Impact of different rearing systems on growth, carcass traits, oxidative stress biomarkers, and humoral immunity of broilers exposed to heat stress

The effects of different rearing systems (RS) including cage rearing systems (CRS), litter rearing systems (LRS), and perforated plastic slate rearing sys-tems (PSRS) on the productive performance, carcass traits, blood hematological and biochemical parameters, and humoral immunity in broiler chickens exposed to heat stress were investigated. A total of 270 1-day-old Avian 48 chicks were randomly assigned to 3 groups equally, each was divided into 9 replicates (each of 10 birds) housed in studied RS. Results revealed that CRS had higher (P < 0.001) body weight and weight gain at all experimental periods (except in the sixth wk for weight gain) followed by LRS. Birds housed in PSRS consumed lower (P < 0.001) feed than those in CRS (during the fourth to sixth and overall periods) and LRS (during all experimental periods except the second one). Best values of feed conversion ratio and European broiler index were shown in CR birds. All carcass traits were not altered by different RS except the percentages of dressing, liver, breast, and left filet, which were elevated (P < 0.05) in caged birds. Eosinophil, lymphocyte, basophil, and monocyte counts and phagocytic index and activity were reduced (P < 0.05 or P < 0.01) in LRS. Humoral immune response against the Newcastle disease virus and avian influenza were not differed. Birds in LRS showed higher (P < 0.05) serum cholesterol, uric acid, and lactate de-hydrogenase as well as liver and muscle cholesterol con-tents. Lipid peroxidation was reduced (P < 0.05) in the LRS and PSRS groups, whereas superoxide dismutase was elevated (P < 0.05) in CRS and LRS. Thus, CRS and LRS were preferred for better growth performance and carcass traits of heat-stressed broilers, whereas CRS and PSRS were better in reducing tissue cholesterol under the conditions of our study.