A trial was conducted over 2 years in which the comparative wool growth rates of wethers and dry, single and twin-rearing ewes were measured. The sheep were pasture fed according to 3 regimes of either continuous maintenance or alternating 3-monthly periods of either high or low plane and maintenance feeding. At any one time, groups of sheep were either gaining, maintaining or losing live weight. This paper reports preliminary analyses of the effects on wool growth of year, breed, sheep age and rearing status. Coopworths were consistently heavier than Romneys. As a result of practical constraints associated with the trial design, ewes which reared twins were lighter at the end of the trial than ewes which reared singles which were lighter than wethers and ewes which did not raise any lambs. Romneys grew more wool than Coopworths with no difference in wool production between wethers and ewes which did not rear a lamb. Overall, the clean wool growth rate of the dry sheep was a minimum of 7.2 g/d in July/August and a maximum of 12.5 g/d in November/December. Wool growth rates of the single and twin rearing ewes relative to the dry sheep (100) were 63 and 55 in July/August and 90 and 82 in November/December respectively. Wool growth rates after weaning did not differ between rearing status groups. The combined effect of these differential wool growth patterns on clean fleece weight of single and twin rearing ewes relative to the dry sheep (100) were 86 and 77 in December and 99 and 97 in May respectively. Despite the apparent large reduction in wool production associated with rearing lambs it is still economic at present prices for most farmers to run breeding ewes rather than dry sheep of the same breed.
Proceedings of the New Zealand Society of Animal Production, Volume 49, , 171-174, 1989
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