted fish silage, aged (e.g. 3
months) de-fatted fish silage, the wet mash, and the control feed.

pH
Dry matter content (% of diet)
Protein content (g kg Dry Matter-1
)
Fat content (g kg Dry Matter-1
)
Ash content (g kg Dry Matter-1
)
Crude fiber (g kg Dry Matter-1
)
Nitrogen free extracts (g kg Dry Matter-1
)
Fatty acid composition (g kg Dry Matter-1
)
Calcium (g kg Dry Matter-1
)
Phosphorus (g kg Dry Matter-1
)
Magnesium (g kg Dry Matter-1
)
Metabolizable energy (MJ kg Dry Matter-1
)
Table 1: Quality parameters for the feed and feed ingredients
Feeding and Diets
If not otherwise stated, feeding and diets follow Kjos (2001, 2000 and 1999)’s recommendations. In
order to be able to draw valid conclusions on the bioequivalence of fish silage as a protein source, the
test and control diets are isoenergetic, i.e. balanced on a metabolizable energy basis.
Feeding scheme
Contingent on the farm habits, pig rations are provided once or twice a day. The pigs are fed
individually. Feed quantity is adjusted daily following a standard feeding/growth chart (e.g. Thomke et
al., 1995). From Kjos (1999)’s observations, the average daily feed intake can be assumed to be
approximately 1.89-1.99 kg day-1
. Following Kjos (1999)’s recommendation for the prevention of adverse
effect on sensory quality of the meat, the experimental diet is fed until slaughter only if the de-fatted
fish silage’s fat level is lower than 3.4 g kg–1
DM; if the fat level is up to 5.7 g kg–1
DM, the experimental
diet can be fed until 60 kg liveweight, and control feed is fed for the remainder of the finishing period
(until 100 kg).
For broiler chickens, feed and water are provided ad libitum. From Kjos (2000)’s observations, the
average net feed intake can be assumed to be approximatively 79.1-82.9 g kg-1
. Following Kjos (2000)’s
recommendation for the prevention of adverse effect on sensory quality of the meat, the experimental
diet can be fed until slaughter if the de-fatted fish silage’s fat level is lower than 10 g kg-1
DM;
For laying hens, feed and water are provided ad libitum.
Test diet
Test diet compositions for pigs, broiler chickens and laying hens are presented in Table 2. All test diets
are a compound feed based on a non-protein commercial mix (e.g. barley, oat, wheat, corn, canola), and
protein is supplied by fish silage and soybean meal; fish silage is supplied at the maximum proportion
recommended in the literature to prevent adverse effect on production performance, and the
remainder of necessary protein supply is provided by soybean meal. Rendered animal fat is used to
adjust the metabolizable energy with that of the control diet; for instance, Kjos (2001, 2000, 1999)

utilized rendered fat consisting of approximately 70% lard and 30% tallow. Vitamin E is added to prevent
lipid oxidation in meat tissues and prevent adverse effect on sensory quality of the meat. Lysine,
methionine and tryptophan are added in order to meet or exceed the National Research Council
requirements for amino acids for poultry (1994) and for swine (1998). In the same way, vitamins are
added in order to supply surplus amounts according to requirements (ref), and to equalize diets. Diet
compositions are provided here on a relative basis, and final individual ingredient weights will need to
be determined from the fish silage quality data (starting with protein content).
For pigs, the fish silage is provided in a proportion of 9% of the total dietary protein; in Kjos(1999)’s
experiment, for instance, 9% of the total dietary protein content corresponded to 50 g fish silage / kg
diet (circa 5% of the total diet on a weight basis). The remainder of the protein need is supplied by
soybean meal; in Kjos(1999)’s experiment, for instance, 162 g kg-1
was necessary to complete protein
requirements. From Kjos (1999)’s experiment, it can be approximated that 25% of the soybean meal
that would be necessary to complete dietary protein requirements (circa 210 g kg-1
) can be replaced by
fish silage. For illustrative purpose, the metabolizable energy level in Kjos (1999)’s diets was 14.4-14.8
MJ kg-1
DM).
For broiler chickens, the fish silage is provided in a proportion of 21% of the total dietary protein; in Kjos
(2000)’s experiment, for instance, 21% of the total dietary protein content corresponded to 100 g fish
silage / kg diet (circa 10% of the total diet on a weight basis). For illustrative purpose, the metabolizable
energy level in Kjos (2000)’s diets was 11.32-11.77 MJ kg-1
DM).
For laying hens, the fish silage is provided in a proportion of 12% of the total dietary protein; in Kjos
(2001)’s experiment, for instance, 12% of the total dietary protein content corresponded to 50 g fish
silage / kg diet (circa 5% of the total diet on a weight basis). For illustrative purpose, the metabolizable
energy level in Kjos (2001)’s diets was 10.6-10.7 MJ kg-1
DM).
Pigs Broiler Chickens Laying Hens
Commercial non-protein feed Basis Basis Basis
De-fatted fish silage 9% of the total
dietary protein
content
21% of the total
dietary protein
content
12% of the total
dietary protein
content
Soybean meal To complete
protein needs
To complete
protein needs
To complete
protein needs
Rendered Animal fat To adjust
metabolizable
energy
To adjust
metabolizable
energy
To adjust
metabolizable
energy
Vitamin E Yes ? ?
Lysine Yes ? ?
Methionine Yes ? ?

Tryptophan ? ? ?
Vitamin premix Yes1
Yes2
Yes3
Table 2: Test diet composition for pigs, broiler chickens, and laying hens. The relative proportion of each
ingredient is indicated in the column for the specific animal production.
Control diet
Control diet compositions for pigs, broiler chickens and laying hens are presented in Table 3. All control
diets are a compound feed based on a non-protein commercial mix (e.g. barley, oat, wheat, corn,
canola), and protein needs are supplied by soybean meal entirely. Rendered animal fat is used to adjust
the metabolizable energy with that of the test diets. Vitamin E, essential amino acids, and Vitamin
premix are also added, in the same way as for the test diets. Control diets compositions are provided
here on a relative basis, and final individual ingredient weights will need to be determined from the
ingredient’s quality data.
Commercial non-protein feed Basis Basis Basis
De-fatted fish silage None None None
Soybean meal Entire protein
needs
Entire protein
needs
Entire protein
needs
Rendered Animal fat To adjust
metabolizable
energy
To adjust
metabolizable
energy
To adjust
metabolizable
energy
Vitamin E Yes ? ?
Lysine Yes ? ?
Methionine Yes ? ?
Tryptophan ? ? ?
Vitamin premix Yes4
Yes5
Yes6
Table 3: Control diet composition for pigs, broiler chickens, and laying hens. The relative proportion of
each ingredient is indicated in the column for the specific animal production.
1 Trace elements and vitamins included to provide the following amounts per kg of diet: 70 mg of Zn; 50 mg of Fe; 40 mg of Mn; 10 mg of Cu;
0.5 mg of I; 0.2 mg of Se; 6000 IU of vitamin A; 400 IU of cholecalciferol; 40 mg of dl- -tocopheryl acetate; 3 mg of riboflavin; 10 mg of d-
pantothenic acid; 20 μg of cyanocobolamine; 20 mg of niacin; 0.2 mg of biotin; 1.5 mg of folic acid; 2 mg of thiamin; 3 mg of pyridoxine.
2 Trace elements and vitamins provide the following amounts per kg diet: 70 mg of Zn; 50 mg of Fe; 40 mg of Mn; 10 mg of Cu; 0.5 mg of I; 0.2
mg of Se;6000 IU of vitamin A; 400 IU of cholecalciferol; 40 mg of d1-a-tocopheryl acetate; 8 mg of riboflavin; 15 mg of d-pantothenic acid; 20
mg of cyanocobolamine; 60 mg of nicacin; 0.2 mg of biotin; 2 mg of folic acid; 4 mg of thiamin; 6 mg of pyridoxine.
3 Trace elements and vitamins to provide the following amounts per kg of diet: 60 mg of Zn; 25 mg of Fe; 100 mg of Mn; 5 mg of Cu; 0.5 mg of I;
0.2 mg of Se; 12,000 IU of vitamin A; 3000 IU of cholecalciferol; 40 mg of d1-a-tocopheryl acetate; 8 mg of riboflavin; 15 mg of d-pantothenic
acid; 30 mg of cyanocobalamine; 40 mg of niacin; 0.1 mg of biotin; 1 mg of folic acid; 4 mg of thiamin; 6 mg of pyridoxine
4
Same as in experimental diet
5
idem
6
idem

