The Influence of Broilers’ Growth Rate and Feed Intake on Inflammatory Response

To evaluate the effect of broiler growth rate and feed intake on development of the inflammatory response‚ commercial broiler diets were fed to 275 day–old chicks of the modern 2000 strain and 1957 random-bred strain. Half of the chicks had free access to feed while others were restricted. Twelve birds from each strain and group pens were removed‚ weighed, and housed in individual cages by their original feeding programs on 0‚ 7‚ 14, and 28 days. Three feed-restricted and three ad libitum birds from each strain were injected with 1-3 ml of 100 μg/ml solution of Salmonella typhimurium lipopolysaccharide on days 6‚ 13‚ 27‚ and 41, and 3 birds of each group were not injected‚ serving as controls. All birds were weighed and the liver‚ breast muscle‚ thymus gastro intestinal tract and bursa were removed on the day after injection. The thymocytes of the control birds were subjected to an interleukin–1 responsiveness assay. The 1957 strain birds were more severely affected by an inflammatory challenge going almost completely off feed‚ but the 2000 strain birds experienced a more drastic decline in growth rate after injection. Thymocytes of ad libitum birds were more sensitive to IL-1 than the restricted birds in week 4 (P=0.056). Interleukin-1 stimulated thymocytes of 2000 birds more effectively than the 1957 strain ones. In conclusion‚ the broiler inflammatory response was affected by growth rate and feed intake.