Ž . Applied Animal Behaviour Science 64 1999 235–240 Yearling rams initially disinterested in estrous ewes subsequently exhibit subnormal sexual performance Edward O. Price ) , Agustin Orihuela 1 , Valli Parthasarathy 2 , R. Borgwardt, M.R. Dally 3 Department of Animal Science, UniÕersity of California, DaÕis, CA 95616-8521, USA Accepted 12 April 1999 Abstract Sexual performance tests are useful in describing and predicting relative differences in the sexual performance of male ungulates. A significant percentage of domestic yearling rams are sexually inhibited when first exposed to estrous ewes. The following study demonstrates that such sexually-inhibited yearling rams subsequently exhibit subnormal sexual performance once they Ž . become sexually active. Individual 30-min sexual performance serving capacity tests were Ž . administered to 73 Targhee rams at 18–19 months of age. Forty-one rams 56% successfully Ž . Ž . 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 rams were compared for Ž frequency of mounts with and without ejaculation plus a measure of mount efficiency mounts per . ejaculation during the third and fourth tests in which they serviced females. Rams that Ž . 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 or 4 or after continuous exposure to females. Ejaculation frequencies were similar for the two delayed groups. The three groups did not differ for mounts without ejaculation or mating efficiency. It was concluded that the sexual performance of yearling rams who initially fail to mate with estrous ewes is likely to be ) Corresponding author. Tel.: q1-530-752-6789; e-mail: eoprice@ucdavis.edu 1 Present address: Pedro de Alvarado 204-A, Col. Lomas de Cortes, Cuernavaca, Morelos 62240, Mexico. 2 Present address: Department of Psychology, 228 Psychology Building, University of Georgia, Athens, GA, 30602-3013, USA. 3 Present address: UC Hopland Research and Extension Center, 4070 University Rd., Hopland, CA 95449, USA. 0168-1591r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0168-1591 99 00041-6