Equine Chorionic Gonadotropin (eCG) improves bucks' semen quality during the nonbreeding season.

ABSTRACT

In most goat breeds, testosterone serum concentration and semen quality decrease during the nonbreeding season. However, bucks reproductive activity may be stimulated with the administration of equine chorionic gonadotropin (eCG). Therefore, the aim of this study was to determine whether the repeated administration of eCG stimulates the reproductive status of bucks during the nonbreeding season. The study was performed with 19 bucks that were assigned to a group that was treated with eCG (GeCG) and an untreated control group (GCon). The GeCG bucks received an initial dose of 800 IU of eCG (Day 0), followed by four doses of 500 IU administered every 5 days beginning on Day 5. Serum testosterone and anti-eCG antibody concentrations, testicular and seminal traits were determined until Day 60. Testosterone concentration (from Day 3 to 21 p < 0.0001), anti-eCG titre (from Day 12 to 44 p ≤ 0.01), percentage of motile spermatozoa (Day 6 p = 0.006 and 14 p = 0.001) and of spermatozoa with progressive motility (Day 6 p = 0.01 and 14 p = 0.002) and the percentage of spermatozoa with functional membrane (Day 6 p = 0.02 and 22 p = 0.008) were higher in GeCG than in GCon bucks. Also in frozen-thawed samples, the percentage of motile spermatozoa tended to be higher in GeCG than that of GCon bucks (p = 0.07). In conclusion, the administration of eCG during the nonbreeding season stimulated the secretion of testosterone and improved fresh and possibly frozen-thawed semen quality. However, it also resulted in an increase in anti-eCG antibody titre.