Response variables
Measurements are taken throughout the experiment to assess bioequivalence of the experimental diet
and the control diet. Response variables can be categorized in terms of production performance,
economics, metabolism data, physical characteristics of the end product, sensory quality of the end
product, and nutritive quality of the end product. If not indicated otherwise, all response variables are
measured same as in Kjos (2001, 2000 and 1999). According to budget, logistics, and technical feasibility,
measurements of some response variables might be prioritized, modified, or eliminated.
Production performance
Production performance metrics for pigs, broiler chickens, and laying hens are presented in Table 4.
Weight of each individual is measured at the beginning and at the end of the experiment, and net
weight gain is calculated from these observations. The number of days necessary to fatten up to market
weight (circa 100 kg for pig and circa 2.5 kg for broiler chickens) is recorded, and average daily gain is
calculated from these observations. For pigs, weight is also recorded every 14th
day; for broiler chickens,
weight is also recorded every 7th
day.
For pigs, feed intake is recorded daily; if any feed is rejected, it is measured and subtracted from the
ration weight. For broiler chickens and laying hens, feed consumption is recorded every 7th
day. Net feed
intake is calculated using this observation and the average daily feed intake is calculated, integrating the
number of days the experiment unfolded. Feed efficiency equates to a feed-to-gain ratio, and is
calculated as net feed intake over net weight gain. Net energy intake and average daily energy intake
are calculated by integrating the metabolizable energy value of the feed. Energy efficiency (energy-to-
gain ratio) is calculated as energy intake over weight gain.
For laying hens, eggs are collected and counted daily, and an average daily egg quantity and egg weight
production is calculated once a week. Hen-day production represents the average quantity of eggs that
is produced per hen per day and is calculated as:

Initial weight (kg) X X X
Final weight (kg) X X X
Net Weight gain (kg) X X X
Number of days to market X X
Average daily gain (kg day-1
) X X X
Net feed intake (kg) X X X
Average daily feed intake (kg day-1
) X X X
Feed efficiency (kg kg-1
gain) X X X
Average daily energy intake (MJ day-1
) X X X
Energy efficiency (MJ kg-1
gain) X X X
Average daily egg production (quantity day-1
) X
Average daily egg weight production (g day-
1
)
X
Average hen-day egg production (%) X
Table 4: Production performance metrics for pigs, broiler chickens, and laying hens. Those metrics
marked with an “X” in the column are suggested for the specific animal production.
Economics
Economical metrics for pigs, broiler chickens, and laying hens are presented in Table 5. All economical
metrics are calculated considering a fish silage cost of CAD 200/metric ton.
Economical metric Pigs Broiler Chickens Laying Hens
Cost per weight gain (S/kg) X X X
Cost per egg produced ($/egg) X
Cost per energy intake ($/MJ) X X X
Return on investment ($/$) X X X
Table 5: Economical metrics for pigs, broiler chickens, and laying hens. Those metrics marked with an
“X” in the column are suggested for the specific animal production.
Metabolism data
Metabolism metrics for pigs and broiler chickens are presented in Table 6 (no metabolism data for laying
hens). For pigs, blood samples are taken at start of the experiment (circa 25 kg), at 60 kg live weight, and
immediately before slaughter (circa 100 kg); the blood samples are taken from the jugular vein,
approximately 1 h after the morning feeding, using heparinized vacutainers for the plasma samples and
polyethylene tubes (TT tubes) for whole blood. For broiler chickens, blood samples are taken from the
jugular vein of all chicks immediately after slaughter, using heparinized vacutainers for the plasma
samples and polyethylene tubes (TT tubes) for the whole blood samples. Vitamin E is determined in
blood plasma using the method of McMurray and Rice (1982) with modifications indicated in Kjos (2000

and 1999). Ceruloplasmin is determined in blood plasma according to Schosinsky et al. (1974).
Glutathione peroxidase is analyzed in whole blood following the method of Paglia and Valentine (1967).
Pigs Broiler Chickens
Vitamin E X X
Ceruloplasmin X X
Glutathione peroxidase X X
Table 6: Metabolism metrics for pigs and broiler chickens. Those metrics marked with an “X” in the
column are suggested for the specific animal production. No metabolism metrics are suggested for
laying hens.
Physical characteristics of the end product
Physical characteristic metrics for pigs, broiler chickens and laying hens are presented in Table 7.
For pigs, carcass characteristics are measured 1 d after slaughter. Lean percentage is determined using a
GP2Q pistol (Hennessy System), measuring the diameter of the loin muscle (longissimus thoracis et
lumborum) and backfat thickness at two sites (between the last 3rd and 4th rib, 6 cm from the midline,
and behind the last rib, 8 cm from the midline). A tracing of a cross section of the cutlet, behind the last
rib, is made using tracer paper. Meat area in the cutlet is determined with a planimeter (Coradi AG,
Zürich, Switzerland). The P2 backfat thickness is measured 8 cm from the midline behind the last rib
using tracer paper and a ruler. Subjective evaluation of subcutaneous fat firmness using a scale from 1
to 15, in which 15 is the firmest score. Subjective evaluation of fat colour using a scale from 1 to 15, in
which 15 is the most favorable colour.
For broiler chickens, carcass weight and weight of the abdominal fat pad are registered at the time of
slaughter.
For laying hens, egg characteristics are taken on all eggs from two randomly chosen days within the first
and the second half of the experimental period, respectively. The eggs are stored at 4oC and the
analyses must take place within 10 days. Thickness of albumen is determined on cracked eggs using a
micrometer. Haugh unit is calculated on the basis of thickness of albumen and egg weight. Yolk color
index is evaluated by Roche Yolk Colour Fan (F. Hoffmann La Roche Ltd., Basel, Switzerland), on a scale
of 1–14 (1 = very pale yellow; 14 = very dark orange).

Slaughter weight (kg) X X
Carcass weight (kg) X X
Dressing percentage (%) X X
Lean (%) X
Meat area in the cutlet (cm2
) X
P2 backfat thickness, P2 (mm) X
Subcutaneous fat firmness (1-15) X
Fat colour (1-15) X
Weight of the abdominal fat pad X
Thickness of albumen X
Yolk color index X
Table 7: Physical characteristics of the end product for pigs, broiler chickens, and laying hens. Those
metrics marked with an “X” in the column are suggested for the specific animal production.
Sensory/organoleptic quality
Organoleptic quality (meat and egg acceptability) metrics for pigs, broiler chickens, and laying hens are
presented in Table 8.
For pigs, sensory quality analysis is conducted on samples of loin, flank, and belly that have been stored
in a freezer at –16°C, for 1 mo (short time storage) or for 6 mo (long time storage). The samples of belly
are processed (cured and smoked) to make bacon. Meat for sensory analysis is vacuum-packaged
prior to storage. The sensory analysis is conducted according to international standards (ISO 3972
Sensory analysis — Methodology — Method of investigating sensitivity of taste); a trained panel of eight
members evaluate the samples, using a scale from 1 to 9, where 1 is the lowest and 9 the highest
intensity, for all parameters. The sensory analysis can be conducted at the Norwegian Meat Research
Laboratory, Oslo, Norway.
For broiler chickens, sensory quality is analyzed on thigh meat taken from 15 chicks of each dietary
treatment, randomly chosen from each of the replicate pens. The samples are taken 1 h post-mortem,
and are frozen immediately. Sensory quality analysis is conducted on pieces of meat that have been
frozen for 1 mo and 6 mo and with the same method as described for pigs (see hereinabove).
For laying hens, sensory analysis is conducted on two sets of 12 eggs, collected from two randomly
chosen days. The eggs are stored at 4oC and analyzed for sensory evaluation after 7 days and after 35
days, respectively. The sensory analysis is conducted according to international standards (ISO 3972
Sensory analysis – Methodology – Method of investigating sensitivity of taste). Similar to Kjos (2001),
sensory analysis can be conducted at the Norwegian Food Research Institute, Ås, Norway, using a
computerized system for recording of data (Compusense Five, Compusense, Guelph, ON). The eggs are
boiled for 10 min and then cooled in cold water for 5 s before sensory evaluation. A trained panel of 11
members evaluate both albumen and yolk for the parameters odor, off-odor, taste, off-taste, whiteness
and hardness. Each assessor evaluates the samples on the computerized system, using a continuous

