BIOLOGY OF OVARIAN CYCLES, PREGNANCY AND PSEUDOPREGNANCY IN THE DOMESTIC CAT

Puberty in the female cat occurs between the ages of 8 and 10 months. Cats are seasonally polyoestrous, reflex ovulators. The oestrous cycle can occur as often as every 2-3 weeks. Ovulation usually occurs 24-36 h after copulation, and implantation occurs 12-13 days after copulati on. The duration of gestation in the cat is 64-67 days (average 66 day s). The corpora lutea secrete increasing amounts of progesterone, star ting 1-2 days after ovulation. If implantation occurs, progesterone co ncentrations continue to increase throughout days 25-30, then slowly d ecline throughout the rest of pregnancy. In the absence of pregnancy, the corpora lutea reach their peak progestational activity within 10-1 5 days and then decline, with basal progesterone values being noted by days 30-35. Relaxin is produced by the fetoplacental unit beginning a t about day 20 of gestation and continuing throughout the rest of preg nancy. Prolactin production increases from about day 35. Like those of prostaglandin F2alpha, concentrations of prolactin plateau at about d ay 50 and increase abruptly just before delivery.