Effect of the presence of a dominant bull on performance of two age group bulls in libido tests

It is not clear if the presence of a dominant bull affects in different way s the sexual behavior of two age groups of young bulls, and if its effect i s different when this mature bull is maintained in an adjacent pen, rather than when he has physical contact. Twelve 15 month old and ten 27 month old sexually naive Simmental bulls were libido tested under the presence or ab sence of a dominant bull under two trials: (1) individual sexual performanc e tests were conducted, On alternate tests days, a mature bull was present in an adjacent pen where the stimulus female stanchion was attached, In tri al (2), same age animals, as a group, were exposed to a female, and on alte rnate test days, a mature bull was present, allowing physical contact with the tested bulls. In trial (1), no difference was found in sexual behavior activities or libido scores within age groups between treatments (P > 0.05) . Nevertheless, in the older age group, the time spent close to the stimulu s female was reduced during mature male presence (P = 0.02). In trial (2), both age groups of bulls were affected by the physical presence of the matu re bull, reducing the number of times that the animals were seen in sexual proximity with the stimulus female (P < 0.01). It was concluded that the se xual behavior of both age groups was affected in different ways when a domi nant bull was present. (C) 1999 Elsevier Science B.V. All rights reserved.