Effect of feed restrictions on performance, blood variables and immunity of broiler chickens

Genetic selection has led to an increase in performance and lean tissue deposition in broiler chickens which have become increasingly susceptible to disease. To reduce this susceptibility, various feed restriction programs have been proposed, albeit with highly variable results. This study investigated the effects of the duration and intensity of quantitative feed restriction in the early rearing period on the performance, blood parameters and immunity of broiler chickens. Two hundred and seventy chicks were randomly assigned to a 4 × 2 factorial arrangement to examine the effects of 2 durations (7 and 14 d) and 4 levels of feed restriction (5, 10, 15, and 20%). One control (Con) group was included. Feed intake (FI) and weight gain (WG) were recorded, and the feed conversion ratio (FCR) calculated weekly. At slaughter (42 d of age), blood was collected, and the carcass composition and characteristics of the gastrointestinal tract were assessed. In comparison with the Con, feed restrictions improved FCR (P<0.01), increased relative weight (RW) of the breast (P<0.05), and abdominal fat (P