Sexual behavior and semen characteristics of rams exposed to their own semen or semen from a different ram on the vulva of the ewe

Eighteen Katahdin yearling males were used. to evaluate sexual behaviors, i nter-ejaculation intervals and semen characteristics of rams exposed to the ir own semen or semen from a different ram in the vulva of the ewe. Each ra m participated in three experimental sessions spaced 8 days apart. In treat ment one, the first and second ejaculation of each individual male was coll ected with an AV (artificial vagina). In treatment two, animals were collec ted as in treatment one, but their own semen from the first ejaculation was spread on the vulva of the stimulus female immediately after the first eja culation was achieved. Treatment three was similar to treatment two, but se men from a different ram was deposited on the vulva of the stimulus female. Latency between ejaculations, number of mounts and genital sniffs before t he first and second ejaculation were recorded and both ejaculates evaluated for volume and sperm number. The inter-ejaculatory intervals in the first two treatments were longer (P = 0.01) than in the third (404.4 +/- 91.3, 39 1,7 +/- 160.2 and 211 +/- 72.4 s, respectively). No difference (P > 0.05) w as found in the number of mounts or genital sniffs before the first and sec ond ejaculation among treatments. The only significant (P > 0.05) correlati on was found between sperm concentration in the first and second ejaculatio n (r = 0.73). No difference (P > 0.05) was found among treatments between t he first and second ejaculation with respect to volume or sperm number. It was concluded that spreading semen from a different ram in the vulva of the stimulus animal was more efficient than spreading semen of the same male o r the absence of semen, in shortening the inter-ejaculatory interval. Howev er, no relationship was found between this effect and semen characteristics . (C) 2001 Elsevier Science B.V. All rights reserved.