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This Article Free Via Open Access Full Text Full Text (PDF) All Versions of this Article: jas.2008-1508v1 87/6/1856    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Johnson, P. L. Articles by McEwan, J. C. PubMed PubMed Citation Articles by Johnson, P. L. Articles by McEwan, J. C.

Investigations into the GDF8 g+6723G-A polymorphism in New Zealand Texel sheep¹

P. L. Johnson^*,2, K. G. Dodds^*, W. E. Bain^*, G. J. Greer^*, N. J. McLean^*, R. J. McLaren, S. M. Galloway^*, T. C. van Stijn^* and J. C. McEwan^*

^* AgResearch Invermay, Puddle Alley, Private Bag 50034, Mosgiel, New Zealand Health and Safety Compliance Office, University of Otago, Dunedin, New Zealand

² Corresponding author: tricia.johnson{at}agresearch.co.nz

This work investigated effects of carrying 0, 1, or 2 copies of the A allele resulting from the g+6723G-A transition in growth differentiation factor gene (GDF8) in New Zealand Texel-cross sheep at different lamb ages and carcass weights. Two Texel-cross sires carrying 1 copy of the A allele were mated to approximately 200 ewes carrying 0, 1, or 2 copies of the A allele. A total of 187 progeny were generated and genotyped to determine whether they were carrying 0, 1, or 2 copies of the A allele. The progeny were assigned to 1 of 4 slaughter groups balanced for the 3 genotypes, sex, and sire. The 4 groups were slaughtered commercially when their average BW (across all progeny in the slaughter group) reached 33, 40, 43, and 48 kg, respectively. Measurements of BW, and carcass dimensions and yield were made on all animals using Viascan (a commercial 2-dimensional imaging system that estimates lean content of the carcass as a percentage of total carcass weight). Additional measurements were made on the fourth slaughter group, which was computed tomography scanned at each slaughter time point to obtain 4 serial measures of lean and fat as estimated from the computed tomography images. The A allele did not have an effect on any BW traits. The A allele was associated with increased muscle and decreased fat across the variety of measures of muscling and fat, explaining between 0.2 and 1.1 of a residual SD unit. Estimates for an additive effect were significant and were positive for muscle and negative for fat traits. No dominance effect estimates (positive or negative) were significant. There was no significant interaction between A allele number and carcass weight or slaughter group for any trait. This is the first systematic study of the effect of the A allele copy number over a range of carcass weights (13 to 20 kg) and ages and results suggest the size of the effect across these endpoints is proportionately the same. Testing for the A allele therefore offers breeders the potential to improve rates of genetic gain for lean-meat yield across most production systems.

Key Words: computed tomography • growth differentiation factor gene • lamb • meat yield • Texel • Viascan