Rumen Manipulation to Enhance Feed Conversion Efficiency

Introduction 

Rumen is well recognized as an essential fermentation vat that is capable of preparing end-products particularly volatile fatty acids and microbial proteins as major energy and protein for the host animal. The more efficient the rumen is, the better the fermentation end-products being synthesized. In the tropics, most ruminants have been fed on low quality roughages, agricultural crop-residues, and industrial by-products which basically contained high levels of lingo cellulosic materials, a low level of fermentable carbohydrate and a low level of good-quality protein. In addition, long dry seasons, a prevailing harsh environment, especially high temperature, low soil fertility and less feed available throughout the year, all influence Rumen FermentationDuring digestion process some anaerobic chemical reactions take place in the large stomach of ruminents. These reactions are called rumen fermentation..

Alteration in ruminal microflora for improvement in growth and productivity can be achieved by means of additives that selectively affect rumen population. Please keep in mind that changes in one component of the rumen have several consequential effects on the other components. Microbial activity in the rumen is negatively altered by feeding large amounts of certain feed constituents (fats, starch) or minerals (buffer substances) which results in impaired anaerobic fermentation of forages and microbial protein synthesis. Modification of the rumen microbial population is now considered as a possible approach to rumen manipulation.

Objective of Rumen Manipulation

Some of the major objectives of rumen manipulation are:

1. To increase the fibre degradation mainly through manipulation of lignin- cellulose bonds in feeds as the rumen microbes are the only degraders of cellulose and hemicellulose,
2. To enhance microbial protein synthesis in the rumen
3. To make provision of an alternate hydrogen sink in the rumen and help in availability of the digestible energy (DE) for breeding and production. This will also result in the reduction in methanogenesis
4. Help in preventing acidosis in high grain fed animals, the level of lactic acid can be controlled to avoid acidosis and inhibition of feed utilization due to lowered pH of the rumen liquor,
5. Shifting the production of acetate to propionate, especially in fattening lambs as the production of propionate in the rumen at the expense of acetate may be helpful.
6. Enhance neutralizing of plant toxins: Rumen fermentation can be manipulated for efficient utilization of feeds which contain anti nutritional factors viz. tannin, saponin, mimosine etc.

Physical Methods of Rumen Manipulation 

Microbial feed additives (probiotics): The digestion process in ruminant occurs by chemical reaction and by the fermentation provided by the rumen microbial flora. The rumen as well as intestinal microbial flora balance have been recognized as the main factors to manipulate in order to obtain the best growth performance of the animals. Supplementation of different probiotics (fungi/yeast and bacteria) results in improved nutrient status and productivity of the ruminants under certain conditions.

Probiotic is “A live microbial feed supplement which beneficially affects the host animals by improving its intestinal microbial balance.”

Bacterial origin: Bacillus licheniformis, Lactobacillus casei, Bacillus subtilis etc.

Yeast origin: Lactobacillus brevis, Aspergilusoryzae, Saccharomyces cerevisiae etc.

The utilization of probiotics in farm animals helpful in the growth promotion, improved feed conversion efficiency, better absorption of nutrients by control of gut epithelial cell proliferation and differentiation, improved metabolism of carbohydrate, calcium and synthesis of vitamins, neutralization of anti-nutritional factors i.e., trypsin inhibitor, phytic acid etc, microbial enzyme production, compensating for deficient intestinal enzyme activities of the host, control of intestinal microorganisms producing sub clinical or clinical diseases and, stimulation of non-specific and specific immunity at the intestinal level.

Administration of probiotics in livestock may be most effective when fed immediately after birth to encourage early establishment of beneficial rumen microflora. It is also helpful following antibiotic treatment and when high pathogen load of enteric bacteria, such as, E. coli, Salmonella, Coccidia is suspected.

Effect of probiotic feeding on animals: Probiotic supplementation enhances dry matter intake and nutrient digestibility. Significant improvements has been reported in digestibility of dry matter, organic matter, crude protein and fibre in yeast fed animals. Supplementation of lactobacillus culture to the milk fed dairy calves also improved the growth rate and milk production.

Defaunation: The process of making the rumen of animals free of rumen protozoa is called defaunation and the animal is called defaunated animal. Rumen protozoa are the largest in size among rumen microbes and contribute 40-50% of the total microbial biomass and enzyme activities in the rumen.

Methods of Defaunation

1. Weaning of new-born animals; This is the easiest and cheapest method of the defaunation. In this method the new born calf separated from dam within 2-3 days of calving. Proper care should be taken so that the isolated animals do not come in contact with any adult animals as well as any contamination from the handlers who look after faunated and defaunated animals.
2. Chemical treatment; The chemicals which have been widely used to defaunate the animals are copper sulphate, sodium lauryl sulphate and manoxol. Chemicals can be used either orally (by stomach tube) or through rumen fistula. These chemicals kill the rumen protozoa. Side effect of chemical treatment is decreased feed intake and dehydration
3. Dietary manipulation; This is possible through feeding ,by change in the diet of animal offering high energy feed (especially cereal grains like barley, maize etc.) to the starved (for 24 hours) animals, creates acidic condition in the rumen and rumen pH fall below 5.0( because rumen protozoa are highly susceptible for low pH). This fall in rumen pH eliminates the ciliate protozoa completely and the animal become defaunated. Chances of developing acidosis in treated animal is higher. The drenching of vegetable oil is helpful in elimination of rumen protozoa.

Conclusion

Rumen is a natural fermentative anaerobic ecosystem which can be manipulated positively by altering the composition of rumen microflora. There is ample scope to manipulate the rumen by feeding local plants or tree leaves or agro-industrial by-products to defaunate and achieve improved productivity. Introduction of naturally occurring microorganism from digestive system of one species to another species for efficient degradation of plant toxins as well as for efficient utilization of nutrients will be one of the major thrust area in near future for rumen manipulation. Genetically manipulation of rumen microorganism for efficient ruminal fermentative digestion has enormous potential. However, in tropical countries, more emphasis should be given on manipulating the rumen to increase cellulolytic activity for efficient utilization of low -grade roughage.