Effect of Hot Humid and Winter Season on Circulatory Catecholamine, Milk Composition and Physiological Responses in Cows

Two sets of experiments were carried out on lactating crossbred cows during hot humid (HH) (temp. 2434°C, RH 98%)and winter season (temp.1.97-19.90°C, RH 60-70%). The cows were managed in a loose housing system and was producing milk yield of9.00 to 10.11kg /d. Samples of milk and blood were collected and the physiological responses were recorded at weekly interval in the morning and afternoon (interval). Maximum, minimum and dry and wet bulb temperatures were recorded in both the seasons. Temperature humidity index (THI)was significantly higher in hot-humid season (p<0.01) than the winter season.Higher THI score during HH season resulted in increasedcortisol leveland physiological responses(ST, RT, RR and PR) wasgreater (p<0.01) in comparison to winter season.Howeverepinephrine(E), nor-epinephrine (NE), glucose, NEFA, and milk composition was not influenced. Low THI score in winter season significantly (p<0.01) decreased plasma E, NEFA and increased NEconcentration howeverplasma cortisol, milk composition and physiological responseswere unaffected. Plasma E concentration was higher (P<0.01) in HH season while NE was more (P<0.01) in winter season. Plasma glucose concentration was significantly higher (p<0.01) in morning then in the afternoon in winter seasonbut was nonsignificant in HH season. The diurnal variation in morning and evening PR,RR,RT and ST was significant (P<0.01)in HH season and varied non-significantly in winter. It was concluded that increase or decrease in THI score significantly influence plasma NE and cortisol levels and are reliable marker of heat and cold stress in crossbred cows. Further THI score (>75) adversely influence physiological responses and milk composition inHH season.