58 OVARIAN DOWN-REGULATION WITH ORAL PROGESTIN FOR FIXED-TIME LAPAROSCOPIC OVIDUCTAL ARTIFICIAL INSEMINATION WITH FRESHLY COLLECTED AND FROZEN-THAWED SPERMATOZOA IN DOMESTIC CATS

Abstract

Laparoscopic oviductal AI (LO-AI) with low numbers of freshly collected or frozen-thawed spermatozoa has resulted in high pregnancy success (50–70%) in domestic cats. However, proper timing of AI depends on identifying anestrual, non-luteal queens before exogenous gonadotropin injection, confounding AI scheduling and limiting applicability with felids housed at distant institutions. Recent research (Stewart et al. 2012 Biol. Reprod. 87, 1–11) has shown that daily oral progestin treatment is effective for down-regulating ovarian activity in cats and allowing synchronized stimulation with exogenous gonadotropins. Our study objectives were to (1) assess the effect of oral progestin treatment on pregnancy success following LO-AI in domestic cats and (2) compare relative fertility following LO-AI of each female with low numbers of freshly collected versus frozen-thawed spermatozoa. Young (<2 years old), nulliparous domestic cats were assigned to either control (Con; n = 8) or oral progestin (OP; n = 7) treatment groups. Con females were monitored daily for behavioural oestrus and blood samples from anestrual females assessed for progesterone concentration to confirm non-luteal status before exogenous gonadotropin treatment [100 IU of eCG followed 85 h later with 1000 IU of porcine LH (pLH)]. Oral progestin females were fed altrenogest (Regu-Mate; 0.088 mg kg^–1 of body weight) mixed in moist cat food for 38 consecutive days and then treated with exogenous gonadotropins 6 days after altrenogest cessation. At 31 to 33 h post-pLH treatment, each female was inseminated via laparoscopy in 1 oviduct with freshly collected sperm (motile) from 1 male and frozen-thawed sperm (motile; frozen in a soy lecithin-based cryomedium) from a second male. Ultrasonography was conducted approximately Day 21 post-AI for pregnancy diagnosis. Pregnant females were spayed immediately and recovered fetuses assessed for paternity using short tandem repeat molecular marker analysis to determine relative fertility of fresh versus frozen semen. All females ovulated following gonadotropin treatment, averaging ( ± standard error of the mean) 20.6 ± 1.7 corpora lutea per queen. Most [12/15 (80%)] females conceived following LO-AI, producing an average of 8.1 ± 1.4 implantations and 5.9 ± 1.2 fetuses per pregnancy. There was no difference (P > 0.05) between Con and OP cats in pregnancy success [Con: 6/8 (75%); OP: 6/7 (86%)] or in mean implantation number (Con: 6.0 ± 1.8; OP: 10.2 ± 2.0) or fetal number (Con: 4.3 ± 1.6; OP: 7.5 ± 1.6) in pregnant cats. Paternity assessment revealed that freshly collected and frozen-thawed spermatozoa were equally effective (P > 0.05) in producing pregnancies (fresh: 11/15 (73%); frozen: 10/15 (67%)], with no difference (P > 0.05) in total fetal numbers [fresh: 37/69 (54%); frozen: 32/69 (46%)]. These results indicate that oral progestin treatment may be used to down-regulate ovarian function in felids for fixed-time AI without compromising fertility in vivo, and that LO-AI with low numbers of cat sperm frozen in a soy lecithin medium may produce high pregnancy percentages and normal litter sizes.