Efficacy, safety and interval from end of treatment to estrus in cats treated with an ultra-low dose megestrol acetate protocol for suppression of reproductive activityPereira, Maria (Avtor) Grassi, Anna (Avtor) Zakošek, Maja (Avtor) Contato, Giulia (Avtor) Dal Ponte, Giada (Avtor) Ghezzo, Anna (Avtor) De Cramer, Kurt G. M. (Avtor) Romagnoli, Stefano E. (Avtor) catsreproduction controlprogestogensmegestrol acetatecontraceptionCat breeders need safe, predictable and fully reversible temporary control of reproduction in queens. Megestrol acetate (MA), a short-acting progestogen was investigated in this study designed to determine whether low-dose treatment is both effective and safe in cats for periods up to 6 months. Twenty-eight queens were treated orally with 11.5 μg/kg/day of MA for one to six months. A physical examination, vaginal cytology, and reproductive ultrasound were performed before, during and after treatment, whilst urinalysis and hematological/biochemical tests, including progesterone assay, were performed before and after treatment. MA suppressed reproductive function effectively in 27/28 queens. Transient mammary and uterine hyperplasia were detected in four (14 %) and three (11 %) queens, respectively, treated for more than four months, without associated clinical signs. Pyometra was observed in only one queen following her first estrus cycle post-treatment. Significant but reversible weight gain was observed in 85 % of the animals. The resumption of cyclicity occurred on average 6 weeks after the end of treatment but was influenced by the duration of treatment and seasonality. An ultra-low dose MA treatment was effective in suppressing estrus in queens treated up to 6 months. Close monitoring should be paid to queens treated for longer than 4 months as the incidence of side effects, albeit minor and manageable, increases thereafter. Mammary gland assessment and progesterone assay are indispensable before treatment. Fertility is preserved, making MA a valuable option for temporary control of reproductive activity in queens, who otherwise cycle continuously leading to both unwanted behavior and pregnancies.20252025-07-21 10:52:43Članek v reviji170892UDK: 618.2/.7:636.09ISSN pri članku: 1879-3231DOI: 10.1016/j.theriogenology.2025.117530COBISS_ID: 243038467sl