The document discusses exogenous enzymes used in ruminant feed to improve feed efficiency and animal performance. It describes how enzymes from bacteria and fungi sources are used to eliminate anti-nutritional factors and enhance nutrient digestibility. Exogenous enzymes can improve fiber digestibility in the rumen through direct hydrolysis and synergistic effects with ruminal microbes. This leads to greater feed conversion efficiency and increased milk production or weight gain. The greatest responses are seen in high producing dairy cows and feedlot cattle when energy limits productivity. While exogenous enzymes show potential, more research is needed to understand their modes of action and identify optimal enzyme activities and dosages.

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Mohammad A. AlSaleh : 00962-799995057
Exogenous Enzymes in Ruminant Feed
Eng. Mohammad A. AlSaleh
Technical Company for Industry and Trade.
technovet@yahoo.com
______________________________________________________________________________
Introduction
A long-cherished dream of ruminant nutritionists has been to manipulate and improve the
efficiency of ruminal fermentation. Research is continued to find a sole feed supplement that can
improve the rate, efficiency and/or quality of gain, production, reproduction, to prevent certain
diseases or preserve feeds. One such class of these compounds is exogenous enzymes.
Exogenous enzymes have been used mainly to eliminate anti-nutritional factors from feeds, to
enhance the digestibility of nutrients and to supplement the activity of the endogenous enzymes
of poultry (Bedford M.R. & Partridge G.G., 2001).
In ruminant it has been interest to using enzymes in ruminant diets in last decades. Because of
high cost of ruminant livestock production, the new technology of enzyme production and the
economic profit returns to be realized with effective enzyme supplements (Beauchemin et al.,
2000). Ruminant producers are always seeking ways of improving feed conversion efficiency
and animal performance. Most of the research on ruminant enzymes has focused on fibrolytic
enzymes to improve fiber digestibility, because increasing fiber digestibility can increase the
intake of digestible energy by the animal. Which lead to less feed is need to produce 1 kg of milk
or liveweight gain or, alternatively, more milk or weight gain results per kilogram of feed
consumed by the animal (Beauchemin K.A., Holtshausen L., 2011).

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Mohammad A. AlSaleh : 00962-799995057
The significant effects of using enzymes to ruminant diets have been reported recently for
commercial ruminant farms (Beauchemin et al., 2000).
Enzyme sources
Enzymes are naturally occurring biocatalysts produced by living cells to bring about specific
biochemical reactions. In the condition of feed additives for ruminants, enzymes are act to
catalyze the degradative reactions by which substrates (i.e. feedstuffs) are digested into their
chemical components (e.g. simple sugars, amino acids, fatty acids). These are in turn used for
cell growth, either by ruminal microorganisms or by the host animal (Bedford M.R. & Partridge
G.G., 2001).
Enzyme products in market are derived primarily from only four bacterial (Bacillus subtilis,
Lactobacillus acidophilus, L. plantarum and Streptococcus faecium) and three fungal
(Aspergillus oryzae, Trichoderma reesei and Saccharomyces cerevisiae) species (Bedford M.R.
& Partridge G.G., 2001).
Enzyme products are produced by a batch fermentation process, beginning with a seed culture
and growth media (usually containing nitrogen, carbohydrates, minerals, and surface-active
agents). Industrial fermentations usually take 3 to 7 d depending upon the microorganism and
conditions for growth. Once the fermentation is complete, the enzymes are separated from the
fermentation residues and source organism. The types and activity of enzymes produced can vary
widely depending on the strain selected and the growth substrate and culture conditions
employed for enzyme production (Beauchemin et al., 2003).