scale. The computer translates the responses into numbers between 1 to 9, where 1 equals no intensity
and 9 equals high intensity of the parameter.
Loin [odour, off-odour, taste, off-taste,
juiciness, tenderness] (1-9)
X
Flank [odour, off-odour, taste, off-taste] (1-9)
X
Belly [odour, off-odour, smoke odour, taste,
off-taste, smoke taste, salt taste] (1-9)
X
Thigh meat [odour, off-odour, taste, off-taste,
rancid taste, juiciness, tenderness] (1-9)
X
Albumen [odor, off-odor, taste, off-taste,
whiteness, hardness]
X
Yolk [odor, off-odor, taste, off-taste,
yellowness, hardness]
X
Table 8: Sensory quality of the end product for pigs, broiler chickens, and laying hens. Those metrics
Nutritive quality of the end product -contents of fatty acids
Nutritive quality metrics for pigs, broiler chickens, and laying hens are presented in Table 9.
Fatty acid results are presented as relative distribution of the individual fatty acids (g 100 g–1 of total
fatty acids). Total poly unsaturated fatty acids (PUFA) include the long-chain omega-3 fatty acids C22:6
(DHA), C22:5 (DPA) and C20:5 (EPA). Fatty acids composition is analyzed by GLC procedures according to
the methods described by Ulbreth and Henninger (1992) for extracted/methylated samples. The fatty
acid methyl esters are determined on a Perkin Elmer Autosystem gas chromatograph (Perkin Elmer
Corp., Norwalk, CT) with a SGE capillary column no. 5QC3/bpx70, 0.25, 25 + 25 m (SGE International Pty.
LTD, Ringwood, Victoria, Australia).
For pigs, the content of fatty acids is measured in subcutaneous fat. For broiler chickens, fatty acids
composition is analyzed on (samples of) the abdominal fat pad of all the chicks and (of) the breast meat
of five chicks of each treatment randomly chosen.
For laying hens, nutritive quality (cholesterol and fatty acid content) is measured on 4 eggs collected
randomly throughout the experiment period. The eggs are stored at 4oC and analyzed within 10 days.
Cholesterol in egg yolk is determined spectrophotometrically in Encore Chemistry System (Baker
Instruments, UK), using Cholesterol Enzumatique PAP 100, kit. Ref. 61 224 from bioMeriedux (France).

Proportion of individual fatty acids (in
meat/in yolk) (g 100 g total fatty acids-1
)
C14:0
C16:0
C16:1
C18:0
C18:1
C18:2 (n-6)
C18:3 (n-3)
C20:1
C20:4
C20:5 (n-3)
C22-1
C22:5 (n-3)
C22:6 (n-3)
X X X
Proportion of poly unsaturated fatty acids
(PUFA) (g 100 g total fatty acids-1
)
X X X
Cholesterol in egg yolk X
Table 9: Nutritive quality of the end product for pigs, broiler chickens, and laying hens. Those metrics

PHOTOS AND FIGURES
Figure 1: Typical fish silage installation (adapted from Jangaard, 2007)
Figure 2: Processing method for concentrated, defatted fish silage (adapted from Kjos, 1999).

Figure 3: English Large Black sow and her 6 piglets at Grizzly Pigs Farm (July 2015)
Figure 4: Pink sow at Grizzly Pigs Farm (July 2015)

Figure 3: Example of a small pig hutch at Grizzly
Pigs Farm (July 2015
)
Figure 4: Feed bowls for individual pigs
Figure 5: Commercial Grower Feed
utilized for pigs, broiler chickens and
laying hens at Grizzly Pigs Farm

ANNOTATED BIBLIOGRAPHY
Addcon, 2015. The principle of making fish silage to preserve by-products for the feed industry.
Webpage.
Notes
This document presents how to use ENSILOXR
, a product that can be used for making fish silage.
This product consists of formic acid and an antioxidant, the latter helping in protecting the oil
content. Addcon is based in Germany.
Al-Marzooqi, W., Al-Farsi, M., Kadim, I., Mahgoub, O., Goddard, J., 2010. The effect of feeding different
levels of sardine fish silage on broiler performance, meat quality and sensory characteristics under
closed and open-sided housing systems. Asian-Australasian Journal of Animal Sciences. 23 (12), 1614-
1625.
Abstract
Two experiments were conducted to evaluate the use of fish silage prepared from Indian oil
sardines, Sardinella longiceps, as partial replacement of soybean meal as a sole source of protein
for growing broiler chickens. The main objective of Experiment 1, an ileal digestibility assay, was
to assess the nutritional value of fish silage compared with soybean meal for feeding broiler
chickens. The two test ingredients, soybean meal and dried fish silage, were incorporated into
semi-synthetic diets, as the only component containing protein. The ileal digestibility coefficients
of amino acids of fish silage were considerably higher than those of soybean meal (p<0.001). The
lower digestibility of amino acids from soybean meal was related to the presence of anti-
nutritional factors such as trypsin inhibitors. Fish silage had higher levels of sulphur-containing
amino acids than soybean meal. The objective of Experiment 2, a growth study, was to evaluate
the effect of feeding fish silage on performance and meat quality characteristics of broiler
chickens raised under closed and open-sided housing systems. Four diets containing various
levels of fish silage (0, 10, 20 and 30%) were evaluated. Daily feed intake, body weight gain and
feed conversion ratio were measured. At the end of Experiment 2, 96 birds were randomly
selected and slaughtered to evaluate meat quality characteristics. Housing type had significant
effects on feed intake and body weight gain (p<0.01). Birds in the open-sided house consumed
4.7% less amount of feed and gained 10.6% less than their counterparts in a closed house. Birds
in both houses fed diets containing 10 and 20% fish silage gained more than birds fed 30% fish
silage. The current study produced evidence that fish silage can replace up to 20% of soybean
meal in broiler diets without affecting either growth performance or the sensory quality of
broiler meat.
Arruda, L.F.d., Borghesi, R., Oetterer, M., 2007. Use of fish waste as silage: a review. Brazilian Archives of
Biology and Technology. 50 (5), 879-886.
Abstract
The use of fish silage as a substitute for protein ingredients in rations for aquatic organisms is an
alternative to solve sanitary and environmental problems caused by the lack of adequate
disposition for the waste from the fish industry. Besides, it is also a way of decreasing feeding
costs, and, consequently, fish production costs, since feeding corresponds to about 60% of the
overall expenses with production. The objective of this review was to discuss the use of fish
waste, the elaboration of chemical silage and the use of this ingredient in feed for aquaculture.

Association of Official Analytical Chemists 1990. Official methods of analysis. 15th ed. AOAC,
Washington, DC.
Methods for analysis the quality of the fish silage can be found in there (Kjos, 1999).
Balios, J., 2003. Nutritional value of fish by-products, and their utilization as fish silage in the nutrition of
poultry. Proceedings of the 8th International Conference on Environmental Science and Technology8-10.
Abstract
It can be concluded from the experiments that fish silage is a very good alternative source of
protein when partly replacing other more expensive sources of protein. In our days, with
consumers being more and more sensitive in matter related to the pollution of the environment,
fish silage provides the means of utilizing fish waste from the canning industry, instead of being
thrown away. Among the advantages of making fish silage are: Fairly low capital cost, can be
made by unskilled workers, there is no smell of the final product and can be stored, under
favourably conditions, for up to two years. Disadvantages are, the high transportation cost and
also that high inclusions in the diet of the farm animals can affect negatively the flavor of meat
and eggs (fishy taint).
Bimbo, A., 2012. Alaska seafood byproducts: potential products, markets and competing products.
Anchorage, Alaska: Alaska Fisheries Development Foundation. 277.
Summary
“Composts, hydrolyzates, digests and silage must be market driven since they are either very
high in water content (silage) or bulky thus making transportation costs a key factor. There is a
tendency to interchange hydrolyzates, silage and digest nomenclature. For our purposes, fish
solubles is the concentrated stickwater from fishmeal production. Silage is the autolysate or fish
digest using the internal enzymes in the fish plus acid for stability. The acid inhibits and destroys
the bacteria allowing the internal fish enzymes to digest the fish mass. Cold silage is the product
that represents the fish material in liquid form without removal of water or oil. Hot or
concentrated or advanced silage involves oil and water removal and evaporation and results in a
more concentrated product. If the raw material is low in fat, no oil removal is needed. Fish
solubles are sometimes marketed as hydrolyzates or something similar. […]A recent headline
from Alaska indicates that fertilizers are in short supply and the prices have increased 400% so
there could be a market for fish waste in agriculture now. Liquid silages, fish solubles etc. are
used as organic fertilizers and have found niche markets for golf courses, the growing of
cranberries etc. […] (Table 103-11- present the composition of branded fish silages (e.g. ash
content, proteins, energy, amino acidsetc.)) […]About 40,000 tons of raw silage is processed
with finished products shipped to Norway, Finland, Denmark, France and Holland. A similar co-
op set up could be put in place in Alaska as well but this must be market driven. […] SCANBIO
SCOTLAND LTD ENSILER EQUIPMENT: manufactures off the shelf silage plants of all sizes and
shapes that can be moved from place to place. […] As already mentioned, there is a shortage of
fertilizer in Alaska so perhaps silage production could fill that need. […]There is very little
information available on the price structure for Fish Silage, Hydrolyzates And Fish Solubles. The
only information is on the internet and this only reflects retail sales of products in pint and quart

