Effect of early experience on the sexual performance of yearling rams

Abstract

The following study examines the effect of early sexual experience on the sexual performance of yearling rams. Forty-eight rams were given four individual 30 min exposures to estrous ewes at 10 months of age (experimental Ss). Forty-seven male counterparts were given no early heterosexual experience (control Ss). All subjects were maintained in a single all-male group from weaning (3 months of age). At 22 months of age, experienced and control rams were individually exposed to four estrous ewes for 30 min on four occasions at weekly intervals. Sexual behaviors observed included courship, mounting and ejaculation frequencies. Significantly fewer experienced rams than control rams ( P < 0.01) failed to show sexual interest in ewes on Test Day 1 (1 of 48 vs. 13 of 47 rams, respectively). In addition, sexually active experienced rams exhibited higher ( P < 0.01) rates of ejaculation than sexually active control rams on all four test days ( x = 4.17 vs. 3.45 per 30 min , respectively). Follow-up studies on non-performing rams revealed that continuous exposure to ewes usually activated sexual interest in females. It was concluded that lack of exposure to ewes during early development can inhibit the expression of sexual behavior in rams. This effect has not been reported in the sexual development of male cattle and swine.