All components of food are not digested in mono-gastric animals like poultry and pigs. It is now common to supplement enzymes to their diet for improved performance. Plant cell walls are fibrous in nature and cannot be digested by endogenous enzymes produced in poultry and pigs. With advances in Biotechnology enzymes are now produced in large quantities and at low cost. Cellulose enzyme can improve the availability of Starch, oils and proteins by digesting the plant cell walls. Addition of cellulose in pigs and poultry resulted in 5 to 10% improvement in growth rate and 10% improvement in feed conversion ratio. Beta glucans and arabinoxylons present in cell walls are resistant to break down and they hinder the digestion and absorption of other nutrients by forming a viscous gum. Increase in viscosity of digesta disturbs peristalsis and pancreatic secretion and results in poor performance and sticky droppings in poultry. Supplements of beta gluconase to barley and sorghum based diets improved the performance of broilers and reduced litter problems. Viscous digesta prevents proper mixing of endogenous enzymes with digesta and thereby prevents release of nutrients. nzyme is not produced in poultry and pigs and therefore addition of phytase to the diets of poultry and pigs results in greater availability of phosphorous from cereal grains and oilseeds and the amount of inorganic phosphorous added in the diet can be reduced.
In young animals rate of endogenous enzyme production is low and supplementation of amylase, protease and lipase increased the availability of nutrients and improved performance of young animals. Enzyme supplementation increased the digestion and absorption of nutrients in small intestine rather than allowing fermentation of nutrients in the hind gut which results in production of lower value like volatile fatty acids and also prevents diarrhea.
In order to be effective supplemented enzymes must survive storage at ambient temperature, fluctuation in PH of the gut and should be resistant to intestinal proteases. Commercial enzymes are derived from In order to be effective supplemented enzymes must survive storage at ambient temperature, fluctuation in PH of the gut and should be resistant to intestinal proteases. Commercial enzymes are derived from certain fungi such as Aspergillus niger, Humicola insolens . Addition of exogenous enzymes is not necessary in the diet of ruminants since rumen microbes produce the required enzymes.
Oligosaccharides( 2 -20 monosaccharide units) act as beneficial nutritional modifiers for mono-gastric animals. Generally they are known as pre-biotics which are defined as compounds other than dietary nutrients that modify the balance of microbial population by promoting the growth of beneficial bacteria. The addition of a limited amount of oligosaccharides to animal feeds (below 1%)can result in significant improvement of growth rate , Feed conversion ratio and health status of the animal. Commonly used pre-biotics are galacto-oligosaccharides (GOS) fructo-oligosaccharides (FOS),mful bacteria to the gut wall. Species such as Salmonella and E-coli have a mannose–specific lectin which binds to mannose residues on the gut mucosal surface. By adding MOSThese pre-biotics are not digested by host digestive enzymes and pass into the hindgut and fermented by favorable bacteria which shifts microbial population away from harmful species. Pre-biotics interfere with attachment of harmful bacteria to the gut wall. Species such as Salmonella and E-coli have a mannose–specific lectin which binds to mannose residues on the gut mucosal surface. By adding MOS in the diet, the binding by pathogenic bacteria is disrupted and instead they bind to the oligosaccharides and are excreted. Yeast has mannose in the cell wall structure and thus yeast products are useful.
A pro-biotic is defined as a live microbial food supplement that beneficially affects the host animal by improving the intestinal microbial balance. Inclusion of pro-biotics in foods is designed to encourage certain beneficial bacteria in the gut at the expense of harmful bacteria. ial environment. In poultry at the time of hatching the intestinal tract is sterile but becomes rapidly colonized by microorganisms from the environment. Within a few hours lactobacilli appear in the crop and persists there throughout life. It takes several weeks for the complete establishment of adult type micro-flora.
The beneficial micro-organisms produce enzymes which complements the digestive ability of the host and their presence provides a barrier against invading pathogens. Digestive upsets are common at times of stress such as weaning but feeding with desirable bacteria such as Lactobacilli in these situations is preferable to using antibiotic which destroy the desirable bacteria as well as harmful species.
