Hourly distribution of time of parturition in the domestic goat

Data on 2589 records collected during 12 years in one breed of dairy goats that were maintained in stables were analysed to examine the influence of various factors on the time of parturition. Parturitions were observed from mid-January to the end of April. Hourly frequencies of birth showed an unimodal distribution with maximum births at midday and minimum births around midnight with 90.6% of deliveries occurring between 0600 and 2000 h. The distribution showed a noticeable homogeneity when the following parameters were taken into account: litter-size, litters with live or stillborn kids, time of the year and length of gestation. In two other herds, 117 and 166 records obtained after 4 and 3 years of observation were studied. As in the first herd, births were more frequent between 0700 to 1900 h (day; 72.3 and 70.2 %, respectively) than between 1900 and 0700 h (night; P<0.001). These observations on the time of birth of the domestic goat suggest a regulation of the birth process by circadian events which themselves remain unknown.