REPRODUCTION IN THE QUEEN REVISITED: INSIGHTS INTO OVULATION, HORMONAL CONTROL, REPRODUCTIVE BEHAVIOR AND VAGINAL CYTOLOGY

Female cats are seasonal polyestrous long-day breeders. Reproductive activity is dependent on the photoperiod, with periods of active cyclicity between mid to late Winter and early Autumn in the Northern Hemisphere. Queens typically cycle every 2–3 weeks unless ovulation occurs—either spontaneously or induced by mating—in which case non-gestational or gestational diestrus ensues, respectively. Following pregnancy and weaning, queens quickly resume cyclicity, allowing for multiple pregnancies within a single reproductive season. This rapid return to fertility facilitates unplanned and undesired matings. In stray populations, such reproductive traits contribute to overpopulation, with associated public health and wildlife conservation concerns. In privately owned or breeding cats, the accelerated reproductive rhythm may result in unwanted pregnancies that conflict with breeding regulations and compromise animal health. The need for effective methods of reproduction control in this species is evident. While surgical gonadectomy remains the most widely employed approach, the pursuit of medical and reversible alternatives drove the focus of this work. This doctoral thesis explored key features of female cat reproduction, including ovulation, medical contraception, behavioral responses to sterilization, and the role of vaginal cytology in clinical reproductive assessment. The main aim was to advance understanding of queens’ reproductive physiology and their response to contraceptive drugs, thereby supporting the safe use of reversible, pharmacological options for feline reproduction control. The thesis is organized into five studies. The first investigated spontaneous ovulation in queens using 31 serum samples for progesterone assay. Progesterone levels exceeded 2.0 ng/ml in 9/31 samples without accompanying evidence of male-induced vaginal stimulation, indicating a 31% spontaneous ovulation rate in both cycling and non-cycling queens. These findings suggest that a reassessment of the traditional classification of cats as an induced-ovulation species might be considered. The second study evaluated the efficacy and implantation site effects of a 9.4 mg deslorelin subcutaneous implant for long-term, reversible sterilization. Fourteen queens received treatment at either interscapular or periumbilical sites. Reproductive activity was suppressed for an average of 790±155 days, with weight gain as the only significant side effect. No differences were observed between implantation sites. The third study assessed behavioral outcomes of deslorelin-induced pharmacological sterilization compared to surgical gonadectomy. Anonymous questionnaires were distributed to owners of surgically sterilized or deslorelin-implanted cats, addressing 19 hormone-related behaviors. Responses revealed greater behavioral improvements with pharmacological sterilization. Age at implantation emerged as a key factor influencing behavioral change. In the fourth study, megestrol acetate—a short-acting progestin—was administered orally (11.5 µg/kg daily) to 28 queens for 1 to 6 months. Estrous cyclicity was effectively suppressed during treatment and resumed on average 40 days after withdrawal, with recovery time correlating with treatment duration. Side effects were generally mild and transient, including mammary and uterine hyperplasia in queens treated for ≥4 months. One case of pyometra occurred in a spontaneously ovulating queen. Progesterone assays and full reproductive examinations proved essential for ensuring safety and predictability. Finally, vaginal cytology was evaluated using 39 smears from intact post-pubertal queens in various cycle stages. Cytological estrus was defined as ≥90% epithelial keratinization in a clear background. Neutrophils were present in all cycle phases without pathological significance. Notably, high keratinization was also observed in some anestrus samples, warranting further investigation.