In the summer of 1998/9, 220 mixed-age breeding ewes were obtained from eight North Island farms. Half of these ewes had had a bearing in 1998 (PB ewes) and the other half were flock mates that had not (NB ewes). Ewes were fed in excess of their requirements from eight weeks before lambing and ewe condition had increased by 0.4 CS units by lambing. At scanning 15% of PB ewes were dry compared to 10% of the NB ewes. Pregnant PB and NB ewes also had similar scanning percentages (151% vs 142% respectively). Twenty percent of PB ewes had a bearing in 1999 (17% in single and 29% in twin pregnant ewes) compared with 0% in NB ewes (P<0.001). Pre-lambing bearings occurred 18 ±2 days (2-33 days) before lambing. There was a 5% bearing incidence after lambing. Eleven percent of the ewes treated for bearings died before lambing and 78% of surviving treated ewes produced a live lamb. In conclusion, high feeding levels in late pregnancy do not necessarily cause bearings. Ewes with bearings should be clearly identified and culled as they are more likely to have bearings the following year.
Proceedings of the New Zealand Society of Animal Production, Volume 60, Hamilton, 44-46, 2000
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