HETEROSEXUAL EXPERIENCE DIFFERENTIALLY AFFECTS THE EXPRESSION OF SEXUAL-BEHAVIOR IN 6-MONTH-OLD AND 8-MONTH-OLD RAM LAMBS

The sexual performance of 6- and 8-month-old ram lambs (175 and 26 sub jects, respectively) was quantified when individually exposed to four estrous ewes for 30 min on four occasions 7 days apart. In addition, h alf of the animals in each age class (experimental subjects) were expo sed to 16 estrous females for 6, 16 or 24 h after testing on Test Days 1, 2 and 3. Control subjects received no additional exposure to femal es. Sexual performance improved for all groups over the 4 weeks of tes ting. However, 6-month control rams improved at a slower rate than 6-m onth experimental rams. By the fourth weekly test, 58% of the control rams and 85% of the experimental rams had attained ejaculatory compete nce. Treatment did not affect the sexual performance of the 8-month-ol d subjects; both control and experimental groups had attained 100% eja culatory competence by the fourth week. Length of the extended exposur e to females did not affect the results. It was concluded that the sex ual responsiveness of ram lambs toward females is sufficiently undevel oped at 6 months (i.e. puberty) that extended exposure to sexually rec eptive ewes is needed for many males to exhibit adult levels of sexual performance. At 8 months, the sexual development of ram lambs has suf ficiently matured so that relatively brief encounters with estrous fem ales releases the full expression of adult sexual behaviors. These fin dings may be of benefit to sheep breeders who wish to use ram lambs in their breeding programs.