bottles and 5 gallon pails. Some of the hydrolyzates from France have sold in the US$900+/ton
range for early weaned pig and milk replacer diets. However, the early weaned pig market is
only 8 weeks out of the life of the pig. Omega Protein is the only company that sells fish solubles
as a separate product. Based on their SEC filing, during the period 1998-2007 as shown in the
following figure, fish solubles sold in the US$175 – $432/metric ton over that period. If we
assume that the fish solubles are 50% solids and that conventional cold silage is 20% solids and
that the nutrient composition is comparable, we could estimate that over that same period of
time, cold crude fish silage would have sold in the $70 - $173/metric ton. […]”
Coates, J.W., Holbek, N.E., Beames, R.M., Puls, R., O'Brien, W.P., 1998. Gastric ulceration and suspected
vitamin A toxicosis in grower pigs fed fish silage. The Canadian Veterinary Journal. 39 (3), 167.
Abstract
In 3 feeding trials, gastric ulceration was diagnosed in 2 of 12 lame and recumbent grower pigs
fed a diet of 50% fish silage produced from the offal of farmed Atlantic salmon. Premature
femoral physeal closure and elevated serum retinyl palmitate levels, features of vitamin A
toxicosis, were also observed.
Cameron, C. D. T. Acid fish offal silage as a source of protein in growing and finishing rations for bacon
pigs. Canadian Journal of Animal Science 42.1 (1962): 41-48.
Abstract
Three factorially designed experiments, involving 136 growing-finishing Yorkshire pigs, were
carried out to determine the feeding value of acid-ensiled cod and haddock offal. Rate of gain,
feed efficiency and carcass characteristics indicated that this product was a satisfactory source of
supplementary protein. However, a moderate off-flavor was detected in the meat from pigs
fedfish silage to market weight. The intensity of the off-flavor was not affected by removal of fish
silage from the ration of pigs at approximately 170 pounds body weight when slaughtered at 200
pounds. The results from discontinuing the feeding of fish silage when the pigs reached body
weights of 100 and 150 pounds on off-flavor in the meat were not conclusive.
Canadian Council on Animal Care 1993. Guide to the care and use of experimental animals. Vol. 1, 2nd
ed. Canadian Council on Animal Care, Ottawa, ON.
Collazos, H., Guio, C., 2007. The effects of dietary biological fish silage on performance and egg quality of
laying Japanese quails (Coturnix coturnix japonica). World Poultry Science Association, Proceedings of
the 16th European Symposium on Poultry Nutrition, Strasbourg, France, 26-30 August, 2007: World's
Poultry Science Association (WPSA). 37-40.
Abstract
An 8 week experiment was conducted to evaluate the effects of biological fish silage
supplementation in laying Japanese quails diets on performance and egg quality. A total of 120,
60 d-old laying japanese quails were allotted in a randomized experimental design with four
treatments (Controls, 2, 4 and 6% of biological fish silage), with five replicates and 6 birds per
replicate. Diets were formulated to meet or exceed NRC recommendations. Feed and water were
supplied ad libitum and light was scheduled for 16 hours of light and 8 hours of dark each day.
Feed consumption was measured weekly and feed conversion was calculated. Laying percentage,

egg weight, and egg mass were recorded daily during 8 to 16 wk of age. Random samples of 8
eggs from each treatment were collected weekly to measure egg quality: such as, eggshell
thickness, Haugh units, egg specific gravity, and yolk percentage. Productive parameters such as
feed intake, egg weight, feed efficiency, body weight variation, and egg mass were not affected
(P>0.05), only laying percentage was affected (P<0.01) by treatments. Egg quality parameters
were no affected (P>0.05) by dietary treatments. Results obtained indicate that biological fish
silage can be included in laying diets of Japanese quails up to 6% without adverse effects.
Introduction
A particular problem in animal nutrition is the lack of quality protein sources with a good
amino acid profile, due to availability and relative high cost.
Objective
Determine the effects of (biological) fish silage supplementation in laying Japanese quails diets
on performance and egg quality when supplemented over standard corn and soymeal diet.
Materials and Methods
Experiment with biological fish silage.
Experiment performed on Japanese qualis. Completely Randomized experimental design. 4
treatment groups. 120 quails used. 6 quails per (replicate) cage. 5 (replicate) cages. Each cage
was the experimental unit. Metallic cages were used. Initial age of 60 days.
The (biologica) fish silage was prepared following FAO procedures (FAO, 1992), from slaughter
by-products (heads, guts, remains after deboning) of tilapia (oreochromis spp). Wastes were
washed, ,cooked for 15 minutes to reach 91oC, in order to avoid contamination problem,
drained and fine grounded (2mm), and added 15% molasses. The fish silage was preserved by
mean of lactic acid bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus), the
microbial culture was previously prepared, to be added to the substract and molass (5%
W:W).The culture microorganisms concentration was of 10 x 108 cfu. The mixture was placed in
a incubator at 40oC for 96 hours, in anaerobic conditions. The biological fish silage had 29.10%
crude protein and 48.90% Dry Matter.
Base ration was based on corn and soybean meal as main ingredients. Diets were formulated to
meet or exceed NRC recommendations (NRC 1994) and contained 20% of Crude protein and
2605 Kcal/kg of ME.
Control diet (CO): No fish silage
Diet 1: 2% biological fish silage
Metrics
(Performance): Weight gain (Average daily gain); Feed intake (Average ME intake); Feed
efficiency
(Egg Production): Laying percentage (hen-day egg production (%)?); Egg weight; Egg mass
(Egg Characteristics): Eggshell thickness; Haugh units; Egg specific gravity; Yolk percentage

Results
(Performance and Egg production): Productive parameters such as feed intake, egg weight, feed
efficiency, body weight variation, and egg mass were not affected (P>0.05). The level of fish
silage affected egg production (laying percentage), which was higher (77.03%) in controls, and
lower in T2 (67.84%). Egg weight, Weight gain, and eggshell thickness, and yolk percentage
increased linearly as level of silage increased.
(Egg Characteristics): Egg quality parameters were no affected (P>0.05) by dietary treatments
Conclusion
The results obtained in this experiment showed that biological fish silage supplementation to the
diet tended to improve egg weight, weight gain, eggshell thickness, and yolk percentage. Fish
silage can be included in laying diets of Japanese quails up to 6% without adverse effects.
National Research Council, 1994. Nutrient requirements of poultry. National Research Council. National
Academy Press Washington USA.
National Research Council, 1998. Nutrient requirements of swine. National Academic Press, Washington,
DC.
Dapkevicius, M.L.E., Nout, M.R., Rombouts, F.M., Houben, J.H., Wymenga, W., 2000. Biogenic amine
formation and degradation by potential fish silage starter microorganisms. Int. J. Food Microbiol. 57 (1),
107-114.
Abstract
Fish waste can be advantageously upgraded into animal feed by fermentation with lactic acid
bacteria (LAB). This procedure is safe, economically advantageous and environment friendly. The
pH value of the fish pastes decreases to below 4.5 during ensilage. This pH decrease is partly
responsible for preservation. Decreased pH values and relatively low oxygen concentrations
within the silage facilitate decarboxylase activity. Biogenic amines may constitute a potential risk
in this kind of product since their precursor amino acids are present in fish silage. It is of great
importance to ensure that the LAB strains chosen for starters do not produce biogenic amines.
Some bacteria, among which some LAB species, are able to degrade these metabolites by means
of amino oxidases. This could be of interest for fish silage production, to control biogenic amine
build-up in this product. Seventy-seven LAB cultures isolated from fish pastes submitted to
natural fermentation at two temperatures (15 and 22°C) and selected combinations of these
isolates were examined for histamine, tyramine, cadaverine and putrescine production. Of the
isolates tested, 17% were found to produce one or more of these biogenic amines. The
behaviour of diamine oxidase was tested under the conditions present in fish silage. Addition of
12% sucrose or 2% NaCl did not affect histamine degradation. Addition of 0.05% cysteine
decreased histamine degradation. Degradation occurred at all temperatures tested (15, 22 and
30°C), but not at pH 4.5. Forty-eight potential fish silage starters were tested for histamine
degradation in MRS broth containing 0.005 g l−1 histamine and incubated at 30°C. Indications
were found that five of these isolates could degrade as much as 20–56% of the histamine added
to the medium within 30 h, when used as pure cultures. No histamine degradation was observed
with combinations of cultures. Histamine degradation (50–54%) by two of these isolates was also
observed in ensiled fish slurry.

