128 BOVINE SEMINAL PLASMA INDUCES OVULATION IN LLAMAS

Abstract

Ovulation-inducing factor (OIF) is a protein present in the seminal plasma of several species, including llamas, alpacas, pigs, cattle, sheep, horses and rabbits. In an initial study (Ratto et al. 2006 Theriogenology 66, 1102–1106), bovine seminal plasma induced ovulations in 26% (5/19) of llamas compared with 0% (0/19) in the placebo group, but induced proportionately less than in llamas treated with alpaca or llama seminal plasma (100%). It is important to highlight that treatments were based on volume of seminal plasma; the actual dose of OIF was unknown. In a later study (Tanco et al. 2011 Biol. Reprod. doi:10.1095/biolreprod.111.091876), OIF from llama seminal plasma had a dose-dependent effect on ovulation rate, corpus luteum (CL) diameter and progesterone production in llamas. The present study was designed to test the hypothesis that bovine seminal plasma induces ovulation and CL development in llamas comparable with that of llama seminal plasma, based on total dose of OIF. Within species, seminal plasma was pooled from 1 to 4 ejaculates per male (n = 145 bulls, n = 4 llamas). The concentration of OIF in the pooled seminal plasma was measured by radioimmunoassay and the volume of seminal plasma used for treatment was adjusted to reach a total dose of 250 μg of OIF. Mature female llamas were assigned randomly to 4 groups and given a single intramuscular dose of 10 mL of PBS (negative control, n = 5), 50 μg of gonadotropin-releasing hormone (GnRH; positive control, n = 5), 6 mL of llama seminal plasma (n = 6), or 12 mL of bull seminal plasma (n = 6). Ovulation and CL development were monitored by transrectal ultrasonography. The incidence of ovulation was compared among groups by Fisher's exact test. Nonserial data (i.e. follicle size at treatment, maximum CL diameter, day of maximum CL diameter and first day of CL detection) were compared among groups by ANOVA. The diameter of the preovulatory follicle at treatment did not differ among groups (P = 0.10). The incidence of ovulation was 0/5, 4/5, 3/6 and 4/6 in the groups treated with PBS, GnRH, llama seminal plasma and bovine seminal plasma, respectively (P < 0.05). The incidence of ovulation did not differ among llamas treated with GnRH, llama seminal plasma, or bovine seminal plasma. Among the treatments that elicited ovulation, neither the maximum CL diameter nor the day of maximum CL diameter differed (P = 0.30 and P = 0.24, respectively). In addition, no difference was detected in the day of first detection of the CL (P = 0.25). Results document the bioactivity of OIF in the bovine seminal plasma of Bos taurus. These findings further support the notion that OIF is highly conserved among mammals and that seminal plasma exerts its effect in an OIF dose-related manner.

This research was supported by the Natural Sciences and Engineering Research Council of Canada.