Rumen Manipulation: Strategy to Enhance Productivity in Ruminants

Rumen Manipulation: Strategy to Enhance Productivity in Ruminants

Swati Thakur,  Meetu Lomror, Jakhar Ritu and Madan Jyotsana

College of Veterinary and Animal Sciences, LUVAS, Hisar, Haryana, India

 

Animal husbandry has made sizeable contribution to human being in the past century. Animal products provide one sixth of human food energy and more than one-third of the protein on global basis. Ruminants are fore gut fermenters and their stomach has four distinct compartments consisting of rumen, reticulum, omasum and abomasum. The rumen, which is located at the beginning of the tract, plays a major role as at least 50% of the total digestion occurs there. Although a myriad of microorganisms are found throughout the digestive tract of ruminant, still only the micro-biota inhabiting in the rumen have true symbiotic relationship with the host. Individual rumen microbial species have developed in a complex process of evolution extending over long period and provide nature’s best example of microbial symbioses. These rumen microorganisms are predominantly bacteria, protozoa and fungi. The mammalian system is devoid of enzymes to degrade structural carbohydrate and hence, the symbiotic microbes inhabiting in rumen elaborate enzymes for fermentation digestion of large amounts of fibrous feed consumed by the ruminants. By providing a suitable habitat for these microorganisms, the ruminants are able to utilize the end products of microbial fermentation to meet their own nutritional need. Rumen is an ecosystem in which feed consumed by the animal is fermented by rumen microbes to volatile fatty acids (VFAs) and microbial biomass serve as source of energy and protein for the host animals. The rumen microbial ecosystem is an efficient anaerobic fermentation system that confers added advantages on ruminants over monogastrics or non-ruminants animals. These are:

1. Ruminants can digest large amount of fibrous feeds (ligno-cellulosic materials) efficiently
2. They can use non protein nitrogen (NPN) sources like urea as a source of nitrogen to meet demand of their protein requirement
3. They can detoxify many toxic ingredients present in feeds of plant origin

 

Need of rumen manipulation

Some of the major objectives of rumen manipulation are:

1. Enhance fibrolytic activity: To increase the fibre degradation mainly through manipulation of lignocellulosic bonds in high lignocellulosic feeds as the rumen microbes are the only degraders of cellulose and hemicellulose.
2. Increase microbial protein synthesis: A major portion of the amino acid reaching the duodenum are of microbial protein origin. Therefore, attempts should be made to maximize microbial protein synthesis in the rumen.
3. Reduction in proteolysis: Hydrolysis of feed protein, deamination of amino acids and reutilization of ammonia for microbial protein synthesis are all energy consuming process, hence the degradation of protein and deamination of amino acids in the rumen should be discouraged.
4. Reduction in methanogenesis: Methane (CH₄) generation in the rumen is a wasteful process as 5-10% of GE intake of ruminants is converted in to methane. The provision of an alternate hydrogen sink in the rumen may help in increasing digestible energy (DE) availability for production.
5. Prevention of 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.
6. Shifting acetate to propionate production: In fattening animals, the production of propionate in the rumen at the expense of acetate may be helpful.
7. Novel microbes: The quality of protein is important in high producing ruminants. Microbes can be tailored to synthesize the amino acids in the form of the peptides and supply to the animals in the intestine.
8. Metabolism of plant toxins: Rumen fermentation can be manipulated for efficient utilization of feeds which contain anti nutritional factors viz. tannin, saponin, mimosine etc.

 

Methods of rumen manipulation

Broadly the methods of rumen manipulation can be classified in two type: genetic manipulation and non-genetic manipulation. In genetic manipulation, attempts were made to develop genetically engineered rumen microbes by gene transfer/manipulation technique to enhance the animal productivity. However success in the field of genetic manipulation of rumen microbes is very poor. Non genetic manipulation of the rumen can be done by physical methods (dietary manipulation) and by using suitable chemicals or feeding microbes (probiotics).

