Can Selection For Skin Traits Increase the Rate of Genetic Progress in Merino Breeding Programs?
By P. L. Hynd¹, R. W. Ponzoni² and J. A. Hill¹
This is a fascinating article about the relationship between skin traits and economically important fleece traits. Alpaca breeders who are taking skin biopsies and making selection decisions based on the secondary to primary fiber ratios and follicular density should read the entire article.
The authors found, contrary to popular opinion in the alpaca industry that follicular density in the skin does not necessarily correlate with higher fleece weights. For those of you who do not want to read the entire study, here is it’s conclusion.
The increases in genetic progress towards the breeding objective, which were conveyed by addition of some skin traits, while not spectacular, were of sufficient magnitude to suggest they may be usefully incorporated into some Merino selection programs, particularly those in which selected sires are likely to be used over a large number of ewes. The extra benefit obtained by including the skin traits was greater than that reported by other workers (Skerritt 1995; Purvis and Swan 1997). This may reflect differences in the genetic parameters established for the different strains and flocks (Tables 1 and 2), differences in the skin traits used, or both. For instance in the Finewool sheep the genetic correlation between follicle density and clean fleece weight was only 0.13 (Purvis and Swan 1997) whereas in the Strongwool sheep in our study the genetic correlation between density and fleece weight was 0.54. This may reflect real differences in the association between these characters in the two strains but may also reflect the fact that density was measured by two different methods in the two trials. However, in none of the selection exercises conducted to date using skin traits as selection criteria has there been evidence of spectacular increases in the rate of progress towards the breeding objective of increased fleece weight and decreased fibre diameter. Our results point to moderate additional gains but do not support suggestions that selection for skin traits will result in large changes in fleece quantity and quality. Note that this could be due to the specific sub-set of skin traits measured to date. It remains to be seen whether consideration of criteria based on the efficiency of fibre production at the follicle level, or on fibre composition, will result in more substantial increases in the efficiency of identification of superior wool producing genotypes.
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