English

Abstract

Probiotics, live cells with different beneficial characteristics have been extensively studied and explored commercially in many different products in the world. Their benefits to human and animal have been supported in hundreds of scientific papers. Ruminant animals principally depend on microbial degradation of their feed rather than on direct enzyme degradation as in most non-ruminants. Microbial feed additives used in ruminant feeds are mainly for stabilization of the intestinal flora, enhance the development of the adult rumen microflora, improve digestion and nitrogen flow towards lower digestive tract, and improve meat and milk production. Beneficial microorganisms supply protein, vitamins and short-chain organic acids for the animal host. In a normally functioning ruminant, little or none of the sugars and proteins originally present in the feed are directly incorporated in to the animal: they are first processed by bacterial fermentation in the rumen. Given the importance of the microbial population in feed conversion, it is also important in manipulating rumen fermentation to boost animal productivity and reduce the productivity loss that is associated with rumen acidosis. Probiotics administration improves the health status of the animal by competing the nutrient utilization of the pathogenic microbes by having a positive influence on gut microflora. Furthermore, their anti-pathogenic activity may reduce the stress on animal. Microorganisms that are used in direct fed microorganisms for ruminants may be classified as lactic acid producing bacteria, lactic acid utilizing bacteria, or other microorganisms and yeasts. However, numerous contradictory reports, such as dosages, dietary and management constraints, and effects on different animal conditions have been shown to markedly affect the structure and activities of gut microbial communities in ruminant animals. Therefore, this review article is an attempt to summarize the mode of actions and the effects of feeding probiotics on different aspects of health and productivity of ruminant animals. Key words: Bacteria, fiber degradation, probiotics, ruminant, yeast