Effect of early fenceline exposure to estrous ewes on the sexual performance of yearling rams

Previous research has demonstrated that early heterosexual (mating) experie nce improves the sexual performance of yearling rams. The present study exa mines the effect of early fenceline (FL) contact of young ram lambs with es trous females on their sexual performance as yearlings. A total of 104 rams , 7-8 months of age, were given either no contact (NC), direct contact (DC) or FL exposure to estrous ewes during a 3-week period in the fall breeding season. When initially tested for sexual performance as yearling rams at 1 8-19 months, 8 of 21 (38%) FL rams exhibited no sexual interest in estrous females (did not court or mount females), a result that was intermediate to and not significantly different from (P > 0.05) the incidence of sexual di sinterest exhibited by NC (59%) and DC rams (15%). The difference between N C and DC rams was significant (P < 0.002). In addition, 12 of 21 (57%) year ling FL rams initially mounted estrous ewes, a result that was intermediate to and not significantly different from (P > 0.05) the incidence of mounti ng by NC and DC males (41% vs. 85%, respectively). Again, NC and DC rams di ffered from one another (P < 0.002). Treatment did not affect frequencies o f mounting with and without ejaculation by the sexually active rams (P = 0. 11 and 0.36, respectively). FL rams that were sexually inactive in year 2 s pent less time (P < 0.02) in year 1 within a body length of the fence separ ating them from the ewes than FL rams that were sexually active in year 2. FL proximity scores in year 1 were positively correlated (r(s) = 0.49; P < 0.05) with ejaculation frequencies in year 2. It was concluded that early F L contact with ewes only partially substitutes for direct heterosexual (mat ing) experience in enhancing the sexual performance of yearling rams. Also, measures of FL proximity to estrous ewes can serve as an aid in predicting relative levels of sexual performance in rams. (C) 1999 Elsevier Science B .V. All rights reserved.