Immediate and delayed effects of heat stress on follicular development and its association with plasma FSH and inhibin concentration in cows.

摘要: The aim of this study was to characterize the immediate effects heat stress on plasma FSH and inhibin concentrations, its involvement in follicular dynamics during a complete oestrous cycle, examine possible delayed effect development. Holstein dairy cows were synchronized randomly assigned either cooled (n = 7) or heat-stressed 6) treatment groups. During control cows, which cooled, maintained normothermia, whereas exposed direct solar radiation, developed hyperthermia. At end cycle (treated cycle), both groups normothermia for first 10 days subsequent cycle. Throughout period, development examined by ultrasonography, samples collected. second wave treated significantly larger cohort medium sized follicles (6-9 mm) found than (P /= mm), preovulatory surge higher < 0.01). also observed cycle: postovulatory concentration 0.01), but fewer developed, decreased at slower rate previously (0.40 0.71 per day, respectively). This shows dynamics, associated with high low concentrations plasma. These alterations may have physiological significance that could be fertility cattle summer autumn.