The document discusses the complex ecosystem of the rumen, emphasizing the role of various microorganisms in fiber digestion and their interactions with the host animal, which are significantly affected by diet. It outlines manipulation strategies for improving rumen function and livestock productivity, including adjustments to the concentrate-to-roughage ratio, feeding bypass or escaped nutrients, defaunation, and the use of probiotics and anaerobic fungi. Additionally, it highlights the potential benefits associated with dietary supplements and additives that enhance microbial activity and overall nutrient utilization in ruminants.

1. Introduction:
 The rumen has a very complex eco-system of anaerobic micro
organism bacteria, protozoa and fungi representing various
microbial groups.
 These organism in ruminants are responsible for degradation of
complex dietry fibers which makes major component oftheir diet.
 The rumen environment has a very strong buffering action due to
capacious production of saliva, which contains salts of phosphate
and bicarbonates but microbial diversity and size, as well as
activities of microbial population, which governs the rumen
funtion, is under the influence of dietry conditions, specially its
composition.
 The efficiency of microbial fiber digestion in rumen depends
upon the level of coordination between microbes and the host
animal. In this symbiotic system, the host animal constantly
mantains the favourable environmental conditions in the rumen
and continuous supply of plant materials.
 In return, the rumen microbes degrade the complex dietry
carbohydrates and provide the animal with easily utilizable forms
of carbon or energy and protein sources as the microbial biomass.
Thus changes in feeding regimen or pretreatments of feeds
may cause a remarkable diversion from normal microbial rumen
activities.
The best and common way to improve the rumen function is by altering
the feeding pattern in the ruminant animal.
 The correction of concentrate to roughage ratio can show
tremendous effect on rumen activity.
 Its functions can also be altered to the beneficial level by feeding
protected by-pass or escaped nutrients, prepared by physical,
like compaction of feed to make complete feed block or chemical
treatments including urea or ammonia treatment.

2.  Incorporation of additivies in the feed including probiotics,
enzymes etc., and recently biotechnological approach like gene
transfer has also been tried.
1. Correction of concentrate to roughage ratio
Feeding of crop residues and dry grasses, rich in structural
carbohydrates, favours the type of microbial fermentation in the rumen,
which causes increase in population of methanogenic bacteria, which
result into increase in methane production. Methane production is
wastage of dietry energy, Supplementation of concentrate to straw
based diet can reduce methane production in rumen. The saved energy
can be utilized for production purposes. Feeding of urea molasses
mineral blocks fed as a lick to ruminants has decreased methane
production in rumen by improving the rumen environment and
providing readily available nutrients for profileration of cellulolytic
bacteria.
The rumen function can also be improved by the dietry mineral
(UMMB) or supplementation of starch rich concentrates and
ionopheres like monensin/rumensin and antibiotics. The beneficial
effect of these supplements is achieved through reduction in methane
production and obviously increases the livestock production.
Urea can be recycled and used as a source of nitrogen for the
rumen microorganisms.
(1) Urea is used in ruminant feeding both as fertilizer grade as well as
feed grade. It can be administered through feed along with other feed
ingredients in a compounded ration.
(2) Urea can also be given as liquid nitrogen i.e. it could be dissolved
in H2O and offered as drinking water to the animals.
(3) It could also be constituted as urea-molasses multi-nutrient feed
block held together by a binder. The animal by abrrection licks off urea
from the block. Experiment over the years have shown that urea could

3. be utilized as whole ingredient to feed at levels between 1% - 5% which
defines a save utilization level.
2. Feed bypass or escaped nutrients
Feeding of protected or escaped nutrients is an indirect approach
to manipulate the rumen activity. By feeding such nutrients the site of
digestion of nutrients shifts from rumen to lower digestive tract. It is
generally done to reduce the attack the proteolytic enzymen on dietry
protein in the rumen, and to increase the supply of amino acids to
duodenum.
The points to be stressed are that:
 By-pass protein because of its effects on feed intake almost
always stimulates milk production and depending on the
imbalance in nutrients (fermentation pattern) may cause animals
to mobilize body reserves. This may be prevented by the use of

4. high-fat, high-protein meals that supply both protein and long
chain fatty acids for digestion post ruminally.
 By-pass starch or manipulation of the rumen to give higher
propionate production, because it balances nutrients for milk
production, may prevent mobilization of body reserves without
large effects on feed intake and therefore on milk production. But
because it balances the nutrients for milk production, efficiency
of energy utilization is increased and body weight is often
increased.
The main benefit of ‘bypass’ protein is that;
 The original amino acids in the protein meal are absorbed in the
small intestine instead of converted to microbial protein in the
rumen, thereby providing a different balance of essential amino
acids for better animal nutrition hence, production.
 Another benefit of feeding meals with high ‘bypass’ protein is
that the portion of the protein that is rumen degradable (RDP)
breaks down in the rumen very slowly. This allows animals to
source small amounts of protein over longer periods for microbial
protein production, long after urea has been degraded and used in
the rumen by the animals.
 Small quantities of ‘bypass’ protein fed at strategic times, have
an enormously beneficial effect on production. ‘Bypass’ protein
also provides an important protein source when the animal’s
requirements for protein exceed those provided by microbial
protein.

