PARENT SESSION

(M712) ORAL PROGESTOGEN, ALTRENOGEST, PROVIDES SHORT-TERM INHIBITION OF OVARIAN ACTIVITY IN THE DOMESTIC CAT.

Bauer, Rosemary^{1, 2}, Pelican, Katharine¹, Wildt, David¹, Ottinger, Mary Ann², Howard, JoGayle¹, ¹ Smithsonian's National Zoological Park, Front Royal, VA² University of Maryland, College Park, MD

ABSTRACT- Pregnancy success following artificial insemination (AI) is low in endangered felids. Short-term ovarian suppression prior to gonadotropin-induced ovulation has improved AI efficiency in many species. This study assessed the influence of oral altrenogest (Regu-Mate, ALT) dosage on estrous cycle characteristics in the domestic cat using non-invasive fecal steroid monitoring. Queens were assigned to one of four treatments administered daily for 38 d: 1) 0.044 mg/kg ALT (n = 5 cats, LOW); 2) 0.088 mg/kg ALT (n = 6 cats, MID); 3) 0.352 mg/kg ALT (n = 6 cats, HIGH); and 4) placebo (n = 5 cats, control). Fecal samples were collected daily and estrogen (E) and progestin (P) metabolites quantified for 60 d before (PRE), during and 60 d after (POST) treatment. Estrus was defined as E peaks greater than 2 SD above baseline. During treatment, estrus was not suppressed in the control group (2-4 E peaks/cat), whereas no E peaks were observed during any ALT treatment. In females with elevated E on Day 1 of ALT treatment (n = 5), a normal follicular phase was completed before E concentrations returned to baseline by Day 6 and remained suppressed. All cats receiving ALT returned to estrus after treatment withdrawal. However, MID cats exhibited a more synchronized response (estrus within 10-16 d) than LOW (2-12 d) or HIGH (9-35 d) cats. Number (± S.E.M.) of E peaks during the POST period was greater (P < 0.05) in LOW (2.8 ± 0.2 peaks/60 d) and MID (2.5 ± 0.3), but not HIGH (2.3 ± 0.3) cats, compared to controls (1.6 ± 0.4). Nonetheless, number of POST E peaks within a treatment did not differ (P > 0.05) from PRE values. Mean (± S.E.M.) peak E during estrus did not differ (P > 0.05) across time (455.3 ± 26.5 ng/g dry feces). Overall, baseline E and P concentrations were 191.3 ± 8.3 ng/g and 3.0 ± 0.2 g/g dry feces, respectively. Following ALT treatment, mean baseline E was elevated (P < 0.05) in HIGH cats (PRE, 160.5 ± 6.3 ng/g vs. POST, 185.9 ± 9.6 ng/g dry feces). In contrast, baseline E was similar (P >0.05) across time in LOW (213.6 ± 28.9 ng/g dry feces) and MID (199.35 ± 13.6 ng/g dry feces) cats. Fluctuations in baseline P were not observed (P > 0.05) across time in any treatment. Results indicate that altrenogest provides rapid, reversible inhibition of ovarian activity in the domestic cat and may be useful for estrous cycle control prior to ovulation induction and AI in felids.

KEY WORDS: cat, altrenogest, fecal steroids, estrous cycle control