Inherited bareness of the belly reduces the time taken to shear ewes and hoggets

Abstract

A series of three related experiments are described in which genetic parameters associated with belly bareness were estimated, and the fleeceweight and time taken to shear ewes and hoggets with a range of belly bareness were compared. The naturally bare area of skin on the belly was scored on lambs at weaning from a composite flock of New Zealand crossbred sheep. Belly bareness was scored on a scale from 1 where wool was found deep in the axilla and very small patches of bare skin were showing, to 5, where the entire belly was free of wool. The estimated heritability for bareness of the belly at weaning (n = 1749) was 0.31 ± 0.06. Lambs were shorn following weaning, and shorn again as hoggets (n = 876) 6 months later. Greasy fleeceweight at hogget shearing was genetically (–0.25 ± 0.13) and phenotypically correlated (–0.18 ± 0.04) with belly bareness recorded at weaning. Adult ewes of the composite flock (n = 195) were run with adult Romney ewes (n = 91) and all were scored for belly bareness before shearing. The time taken to shear each composite ewe declined (P < 0.001) from 88 s in ewes with woolly bellies to 68 s in sheep with no belly wool at all (score 5). Ewes from the composite flock had very bare bellies (mean score 4.2), and produced an average of 19 g of belly wool, 131 g of fleece skirtings and 2.2 kg of skirted fleece. Total weight of greasy wool declined with increasing belly bareness score (P < 0.001) within the composite flock from 3.3 kg for ewes with woolly bellies to 2.3 kg in sheep with no belly wool at all (score 5). In contrast, Romney ewes were shorn in 150 s and had very woolly bellies (mean score 1.1) with 364 g of belly wool, 525 g of fleece skirtings and 3.76 kg of skirted fleece. Romney ewes and composite flock ewes were mated at random to one of six sires from the composite flock. There was a decrease in fleeceweight as belly bareness score increased in the progeny of composite (P < 0.001) and Romney ewes (P = 0.037). Increasing belly bareness score reduced the time taken to shear each hogget (P = 0.015) from over 100 s for woolly bellies to 70 s for the barest (score 4). As hoggets, the progeny of Romney ewes (n = 46) carried more belly wool (251 versus 116 g), fleece skirtings (268 versus 119 g) and skirted fleece (2.1 versus 1.5 kg) than the progeny of ewes from the composite flock (n = 75). Collectively these experiments show that belly bareness is inherited, fleeceweight will decline with increased belly bareness and shearing speed will increase with increased belly bareness.