Pro-biotics exert competitive exclusion process of harmful bacteria such as E-coli by attaching themselves with specific oligosaccharide receptor sites of gut wall. They neutralize the endo-toxin produced by pathogenic bacteria. Lactobacilli ferment lactose to lactic acid reducing the PH which cannot be tolerated by harmful bacteria. Hydrogen peroxide is also produced which inhibits growth of gram-negative bacteria. Some pro-biotics also produce antibiotics which kill the harmful bacteria. Pro-biotics also prevent synthesis of amines by Coli form bacteria which are toxic and produce diarrhea. They also enhance immunity. To be effective the beneficial microbes should not be harmful to the host, should be resistant to bile, should colonize the gut efficiently, should inhibit pathogenic activity and should be viable under manufacturing and storage conditions.
In ruminants the yeast Saccharomyces cerevisiae proved effective in beneficially modifying rumen fermentation. Live yeast cultures scavenge oxygen and maintain anaerobic conditions in rumen. It also improves live weight gain, milk yield and milk fat contents.
ROLE OF VITAMINS IN ANIMAL NUTRITION
The vitamins are divided into fat soluble (vitamins A,D,E K) and water soluble vitamins (B complex vitamins and vitamin C).
- Vitamin A: Vitamin A is concerned with vision in dim light and its deficiency may cause night blindness. It is also concerned with the formation and protection of epithelial tissues and mucous membranes. Ruminants do not suffer from Vit A deficiency as they consume pasture grass which has high Beta- carotene the precursor of Vitamin A. Poultry require supplementation of Vitamin A as most of the concentrate foods are lacking in Vitamin A or its precursors.
- Vitamin D: Ruminants which are on pastures do not suffer from Vitamin D deficiency as the pro vitamins are converted into vitamin D on exposure to sun light. Poultry require Vitamin D3 supplementation as they are not exposed to sun light. Deficiency of Vitamin D causes rickets in young animals and osteomalacia in adult animals.
- Vitamin E: This vitamin works as antioxidant along with Selenium . Vitamin E deficiency causes muscular dystrophy in cattle and pigs. Vitamin E deficiency causes muscular dystrophy, Encephalomalacia and exudative diathesis in poultry.
- Vitamin K: Vitamin K is very important for blood clotting process. This vitamin is present in adequate amount in many foods. Therefore Vit K deficiency rarely occurs.
Most of the Vitamins in B complex function in the body act as coenzyme or prosthetic group
- Thiamine: Thiamine is widely distributed in foods and therefore deficiency may not arise.
- Ribo-flavin : Riboflavin occurs in all biological materials. Chicks reared on a riboflavin deficient diet grow slowly and develop curled toe paralysis.
- Nicotinamide: Nicotinic acid is synthesized from the amino acid tryptophan in body tissues. Deficiency symptoms in pigs cause poor growth. Deficiency in poultry causes feathering abnormalities and bone disorders. .
- Vitamin B6: The vitamin acts as a coenzyme for many enzymes and plays important role in protein metabolism. In practice vitamin B6 deficiency is unlikely to occur because of its wide distribution. .
- Pantothenic Acid: This vitamin is widely distributed in foods. It is a constituent of Coenzyme A which is required in metabolism of nutrients. .
- Folic Acid: Folic Acid is widely distributed in foods and a deficiency condition rarely occurs. .
- Biotin: Biotin is widely distributed in foods. Biotin is essential as a prosthetic group of several enzymes.
- Choline: It is a component of Lecithin. It plays important role in lipid metabolism. Fatty infiltration of liver occurs in of chicks and pigs. Green leafy materials, yeast, egg yolk and cereals are rich sources. .
- Vitamin B12: It is synthesized by microorganisms. The main natural source of the vitamin are foods of animal origin. Adult animals are less affected by Vitamin B12 deficiency than are young growing animals in which growth is retarded and mortality is high. A dietary source of cobalt is required for synthesis of Vitamin B12 by rumen microbes.
Rumen microbes generally synthesize all B Complex vitamins required by ruminants and therefore ruminants are unlikely to suffer from deficiency of B Complex vitamins. However Cobalt should be added in sufficient quantities in the diet of ruminants for rumen microbes to synthesize Vit B12.
- Vitamin C: Well known sources of this vitamin are citrus fruits and green leafy vegetables. As an antioxidant, Ascorbic acid works in conjunction with vitamin E in protecting cells against oxidative damage caused by free radicals. Farm animals can synthesize this vitamin from glucose. .
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