Determining the mode of inheritance of the undesirable Australian Piebald condition of Merino sheep is highly relevant to both conventional breeding practice and to current attempts to identify the gene(s) responsible. Despite attracting the interestof animal breeders over decades, there is a scarcity of data and this study shows that the inheritance cannot be conclusively determined on this basis. Considering a range of possible inheritance scenarios will ensure that the gene discovery experiment is designed optimally. There are many documented loci associated with pigmentation in sheep. The Australian Piebald locus (AsP) in Merino sheep is held responsible for a form of pigmented fleece spots (COGNOSAG 1996). This is characterised by one to several rounded spots of black to grey or chocolate to cinnamon brown covering a proportion of the fleece area ranging from 0.0003 to greater than 0.5 (Brooker and Dolling 1969). Location is apparently random but with a degree of familial resemblance. Australian Piebald creates the risk of contamination of white fleece wool with dark fibres and inflicts further economic losses associated with culling. Australian Piebald phenotypes occur throughout Australian Merino flocks at a low frequency and the conditionis known to persist despite culling. This distinct form has not been recorded outside Australia.
展开▼