de Lurdes, M., Dapkevičius, E., Batista, I., Nout, M.R., Rombouts, F.M., Houben, J.H., 1998. Lipid and
protein changes during the ensilage of blue whiting (Micromesistius poutassou Risso) by acid and
biological methods. Food Chemistry. 63 (1), 97-102.
Abstract
Fish waste is a potential source of protein for animal nutrition. Ensilage could provide an
advantageous means of upgrading these residues. Careful control of the degree of proteolysis
and lipid oxidation is required to produce silages of high nutritional value. This paper studies the
changes in lipids and protein during storage (15 days) of acid silages (with 0, 0.25 and 0.43%,
w/w, of formaldehyde) and biological silages (with 10 and 20% molasses or dehydrated whey)
prepared from blue whiting. A remarkable reduction in protein solubilisation values was
achieved by adding formaldehyde. However, formaldehyde addition led to an increase in the
peroxide value of the oil extracted from the silages. Ensiling by biological methods seems
promising. It yielded both a considerable reduction in protein solubilisation and in basic volatile
nitrogen when compared with acid ensilage. In addition, the oil from biological silages had lower
peroxide values than the oil from acid silages with added formaldehyde.
DFO-MPO, 1987. Fish Silage Workshop. in: DFO-MPO, ed. Atlantic Fisheries Development. Université
Sainte-Anne, Church Point, Nova Scotia 103.
Abstract
This publication contains the proceedings of the Fish Silage Workshop held at Church Point, Nova
Scotia, June 16-17, 1987. The workshop was sponsored by the Canadian Department of Fisheries
and Oceans under the Fisheries Development Program and attracted about 130 participants.
The proceedings contain fourteen papers presented or distributed at the workshop. Included is a
review of recent developments in the production and use of fish silage concentrate especially in
Norway and two papers by manufacturers of silage processing equipment. Several papers
describe feeding trials with trout and salmon, and several domestic animals. Other papers give
details of recent activities in Canada's Atlantic provinces, including various pilot plant studies and
trials with the use of fish silage for fertilizer. The workshop was designed as an information
workshop and no recommendations for future development were formulated.
Enes Dapkevicius, M.L., Nout, M.R., Rombouts, F.M., Houben, J.H., 2007. Preservation of Blue-Jack
Mackerel (Trachurus Picturatus Bowdich) silage by chemical and fermentative acidification. Journal of
food processing and preservation. 31 (4), 454-468.
Abstract
We compared acidified and lactic acid fermented silage approaches for the preservation of blue-
jack mackerel. Silages acidified with formic and propionic acids had stable pH (3.8) and low
(19 mg/g N) levels of volatile nitrogen compounds (total volatile basic nitrogen, TVBN), but
relatively high (82 g/100 g) final non-protein-nitrogen (NPN) values.
The silage was fermented with Lactobacillus plantarum LU853, a homofermentative lactic acid
bacterium with a high growth (0.51/h) and acidification rate at 37C (optimum temperature), able
to grow in the presence of 40 g/L NaCl and to ferment sucrose and lactose. The silages at 37C
reached safe pH < 4.5 values within 48–72 h, either (F2a) or not (F0), in combination with
20 g/kg salt addition; F2a acidified more rapidly, which may be an advantage for its
microbiological stability. Proteolysis resulting in 53–59 g NPN/100 g N was lower in fermented
than in acidified silages; however, in fermented silages, the levels of TVBN were much higher
(50–80 mg TVBN/g N) than generally considered acceptable.

Groesbeck, C. N., 2003 “Use heart girth to estimate the weight of finishing pigs,” Kansas State University
Cooperative Extension Service Swine Update Newsletter Spring, 2003.
Haskell, S. R., et al. Flavour studies on pork from hogs fed fish silage. Canadian Journal of Animal
Science 39.2 (1959): 235-239.
Jangaard, P., 1987. Fish silage: A review and some recent developments. In Proceedings of Fish Silage
Worksho p 8-33. DFO-MPO, ed. Atlantic Fisheries Development. Université Sainte-Anne, Church Point,
Nova Scotia. 103 p.
Abstract
A brief summary of various enzymatic processes for preserving fish is given with emphasis on
Canadian contributions. Recent developments in Norway are described in some detail as a result
of a visit to that country in March 1987. These include research and development work on acid
fish silage and silage concentrate and their use as a feed especially for salmon and fur animals.
Summary
Introduction
Capital costs for (fish silage production) equipment are considerably lower than for a comparable
fish meal plant and there are no odor problems. One disadvantage is that transportation of
silage involves large quantities of water, and users should therefore be located as close as
possible to the plant.
Historical
A better word to describe fish silage would perhaps be “liquid fish”, “liquefied fish protein” or
when more concentrated, “protein concentrate”. In this report, fish silage is defined as silage
produced by adding inorganic and/or organic acids to lower the pH sufficiently to prevent
bacterial spoilage. The fish silage becomes liquid because the tissue structures are degraded by a
process called autolysis by enzymes naturally present in the flesh.
Lactic acid fermentation
One reason fish spoils more quickly than flesh or warm blooded animals is that tissues become
less acid post mortem in contrast to mammalian tissues. By encouraging the growth of lactic acid
bacteria, the spoilagerprocesses leading to the reduction of trimethylamine oxide to
trimethylamine and the degradation of amino acids to ammonia by spoilage bacteria are
suppressed. Lactic acid bacteria are well-known in dairy products such as yogurt. Although these
bacteria are natural inhabitants of fish, they are present in low numbers. Fish also contains only
small amounts of free sugar which is the essential substrate for growth of such bacteria (Raa et
al., 1983; Mackie et al., 1971). Therefore, to preserve fish or animal waste products by
fermentation, it is essential to add a sugar source, preferably with a starter culture of proper
lactic acid bacteria which, by rapid conversion of the sugar to acid, preserves the whole mass. A
considerable amount of fermentable sugar must be added to obtain a stable silage with a pH
around 4; for example, 20 kg of a dry mixture of malt and oatmeal was required for 100 kg of
fresh herring (Nelson and Rydin, 1963), or more than 10% molasses (Roa, 1965). […] Both
spoilage bacteria and lactic acid bacteria will contribute to the initial acid production because
the conditions are anaerobic and sugars are available, but growth of the lactic acid bacteria will
be favored as the silage becomes more acidic. If the pH falls to below 4, lactobacilli will become
the predominant organism present and harmful bacteria (coliforms, enterococci, typhoid

bacteria and even spores of Clostridium botulinum) are destroyed in such a silage (Raa et al.,
1983). If oxygen is admitted to any extent, then aerobic microorganisms such as yeasts may
develop. Yeasts are capable of growth at relatively low pH and utilize carbohydrate and protein.
Mold spoilage may also be a problem, especially if any drying occurs, for instance at exposed
surfaces (Mackie et al., 1971). A company in Tromsö, Norway, called BIOTEC Ltd. has developed a
protein concentrate aimed at the fur animal market […]. The fish is heat treated first to
deactivate thiaminase and other enzymes and to stop microbial activity; fat can be removed by a
decanter and formic acid, molasses and antioxidants added. When cooled, the lactic acid
bacteria and finally a binder meal are added to give the product its desired consistency. It is
claimed that the product can be stored for several months, that the lactic acid bacteria also acts
as an antioxidant and that the flavor is superior to the bitter taste of acid silage.
Acid silage
In 1936, experiments were started in Sweden with the A.I. Virtanen (AIV) process for
preservation of fish and fish offal intended for use as animal feeds. Results of the trials were
published by Edin (1940) and Olsson (1942). The Swedish experiments included, besides the AIV
process (Hydrochloric + sulphuric acids) two other acid preservation methods: the Sulfuric
Acid/Molasses Method and the Formic Acid Method (H. Peterson, 1953). The chief advantage of
AIV acid over organic acids is its low cost, but this is probably outweighed by the disadvantage in
that it is a highly corrosive liquid producing a corrosive product which requires neutralization.
Olsson found that formic acid limited the growth of bacteria at a relatively high pH (4.0) as
compared to mineral acids like sulphuric acid (pH 2) and that no neutralization was necessary
before feeding the silage to animals. Backhoff (1976) found that the enzymes mainly responsible
for the liquefaction of fish were those of the gut, skin and other parts of the fish, tather than
those of the flesh. Work in Canada on acid fish silage was carried out at the Halifax Technological
Station of the Fisheries Research Board of Canada by Freeman and Hooglan (1956, a,b ). It was
found that the rate of autolysis increased with temperatures from 15oC to 37oC and reached a
maximum after three days at 37oC. Researchers from the Vancouver Technological Station of
the Fisheries Research Board of Canada found that liquefaction of the fish in an acid medium
was achieved in 72 hours at 37oC. A study by Strasdine and Jones (1983) carried out at the
British Columbia Research Council Laboratory on silage from dogfish wastes found established
that by adding 1.5% formic acid and heating to 45oC, almost complete liquefaction was achieved
in 24 hours. In the 1980s, the Province of Nova Scotia Department of Fisheries supported the
construction and operation of a small fish silage plant at Casey Fisheries in Victoria Beach, Nova
Scotia. Silage from this plant has been used for feeding trials with pigs at the Agriculture Canada
Research Station in Nappan, Nova Scotia.
Acid silage production
Plant and Equipment
It is important for a plant of any size to have at least automated acid addition with a pH meter
downline controlling the rate. It is claimed that it is better to stop autolysis soon after
liquefaction to cut down on bitter flavors (peptides), fat autolysis (free fatty acids) and complete
protein autolysis to amino acids. It might therefore be desirable to have a heat exchanger and
holding cell to be able to heat the silage to 85oC or so and hold it to inactivate enzymes. The
next step would be to add a decanter/separator to remove the oil from the silage. The last

