EFFECT OF LACTATION ON OVARIAN FUNCTION IN THE RABBIT

Ovarian function was studied in thirty-eight does suckling at least four, and usually six to eight, young each. A balanced pellet diet was available at all times. Under these conditions, ripe follicles were present in the ovaries but the corpora lutea regressed rapidly following parturition and the size of the ovaries and uterus decreased as suckling continued. A basal progesterone output could not be quantified but the release of 20\g=a\-hydroxypregn-4-en-3-one,expressed as \g=m\g/govary/hr, tended to rise throughout lactation. In six of the seven suckled does which were allowed to mate post partum, pregnancy was maintained, indicating that sufficient oestrogen was produced by the follicles to maintain luteal function. The results support the concept that neither lactation nor the suckling stimulus suppresses fsh and lh release, since the presumed oestrogen production continues when adequate nourishment is available.