[Duration of pregnancy and diurnal distribution of lambing in sheep with different genotypes]

Based on 1103 lambings the duration of pregnancy was determined for the breeds German Mutton Merino, German Blackhead Mutton and their Booroola crosses. Furthermore the influence of age and body mass of the ewes as well as number, sex and body mass of the born lambs were considered. German Blackhead Mutton have with 145/146 days on average a 4-5 days shorter duration of pregnancy than German Mutton Merino with 150 days. The examined effects influenced the pregnancy duration only insignificantly or not at all. An influence of the breed, however, was determined. In the pen with limited light during the night all genotypes lambed mostly between 9.00 a.m. and 3.00 p.m. During the day time 12-26% more ewes lambed than during the remaining 12 hours of the day.