An assortative breeding programme was carried out in 4 industry Perendale flocks and at Whatawhata using Cheviot, Perendale, Romney and Coopworth sheep. Within the industry flocks rams of high and low loose wool bulk were progeny tested. At Whatawhata Cheviot and Perendale rams of high, medium and low loose wool bulk were mated to ewes of equivalent bulk type within their own breed. High and low loose wool bulk Cheviot and Perendale rams and high loose wool bulk Romney rams were also mated to randomly allocated groups of Romney and Coopworth ewes. Progeny data provided an estimate of the phenotypic correlation between loose wool bulk measured at lamb and hogget shearing of 0.5. Breed effects on hogget loose wool bulk were essentially additive and complementary to the effects of sire selection within breeds. Statistical methods for evaluating heterogeneity of within-family variance of loose wool bulk at hogget shearing were used to investigate the possibility of a major gene influencing loose wool bulk. These methods could not confirm the hypothesis of a major gene controlling loose wool bulk. Offspring-parent relationships were consistent with previously published heritability estimates of around 0.5.
Proceedings of the New Zealand Society of Animal Production, Volume 49, , 261-264, 1989
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