THE MALE EFFECT IN THE AUSTRALIAN CASHMERE GOAT .1. OVARIAN AND BEHAVIORAL-RESPONSE OF SEASONALLY ANOVULATORY DOES FOLLOWING THE INTRODUCTION OF BUCKS

The ovulatory and oestrous responses of seasonally anovulatory Austral ian cashmere does to the introduction of bucks in six experiments are reviewed. Experiments were carried out at Wollongbar (28-degrees-48'S, 153-degrees-25'E) in February (Experiment 5), March (Experiments 2 an d 6), April (Experiments 1 and 3) and October (Experiment 4). Treatmen ts from these experiments in which groups of does (n = 5-20) were expo sed to one or two bucks for 10 days in small paddocks or pens are desc ribed here. Ovarian activity was determined by laparoscopy pre-experim entally, and on Days 5 and 10 after buck introduction. Oestrus was ass essed daily by examination for raddle marks. Overall, 74% of 319 anovu latory does ovulated and 59% exhibited oestrus during the 10 days foll owing buck introduction. Of those does ovulating, 57% ovulated twice d uring the 10 days, with a short luteal phase separating the ovulations , 25% ovulated once only between Days 6 and 10, 13% ovulated by Day 5 followed by a short luteal phase and a lapse into an anovulatory state , and 5% ovulated before Day 5 followed by formation of a corpus luteu m that was still functional on Day 10. Differences between experiments in the proportions of does ovulating appeared to be due to the intens ity of the buck stimulus used, rather than variation in female respons iveness. The ovulation rate (mean 1.28, range 1.07-1.44) was positivel y correlated with doe liveweight within and between experiments and di d not differ between the first and second ovulations in does ovulating twice. The incidence of oestrus peaked on Days 2-3 (25% of does) and on Days 7 and 8 (33% of does) with a mean (+/- SEM) oestrous interval of 5.4 +/- 0.14 days. The incidence of oestrus at the first induced ov ulation varied widely between experiments (mean 45%, range 14-70%), wh ereas it was uniformly high at the second ovulation (mean 89%, range 6 7-92%). The percentage of does exhibiting oestrus at the first ovulati on was positively correlated with doe age (r = 0.91, n = 6, P < 0.05) and was significantly higher amongst does that ovulated twice compared with those ovulating only once. These findings confirm that the male effect is an effective means of inducing ovulation and oestrus in seas onally anovulatory Australian cashmere does and they suggest that the female response may be influenced more by the intensity of the buck st imulus applied, and the age and liveweight of the does, than by season al variation in the responsiveness of does.