Acclimatization dynamics to extreme heat stress in crossbred cattle
2021
Yadav, Brijesh | Gyanendra Singh, | Wankar, Alok
The adaptability of cattle to thermal stress has been extensively studied however the exact dynamics of acclimatization is still less investigated. The present study was conducted to assess the acclimatization dynamics in crossbred cattle. In the present experiment non-pregnant dry crossbred cattle (n = 4) were exposed to 25°C and 40°C temperature with a relative humidity of 40–50% in a psychrometric chamber from 10:00 to 15:00 h/day for 21 days. The physiological parameters were recorded and blood samples were collected at 15:00 (after exposure) hours on day 1, 6, 11, 16 and 21. All the studied parameters except T₃ altered significantly (P < 0.05) at 40°C temperature as compared to 25°C. At 40°C exposure a significant (P < 0.05) acclimatization response in respiratory rate was first observed on day 11. The dry matter intake increased significantly (P < 0.05) from day 6 onwards whereas water intake decreased at day 21 only. The LDH, AST, ALT activity, urea concentration and redox status did not reach to pre-stress levels even at day 21. Acclimatization in T₄ and cortisol levels was observed on day 11 and 16, respectively. It can be concluded that in extreme heat stress conditions an acclimatization period of 6 to 21 days was required in crossbred cattle.
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