scenario, and of course the most expensive, would be to have an evaporator to produce silage
concentrate. A simplified sketch of a basic silage plant is shown in Figure 4. The raw material is
brought to a feeding hopper with a screw feeder on the bottom. Formic acid (and antioxidant)
held in tan acid tank of suitable resistant material (fiberglass or plastic coated, etc.) is fed to the
fish with a metering pump before the grinder, thereby ensuring good mixing of acid with the
fish. The fish should be ground so that no pieces are larger than 3-4 mm in diameter (Tatterson,
1976). The mass is then pumped in a Progressive Cavity Pump (Mono pump), where acid and fish
are further mixed. A pH meter in the line adjusts the addition of acid automatically, or stops the
plant, if the pH is not in the desired range (3.8 - 4). Example of addition of an evaporation step is
at the Royal Seafood Ltd. plant in Bjugn, Norway, the silage is first heated to 95°C, passed
through a decanter and centrifuge to separate oil and sludge (Sobstad, 1987). The water phase is
passed through a flash evaporator at 55°C where it cools to 35°C, is reheated and flash
evaporated again until the solid content reaches 50-55%. A second effect evaporator operating
at 35° and lower vacuum makes the system more energy efficient.
The process
The enzymes of importance in silage are various proteinases that break down proteins into
peptides and individual amino acids and lipases that break down fats into free fatty acids and
glycerol.
Protein changes
A silage gradually liquefies as connective protein tissues are broken down (into peptides and
individual amino acids) by enzymes in the fish and become water soluble. This self-digestion is
called autolysis and the rate is dependent on the activity of digestive enzymes in the raw
material, the physiological condition of the fish when caught, the pH, the temperature and the
preservative acids. The enzymes mainly responsible for liquefaction are from the viscera, skin
and other parts of the fish other than flesh. The rate of autolysis is temperature dependant, and
is quite low at temperatures below 10oC (Figure 15). As autolysis progresses, oil will be liberated
and float to the top and bone fragments and undissolved tissues go to the bottom. It is
important that a means of stirring the silage in the tank is provided for. There will always remain
a fraction of the protein which is resistant to enzymatic digestion, for reasons not completely
known. One drawback of acid fish silage is that the product often has a bitter flavour that could
have an effect on animal acceptability of the product. Several authors have linked the bitter
flavours to certain types of polypeptides formed as the protein molecules are broken down in
the autolysis.
Lipid (Fat) changes
Free Fatty Acids (FFA) increase with the storage period, and with the temperature. An
antioxidant should be added to the fish silage, in order to limit oxidation of the fat. Common
practice in Norway is to add the antioxidant to the formic acid (200 ppm ethoxyquin). An inert
gas (C02, N2) could also be used over the silage in the storage tanks. Other antioxidants
possible are gallates, hydroxyquinone, BHA, BHT and anisole. If the silage is to be used to
feed livestock, it is better to remove the oil as soon as it is feasible and store it separately.

The product
Quality and Analytical methods
For formic acid silage, the pH is recommended to be between 4.0 and 4.3. If pH is above 4.5,
there is the danger of bacterial activity, decomposition and perhaps formation of toxic
compounds. The pH value is not constant and should be checked regularly, especially when the
silage is freshly produced, the temperature is high or the ash or bone content is high. Silage from
fish and fish products has a certain buffering action. This means that relatively large quantities of
formic acid can be added without the pH dropping correspondingly. It is therefore of interest for
the user to find out how many kilos have been used per tonne raw material. When formic acid
alone is used, the pH should not be below 3.8. The lower the pH, the better the storage ability.
The higher the pH, the less acidic the finished feed will be. There has to be a balance between
the two (Pedersen, 1987).
A working group was formed in Norway to establish quality standards for fish silage. The group
has recommended that in addition to protein and fat, both ash and dry matter (not fat-free
solids) be given. The reason for this is to be able to have a certain control over how well fat and
protein analyses were carried out by the laboratories. Since % protein + % fat + % ash = % dry
matter, it is then possible to double check if the protein, and especially the fat analyses, are
correct. The value for ash will indicate if the silage was made from whole fish, mostly viscera or
bony offal. The ash content of whole fish is usually in the 2-3% range.
The concept of the term quality is difficult to define. In commercial terms, it is often limited in
the case of fish silage to pH and the contents of protein, fat, dry matter and ash. Total volatile
nitrogen (Tot. Vol N) also often is cited, as well as the Trimethylamine nitrogen (TMA-N) and
Trimethylamine oxide nitrogen (TMAO-N) content.
Just, A. 1982. The net energy value of balanced diets for growing pigs. Livest. Prod. Sci. 8: 541–555.
Kjos, N., Herstad, O., Skrede, A., Øverland, M., 2001. Effects of dietary fish silage and fish fat on
performance and egg quality of laying hens. Canadian Journal of Animal Science. 81 (2), 245-251.
Abstract
A total of 45 laying hens were fed a control diet, or one of four diets containing 50 g kg–1 fish
silage and different levels of fish fat (1.8, 8.8, 16.8 or 24.8 g kg–1), to determine the effect of fish
silage and fish fat in the diet on performance and egg quality. Fish silage did not affect feed
intake, egg production, fatty acid composition of yolk, yolk color or sensory quality of eggs,
compared with the control. The diets with 16.8 or 24.8 g kg–1 fish fat decreased feed intake (P <
0.001), egg production (P < 0.001), and hen-day egg production (P < 0.04), and increased yolk
color index (P < 0.003). The proportions of the fatty acid C22:1 (P < 0.001), and PUFA as the sum
of C18:2 n-6, C20:5 n-3, C22:5 n-3 and C22:6 n-3 (P < 0.02) in egg yolk were highest for the fish
silage diets with 24.8, 16.8 or 8.8 g kg–1 fish fat, and lowest for the diet with 1.8 g kg–1 fish fat.
Proportions of C18:1 (P < 0.001) and C20:1 (P < 0.001) were lowest for the diets with 16.8 or 24.8
g kg–1 fish fat. Egg yolk cholesterol did not differ among treatments. The diet with 16.8 g kg–1

fish fat resulted in a more intense egg albumen whiteness as measured by the sensory study,
compared with the other diets (P < 0.05). There was a linear relationship between dietary fish fat
level and increased off-taste intensity of egg yolk (P < 0.03).
Introduction
Krogdahl (1985) reported that hens performed well on diets containing fish silage, without
affecting the quality of eggs. Experiments with fish oils in diets for laying hens have shown that
the levels of polyunsaturated fatty acids (PUFA) in egg yolk is positively related to the level of fish
oil in diets (Van Elswyk et al. 1994; Herstad et al. 2000; Meluzzi et al. 2000). Fish silage contains
3–5% fat with a high level of PUFA, including the long-chain n-3 fatty acids C22:6 (DHA), C22:5
(DPA) and C20:5 (EPA). Fish silage may, therefore, increase the content of these long-chain PUFA
in eggs, and this may affect sensory quality of eggs. However, n-3 enriched eggs may serve as a
good source of these fatty acids in human nutrition. It is reported that consuming n-3 fatty acid
enriched eggs affects human plasma lipids, thus such eggs may improve human health by
reducing the risk of cardiovascular diseases (Hargis et al. 1991; Leskanich and Noble 1997).
Objective
Determine the effect of (defatted) fish silage and fish fat on performance and egg quality when
compared to fish meal.
Experiment with formic acid fish silage, defatted, and fish fat.
Experiment performed on laying hens. RCBD experimental design. 5 treatment groups. 45 hens
used. 9 (replicate) hen per treatment group. Each hen was the experimental unit. Individual wire
cages of 47 X 22.5 cm2 were used. Initial age of 22 weeks. Experiment conducted over two
consecutive periods of 28 days (56 days total).
The fish silage was prepared same as in Kjos (1999) (from slaughter by-product of farmed
Atlantic salmon), except that Ethoxyquin was added as an antioxidant at 250 ppm wet weight.
Crude fat as HCl-ether extract was analysed in fish silage and diets according to standard
procedures described by the Association of Official Analytical Chemists (1990). Metabolizable
energy of the diets was determined according to procedures described by Krogdahl (1985).
Thickness of albumen was determined on cracked eggs using a micrometer, and Haugh unit was
calculated on the basis of thickness of albumen and egg weight. Yolk color index was evaluated
by Roche Yolk Colour Fan, (F. Hoffmann La Roche Ltd., Basel, Switzerland). Cholesterol in egg yolk
was determined spectrophotometrically in Encore Chemistry System (Baker Instruments, UK),
using Cholesterol Enzumatique PAP 100, kit. Ref. 61 224 from bioMeriedux (France). Sensory
analysis was conducted according to international standards (ISO 3972 Sensory analysis –
Methodology – Method of investigating sensitivity of taste).]), using a computerized system for
recording of data (Compusense Five, Compusense, Guelph, ON).
Base ration was based on barley, oats, maize gluten meal and soybean meal as main ingredients
(and fish meal). The diets were designed to meet or exceed the National Research Council
requirements for amino acids (NRC 1994). Rendered fat consisting of approximately 70% lard and
30% tallow was used to balance the level of metabolizable energy (ME) in all diets (11.8 MJ ME