Genetic rumen manipulation

These techniques could allow the introduction or increase of desired activities such as cellulolysis and detoxification or reduction of undesirable activities such as proteolysis, deamination and methanogenesis. This can be done by:

1. Selection of desirable gene and its expression in predominant rumen bacteria
2. Naturally present microorganisms in rumen can be genetically modified to enhance their capacity of defined function or to add new function

However, establishment of genetically engineered rumen bacteria is too complex and existing regulations about the release of genetically engineered microbes in the atmosphere is also a limitation.

Non genetic rumen manipulation

1. Feed manipulation

Forage:

• Forage quality influences CH₄ production in the rumen. High quality forage can reduce CH₄ production by altering the fermentation pathway because young forage contains higher amounts of easily fermentable carbohydrates and less NDF, leading to higher digestibility and passage rate.
• Different types of forage can also effect CH₄ emission due to difference in their chemical composition. C₄ grasses yield more CH₄ than C₃
• Legume forage has a lower CH₄ yield due to the presence of condensed tannins, a low fibre content, a high dry matter intake and faster passage rate.
• Forage processing and preservation also affect CH₄ emission (chopping and pelleting). Methanogenesis is lower in ensiled forages, possibly due to partial fermentation during ensiling process.
• Supplementing small amount of grain with forage.

 

Concentrates

• Concentrates with higher density of nutrients, readily fermentable carbohydrates (starch and sugar) and less fibre favour propionic acid production, decreasing CH₄
• Feeding more starch to ruminants reduces enteric CH₄ energy loss as compared to a forage diet.
• Starch fermentation promotes propionic acid production in the rumen by creating alternate H₂ sink, a lower rumen pH, inhibiting the growth of methanogens, decreasing the rumen protozoa number and decreasing interspecies H₂ transfer between methanogens and protozoa.
• Feeding starch which can escape rumen fermentation could potentially provide energy to the host animal while avoiding rumen fermentation. Up to 30% starch from corn can escape rumen fermentation and digested in small intestine. Bypass starch has limited digestibility (60%) in the small intestine.

Fat supplementation

• If energy supplementation in ruminant’s diet changes from carbohydrate to fat, less fermentation and CH₄ emission will occur. The CH₄ suppressing mechanism of fat is induced by organic matter fermentation, fibre digestibility, direct inhibition of methanogens and methanogenic pathway by hydrogenation of unsaturated fatty acids.
• Unsaturated fatty acids act as alternate H₂ sink in the rumen through dehydrogenation, although hydrogenation contribute only 1% to rumen H₂. Medium chain fatty acids are more effective in CH₄
• Fats are not metabolized in the rumen, therefore, no contribution in methanogenesis.
• Fat supplementation reduces carbohydrate fermentation due to toxic effect of fat on cellulolytic bacteria and protozoa, while starch fermentation remains unaffected.

Organic acids

• Through treatment of roughage, concentrate and strategic supplementation with organic acids.
• Improve rumen efficiency by maintaining higher pH, optimum ammonia nitrogen (NH₃-N), thus CH₄ and increasing microbial protein synthesis and essential VFAs.
• Effect on rumen fermentation analogous to ionophores (CH₄, lactate and propionate). However, their mode of action is different than ionophores.
• Organic acids stimulate rather than inhibit some specific ruminal bacterial population
• Malic acid, fumaric acid and aspatic acid: commonly used organic acids feed additives.

Ionophores

Ionophores are antibiotics and these include monensin, lasalocid, tetronasin, salinomycin, lysocelin, narasin, nigericin and valynomycin.

Effect of ionophores on rumen end products are:

1. Decrease in H₂, a precursor of methane
2. Favours propionate production
3. Inhibit G +ve bacteria
4. Potential increase in production of propionate and associated decrease in production of methane

Monensin is safe for human consumption, biodegradable in manure and soil and non-toxic to crop plant.

