Effect of Feed Restriction on Performance and Immune Response of Two Commercial Broiler Strains

This experiment was conducted to determine the effects of feed restriction (FR) on performance and the immune system of Arian and Ross strains. Feed efficiency was significantly better for restricted birds. Body weight (BW) of the restricted chickens was significantly lower than those of the ad libitum group at day 42. Arian strain had lower BW at day 21 but higher BW at day 42 th an Ross strain. Birds in FR group showed a significant increase in percentage of CD4+ (helper T cell) and decreased CD8+ (cytotoxic T cell) at day 21 and 42. T cell subsets of Ross and Arian birds was not significantly different on day 21, but in day 42 the Arian chickens had higher CD4+ and lower CD8+ than those of Ross chickens. Antibody response to sheep red blood cells was significantly higher in the birds on the FR group at day 21. Antibody titer was not affected by strain at day 21 but Ross chickens had higher antibody liter than Arian chickens at day 42. The results indicate that the feed restriction may have sorne adavantages, mainly by increasing feed efficiency and immune system competence.