Sexually inexperienced bucks, photostimulated or not, showed increased plasma testosterone and sexual behaviors with nulliparous and multiparous goats outside of breeding season

Abstract

The objectives of this study were to determine whether sexually inexperienced photostimulated and nonphotostimulated males had increased plasma testosterone levels and sexual behaviors during their first contact with nulliparous (N) and multiparous (M) females and whether these males could induce sexual responses in females outside of breeding season. Six photostimulated (PH) males were artificially subjected to long days (16 h/light/day/2.5 months), and six nonphotostimulated (NO) males were exposed to the natural photoperiod. Three PH males were exposed to N females (n = 30), and three PH males were exposed to M females (n = 30). Three NO males were exposed to N females (n = 30), and three were exposed to M females (n = 30). In spring (March-April), the males and females remained together for 15 days. The PH males had increased plasma testosterone levels compared to baseline levels during first contact with the N (10.8 ± 2.6 ng/mL) and M females (9.3 ± 1.9 ng/mL) (P < 0.001). Similarly, the NO males had increased plasma testosterone levels during their first contact with N (11.4 ± 1.1 ng/mL) and M females (11.0 ± 0.6 ng/mL) (P < 0.001). Nudging, anogenital sniffing, and mounting attempts varied between the PH and NO males (P < 0.001), whereas mounting with intromission did not differ (P > 0.05). Estrous behavior and ovulation did not differ between N and M females in contact with PH males or between M females in contact with NO males (P > 0.05), whereas the N females in contact with NO males had the lowest response (P < 0.05). We conclude that sexually inexperienced photostimulated and nonphotostimulated males exhibit increased plasma testosterone levels; exhibit sexual behaviors during their first contact with nulliparous and multiparous females; and can stimulate sexual activity in females outside of breeding season.