Mode of action and complementary effect of antibiotics in feed on broiler performance

الملخص EN

The effect of administering various antibiotics on the performance of broiler chicks was investigated in an attempt to assess the mode of action of these antibiotics.

Bacitracin, Chlortetracyclin, Procaine penicillin, were fed at the rate of 50 ppm per feed either singly or in combination, to a group of one thousand unsexed chicks, from one-day-old till 49 days of age.

In the last week of the experiment, all birds received the feed without antibiotics to minimize residues from tissues.

The antibiotic administration improved (P< 0.05) the growth rate, feed conversion, and mortality rate.

Combination of all three antibiotics showed significantly (P< 0.05) more improvement than the single antibiotic administration.

Antibiotic treatment reduced (P< 0.05) Clostridium perfringens population in the ileum .

No measurable levels of antibiotic residues (less than 0.5 mg/Kg) were detected in samples of kidney, liver and breast and thigh muscles, as a result of antibiotic administration.

The result showed that antibiotics can promote growth by different modes of action.

The effect of antibiotics on the gastrointestinal micro-organisms can not be regarded as the only reason for the improvements recorded for growth and feed efficiency.