Abstract:
302 Proc. Aust. Soc. Anim. Prod. Vol. 17 THE ARTIFICIAL INSEMINATION OF AUSTRALIAN GOATS STIMULATED BY THE 'BUCK EFFECT' B.J. RESTALL Observations during artificial insemination programs with Australian goats in April of 1985 and 1986 showed that does were not generally ovulating before joining,but exposure to males induced ovulation 3 days later in a high proportion. A small proportion (20-25%) of ovulations was accompanied by oestrus. Does not conceiving appeared to ovulate again 5 days later and most showed oestrus. Fertility to a single insemination of fresh semen at the first oestrus for 1985 and 1986 was 18.9% and 53%, while at the second oestrus it was 82.4% and 81.7% respectively. The exposure to males appeared to initiate reproductive activity in the does, synchronise oestrus and ovulation and potentiate fecundity. Keywords: Goats, buck effect, oestrus, ovulation, fertility. INTRODUCTION Controlled breeding techniques have been extensively studied in Australian feral goats (Moore and Eppleston 1979), but there are no published studies of fertility to artificial insemination (AI) at natural oestrus. Synchronisation of oestrus has been observed in goats following the introduction of males after a period of separation (the 'buck effect')(Shelton 1980; Corteel et al 1982) but AI programs have not used this phenomenon. This paper reports the results of AI following exposure of does to males in the autumn. MATERIALS AND METHODS The observations were carried out at The Goat Research and Development Centre field station at Wollongbar in northern NSW (29'S, 154*E) during 1985 and 1986. A breeding herd of 650 does, the domesticated offspring of feral goats from western NSW, was mated in April of each year by artificial insemination. Vasectomised bucks with mating harnesses and raddles were placed with the does, raddled animals drafted off each morning and inseminated over a 15 day period with at least 200 x 106 fresh sperm (0.1 ml undiluted semen). In 1985 days before, examinations males. Both the ovaries of a random sample of does were examined by endoscopy 7 3 and 16 days after introduction of the males. In 1986 similar were carried out 3 days before, 5 and 12 days after exposure to mated and unmated does were examined in each year. Does were closely supervised at kidding to ensure identification of dam and offspring. The Goat Research and Development Centre, NSW Department of Agriculture, North Coast Agricultural Research Institute, Wollongbar, NSW, 2480. Proc. Aust. Soc. Anim. Prod. Vol. 17 RESULTS 303 A bimodal pattern in the daily incidence of oestrus was observed in both years (Fig. l), with a small peak at 2 to 3 days, and a large peak of oestrus 7-9 days after introduction of males. Over 80% of does mated within 10 days. Fig. 1. Daily incidence of oestrus in Australian goats after the introduction of males. (- 1985 ---1986) The proportion of does inseminated and their fertility for the periods 1-5 days or 6-10 days after the start of AI are shown in Fig. 2. Only a small proportion of does showed oestrus during the first five days'of joining and their fertility was low and variable (52.9% 1985, 18.9% 1986). In contrast, most does were in oestrus during the second period and their fertility based on kidding performance was uniformly high at 82.4% in 1985 and 81.75% in 1986. There was no difference in the incidence of ovulations or the ovulation rate between the mated and unmated does and the resulted are pooled in Table 1. Table 1. Ovulatory activity in Australian goats before and after introduction of males during AI programs in 1985 and 1986.' 304 Proc. Aust. Soc. Anim. Prod. Vol. 17 Very few does were ovulating before joining in either year, but a high proportion ovulated within five days of exposure to males. A similarly high incidence of ovulation was evident at the later examination, and from the size and colour of the corpora lutea it was estimated that these ovulations occurred at the second oestrus peak, 7 to 9 days after joining began. The ovulation rate increased from first to second ovulation in both years. Fig. 2. Proportion of does inseminated and conception rate to AI in Australian goats l-5 days or 6-10 days after exposure to males. 1-1 oestrus incidence [SJ conception rate DISCUSSION The incidence of oestrus and ovulation shown here indicates that reprochctive activity in the doe is initiated by contact with males, the 'buck effect' that has been described for other breeds of goat (Corteel et al 1982). The does were not spontaneously ovulating at the time of introduction of the males; in another study spontaneous ovulations only occurred during May, June and July but does were induced to ovulate between February and September (Restall 1987). The breeding season in these goats appears to be expressed as a change in the sensitivity of the reproductive system to environmental stimuli capable of initiating activity. This contrasts with sheep in which the breeding season is defined as the period of spontaneous oestrus and ovulation (Scaramuzzi 1986). Proc. Aust. Soc. Anim. Prod. Vol. 17 305 Exposure of our goats to males appeared to induce ovulation in a high proportion within 3 days, but only a small proportion exhibited oestrus. Does that had not conceived or were not in oestrus at the first ovulation, ovulated again after a short luteal cycle of five to seven days. This second ovulation was eccompanied by oestrus. This sequence of events has only been described in one other study, in which a similar bimodal pattern of oestrus and ovulation was observed in Creole goats in Guadeloupe (Chemineau 1982). However, it is likely that these events occur whenever a 'buck effect' is evident. While the fertility to insemination at the first induced oestrus is low and variable, it is remarkably high at the second. The absence of e progestational conditioning prior to the first oestrus may account for the variable fertility observed; and the short 'priming' luteal cycle prior to the second induced oestrus may be important for the enhanced fertility. This short luteal phase may also influence the ovulation rate which is higher at the second ovulation. There appears to be three useful features of the 'buck effect': 1. 2. 3. the initiation of reproductive activity in the does, the natural synchronisati'on of oestrus and ovulation, the potentiation of fecundity. This ability of males to synchronise and potentiate reproductive activity in females can be used to devise techniques to maximise reproductive rate in breeding flocks. Cheap, practical and effective AI programs can be carried out in a 10 day period; kiddings can be concentrated or spread as desired and particular mating strategies pursued without using expensive drugs. Other practical problems, such as unwanted 'visits' and matings from feral bucks in extensive enterprises may be alleviated by blocking or manipulating the response of the female. The full extent of the practical value of the 'buck effect' is yet to be realised. ACKNOWLEDG=NTS It is a pleasure to thank W. TaY #Ior, K . Fredericksen and D. Wallace for assistance and care of the animal#S. CHIXMINEAU, P. (1982). .T. Reprod. Fert. 64: 1. CORTBEL, J.M., GONZALEZ, C., and NUN%, J.F. (1982). Proc. Iflrd Intl. ,Conf. Goat Production and Disease, Tucson, Arizona, USA, p 584. MOORE, N.W. and EPPLESTON, 3. (1979). Aust. J. Agric. Res. 30: 965. X RESTALL, B.J. (1987). In 'Role of Non-Milch Goats in Agricultural Production in Australia', SCA Workshop, Dept. Primary Industries, Queensland. SCARAMUZZI, R.J. (1986). In nThe Pastoral Industries of Australia', 2nd Ed. p. 211, editors G. Alexander and O.B. Williams. SHRLTON, M. (1980). Int. Goat and Sheep Res. - 156. 1: