Importance of hormonal changes during the periparturition period in Black Bengal goats

Abstract

Background and Aim: The maintenance of pregnancy in livestock requires specific metabolic and functional changes between conception and the end of gestation, mediated through the interplay of hormones. The objectives of this study were to delineate the changes in plasma progesterone, estradiol, triiodothyronine (T 3 ), thyroxine (T 4 ), insulin, and cortisol concentrations during periparturient period in black Bengal goats and to elucidate the interrelationship between T 4 and cortisol in building up of the estradiol prior to parturition. Methods: The blood samples were collected on days −25, −20, −15, −10, and −5 with respect to the date of expected kidding, on the day of kidding (day 0) and also on days 5, 10, 15, 20, and 25 postpartum. Plasma was separated and stored at −20΀C until assay of hormones by radioimmunoassay. Results: Plasma progesterone concentration declined from day − 25 abruptly to the day of kidding and remained at basal level up to day 25 postpartum; whereas, plasma estradiol concentration declined abruptly from the day of kidding to a lower level than that of prepartum. Plasma insulin concentration declined ( P < 0.05) abruptly from day − 15 to the day of kidding followed by increase by day 10 postpartum. Circulating cortisol concentrations decreased from day 25 prepartum to the day of kidding, but increased by day 15 th postpartum. Plasma T 3 and T 4 concentrations decreased from day 25 prepartum to the day of kidding which increased by day 25 postpartum. Conclusion: Plasma estradiol was positively correlated with cortisol and T 4 indicating that changes in cortisol and T 4 levels contribute to increase in estradiol prior to delivery and therefore may directly influence the process of parturition.