The effect of different levels of organic and inorganic chromium supplementation on immune function of broiler chicken under heat-stress conditions

A study was conducted using 250 broiler chickens to evaluate the effect of Cr supplementation on the immune responses of heat-stressed broiler chicks. All birds were kept under a heat-stress temperature (33 ± 3°C) and divided into 5 treatments, with 5 replicates of 10 birds each. In a completely randomized design, the basal diets were supplemented with 0 (control), 800, or 1,200 ppb of Cr-l-Met and 800 or 1,200 ppb of CrCl3. On d 42, the bursa of Fabricius, spleen, and thymus were collected, weighed, and expressed as grams per 100 g of BW. Antibody titers against Newcastle virus were higher in broilers that received organic Cr supplements at 18 and 30 d of age (P < 0.05). The heterophil-to-lymphocyte ratios decreased in broilers receiving the Cr-l-Met supplements compared with those in other treatments (P < 0.05). The albumin-to-globulin ratios were not affected by treatments at 28 d but were increased in the 1,200 ppb of CrCl3 treatment at 42 d (P < 0.05). Serum cortisol concentrations were lower in the 1,200 Cr-l-Met group (P < 0.01), and serum IgG concentrations were higher in this group (P < 0.01). Lymphoid organ weights did not differ between treatment groups. Both the organic and inorganic Cr supplements improved the immune response of broilers under heat-stress conditions, and a more positive effect was observed by addition of 1,200 Cr-l-Met.