Abstract
An experiment was carried out to investigate the relationships between the secretion pattern of sex hormones and infertility in cows.
Nine repeat breeding cows and two normal cows obtained from individual farms were inseminated experimentally. The animals, except one which was held under observation up to 70 days after insemination, were autopsied 1528 days later, and their genital organs were examined. The levels of estrogen and gestagen in the peripheral blood plasma were assayed by the method of SULMAN et al. and of HOOKER & FORBES.
In one of nine repeat breeding cows, a dead fetus was found in the uterus, but not any other cows had fetus or any other conceptus. There was no evidence of bacterial infections in the uterus and oviduct of any of all these cows. Of two normal cows, one had a fetus developed normally in the uterus, and the other continued the normal pregnancy up to days after insemination. At estrus, estrogen levels in the fertile cows reached a maximum 23 days before ovulation. It decreased rapidly to a minimum immediately after ovulation. In the infertile cows, however, the time showing the maximum levels was later 12 days than that of the fertile cows. It appeared on the day of ovulation in four of eight cows. In the infertile cows, except one, the time exhibiting the minimum levels was also late, which appeared 13 days after ovulation. Estrogen levels observed in the luteal stage following insemination were classified to the two groups; i.e. a high estrogen group, and a low estrogen group. The normal pregnant cows were belonged to the later group and the cow having a dead fetus in the uterus to the former group. The gestagen levels showed a peak at around estrus in all three fertile and six of eight infertile cows, almost simultaneously with, or a little later than, the time of estrogen peak. In the luteal stage following insemination, the gestagen levels were relatively high in six infertile cows which formed a peak at estrus, but low in other two infertile cows. In two normal pregnant cows, the gestagen levels increased with advance of the pregnancy, and was maintained at a high level. However, it remained at a low level in the cow having a dead fetus in the uterus.
From these results, it may be postulated that when some abnormal secretions of estrogen and gestagen occurred before and after ovulation, fertilization failure or death of fertilized ova might be induced, and that when it occurred in the luteal stage following insemination, early embryonic death might be induced.
