Does heterosexual experience matter for bucks' homosexual mating behavior?

Our aim was to compare bucks' homosexual mating behavior after mixing 2 groups of bucks, one that was reared in permanent contact and another in complete isolation from female goats, and determine if this behavior was related with testosterone concentration. Two groups of 1-year-old Saanen bucks were reared in permanent contact with 4 adult females until 1 week before the experiment (n = 8; group RF) or isolated from females (n = 9; group RI). When bucks were 1 year old, both groups were mixed (day 0), and mount attempts and matings were recorded on days 1, 3, 6, and 9. Testosterone concentrations were determined by radioimmnoassay from blood samples collected twice daily on days −7, 0, 1, 3, 6, and 9. Each RI male attempted to mate more RF than RI males (31.9 ± 5.1% vs. 16.7 ± 3.6%, respectively; P = 0.01), but there was no difference on the frequency in which RF males attempted to mate RI (19.4 ± 0.1%) or RF (11.1 ± 0.1%) males (P = 0.24). Similarly, RI males mated more RF than RI males (12.5 ± 2.9% vs. 5.6 ± 0.02%, respectively; P = 0.04). Furthermore, there was no difference on the frequency in which RF males mated RI (10.7 ± 8.9%) or RF (3.6 ± 0.02%) males (P = 0.23). Testosterone concentrations tended to be greater in RF than RI (P = 0.054), but no interaction between time and group was observed (P = 0.13). We propose that as RI bucks never had contact with females, they directed their sexual behavior toward other males that had the stimulating effect of the novelty. On the other hand, for RF bucks, although the novelty effect of the new bucks existed, the previous knowledge of females determined that other bucks were not considered as highly sexual attractive. This difference was not related to the differences in testosterone concentration.