Detection of oestrus in cattle by steers treated with oestrogen or testosterone.

Abstract

Animal Production in Australia DETECTION OF OESTRUS IN CATTLE BY STEERS TREATED WITH OESTROGEN OR TESTOSTERONE G.J. SAWYER* and W.J. FULKERSON*** Detection of stockmen as herds testosterone (Kiser but these methods variable response administration of (Fulkerson 1978). oestrogen-(OB) or oestrus in beef and dairy cattle is an increasing problem for become larger. Teaser bulls, or recently, animals treated with et al. 1977) have been used to assist with oestrous detection have disadvantages including spread of disease, high cost, and to testosterone. However, male behaviour has been induced by ovarian steroids in sheep (D'Occhio and Brooks 1976) and cattle The following experiments determined the effectiveness of testosterone-(T) treated steers for detecting oestrus in cattle. In a preliminary experiment, of 33 steers treated with an implant of 800 mg testosterone, an injection of 10 mg OB/week or no hormone, those treated with OB consistently detected heifers in oestrus in less time (PcO.05) and mounted them more often @<0.05) than steers treated with testosterone or controls. A second experiment examined the influence of OB on the degree of development of male behaviour in steers. Animals were injected with 0, 2, 4, 8, 16 mg OB or 250 mg T per 250 kg live weight every week for 15 weeks. They were observed in a standardised l-hour libido test 2, 4, 7, 10, 14, 18 and 21 weeks after treatment commenced. The time to first mount and the number of mounts per animal responding in the presence of oestrous hiefers were recorded and results are presented below. Steers treated with OB proved more successful than untreated or testosteronetreated steers at consistently detecting and mounting oestrous heifers. The order of response based on a consistent high number of mounts was observed in steers dosed with 8, 4, 16 mg of OB, 250 mg T, then 2 and 0 mg of OB. This response declined from 7 weeks onwards in testosterone-treated animals. Administration of OB is a potent method of inducing male behaviour in steers and the most effective dose of oestrogen (8 mg OB/week) has a decided costadvantage over testosterone. In addition, during mounting behaviour by the OBtreated steers we observed no penetration of the vagina whereas this did occur with some of the testosterone-treated steers. Therefore the spread of venereal disease is unlikely with the use of OB-treated steers. D'OCCHIO, M.J. and BROOKS, D.E. (1976). Theriogenology 5: 614, FULKERSON, W.J. (1978). Aust. J. Biol. Sci. ;&: 65. KISER, T-E., BRITT, J.H. and RITCHIE, H.D. (1977). J. Anim. Sci. 44: == 1031. *- Department of Agriculture, Bunbury, W.A. 6230. ** Department of Animal Science, University of W.A., Nedlands, W.A. 6009. -I- Present address: Department of Agriculture, 2 George St, Launceston, Tas. 7250. 493