kg DM–1). Protein from fish silage accounted for 12% of total protein in these treatment diets.
Defatted fish silage used contained 36 g kg–1 crude fat.
Control diet (CO): No fish silage; No fish fat
Diet 1: 50 g kg-1 defatted fish silage + 1.8 g kg-1 fish fat (residual)
Diet 2: 50 g kg-1 defatted fish silage + 8.8 g kg-1 fish fat
Metrics
(Performance): Weight gain (Average daily gain); Feed intake (Average ME intake); Feed-to-gain
ratio (feed efficiency measured as kFUp kg–1 of gain)
(Egg Production): Egg production (g day-1); hen-day egg production (%)
(Egg Characteristics): Albumen height; Yolk colour; Cholesterol; Fatty acid composition
(Sensory Quality of Eggs): Odour, off-odour, taste, off-taste after 35 days and 7 days refrigerated
storage.
Results
(Performance): Fish silage did not affect feed intake, egg production, fatty acid composition of
yolk, yolk color or sensory quality of eggs, compared with the control. Feed intake was highest
for diets CO and A, and lowest for diet C (16.8 g fish fat kg–1) and diet D (24.8 g fish fat kg–1).
(Egg Production): In the present study, an inclusion level of 50 g kg–1 diet, supplementing 12% of
the total protein, had no negative effects on egg production. Egg production and egg weight
were highest for diets CO and A, and were significantly depressed when the contents of fish fat
were 8.8 g kg–1 or higher (diets B, C and D) - high levels of fish fat negatively influence egg
production.
(Egg Characteristics): The diets with 16.8 or 24.8 g kg–1 fish fat increased yolk color index (P <
0.003). The proportions of the fatty acid C22:1 (P < 0.001), and PUFA as the sum of C18:2 n-6,
C20:5 n-3, C22:5 n-3 and C22:6 n-3 (P < 0.02) in egg yolk were highest for the fish silage diets
with 24.8, 16.8 or 8.8 g kg–1 fish fat, and lowest for the diet with 1.8 g kg–1 fish fat. Proportions
of C18:1 (P < 0.001) and C20:1 (P < 0.001) were lowest for the diets with 16.8 or 24.8 g kg–1 fish
fat. Egg yolk cholesterol did not differ among treatments. Adding up to 24.8 g kg–1 fish fat to the
diet causes only minor changes in fatty acid composition of egg yolk when compared with a fish
meal based control. No difference was found in egg yolk cholesterol among diets.
(Sensory Quality of Eggs): There was a linear relationship between dietary fish fat level and
increased off-taste intensity of egg yolk (P < 0.03). To avoid reduced sensory quality of eggs, the
fish fat level should be kept below 24.8 g kg–1. The diet with 16.8 g kg–1 fish fat resulted in a
more intense egg albumen whiteness, compared with the other diets (P < 0.05). There were no
significant differences in any of the sensory traits between eggs from period 1 (stored at 4°C for
35 d) and period 2 (stored at 4°C for 7 d).
(Overall): High levels of fish fat in the diet caused reduced egg production and egg weight, and
tended to cause a modest increase in the level of polyunsaturated omega-3 fatty acids in egg
yolk. The reduction in egg production and egg weight observed for the two highest levels of
dietary fish fat indicate that fish fat in diets for laying hens should be kept below 17 g kg–1.
Discussion

(Performance): Krogdahl (1985) found no differences in feed intake, weight gain and egg
production of laying hens when herring meal was replaced with fish silage (7.4 or 14.2% fish
silage in the diet, respectively). The highest level of dietary fish fat of 17.7 g kg–1 tested by
Krogdahl (1985) did not influence egg production. Hargis et al. (1991) and Meluzzi et al. (2000)
reported that 30 g kg–1 dietary menhaden oil did not affect egg production or egg weight.
Baucells et al. (2000) found no reduction on performance of laying hens when feeding up to 40 g
kg–1 of fish oil. Whitehead et al. (1993) observed that egg weight was depressed when fish oil
was fed in excess of 20 g kg–1, and that feed intake and hen-day egg production (%) was
depressed at 60 g dietary fish oil kg–1. Van Elswyk at al. (1994) found significant differences in
yolk and egg weight when feeding menhaden oil at 30 g kg–1. Scheideler and Froning (1996)
found increased henday egg production but a decrease in yolk size of eggs from hens fed 15 g
kg–1 of fish oil. Both Whitehead et al. (1993) and Scheideler and Froning (1996) described the
decrease in yolk size as an effect of the long-chain fatty acids on the estrogen activity of the hen.
The depression in egg weight by feeding high levels of fish fat, shown in the present study,
confirms the finding of Herstad et al. (2000) that egg weight was significantly reduced on diets
containing 30 g kg–1 of fish oil. Eggshell quality, as well as cholesterol and linoleic acid content of
eggs, was also reduced. Furthermore, the negative effects of feeding fish oil were not prevented
by increased dietary supplements of vitamin E (200 mg kg–1) and synthetic antioxidants. Thus,
several studies have reported a negative effect of fish oil on egg production parameters, but
results are not consistent.
(Egg characteristic): Krogdahl (1985) found no differences in yolk color when feeding fish silage
to laying hens. Hammershøj (1995) reported that feeding laying hens 30 g kg–1 fish oil with a low
content of astaxanthin resulted in a pale colored yolk, while feeding the same amount of fish oil
with a high content of astaxanthin did not influence yolk color. It was concluded that the yolk
color was affected by the diet and the efficacy of naturally occurring astaxanthin in fish oil. This
may explain the effect on yolk color in the present study, because astaxanthin is the principal
pigment of salmonids (Kulås 2000). Herstad et al. (2000) observed a tendency (P > 0.05) towards
reduced egg yolk cholesterol when feeding 30 g kg–1 fish oil. Krogdahl (1985) has suggested that
fatty acid composition of meat changes more readily than that of eggs.
(Sensory Quality): Koehler and Bearse (1975) found that undesirable sensory characteristics of
eggs (rancid or fishy flavors) after feeding 50 or 100 g kg–1 fish oil were intensified when the
eggs were stored for 4 wk at 10°C. Koehler and Bearse (1975) suggested that judging from
the effect on egg flavor, there is an upper limit to the amount of fish meal or fish oil that can be
used in laying hen diets, and that this upper limit varies with the source of fish meal or fish oil.
Krogdahl (1985) found no effect of fish silage on the sensory quality of eggs, and concluded that
hens tolerate more than 10 g kg–1 fish fat without producing eggs with off-flavor. Hammershøj
(1995) found no adverse effect on the sensory quality of boiled eggs when feeding up to 30 g kg–
1 fish oil (sand eel oil), but some of the judges in the sensory panel noticed a “fishy” taste of the
eggs. Also, the present study indicates that high levels of fish fat may reduce sensory quality of
eggs.
Kjos, N., Herstad, O., Øverland, M., Skrede, A., 2000. Effects of dietary fish silage and fish fat on growth
performance and meat quality of broiler chicks. Canadian Journal of Animal Science. 80 (4), 625-632.
Abstract
Two experiments were conducted to study the effect of concentrated fish silage and additional
fish fat on growth performance (exp. 1) and meat quality (exp. 2) of broiler chicks. In exp.1, 600

