Yearling rams initially disinterested in estrous ewes subsequently exhibitsubnormal sexual performance

Sexual performance tests are useful in describing and predicting relative d ifferences in the sexual performance of male ungulates. A significant perce ntage of domestic yearling rams are sexually inhibited when first exposed t o estrous ewes. The following study demonstrates that such sexually-inhibit ed yearling rams subsequently exhibit subnormal sexual performance once the y become sexually active. Individual 30-min sexual performance (serving cap acity) tests were administered to 73 Targhee rams at 18-19 months of age. F orty-one rams (56%) successfully mated with estrous ewes on first exposure (Test 1). Seventeen rams (23%) commenced servicing ewes on Tests 2, 3 or 4. Of the remaining 15 rams, 12 attained ejaculations in subsequent tests but only after being housed continuously with females. These three groups of r ams were compared for frequency of mounts with and without ejaculation plus a measure of mount efficiency (mounts per ejaculation) during the third an d fourth tests in which they serviced females. Rams that successfully mated in Test 1 subsequently exhibited higher frequencies of ejaculation (P < 0. 05) than rams that attained ejaculations for the first time in Tests 2, 3 o r 4 or after continuous exposure to females. Ejaculation frequencies were s imilar for the two delayed groups. The three groups did not differ for moun ts without ejaculation or mating efficiency. It was concluded that the sexu al performance of yearling rams who initially fail to mate with estrous ewe s is likely to be subnormal relative to the sexual performance of rams who successfully mate when first exposed to females. (C) 1999 Elsevier Science B.V. All rights reserved.