Production parameters for a commercial Dorper flock on extensive pastures

Author: S.W.P. Cloete & T.T. de Villiers
Year: 1987
Issue: 3
Volume: 17
Page: 121 - 127

Data of 1483 birth and 1209 weaning records of Dorper lambs in a commercial flock were used to investigate the effects of environmental factors on birth and weaning mass, and on pre-weaning growth and survival. Preweaning survival was relatively high (0,91) and largely independent of the known sources of variation. The effects of dam age, sex and rearing type on birth mass, weaning mass and pre-weaning growth rate were in agreement with literature cited. Weaning mass was also affected by weaning age, with an overall linear increase of 0,167 kg in weaning mass per day of age. A data set containing 813 mating and 720 lambing records was used to investigate factors affecting mating mass and reproduction in adult ewes. Age trends in mating mass, multiple birth rate and lambs weaned/ewe mated (Lw/Em) were in agreement with literature cited. Multiple born ewes maintained a higher multiple birth rate than singles. Mating mass and conception rate were unrelated within and across age groups. There was evidence of a linear relationship between mating mass and multiple birth rate, especially in 2-year-old ewes. The effect of mating mass on multiple birth rate was partially reflected in Lw/Em. The intra-class correlation repeatabilities of mating mass, lambs born/ewe mated (Lb/Em) and Lw/Em were 0,45, 0,08 and 0,07 respectively. Repeatability estimates derived from the regression of subsequent reproduction on initial records at 2 or 3 years suggested that selection in the current flock should be directed against barrenness or failure to rear at least one lamb. The current flock gains attainable by selection are, however, relatively small, and gains of approximately 0,025 Lb/Em or Lw/Em may be achieved.



Keywords: Dorper sheep, ewe reproduction, lamb growth, lamb survival, Repeatability
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