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Mohammad A. AlSaleh : 00962-799995057
Regulatory Status of Enzyme Feed Additives
Producers of enzymes must provide the source of the enzyme (organism) along with information
on enzyme activity, substrates, reaction products and site of enzymatic activity. Enzymes must
come from non-pathogenic organisms. Enzymes from genetically altered organisms are
acceptable if the amino acid sequence of the enzyme has not been significantly altered and if no
altered organisms are in the formulation and no transformable antibiotic resistant DNA is
present. Products must also be safe relative to animal, human and environmental concerns.
Functionality must be proven via in vitro tests (Kung L., J.R., 2006).
Animal responses
Final assessment of the true value of exogenous enzymes for ruminants in terms of improving
feed utilization can only be assessed through the use of animal production trials. A verity of
effects of using cell wall degrading enzymes in ruminant diets has been reported in past and
recent studies. Different domestic ruminants at various stages of production have been used.
Various types of forages have been fed, and the enzyme products in those studies were given to
the animals in diverse ways at the time of feeding; sprayed onto forage, added to concentrate,
sprayed onto the total mixed ration (TMR), added as dry powder to feed, or ruminally infused
(ABOAGYE I.A., 2015).
Animal responses to exogenous enzymes are greatest when energy limits animal productivity, as
is often the case with high-producing lactating dairy cows and rapidly growing beef cattle. dairy

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Mohammad A. AlSaleh : 00962-799995057
cows in early lactation receiving enzyme treated forage produced 9–15% more milk and 16–23%
more energy-corrected milk than did cows fed a control diet. However, milk production was not
increased when cows were in mid lactation at the start of the experiment. Similarly, others have
observed greater production responses during early lactation than during later lactation
(Beauchemin et al., 2006).
Mode of action
Pre-ingestive effects
There is evidence that applying fibrolytic enzymes to feed prior to feeding alters the structure of
the feed, thereby making it more amenable to degradation. While structural changes to the
substrate may be an integral component of the mode of action of feed enzymes in improving
digestion, this explanation does not account for improved dietary fiber digestion when
exogenous enzymes are applied to the concentrate (low-fiber) portion of the diet. Another
important reason for applying enzymes to feed prior to ingestion is to enhance binding of the
enzyme to the feed, thereby increasing the resistance of the enzymes to proteolysis
in the rumen. Enzymes applied to feed prior to ingestion are particularly stable; the presence of
substrate is known to increase enzyme resistance to proteolytic inactivation (Beauchemin et al.,
2006).
Ruminal effects
Recent studies have shown that exogenous enzymes applied to feed are relatively stable in the
rumen. Thus, it is likely that exogenous enzymes survive for a considerable amount of time in

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Mohammad A. AlSaleh : 00962-799995057
the rumen where they probably maintain activity against target substrates. Exogenous enzymes
improve cell wall digestion by increasing the hydrolytic capacity within the ruminal
environment. The extent to which this occurs will depend upon the amount of enzyme applied to
the feed and the activity of the enzymes under ruminal conditions. increasing the enzymic
activities in ruminal fluid using exogenous enzymes increased the rate of forage digestion. Thus,
it is possible that enhanced enzymic activity due to synergy of exogenous enzymes and rumen
bacterial enzymes enhances fiber digestion in the rumen. There is evidence that exogenous
enzymes stimulate the attachment of ruminal microbes to plant fiber. Adherence of ruminal
bacteria to fiber places the enzyme system in close proximity to the substrate, and disrupts the
hydrogen bonding within the cellulose matrix. There is also evidence that adding feed enzymes
to the diet indirectly increases the numbers of nonfibrolytic, as well as fibrolytic, bacteria in the
rumen (Bedford M.R. & Partridge G.G., 2001).
Stability of fibrolytic enzymes in rumen fluid is unlikely to be a limiting factor in their
application as feed additives for ruminants. Particular enzyme activities may, however, be more
labile than others. If such an activity is a key component of the mode of action of feed-additive
enzymes for ruminants, it would appear likely that enzyme activity might be protected by simple
means. The emphasis should now be placed on identifying which, if any, fibrolytic activity is
limiting in the rumen and on devising means of amplifying that activity. Applying enzymes as
feed supplements promises to be the simplest technology for achieving such an amplification in
the immediate future (Morgavi et al., 1999).

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Mohammad A. AlSaleh : 00962-799995057
Postruminal effects
Hydrolysis of complex carbohydrates by exogenous enzymes in the small intestine and
subsequent absorption of released sugars would offer energetic and nitrogen balance benefits to
the animal that would not be accessible if these substrates remained undigested or were
fermented by microbial populations residing in the large intestine. It is possible that exogenous
enzymes work synergistically with the microbes even in the large intestine. Although most of the
benefits of using enzyme supplements in ruminant diets are probably due to ruminal effects, the
possibility of post ruminal effects cannot be discounted (Bedford M.R. & Partridge G.G., 2001).

