Oestrus in the british white goat: Timing of plasma luteinizing hormone surge and changes in behavioural and vaginal traits in relationship to onset of oestrus

Abstract

Length of oestrus and timing of the LH surge was measured in six British White does, housed with a vasectomized buck (experiment 1). The following breeding season, pulsatile LH release during the cycle was measured in eight does and the pattern of behavioural and vaginal traits in relation to onset of oestrus (time 0) determined (experiment 2). In experiment 1, the interval to first oestrus after introduction of the buck on 1st October was 10.3 +/- 3.0 days (n = 6) but in experiment 2, when the buck was put in on 1st September, first oestrus occurred after 39.3 +/- 3.4 days in 7/8 does and 7 days in 1/8 does indicating that adequate exposure to short days is needed before the buck can initiate ovarian activity. LH pulse frequency increased from 0-1 pulses/8 h to 3 pulses/8 h after luteolysis, with no change in pulse amplitude, suggesting that progesterone regulates LH pulse frequency. Mean LH values rose from basal to 102.1 +/- 7.8 ng/ml, 12 +/- 1.5 h after the onset of oestrus, which was 16.3 +/- 1.7 h in length. Does sought out the buck and displayed tail wagging, bleating and restlessness from -60 h to +36 h relative to the onset of oestrus (time 0). The incidence of these activities rose at -12 h and peaked at 0 h. Tail wagging, but not bleating or restlessness, also increased in intensity at 0 h, as did the intensity with which the doe actively sought out the buck. Vulval redness and swelling and onset of a clear thin vaginal discharge were first observed 1-2 days before oestrus, becoming maximal on day 0. It was concluded that onset of frequent tail wagging was the most useful trait for detecting onset of oestrus.