Ovarian Activity, Circulating Hormones and Sexual Behavior in the Cat. II. Relationships During Pregnancy, Parturition, Lactation and the Postpartum Estrus

Publisher Website
Google Scholar
Abstract
Endocrine, ovarian and behavioral responses of cats throughout a mated estrus, pregnancy, parturition, lactation, weaning and the postpartum estrus were studied. Blood samples were analyzed for serum luteinizing hormone (LH), progesterone and estradiol-17.beta. and laparoscopy was used to monitor follicle and corpus luteum (CL) development. Mean (.+-. SEM) duration of the initial mated estrus (5.4 .+-. 0.4 days) was longer (P < 0.05) than the postpartum estrus (3.8 .+-. 0.5 days). Following 3 daily matings throughout each estrus, all cats (12/12) ovulated at the initial estrus and 6 of 8 cats ovulated at the postpartum estrus. The ovulation to parturition interval was 64.2 .+-. 0.4 days (n = 12) and the average litter size was 3.3 .+-. 0.4 kittens. No queen demonstrated estrous behavior during the 6-wk lactation interval. Postpartum laparoscopy indicated that 4 of 12 and 3 of 12 queens had more and fewer CL, respectively, than were detected at the end of the mated estrus. Seven of 8 queens demonstrated estrous behavior within 10-27 days following weaning. The 8th queen had a 133-day weaning to estrus interval. Although 2 of 8 queens failed to ovulate at the postpartum estrus, average CL number for the ovulating queens was not different from that observed at the initial mated estrus. From the initial mated estrus through the 1st half of pregnancy, serum LH and estradiol-17.beta. profiles mimicked patterns reported earlier in queens mated with vasectomized male and experiencing a prolonged luteal phase. Both serum LH and estradiol-17.beta. concentrations became more variable during the 2nd half of gestation and a distinct estradiol-17.beta. surge was detected within the 9-day interval before parturition in 6 of 12 queens. Individual cats varied considerably in their serum progesterone profiles with peak concentrations occurring from days 11-60 (day 1 = 1st day of estrus and mating). Although progesterone titers approached nadir near term pregnancy in the majority of queens, baseline concentrations were not a prerequisite for the onset of parturition. During the 6-wk lactation interval, temporal fluctuations in serum LH and progesterone, and evidence of distinct ovarian follicle development were negligible. Low amplitude, episodic increases in estradiol-17.beta. were measured at 10- to 18-day intervals during this time. Weaning resulted in a reflex elevation in serum LH and estradiol-17.beta. in 6 of 8 cats. Estradiol-17.beta. profiles during the postpartum estrus were similar to the initial estrus. The postovulatory rise in progesterone at the postpartum estrus was delayed and progesterone concentrations measured during the 1st wk after the postpartum estrus were less than half the magnitude detected at the initial estrus. Events associated with pregnancy and the postpartum interval of the cat are correlated. Suckling during lactation could be a potent inhibitor of ovarian follicle development and gonadal and pituitary hormonal secretion, this negative effect being eliminated by weaning. Reproductive efficiency is compromised at the postpartum estrus, as illustrated by delayed or abbreviated estrus, ovulation failure and depressed postovulatory elevations in serum progesterone.