PARENT SESSION
SLIDE SESSION 7: REPRODUCTIVE TECHNOLOGIES
Chairs: Nicola Dean, Jay Baltz, Jamie Cowell (Trainee)
Univ Ottawa-Lamoureaux 122
2:30 PM-4:30 PM
52
SHORT-TERM OVARIAN SUPPRESSION WITH LEVONORGESTREL BEFORE GONADOTROPIN STIMULATION ENHANCES IVF EMBRYO PRODUCTION IN THE DOMESTIC CAT.
Pelican, Katharine1,2, Spindler, Rebecca1, Wildt, David1, Ottinger, Mary Ann2, Howard, JoGayle1, 1 2
ABSTRACT- This study explored approaches for eliciting a more consistent ovulatory/embryo production response after exogenous gonadotropin therapy in the domestic cat. The hypothesis was that short-term estrous cycle suppression with levonorgestrel (Norplant®) or a GnRH antagonist (Antide) prior to equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG) improves ovarian and IVF response. Queens were assigned to one of three treatments: 1) control (C), eCG/hCG only (n = 9 cats); 2) Norplant® (N), six rods implanted for 37 days + eCG/hCG (n = 9); and 3) Antide (A), two 6 mg/kg injections 15 days apart + eCG/hCG (n = 9). Laparoscopy was used to record ovarian activity and to aspirate oocytes that were graded 1-4 (1 = excellent). In 5 cats/group, half of Grade 1 oocytes (n = 41) were assessed for glucose (glu), pyruvate (pyr) and lactate (lact) metabolism using a microfluorescence assay followed by nuclear maturation assessment. Remaining oocytes (n = 185) were inseminated in vitro and assessed for cleavage at 72 h. There were more (P < 0.05) follicles/ovary in N (mean ± SEM; 8.7 ± 0.8) than C (4.4 ± 0.7) or A (5.7 ± 0.6) groups. Treatment had no effect (P > 0.05) on the incidence of premature ovulations (corpora lutea). Oocyte recovery (total oocytes/number of aspirated follicles) was > 25% higher (P < 0.01) in C than N and A cats, with ovaries of the latter groups having more apparently empty follicles. Oocyte quality as assessed by energy substrate uptake (pmol/h; glu, 3.4 ± 0.7; pyr, 5.4 ± 0.6; lact, 12.6 ± 1.2) and nuclear maturation (94.5 ± 2.9%) did not differ (P > 0.05) among treatments. However, number of cleaved embryos/cat was higher (P < 0.05) in N (6.4 ± 1.2) than C (2.7 ± 0.7) or A (3.2 ± 0.9) cats. Data indicate that short-term ovarian suppression in the cat with levonorgestrel before eCG/hCG therapy increases follicle number without compromising oocyte quality. Despite reduced oocyte recovery efficiency, IVF embryo yield is enhanced.
KEY WORDS: in vitro fertilization, levonorgestrel, GnRH antagonist, domestic cat