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Abstract
1. INTRODUCTION
The chicken industry is one of the most dynamic of world agribusiness trade. The importance of feed supplementation in poultry production has increased in the last years with the aim of improving the economic situation of poultry projects. Nowadays, food safety is more seriously considered than before. On the other hand, economy of food production is also a factor which is not ignorable.
Use of antibiotics in poultry feeds has improved growth and feed efficiency. This finding has resulted in much attention being directed toward the improvement of nutrient utilization. Their side effects, however, include development resistant populations of bacteria as well as the intestinal upsets, which often follow oral treatment. The side effects made the subsequent use of antibiotics for therapy a difficult challenge produced a climate in which both consumers and manufactures are looking for alternatives.
Recently, many countries tended to prohibit antibiotics because of their side effects on both bird and man. Researchers are looking to natural means of reducing classical feed additives such as antibiotics in poultry nutrition (Genedy and Zeweil, 2003 and Ibrahim et al., 2005).
Several researchers (Kumprecht et al., 1995, Omar, 1996, and Zeweil et al., 1996) have investigated the beneficial effects of feeding microbial culture to poultry as a possible alternative to antibiotics for growth promotion and improvement of feed efficiency.
Probiotics should or could replace antibiotics as growth promoters but not in the treatment of disease, because the use of antibiotics as growth promoters was a result of the development of resistant population of bacteria which made the subsequent use of antibiotics for therapy was difficult.
In a natural environment, the establishment of a microbial population in the digestive tract of all warm-blooded animals, soon after birth, is