Effect of seasons on physiological responses, milk production and composition in Indigenous cows

The present investigation was carried out to find the effect of seasons on milk production and composition in indigenous Sahiwal, Tharparkar and Gir cows maintained under the intensive management practices at the institute livestock farm. Fifteen lactating cows of Tharparkar (TP), Sahiwal (SW) and Gir breed were selected in early lactation. The experiment was conducted for a period of 10 months and the seasons were categorized as hot-humid, hot-dry, autumn and winter season. Blood and milk samples collected at fortnightly intervals were analysed for minerals and plasma hormones. Physiological responses-respiration rate (RR), pulse rate (PR) and rectal temperatures (RT) were recorded. The results showed that the milk fat, solid not fat SNF and urea levels were higher in TP cows in comparison to SW and Gir cows (p<0.01), however, protein % was lower (p<0.01) in TP cows. Milk Mg, Ca and Na levels were lower in hot-humid season than in winter season (p<0.05) in TP cows in comparison to SW and Gir. Plasma cortisol level was higher and aldosterone level was lower in hot-humid and hot-dry season in all the breeds of cows (p<0.05) than the values observed in winter season. TP cows were found to have higher aldosterone level as compared to SW and Gir cows in all the seasons. The cows response to ambient temperature in terms of RR, RT and PR was higher in hot-humid season and lowest in winter season (p< 0.01) in all the breeds, however changes in RT were of less magnitude in TP cows than SW and Gir cows in hot-hot humid season. It was concluded that TP cows have higher plasma aldosterone, milk urea and sodium levels and less diurnal variation in RT, PR and RR in comparison to SW and Gir cows in hot-dry and hot humid season which makes TP cows more heat tolerant than SW and Gir.