Dietary Inorganic Chromium in Summer-Exposed Buffalo Calves (Bubalus bubalis): Effects on Biomarkers of Heat Stress, Immune Status, and Endocrine Variables Muneendra Kumar & Harjit Kaur & Rijusmita Sarma Deka & Veena Mani & Amrish Kumar Tyagi & Gulab Chandra Received: 25 January 2015 /Accepted: 12 February 2015 # Springer Science+Business Media New York 2015 Abstract 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 treat- ments 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, cor- tisol and thyroid hormones, and Cr levels. Dietary Cr supple- mentation did not have any effect on DMI, growth perfor- mance, and physiological variables. However, lymphocyte proliferation, neutrophil phagocytic activity, plasma immuno- globulin, 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 con- centration 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 toler- ance, immune status without affecting nutrient intake, and growth performance. Keywords Buffalocalves . Chromium . Endocrinevariables . Heat stress . Immunity . Summer Introduction Farm animals have known zones of thermal comfort that are primarily dependent on the species, physiological status of the animals, relative humidity, and the severity of solar radiation [1]. High environmental temperature and humidity are detri- mental to the productivity of commercial farm animals. Among farm animals, buffaloes exhibit signs of great physical distress when exposed to high environmental temperature [2]. This is due to fact that their body absorbs a great deal of solar radiation because of their dark skin and sparse coat or hair. In addition to that, they possess a less efficient evaporative cooling system due to their rather poor sweating ability. Heat stress results in reduced gut motility, ruminal contractions [3], M. Kumar (*) Animal Nutrition Department, College of Veterinary Science and Animal Husbandry, DUVASU, Mathura University, Mathura 281001, India e-mail: muneendra82@gmail.com H. Kaur Agricultural Extension Division, Krishi Anushandhan Bhawan, Indian Council of Agricultural Research, Pusa, New Delhi 110012, India R. S. Deka Krishi Vigyan Kendra, Dhemaji 787059, India V. Mani : A. K. Tyagi Dairy Cattle Nutrition Division, National Dairy Research Institute, Karnal 132001, India G. Chandra Department of Veterinary Physiology and Biochemistry, Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut 250110, India Biol Trace Elem Res DOI 10.1007/s12011-015-0272-0