108 Use of seminal plasma as ovulation inductor in alpacas (Vicugna pacos) embryo recipient and its effect on pregnancy rate

Abstract

Alpacas, like other camelids, are classified as induced ovulators because an external stimulus is required for the occurrence of ovulation. Recent studies have identified the β-nerve growth factor (β-NGF), a protein present in the seminal plasma (SP), as responsible for inducing ovulation in this species and having potent luteotropic function. We speculate that SP can be used in reproductive biotechnologies, such as embryo transfer (ET), to increase the number of genetically superior animals produced in breeding programs. The objective of this study was to evaluate the effect of inducing ovulation with SP or a gonadotrophin-releasing hormone (GnRH) analogue on pregnancy rate in recipients of an alpaca ET program. Semen from 5 adult male alpacas was collected with an artificial vagina and diluted 1:1 (v/v) with phosphate-buffered saline (PBS; Gibco-BRL). The diluted semen was centrifuged for 30 min at 1200 g, and the supernatant or SP was decanted and examined for absence of sperm. Then, the SP was centrifuged again for 20 min at 1200 × g. The SP was stored at −80°C until the use. Female alpacas (n = 38; 6-8 years) with a body condition score of 2.5-3.5 (scale 1-5) were used for the experiment. Animals were evaluated daily by transrectal ultrasonography to determine the presence of a dominant follicle ≥7 mm and randomly assigned to one of two groups: (1) GnRH (n = 20), 0.04 mg of Buserelin acetate IM, or (2) SP (n = 18): 1.0 mL of seminal plasma IM. Seven days after GnRH or SP treatment (Day 0) the recipients received a fresh embryo. Alpaca donors (n = 18) were given GnRH (0.04 mg IM) and treated 36 h later with 700 IU of equine chorionic gonadotropin (ECG). Donors were mated with fertile males 5 days after ECG (Day 0 of recipients), and embryos were recovered 7 days later. Embryos of similar quality were assigned to both groups and transferred nonsurgically to the uterine horn ipsilateral to the corpus luteum. Ultrasonography examinations were performed on Day 2 to confirm ovulation and Day 25 to determine pregnancy in all of the recipients. Data was analysed by chi-squared test. Ovulation rate was not different between groups (100% each). Pregnancy rate was 45% (9 out of 20) and 44% (8 of 18) in GnRH and SP groups, respectively (P = 0.77). In conclusion, SP was effective to induce ovulation in alpacas and was able to produce a pregnancy rate similar to that of GnRH as an ovulation-inducing treatment. Thus, SP can be used as an alternative for ET programs in alpacas.

Research was funded by the project Role of Seminal Plasma in Reproductive Physiology and Application of Biotechnologies in Camelids (149-2017-CIENCIACTIVA).