108 COMPARATIVE EFFICIENCY OF GONADOTROPIN-RELEASING HORMONE AND LUTEINIZING HORMONE IN THE INDUCTION OF OVULATION IN SUPEROVULATED ALPACAS

Abstract

Alpacas are induced ovulators, responding to copulation and (or) exogenous application of ovulation-inducing hormones. The objective of this study was to determine the efficiency of the injection of a gonadotropin-releasing hormone (GnRH) agonist versus LH in the induction of ovulation and the presence and size of non-ovulated follicles at the time of embryo collection and its relationship to the yield of transferable embryos in superovulated alpacas. Twenty-one adult (3 to 7 years old) female alpacas under extensive grazing at 4300 m elevation in the Peruvian Andes that had been synchronized and treated for superovulation were induced to ovulate 6 days after the application of the superovulatory hormone (1000 IU of eCG, Folligon^®, Intervet International BV, Boxmeer, the Netherlands) by mating with fertile males and injection immediately after copulation of either an IM dose of 0.0084 mg of buserelin acetate (Buserelina Zoovet^®, Laboratorio Zoovet, Santa Fe, Argentina) to 10 alpacas (T1) or an IM dose of 5-mg Armour standard of LH (Lutropin^®, Bioniche Animal Health, Belleville, ON, Canada) to 11 alpacas (T2). All alpacas had a second mating 12 h after the first mating and were subjected to ovarian inspection by ultrasonography and previous embryo collection by nonsurgical transcervical embryo flushing 6.5 days after the first mating. On average, the embryo recovery rate for T1 was 34.6% and there were 7.8 ± 3.99 corpora lutea (CL), 2.7 ± 4.08 collected embryos, and 3.6 ± 2.95 total, 0.5 ± 0.85 small (<6 mm), 1.8 ± 1.99 medium (≥6 but ≤14 mm), and 1.3 ± 2.11 large (≥15 mm) non-ovulated follicles. For T2, the embryo recovery rate was 59.4% and there were 6.73 ± 1.49 CL, 4.0 ± 2.57 collected embryos, and 0.64 ± 0.81 total, 0.0 ± 0.0 small, 0.36 ± 0.67 medium, and 0.27 ± 0.47 large non-ovulated follicles. The differences between treatments were nonsignificant (P > 0.05) for all the parameters; however, there was a clear tendency for a better recovery rate, more embryos collected, and lower number of non-ovulated follicles in T2. The Pearson correlation coefficient between the presence of large follicles in the ovaries at the time of embryo collection and the total number of embryos collected was negative (r = –0.26) and highly significant (P ≤ 0.001). The use of LH for ovulation induction of superovulated alpacas seems to be more advisable than the use of GnRH agonist; further comparisons with larger number of observations per treatment are recommended.

This study was financed by the Peruvian Fund for Innovation, Science and Technology (FINCYT).