day-old male and female chicks with an initial weight of 36.3 g ± 0.6 SD were allocated to five
treatment groups. The treatments were a control diet, two test diets with 50 g kg–1 fish silage
and different levels of fish fat (6 or 8 g kg–1), and two diets with 100 g kg–1 fish silage and
different levels of fish fat (8 or 10 g kg–1). In exp. 2, 150 day-old female chicks with an initial
weight
of 36.3 g ± 0.7 SD were allocated to five treatment groups. The treatments were a control diet,
and one of four test diets containing 50 g kg–1 fish silage and different levels of fish fat (2, 9, 17
or 25 g kg–1). In exp. 1, chicks fed diets with fish silage had a greater weight gain (P < 0.001), a
greater feed intake (P < 0.05) and a lower feed-to-gain (MJ ME kg–1) (P < 0.001) than those fed
the control diet. In exp. 2, no significant differences in weight gain or carcass weight were found
among diets. The proportions of the fatty acids C18:3, C20:1, C20:5, C22:5 and C22:6 in
abdominal fat, and C20:1, C22:1, C22:5 and C22:6 in breast meat, increased by the dietary
inclusion of fish silage and fish fat. Increasing levels of dietary fish fat decreased blood plasma
levels of vitamin E and ceruloplasmin. The diets containing the highest levels of fish fat (16.8 or
24.8 g kg–1) caused off-odour and off-taste of thigh meat stored at –16°C for both six months
and one month.
2 experiments. Conducted on broiler chicken.
Introduction
Fat remaining in the silage after defattening may increase PUFA content, including the long-chain
omega-3 fatty acids C22:6 (DHA), C22:5 (DPA) and C20:5 (EPA), in diet and broiler meat. This may
have an adverse effect on the sensory quality of the meat (Raa and Gildberg 1982; Krogdahl
1985). The risk of lower consumer acceptance due to reduced oxidative stability and poorer
storage stability of the lipids in broiler meat limits the usage of fish by-products in broiler
feeding. The positive biomedical effects in human nutrition of an increased level of omega-3
fatty acids in broiler meat may, on the other hand, be beneficial (Carroll 1986; Lands 1986).
Objective
Determine the effect of (defatted) fish silage and fish fat in diets for broilers on growth
performance, plasma levels of vitamin E and ceruloplasmin, and sensory quality of thigh meat,
when compared to fish meal.
____________
Exp 1
Objective
Determine the effect of (defatted) fish silage and fish fat on growth performance of broiler
chicken, when compared to fish meal.
Experiment performed on broiler chicken. RCBD experimental design. 5 treatment groups. 600
chicken used. 120 chicken per treatment group. The birds were kept in pens, each with 15 chicks,
giving eight replicate pens per treatment (the pen was the experimental unit). Pens measuring
1.1 m2, equipped with a feeder, were used. Initial age of 1 day. Initial weight of 36.3 g ± 0.6 SD.
Slaughter age of 36 days.

The fish silage was prepared same as in Kjos (1999), from slaughter by-product of farmed
Atlantic salmon, except that Ethoxyquin was added as an antioxidant at 250 ppm wet weight.
Crude fat as HCl-ether extract was analysed in fish silage and diets according to standard
procedures described by the Association of Official Analytical Chemists (1990). Metabolizable
energy of the diets was determined according to procedures described by Krogdahl
(1985).Sensory analysis was conducted according to international standards (ISO 6564 - 1985
[E]).
Base ration was based on barley, oats and soybean meal as main ingredients (plus fish meal). The
diets were designed to meet or exceed the National Research Council requirements for amino
acids (NRC 1994). Rendered fat consisting of approximately 70% lard and 30% tallow was used to
balance the level of metabolizable energy (ME) in all diets (13.1 MJ ME kg DM–1). The two levels
of fish silage at 50 g kg–1 or 100 g kg–1 accounted for about 10 and 21% of total protein in diets,
respectively. Defatted fish silage used contained 28 g kg–1 crude fat. The content of ME in fish
silage was 6.51 MJ kg–1.
Control diet: No fish silage; No fish fat
Diet 1A: 50 g kg-1 fish silage + 6 g kg-1 fish fat
Diet 1B: 50 g kg-1 fish silage + 8 g kg-1 fish fat
Diet 1C: 100 g kg-1 fish silage + 8 g kg-1 fish fat
Diet 1D: 100 g kg-1 fish silage + 10 g kg-1 fish fat
Metrics
(Performance): Weight gain (Average daily gain); Feed intake (Average ME intale); Feed-to-gain
ratio (feed efficiency measured as kg feed kg gain–1 and as MJ ME kg gain–1).
Results
(Performance): In exp. 1, chicks fed diets with fish silage had a higher final weight (greater
weight gain), a greater feed intake, and a lower feed-to-gain (MJ ME kg–1) than those fed the
control diet. The highest weight gain was found for diet C with 100 g kg–1 fish silage and 9.8 g
kg–1 fish fat. The results showed that replacing fish meal with fish silage protein improved
growth performance of broiler chicks. An inclusion level of up to 100 g kg–1 diet, corresponding
to 21% of the total protein, gave a positive effect on growth performance in the growth
experiment.
___________
Exp2
Objective
Determine the effect of (defatted) fish silage and fish fat on meat quality of broiler chicken,
when compared to fish meal.
Experiment performed on broiler chicken. RCBD experimental design. 5 treatment groups. 150
chicken used (female only). 30 chicken per treatment group. The birds were kept in pens, each of
15 chicks, giving two replicate pens per treatment (the pen is the experimental unit, except for
sensory quality, where individual birds are the experimental units). Pens measuring 1.1 m2,

equipped with a feeder, were used. Initial age of 1 day. Initial weight of 36.3 g ± 0.7 SD. Slaughter
age of 36-37 days.
The fish silage was prepared same as in Kjos (1999), from slaughter by-product of farmed
Atlantic salmon, except that Ethoxyquin was added as an antioxidant at 250 ppm wet weight.
Base ration was based on barley, oats and soybean meal as main ingredients (plus fish meal). The
diets were designed to meet or exceed the National Research Council requirements for amino
acids (NRC 1994). Rendered fat consisting of approximately 70% lard and 30% tallow was used to
balance the level of metabolizable energy (ME) in all diets (13.1 MJ ME kg DM–1). The fish silage
at 50 g kg–1 accounted for approximately 10% of total protein in diets. Defatted fish silage used
contained 36 g kg–1 crude fat. The content of ME in fish silage was 7.54 MJ kg–1.
Control diet: No fish silage; No fish fat
Diet 2A: 50 g kg-1 fish silage + 2 g kg-1 fish fat (residual)
Diet 2B: 50 g kg-1 fish silage + 9 g kg-1 fish fat
Diet 2C: 50 g kg-1 fish silage + 17 g kg-1 fish fat
Diet 2D: 50 g kg-1 fish silage + 25 g kg-1 fish fat
Metrics
(Performance): Weight gain (Average daily gain); Feed intake (Average ME intale); Feed-to-gain
ratio (feed efficiency measured as kg feed kg gain–1 and as MJ ME kg gain–1).
(Carcass Characteristics): Carcass weight; Weight of the abdominal fat pad
(Blood measurements): Blood plasma levels of vitamin E, Ceruloplasmin and Glutathione
Peroxidase in samples taken from jugular vein of all chicks immediately after slaughter.
(Fatty acids composition): Fatty acid composition in abdominal fat and breast meat
(Sensory Quality): Taste, off-taste, juiciness, tenderness of thigh meat (X2) from 15 chicks of each
dietary treatment (randomly chosen from each of the replicate pens) after 1 mo and 6 mo frozen
storage.
Metabolizable energy of the diets was determined according to procedures described by
Krogdahl (1985).
Results
(Performance and Carcass Characteristics): No significant differences among diets were found for
growth performance, carcass weight or weight of the abdominal fat pad. Numerically, the weight
gain and carcass weight for diets C (16.8 g kg–1 fish fat) and D (24.8 g
kg–1 fish fat) than for the control diet. Other authors have found that high dietary levels of fish
fat reduced growth performance of broiler chicks, possibly due to reduced palatability.
(Blood measurements): Dietary inclusion of fish fat reduced plasma levels of vitamin E and
ceruloplasmin, indicating that the use of high-fat fish by-products increases the antioxidant
requirement of chicks.
(Fatty acids composition): Increased level of fish fat in the diet caused an increase in the level of
polyunsaturated omega-3 fatty acids in abdominal fat and breast meat.
(Sensory Quality): The diets containing the highest levels of fish fat (16.8 or 24.8 g kg–1) caused
off-odour and off-taste of thigh meat stored at –16°C for both six months and one month. High
levels of fish fat may reduce sensory quality of broiler meat. In the present study, amounts of

Duteau 2015. Fish Silage Project Final Report

Duteau 2015. Fish Silage Project Final Report

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Duteau 2015. Fish Silage Project Final Report