Dietary Inorganic Chromium in Summer-Exposed Buffalo Calves (Bubalus bubalis): Effects on Biomarkers of Heat Stress, Immune Status, and Endocrine Variables.

The aim of this study was to evaluate the effect of different levels of inorganic chromium (Cr) on heat stress, immune response, and hormonal variation in Murrah buffalo calves during the summer season. Twenty-four growing Murrah buffalo calves were randomly allocated into four treatments for a period of 120 days. Feeding regimen was same in all the groups, except the buffalo calves in treatment groups were additionally supplemented with 0.5, 1.0, and 1.5 mg of inorganic Cr/kg dry matter. Buffalo calves were monitored daily for physiological variables and dry matter intake (DMI) and fortnightly for body weight change. Blood samples were collected at day 0, 15, 30, 45, 60, 75, 90, 105, and 120 and analyzed for heat shock protein 70 (Hsp 70), lymphocyte proliferation, neutrophil phagocytic activity, immunoglobulin, ferric reducing antioxidant power (FRAP) assay, insulin, cortisol and thyroid hormones, and Cr levels. Dietary Cr supplementation did not have any effect on DMI, growth performance, and physiological variables. However, lymphocyte proliferation, neutrophil phagocytic activity, plasma immunoglobulin, FRAP value, and plasma Cr concentration increased significantly (P < 0.05) with increase in levels of Cr. Adding Cr to the diet of summer-exposed buffalo calves did not show any effect on plasma levels of thyroid hormone, while concentration of insulin, cortisol, and Hsp 70 decreased (P < 0.05). Supplementation of inorganic Cr to the diet of buffalo calves reared under high ambient temperature improved heat tolerance, immune status without affecting nutrient intake, and growth performance.