Productivity of three crossbred ewe types mated naturally at 8-monthly intervals over two years [sheep]
1992
Fogarty, N.M. | Hall, D.G. | Atkinson, W.R. (New South Wales Agriculture, Cowra (Australia). Agricultural Research Station)
Productivity is reported for 175 Booroola Merino x Poll Dorset (BD), 288 Trangie Fertility Merino x Poll Dorset (TD) and 248 Border Leicester x Merino (BLM) ewes joined 3 times (February, October and June) in 2 years. Overall joining in February resulted in higher performances (153 percent lambs born, 118 lambs weaned, 24.7 kg weight of lamb weaned, per ewe joined) than were obtained following October and June joinings (129 percent born, 93 percent weaned, 15.3 kg weight weaned per ewe joined). The mean number of lambings per year was 1.28 with an annual lambing rate of 211 lambs born and 160 percent lambs weaned. For lambs born, BD ewes were consistently higher than the other ewes, with BLM ewes having fewer lambs born from October and June joinings. Analyses of the components of reproduction that contributed to overall lamb production showed that although more than 95 percent of ewes expressed oestrus in each season, fertility and litter size were higher from the February joining, while lamb survival was lower following the June joining. Ewe crossbred type was significant for litter size in all seasons. BD ewes carrying the F gene tended to have a higher percentage of lambs born and lower percentage of lambs weaned than non-carriers. Implications for production systems in the lamb industry are discussed.
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