Growth and wool production of wethers and induced cryptorchids in a Poll Merino flock

Abstract

Ram lambs in a Poll Merino flock were either castrated or made cryptorchid at about four weeks of age and then run together in the one flock until 31/2 years old, The induced cryptorchids were heavier than their wether flockmates at each shearing (P < 0.001), the relative superiority increasing with age, from 5.2% at weaner shearing to 16.7% at 6-tooth shearing. Greasy fleece weights were heavier in the cryptorchids at the 4- and 6-tooth shearings only, by 5.3% (P < 0.05) and 1 1.3% (P < 0.01 ), respectively. No differences in visual wool quality were observed between the two groups, and the only difference detected by measurement of midside samples was a lower clean scoured yield percentage in cryptorchid fleeces at 6-tooth shearing (69.9% compared with 74.9% for wethers : P < 0.001 ). This lower yield resulted in similar estimated clean fleece weights at the 6-tooth shearing, but cryptorchids cut more clean wool at 4-tooth (P < 0.05). Clean fleece weight per unit liveweight was significantly higheri (P < 0.05) in the wethers than in the cryptorchids, by 8.7% at the 4-tooth and 11.8% at the 6-tooth shearing. Fleece weight index, a measure of the efficiency of wool production, was similar for both groups at these last two shearings. The possible value of induced cryptorchids as an alternative to wethers for wool production is discussed in the light of these results.