Food and water consumption and the reproductive performance of the heat-acclimated female rat

Food and water consumption, estrus cycle length and regularity, mating rate, number of corpora lutea and morulae and early blastocytes on day 4 of pregnancy, were studied in a group of heat-acclimated female rats (35 ± 1°C). The results were compared with those of rats maintained at control temperature (22 ± 2°C). The heat-acclimated animals consumed the same quantity of food per 100 g of body weight as the controls. Water consumption in the heat was higher. Duration of estrus cycle was prolonged by 24% (p < 0.001), while the number of days associated with proestrus and estrus smears during the experimental period was smaller by 14% and 20% (p < 0.001), respectively. The number of days associated with metestrus and diestrus smears was larger by 25% and 24% (p < 0.001) respectively, in the heat-acclimated group as compared with controls. Mating rate was 47% lower (p < 0.01) in the 35°C group. There was no difference between the two groups in the number of corpora lutea, although the number of 4-day old morulae and early blastocysts in the heat-acclimated rats was 25% smaller (p < 0.01) than that of the control animals.