Abstract
It has been known that the life span of the corpus luteum is prolonged after hysterectomy in various species of animals. In the goat, however, the effects of hysterectomy have been studied only on the corpus luteum of pregnancy.
In the present study, the effect of hysterectomy on the function of luteum of estrous cycle was investigated by measuring progesterone (P) levels in the peripheral venous blood in shiba-goats.
Three animals were used, one was on Day 2 and next one was on Day 4 of the estrous cycle, and the last one was in anestrus (Table 1). They were hysterectomized under xylazine and fluothane anesthesia (Figs. 1-3).
After hysterectomy, P levels in the peripheral venous blood were measured by radioimmunoassay (RIA) every day for 25 consecutive days after operation and at 2-3 days interval thereafter.
In two cyclic goats in which corpus luteum or corpus hemorrhagicum was found at operation, P levels were maintained in a range of 0.7-3.9 ng/ml for about 50 days after hysterectomy (Figs. 4, 5) and during which time the estrus did not return. In an anestrous goat in which no corpus luteum was present, low P levels (about 0.5ng/ml) were maintained.
From these results, it was suggested that the luteolytic factors should have its origin in the uterus in case of shiba-goats in the cycle.
