The present experiment was conducted to evaluate the effect of simulated heat stress on digestibility and methane (CH4) emission. Four non-lactating crossbred cattle were exposed to 25°C, 30°C, 35°C, and 40°C temperature with a relative humidity of 40% to 50% in a climatic chamber from 10:00 hours to 15:00 hours every day for 27 days. The physiological responses were recorded at 15:00 hours every day. The blood samples were collected at 15:00 hours on 1st, 6th, 11th, 16th, and 21st days and serum was collected for biochemical analysis. After 21 days, fecal and feed samples were collected continuously for six days for the estimation of digestibility. In the last 48 hours gas samples were collected continuously to estimate CH4 emission. Heat stress in experimental animals at 35°C and 40°C was evident from an alteration (p<0.05) in rectal temperature, respiratory rate, pulse rate, water intake and serum thyroxin levels. The serum lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase activity and protein, urea, creatinine and triglyceride concentration changed (p<0.05), and body weight of the animals decreased (p<0.05) after temperature exposure at 40°C. The dry matter intake (DMI) was lower (p<0.05) at 40°C exposure. The dry matter and neutral detergent fibre digestibilities were higher (p<0.05) at 35°C compared to 25°C and 30°C exposure whereas, organic matter (OM) and acid detergent fibre digestibilities were higher (p<0.05) at 35°C than 40°C thermal exposure. The CH4 emission/kg DMI and organic matter intake (OMI) declined (p<0.05) with increase in exposure temperature and reached its lowest levels at 40°C. It can be concluded from the present study that the digestibility and CH4 emission were affected by intensity of heat stress. Further studies are necessary with respect to ruminal microbial changes to justify the variation in the digestibility and CH4 emission during differential heat stress.

Heat stress adversely affects the physiological and metabolic status, and the productive performance of buffalo. The present study was conducted to explicate the effect of misting and wallowing cooling strategies during heat stress in lactating Murrah buffalo. The study was conducted for three months (May–July) of which first two months were hot dry and last month was hot humid. Eighteen lactating buffaloes, offered the same basal diet, were blocked by days in milk, milk yield and parity, and then randomly allocated to three treatments: negative control (no cooling), cooling by misting, and cooling by wallowing. The results showed higher (P < 0.05) milk yield in buffaloes of misting and wallowing group compared to control during the experimental period however wallowing was found more (P < 0.05) effective during July (hot humid period). Both the treatments resulted into significant (P < 0.05) reduction in rectal temperature (RT) and respiratory rate (RR) compared to control animals during study period whereas wallowing was found to be effective on pulse rate (PR) only during July. Both treatments were resulted in mitigating the heat stress mediated decrease in packed cell volume (PCV), lymphocytopnoea and neutrophilia whereas decrease in total erythrocyte count (TEC) and monocytes was only mitigated by wallowing. Heat load induced alteration in serum creatinine and sodium concentration was significantly (P < 0.05) ameliorated by misting and wallowing whereas aspartate aminotransferase, alkaline phosphatase and superoxide dismutase activity, and reactive oxygen species concentration could be normalized neither by misting nor by wallowing. The significant (P < 0.05) increment in serum cortisol and prolactin levels observed in June and July period in control animals was significantly (P < 0.05) prevented by misting and wallowing. It can be concluded that misting and wallowing were equally effective in May and June (hot dry period) whereas wallowing was more effective during hot humid period in preventing a decline in milk production and maintaining physiological, metabolic, endocrine and redox homeostasis.

The present study was conducted to investigate the effect of dietary supplementation of zinc (Zn) and selenium (Se) on antioxidative status and testosterone, T₄ and T₃ levels in 12 bucks aged between 2 and 4 years, weighing 25–35 kg. The experimental animals were divided in control and test groups containing six animals each. The animals of the control group were not given any supplementation, whereas test group were given supplementation of Zn and Se in the form of 150-ppm zinc sulphate and 0.50-ppm sodium selenite, respectively, for 105 days. Zn and Se levels in serum and seminal plasma, testosterone, T₄ and T₃ levels in serum and antioxidative status of seminal plasma were estimated at 0, 60, 75, 90 and 105 days of the experiment. After 60 days of supplementation, concentration of Zn and Se in seminal plasma and serum increased significantly (P<0.05) as compared to control. After 60 days, superoxide dismutase (SOD), glutathione peroxidase (GSHPx), glutathione reductase (GSHR) and catalase (CAT) activity in seminal plasma of test group increased significantly (P<0.05), whereas lipid peroxidation (LPO) decreased significantly (P<0.05) as compared to control. After 60 days, serum testosterone, T₄ and T₃ concentration in test group increased significantly (P<0.05) as compared to control. It may be concluded that Zn and Se supplementation can improve the antioxidative status and hormone levels by increasing the Zn and Se level in seminal plasma and serum, respectively.