Six lactating goats were randomly assigned to a crossover experimental design in two groups, under thermoneutral and heat stress conditions. An adaptation period of 28 days were followed by 4-periods of 14 days each, when the animals under heat stress were exposed to an average temperature of 33.34ºC; THI of 86.20; BGT of 36.18 and BT of 32.11ºC from 8 to 17 hours, including simulated solar radiation from 10 to 15 hours. There was no difference for progesterone plasma concentrations but the animals under heat stress showed a reduction of estradiol plasma concentrations as compared to the thermoneutral group. The rectal temperature of the animals under heat stress was higher when compared to the animals under thermoneutral conditions. The goats maintained progesterone plasma concentrations with reduction of estradiol secretion when exposed to repeat stress and intermittent in spite of the occurrence of hyperthermia during heat stress.
goats; estradiol-17b; progesterone; radioimmunoassay; rectal temperature
