ABSTRACT
The microbiota in the gastrointestinal tract of mammals now accepted as a metabolically active organ with its large biodiversity. It is not only involved in digestion and fermentation which is of particular importance in animals but also it has considerable beneficial effects such as; synthesis of vitamins; bioconversion of toxic compounds to nontoxic residues; stimulation of the immune system; maintenance of gut peristalsis and intestinal mucosal integrity, and plays a barrier role against colonization by pathogens. These beneficial effects has led to a better understanding of the major contribution of the gut microbiota to animal nutrition and health. Studies showing that feed and feed additives have a great effect on the host gut microbiota, so it makes them a significant part of the healthy livestock production.
New methods in animal breeding are developed, aiming quality and safety of food, while taking into account the welfare of the animal and respect for the environment. In the past, antibiotics and other medicinal products had been broadly used as antimicrobial growth promoters (AGPs), mainly in order to improve the microbiota and to increase productivity and growth. But the sensitive issues and bans about the antibiotics made probiotics and prebiotics the best alternative to them. High hopes are evoked and clear consensus has started to develop on use of probiotics as functional feed.
The beneficial effects of probiotic added functional feed in animal production have been related to different modes of action. Farm animals are often subjected to environmental stresses (management methods, diet, etc.) which can cause imbalance in the intestinal ecosystem and could be a risk factor for pathogen infections. The other action in animals are related to productivity. These include growth rate, feed intake, feed efficiency, milk composition, egg production and reproduction in ruminants, poultry, pigs and fish.
This chapter is focuses on the use of probiotics in animal feed, their major health benefits in ruminants, poultry, pig and fish and additionally their safety aspects.
