The use of altrenogest to avoid hyperestrogenism after eCG/hCG ovulation induction in southern tigrina (<I>Leopardus guttulus</I>)

Abstract

The goal of this study was to optimize an ovulation induction protocol for use with artificial insemination (AI) in the southern tigrina (Leopardus guttulus). The specific aims were to demonstrate the efficacy of using altrenogest, an oral progestin (Regumate®, MSD Animal Health/ Merck Animal Health) to suppress ovarian activity and prevent follicular hyperstimulation and hyperestrogenism after the administration of exogenous equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG). To monitor ovarian responses, fecal estrogen and progestogen metabolites were quantified by enzyme immunoassay in females before and after i.m. administration of 200 IU eCG/150 IU hCG in two trials, four months apart. During the first trial, there was no use of altrenogest, only the eCG/hCG ovulation induction protocol. In the second trial, the ovulation induction protocol was preceded by the administration of oral altrenogest for 14 days (minimum of 0.192 mg/kg/day). Altrenogest administration resulted in a suppression of follicular activity in three out of six females prior to eCG/hCG administration, based on lower mean estrogen concentrations (p&lt;0.05). It also resulted in four out of six females presenting lower fecal estrogen metabolite concentrations (p&lt;0.05) after ovulation induction, and two out of six individuals showed a reduction (p&lt;0.05) in post-ovulatory fecal progestogen metabolite concentrations, all when compared to the same female&#39;s cycles without the progestin. Fecal estrogen metabolite concentrations were closer to baseline in 50% of these individuals following altrenogest and eCG/hCG treatments when compared to basal concentrations before gonadotropins without the use of altrenogest. This study demonstrated that use of altrenogest in southern tigrina can suppress ovarian activity and avoid hyperestrogenism after administration of eCG and hCG treatment. However, not all females responded uniformly, so more studies are needed to increase the efficacy of ovulation induction for use with AI in this species.