Biology of Reproduction, Vol 13, 470-474, Copyright © 1975 by Society for the Study of Reproduction

Luteal Activity in the Pseudopregnant Cat

¹ Department of Reproduction School of Veterinary Medicine University of California Davis, California 95616

Ovulation was induced in 5 cats by copulation with a vasectomized male and corpus luteum (CL) activity was studied by the determination of peripheral plasma progestins. Luteal activity averaged 36.5 ± 1.1 days (m ± SEM, n = 12) in duration. Progestins rose to peak levels of 25.8 ng/ml plasma at 16 to 17 days postovulation (Day 0 = estimated day of ovulation). Regression of the CL began on about Day 21 postovulatuon. Sexual receptivity (estrus) averaged 7.1 ± 0.8 days (m ± SEM, n = 12). The interestrual intervals averaged 40.7 ± 4.1 days (m ± SEM, n = 10). Sexual receptivity continued for several days despite the presence of significant levels of peripheral plasma progestins. One cat was not allowed to copulate during 2 periods of sexual receptivity. The lack of a rise in progestins in this cat supports the concept that ovulation did not occur and that the cat is an induced ovulator. Interestrual intervals were considerably shorter (13 and 18 days) as compared to interestrual intervals during the pseudopregnancy cycles (40.7 days).