Evaluation of thermo-adaptability between Tharparkar (Bos indicus) and crossbred (Bos indicus X Bos taurus) calves in a controlled environment

The global warming driven climate change has increased the susceptibility of livestock around the globe to heat stress (HS), which reduces animal productivity and threatens the sustainability of marginal farmers. The objective of this investigation was to evaluate thermo-adaptability between Tharparkar calves (TC), an indigenous milch breed of India and crossbred calves (CC) during induced heat stress in controlled environment. For this purpose, 12 apparently healthy male calves (six in each group) aged 5–6 months, were selected. The experiment was conducted at physiologically comfortable temperature (25 °C), moderate HS (31 °C) and severe HS (37 °C) for 21 days each in a psychrometric chamber. In each experimental day, the calves were exposed to 6 h of heat. There were 7 days of acclimatization period before experiment and 10 days of recovery period at ambient temperature between each 21 day exposure period. During experimental period, the blood was collected at 1st, 6th, 11th, 16th, 21st day and among ten-day recovery period the blood was collected at 5th day. Physiological responses, serum electrolytes, metabolic enzymes profiles, antioxidant capacity, oxidative stress status and general endocrine milieu were studied. Relative mRNA expression study of Heat Shock Protein (HSP) 70, HSP90, induced Nitric Oxide Synthase (iNOS) and endothelial NOS (eNOS) were carried out by qPCR. There was significant (p