5. Figure 3 : Degradation depends upon both the nature of the protein
and the length of time it remains in the rumen. As feed intake and
passage rate through the rumen increase, retention time in the rumen
and degradation decrease.
Methods of decreasing protein and amino acid degradation in the rumen
include:
1. Heat treatment
2. Chemical treatment
3. Encapsulation
4. Use of amino acid analogues
5. Selective manipulation of balances of rumen metabolic pathways
6. Oesophegeal groove closure

6. Feeding of fat depresses fiber digestion in rumen. It reduces acetic
acid production. The purpose of protected fat feeding in rumen is to;
 Maintain the supply of long chain fatty acids to the animal.
 Increase energy density of diet, as per unit weight, one unit of fat
give 2.25 times more energy than the carbohydrate or protein
gives.
 To intact production of acetic acid in the rumen.
The choice is always for the cheapest source of fat fed as calcium or
magnesium soap of fatty acid.

7. 3. Defaunation of rumen
The term defaunation represents the elimination of the
microfauna, protozoa from rumen. There are several defaunation
techniques or methods.
 Defaunation can be done by prolonged starvation and
copper sulphate administration. It is fairly effective but
drastically affects both ruminal processes and the animal's
health.
 Heating the rumen contents to 50°C is safe but doesn’t
remove all of the small oligotrichs Diplodinium dentatum
and Entodinium species.
 Defaunation can also be done with aerosol OT (Dioctyl
sodium sulfosuccinate) method.
Many trials conducted on fattening realized supplements of protein rich
forages showed that defaunation significantly increased the nitrogen
retention in organism. Several reports indicate that protozoan consumes
bacteria and transform the bacterial protein into protozoal protein,
which protozoal protein has higher digestibility and superior biological
value in host.
It has been well establish that removal of ciliate protozoa from rumen,
results into an increase in flow of non-ammonia nitrogen and bacterial
nitrogen into the abomazum, suggested that more dietry protein has
been escaping degradation in the rumen, which is feed for the ciliated
protozoa. This indicated the possibility to improve the ruminant
productivity through removal of ciliates population of rumen;
however, beneficial effects can be achieved in the animal fed low
protein high energy diets.

8. 4. Use of yeast as probiotics
The term “probiotics” comes from the Greek words “pro” (in favour)
and “biotic” (life). Probiotics are defined as “live microorganisms that
may beneficially affect the host upon ingestion by improving the
balance of the intestinal microflora”. More recently Havenaar
proposed the following definition: “Mono or mixed cultures of live
microorganisms which, when applied to animal or man, beneficially
affect the host by improving the properties of the indigenous
microflora”. This latest definition is more specific in terms of the host
and types of microorganisms and not restricted to the intestinal
microbial community.

9. For a better understanding of the role and mode of action of probiotics
in ruminants, it is important to understand the function of the rumen.
The rumen is a complex ecosystem that plays a major role in feed
digestion. In adult animals its volume is about 100 litres and it harbours
bacteria (1011 cells/ml), protozoa (105 cells /ml), fungi (103 cells/ml)
and methanogens (109 cells/ml). Major end products from rumen
fermentation are illustrated below:

10. Cattle GI microbial characteristics and relationships with host health
and performance;
Rumen Large intestine
Major groups
in microflora
Bacteroidetes
Firmicutes
Fibrobacter
Archaea
Protozoan species
In preweaned calves:
Bacteroidetes
Firmicutes
Atopobium
Bifidobacteria
in weaned calves or older
cattle:
Bacteroidetes
Firmicutes (including
uncultured groups)
Fibrobacter
Major
microbial
functions
Involved in host nutrition
(digestion of fibrous plant
material and anaerobic
fermentation to short chain fatty
acids, which can be used as an
energy source by the host;
microbial protein synthesis)
Immunological responses
Digestion of polymers
Microbial
dysfunctions
Overgrowth of lactate-producing
bacteria, leading to a decrease in
rumen pH and subsequent rumen
acidosis
Decrease in microbial activity by
Pathogenesis by harmful
bacteria, such asE.
coli and Salmonella.

11. Rumen Large intestine
unbalanced nutrition, leading a
decrease in feed protein efficacy
Probiotics/prebiotics have the ability to modulate the balance and
activities of the gastrointestinal (GI) microbiota, and are, thus,
considered beneficial to the host animal and have been used as
functional foods. Previous studies reported the potential of probiotics
and prebiotics in animal nutrition; however, their efficacies often vary
and are inconsistent, possibly, in part, because the dynamics of the GI
community have not been taken into consideration. Under stressed
conditions, direct-fed microbials may be used to reduce the risk or
severity of scours caused by disruption of the normal intestinal
environment. The observable benefits of prebiotics may also be
minimal in generally healthy calves, in which the microbial community
is relatively stable. However, probiotic yeast strains have been
administered with the aim of improving rumen fermentation efficiency
by modulating microbial fermentation pathways.
Sacchromyces cerevisiae and Aspergillus oryzae can increase fiber
digestibility in the animal maintained on high concentrate diets. These
fungi maintain rumen pH favourably for cellulolytic organisms by
reducing the quantity of starch in the rumen. Supplementation of live
culture of fungi also provides micronutrients for growth of cellulolytic
bacteria. Feeding of S. cerevisiae in milch cows resulted into
significant improvement in milk yeild. The yeast culture not only
increased the digestibilty but also resulted into higher retension of
nitrogen and energy, and above all it reduce the methane production.
Probiotics for adult ruminants have mainly been selected to improve
fiber digestion by rumen microorganisms. Such probiotics have
positive effects on various digestive processes, especially cellulolysis