Plant extracts

Antimicrobial activity of plant extracts or secondary plant metabolites (saponins, tannins and essential oils). These are selective inhibitors of methanogens and are defaunating agents and selective inhibitors of G +ve bacteria. These include Equisetum arvense, Lotus officinalis, Sapindus saponaria, Uncaria gambir, Yucca schidigera.

2. Microbial feed additives (Probiotics)

Microbial cultures are being used nowadays as natural feed additive for enhancing rumen metabolic activity and thereby overall animal production. The effects of probiotics are greatest in the fastest growing animals and diminish with age. The utilization of probiotics in farm animals may contribute in the following aspects:

1. Growth promotion
2. Improved feed conversion efficiency

• Better absorption of nutrients by control of gut epithelial cell proliferation and differentiation

1. Improved metabolism of carbohydrate, calcium and synthesis of vitamins
2. Neutralization of anti-nutritional factors i.e., trypsin inhibitor, phytic acid etc
3. Microbial enzyme production, compensating for deficient intestinal enzyme activities of the host

• Elimination or control of intestinal microorganisms producing sub clinical or clinical diseases
• Stimulation of non-specific and specific immunity at the intestinal level

Administration of probiotics in livestock may be most effective under following conditions:

1. After birth to encourage the early establishment of beneficial rumen microflora,
2. Following antibiotic treatment,

• In the presence of enteric pathogen such as E. coli, Salmonella, Coccidia,

1. During environmental or mangemental stress. In calves, administration of probiotics may be most effective under the following circumstances:
2. After birth,
3. Before and after transportation,

• At weaning,
• Following over eating or antibiotic administration

In adult cattle, administration of probiotics may become more effective under the situation such as ketosis, antibiotic treatment, bloat and difficult calving.

Effect of probiotic feeding on rumen function

1. Yeast feeding has been found to increase the total number of rumen bacteria population along with higher proportion of cellulolytic bacteria
2. The percentage of Entodiniomorphid protozoa decreases and Dasytricha increases in the rumen of yeast culture fed animal

• Lower ruminal ammonia nitrogen and high microbial protein synthesis in animals consuming yeast culture

1. Yeast supplementation in diet increases the activity of carboxymethyl cellulase enzyme in the rumen of animals
2. Yeast acts as O₂ scavenger in the rumen. During feed ingestion, small amount of O₂ enters the rumen along with feed and it adversely affect the rumen environment as well as growth of the rumen microbes
3. The administration of probiotics had an impact on growth performance, disease resistance, improving animal production and providing a cost effective dietary supplement.

 

3. Defaunation

The process of making rumen of the animals free of rumen protozoa is called as defaunation and the animal is called defaunated. Rumen protozoa elimination by defaunation reduces ruminal methane production and increases protein outflow in the intestine, resulting in improved growth and feed conversion efficiency of the animals.

Defaunation can be done by:

1. Isolation of new born animals: Separation of new born animals from their dams after birth and preventing them from any contact with the adult ruminant animals. The new born animals should be separated 2 to 3 days after birth
2. Chemical treatment: Copper sulphate, manoxol and sodium lauryl sulphate

• Dietary manipulation: Ciliate protozoa are very sensitive to change in rumen pH. The activity of ciliate protozoa is adversely affected when the pH of the rumen fall below 5.8. At pH 5.0, the ciliate protozoa are completely eliminated and the animal become defaunated.

Conclusion

Rumen is a natural fermentative anaerobic system which should be manipulated essentially 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 the animals for improving their 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. Genetic manipulation of rumen microorganism for efficient ruminal fermentative digestion has an enormous biotechnological potential. However in tropical countries, more emphasis should be given for manipulating the rumen to increase cellulolytic activity for efficient utilization of low grade roughage.

https://www.pashudhanpraharee.com/potential-approaches-and-benefits-of-modulation-of-rumen-ecosystem/

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