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Mohammad A. AlSaleh : 00962-799995057
Fig.1 Possible modes of action of exogenous enzymes in ruminants. (A) Prior to consumption,
exogenous enzymes may partially digest feed or weaken structural barriers that impede microbial
digestion in the rumen. (B) In the rumen, exogenous enzymes may hydrolyze feed directly or
work synergistically with ruminal microorganisms to enhance feed digestion. (C) In the small
intestine, exogenous enzymes may improve nutrient absorption by reducing intestinal viscosity,
or by hydrolyzing substrates that escape ruminal digestion. (D) In the faces, exogenous enzymes
may increase the rate of decomposition (Bedford M.R. & Partridge G.G., 2001).
Exogenous enzymes and type of nutrition
Ruminant ad libitum is likely to respond better to exogenous enzymes than animals fed for
restricted intake. Fiber digestibility tends to be lower when ruminant is fed ad libitum, because
residence time in the rumen is relatively short and ruminal pH usually drops below the optimum
for fiber digestion. Exogenous enzymes tend to increase the rate of fiber degradation in the
rumen (i.e. degradation after short incubation times) rather than the extent of degradation (i.e.
degradation after long incubation times). Increased rate of fiber degradation in the rumen is most
likely to improve total-tract digestibility when residence time of feed in the rumen is short, as is
the case for animals fed ad libitum. This effect is demonstrated in the study reported by
(Beauchemin K.A., Holtshausen L., 2011) in which the total tract digestibility of DM was 17%
lower when measured in dairy cows compared with sheep (Table 1). Consequently,
supplementing the diet with exogenous enzymes improved total-tract digestibility in dairy cows,
but not in sheep. Thus, enzyme technology is less likely to benefit ruminants fed to meet
maintenance energy requirements; the greatest responses are expected to occur when ruminants
are fed for maximum productivity (Beauchemin K.A., Holtshausen L., 2011).

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Mohammad A. AlSaleh : 00962-799995057
(Table 1) Effects of method of adding an enzyme product to diets fed to either dairy cows in
early lactation or lambs (Beauchemin K.A., Holtshausen L., 2011).
Conclusion
Exogenous enzymes can be a highly effective means of improving performance in ruminants.
However, positive responses are not always obtained and, given the cost of this technology, the
uncertainty of response is a major limitation. The key is to develop a better understanding of the
mode of action and to identify the key enzyme activities and dose rates required, thereby
ensuring cost-effective use of these additives.

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Mohammad A. AlSaleh : 00962-799995057
References
- Bedford M.R. & Partridge G.G. 2001. Enzymes in Farm Animal Nutrition. CABI
Publishing. New York, NY 10016. Pages 273-298.
- Beauchemin K. A., Rode L. M., Maekawa M., Morgavi D. P., & Kampent R. 2000.
Evaluation of a Nonstarch Polysaccharidase Feed Enzyme in Dairy Cow Diets. Journal
Dairy Science 83:543–553.
- Bedford M.R. & Partridge G.G. 2011. Enzymes in Farm Animal Nutrition. 2nd edition
CABI Head Office. Wallingford, Oxfordshire OX10 8DE UK. Pages 206-230.
- Beauchemin K. A., Colombatto1D., Morgavi D. P., Yang W. Z., & Rode L. M. 2003.
Mode of Action of Exogenous Cell Wall Degrading Enzymes for Ruminants. Journal of
Animal Science 84:13-22.
- Kung J.R. 2001. Direct-Fed Microbials and Enzymes for Dairy Cows. Ph.D. University
of Delaware. Newark, Delaware. USA. Pages 69-77.
- Aboagye I.A. 2015. Use of Exogenous Fibrolytic Enzymes to Improve the Nutritive
Value of Preserved Forage for Ruminants. Thompson Rivers University. Canada.
- Morgavi D.P., Newbold C.J., Beever D.E. & Wallace R. J. 1999. Stability and
Stabilization of Potential Feed Additive Enzymes in Rumen Fluid. Elsevier Science Inc.
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