12. and the synthesis of microbial proteins. The main form of probiotic
commonly used in dairy cows is various strains of yeast (mostly
Saccharomyces cerevisiae. Megasphaella elsdenii or
Propionibacterium species, which utilize lactate, have also been
administered as directfed microbials to avoid the accumulation of
ruminal lactate.
Limitations of Yeasts Probiotics: An important part of the variability
in the response to yeast supplementation is due to variation in the yeast
strain used, its viability (survival during pelleting, for example), animal
status and the nature of the diet. Another important factor to consider
is the intrinsic variation between animals of a same herd. In effect,
feeding behaviour factors such as rate of feed and water intake and
physiological factors such as ruminal content turnover and volume of
saliva production are variable from one animal to the other and may
explain the discrepancies in the results reported from different trials.
5. Use of anaerobic fungi
Ruminal anaerobic fungi, an emerging group of animal probiotics,
account for upto 8% of the microbial biomass in rumen and actively
colonize plant cell-walls.
 Observed in the rumen as early as 1910, but were believed to be
flagellate protozoa.
 Confirmed to be a true fungus by the presence of chitin in its cell
wall and designated as Neocallimastix frontalis.
 Identified anaerobic fungi in sheep rumen, each of which had a
motile stage (the zoospore) and a non-motile zoosporangium.
 Found in the rumen and other parts of the gastro-intestinal tract
of herbivorous animals.
 Play an active and positive role in fibre degradation as evidenced
by the presence of different hydrolytic enzymes.
 There is a significant reduction in in-vitro gas production and
degradation of fibrous feeds, indicating a positive role played by
fungi in fibre degradation.

13.  The fibre-based diets stimulate the fungal growth in the rumen of
buffalo in comparison to diets rich in easily fermentable
carbohydrates.
 These fungi prefer to get attached to the most lignified tissues of
plant feed material by producing variety of enzymes.
The anerobic fungi possess well developed polysaccharide degrading
enzyme system, but under normal rumen conditions their numbers
are very low. Increasing fungal biomass or artificially stimulating
fungal growth in rumen can enhance fiber digestion and even rate of
flow of amino acids into small intestine. The rumen fungal biomass can
be augmented by;
 Supplementation of sulphur with wheat straw.
 Defaunation has also resulted into increase in anaerobic fungal
biomass in rumen.
Potential benefits of ruminal anaerobic fungi for improved animal
nutrition and productivity:
 Improved fibre digestion and nutrient utilization
 More feed intake and feed efficiency
 Increased body weight
 Improved milk production
Prospective applications of ruminal anaerobic fungi:
 Direct-fed microbials
 Animal feed additives
 Novel silage inoculants
 For large scale production of enzymes (e.g. cellulase)

14. 6. Other feed additives used for manipulation for rumen
function
There are large number of feed additives like;
 Ionophores
 Antibiotics
 Drugs
 Herbal preparations
 Micronutrients
 Enzymes
These are commercially available and enhance animal productivity.
Galactogougas are said to augment milk production. Ionophores are
feed additives that alter rumen microbial populations through ion
transfer across cell membranes. Although ionophores have been used
widely in the beef industry for improved feed efficiency and control of
coccidiosis, there has been limited use by the dairy industry.
Ionophores like Monensin may have several advantages for dairy
cattle, including improved energy metabolism, increased milk
production, and altered milk components and lasalocid observed to
inhibit proteolytic activity and deamination, and methanogenesis,
which is said to increase propionate production. Thus it enhances the
efficiency of feed utilization in the ruminants.

15. Summary:
Manipulations of rumen function that can augment livestock
productivity are;
 Correction of concentrate to roughage ratio
 Feed bypass or escaped nutrients
 Defaunation of rumen
 Use of yeast as probiotics
 Use of anaerobic fungi
 Use of other feed additives
Reference:
1. Strategies for sustainable livestock production by S. K. Kaushish
2. RUMINANT ANIMAL NUTRITION BY Prof. C. F. I. Onwuka
3. Defaunation: Effects on feed intake, digestion, rumen metabolism
and weight gain BY Arse Gebeyehu1 and Yosef Mekasha
4. BYPASS PROTEIN - THEORY AND CONCEPT by D.L.
Harmon and T.G. Nagaraja
5. http://www.ncbi.nlm.nih.gov
6. www.merckvetmanual.com