Seasonal alterations in plasma cortisol in peripartum Murrah buffaloes (Bubalus bubalis) as assayed by a sensitive enzymeimmunoassay in subtropical climate

Abstract

ABSTRACTThe cumulative effect of seasonal heat stress and peripartum stress in inducing the seasonal alterations in the plasma cortisol levels was studied in Murrah buffaloes (n = 6) on days ±30, ±15, ±5, ±3, ±1 and 0 prepartum and postpartum with respect to the day of parturition (day 0) in each of the two different seasons (hot-humid and spring). The microclimatic Temperature Humidity Index (THI, mean ± SE) during spring season exhibited thermoneutral conditions (60.10 ± 2.56–72.67 ± 0.65) while that in the hot-humid season showed heat stress. Total cortisol in the plasma as assayed by a modified enzymeimmunoassay developed for buffaloes reflected an increase in cortisol level around parturition (days −1, 0 and +1) in both the seasons. Between the two seasons, the cortisol levels were significantly lower in the hot-humid season on days −5 (p < 0.01), +1 (p < 0.055) and +3 (p < 0.051), which indicated adaptation of buffaloes to thermal environment. Substantial exposure to high THI thus plays a significant role in determining the overall stress as reflected by plasma cortisol in circulation during the peripartum periods in Murrah buffaloes in the tropics.