Research Note: Responses of growth performance, immune traits and small intestinal morphology to dietary supplementation of chromium propionate in heat stressed broilers

Abstract This study was conducted to investigate the dose responses of growth performance, immune traits and small intestinal morphology to dietary supplementation of chromium propionate (CrPro) in heat-stressed broilers. A total of 252 1-day-old Cobb 500 male broilers were randomly assigned to 6 treatments with 7 replicate cages of 6 birds per cage. The dietary treatments consisted of the basal diet supplemented with 0, 0.2, 0.4, 0.8, 1.6 and 3.2 mg/kg Cr in the form of CrPro. The birds had ad libitum access to feed and tap water for an experimental period of 42 days. For induction of heat stress, the house temperature was set at 35 ± 2 °C from 22 to 42 d of age. No differences were detected among treatments in growth performance during the experimental period (P > 0.05). Serum IgA concentrations were not affected by treatment (P > 0.05). However, a quadratic response was detected for serum IgG (P