The influence of oral progestin (altrenogest; ALT) on cat ovarian activity was studied using non-invasive fecal steroid monitoring. Queens were assigned to various ALT dosages: (1) 0 mg/kg (control; n = 5 cats); (2) 0.044 mg/kg (LOW; n = 5); (3) 0.088 mg/kg (MID; n = 6); or (4) 0.352 mg/kg (HIGH; n = 6). Fecal estrogen and progestagen concentrations were quantified using enzyme immunoassays for 60 days before, 38 days during and 60 days after ALT treatment. Initiation of follicular activity was suppressed in all cats during progestin treatment, whereas controls continued to cycle normally. Females (n = 6) with elevated fecal estrogens at treatment onset completed a normal follicular phase before returning to baseline and remained suppressed until treatment withdrawal. All cats receiving oral progestin re-initiated follicular activity after treatment, although MID cats experienced the most synchronized return (within 10-16 days). Mean baseline fecal estrogens and progestagens were higher (P < 0.05) after treatment in HIGH, but not in LOW or MID cats compared to pre-treatment values. The results demonstrate that: (1) oral progestin rapidly suppresses initiation of follicular activity in the cat, but does not influence a follicular phase that exists before treatment initiation; and (2) queens return to normal follicular activity after progestin withdrawal. This study provides foundational information for research aimed at using progestin priming to improve ovarian response in felids scheduled for ovulation induction and assisted breeding.
Bibliographical noteFunding Information:
R.A.S. was supported by a Predoctoral Research Fellowship from the Smithsonian’s National Zoological Park and a Matching Tuition Scholarship from the University of Maryland Graduate School. Research was supported by a National Institutes of Health SERCA grant to K.M.P. ( 1KO-01-RR17310-01 ). We are grateful to Michele Sommers, Cathi Morrison and Stacey Wise for providing excellent animal care. We also thank Ryan Berger, David Kersey, Kate MacKinnon, Bernardo Mesa and Nicole Presley for technical assistance. Dry cat food was donated by the Purina Nestlé PetCare Company.
- Estrous cycle
- Fecal hormone monitoring
- Ovarian suppression