author(s)
Madeeha Untoo, MT Banday, Insha Afzal, S Adil, IA Baba and Asra Khurshid

abstract
Feed is one of the largest items of expenditure and accounts up to 70% of the total poultry production, there is also constant increase in the cost of poultry feed ingredients. In order to minimize the cost of feeding, several feed additives were used to enhance poultry production. Probiotic is one such feed additive which eliminates the use of low-dose antibiotics and lead to better and safe poultry production. It avoids the health hazards of antimicrobials to human as well as poultry. Probiotics are live microbial food/feed ingredients that have a beneficial effect on health and stimulate the growth of beneficial microorganisms and reduces the amount of pathogens, thus improving the intestinal microbial balance of the host and lowering the risk of gastro-intestinal diseases. They are “mono or defined mixed culture of live microorganisms which when applied, beneficially affect the host by improving the properties of the indigenous micro biota”. Probiotics improve feed intake, growth performance, meat quality, egg production, and egg quality Probiotic have cholesterol lowering potential, antimutagenic, anticarcinogenic, hypocholesterolemic, antihypertensive, anti-osteoporosis, and immunomodulatory effects. However, contra indicatory effect of probiotics on various parameters has also been observed by a number of researchers. These probiotic are prepared from various species i.e. Lactobacillus bulgaricus, L. acidophillus, L. casei, L. helveticus, L. salvarius, L. plantarum, L. faecalis, Streptococcus thermophilus, Enterococcus faecium, Enterobactris faecalis, Bifidobacteria species, Saccharomyces cerevisiae, Toulopsis sphaerica etc. and Lactobacillus, Bifidobacterium, Leuconostoc, Enterococcus, Lactococcus, Bacillus, Saccharomyces, Aspergillus and Pediococcus species are some commomly used species in poultry production. However, an accurate dosage of administration has yet to be established despite the wide-use of probiotics. In this review, the history, function, characteristics, species, mode of action and the effect of probiotics on different parameters in poultry is discussed.