Across population genetic parameters for wool, growth, and reproduction traits in Australian Merino sheep. 2. Estimates of heritability and variance components
E. Safari A G , N. M. Fogarty A , A. R. Gilmour A , K. D. Atkins A , S. I. Mortimer B , A. A. Swan C , F. D. Brien D , J. C. Greeff E and J. H. J. van der Werf FA The Australian Sheep Industry Cooperative Research Centre, NSW Department of Primary Industries, Orange Agricultural Institute, Orange, NSW 2800, Australia.
B NSW Department of Primary Industries, Agricultural Research Centre, Trangie, NSW 2823, Australia.
C CSIRO Livestock Industries, Armidale, NSW 2350, Australia.
D South Australian Research and Development Institute, Roseworthy, SA 7371, Australia.
E Department of Agriculture and Food, Western Australia, Great Southern Agricultural Research Institute, Katanning, WA 6317, Australia.
F School of Rural Science and Agriculture, University of New England, Armidale, NSW 2351, Australia.
G Corresponding author. Email: alex.safari@dpi.nsw.gov.au
Australian Journal of Agricultural Research 58(2) 177-184 https://doi.org/10.1071/AR06162
Submitted: 12 May 2006 Accepted: 16 October 2006 Published: 22 February 2007
Abstract
Precise estimates of genetic parameters are required for genetic evaluation systems. This study combined data from 7 research resource flocks across Australia to estimate variance components and genetic parameters for production traits in the Australian Merino sheep. The flocks were maintained for several generations and represented contemporary Australian Merino fine, medium, and broad wool bloodlines over the past 30 years. Over 110 000 records were available for analysis for each of the major wool traits, and 50 000 records for reproduction and growth traits with over 2700 sires and 25 000 dams. A linear mixed animal model was used to analyse 6 wool traits comprising clean fleece weight (CFW), greasy fleece weight (GFW), fibre diameter (FD), yield (YLD), coefficient of variation of fibre diameter (CVFD), and standard deviation of fibre diameter (SDFD), 4 growth traits comprising birth weight (BWT), weaning weight (WWT), yearling weight (YWT), and hogget weight (HWT), and 4 reproduction traits comprising fertility (FER), litter size (LS), lambs born per ewe joined (LB/EJ), and lambs weaned per ewe joined (LW/EJ). The range of direct heritability estimates for the wool traits was 0.42 ± 0.01 for CFW to 0.68 ± 0.01 for FD. For growth traits the range was 0.18 ± 0.01 for BWT to 0.38 ± 0.01 for HWT, and for reproduction traits 0.045 ± 0.01 for FER to 0.074 ± 0.01 for LS. Significant maternal effects were found for wool and growth, but not reproduction traits. There was significant covariance between direct and maternal genetic effects for all wool and growth traits except for YWT. The correlations between direct and maternal effects ranged from –0.60 ± 0.02 for GFW to –0.21 ± 0.10 for SDFD in the wool traits and from –0.21 ± 0.03 for WWT to 0.25 ± 0.08 for HWT in the growth traits. Litter effects were significant for all wool and growth traits and only for LS in reproduction traits. The mating sire was fitted in the models for reproduction traits and this variance component accounted for 21, 17, and 8% of the total phenotypic variation for FER, LB/EJ, and LW/EJ, respectively. The implications of additional significant variance components for the estimation of heritability are discussed.
Additional keywords: direct heritability, maternal heritability, litter effect.
Acknowledgments
Funding for this study was provided by the Commonwealth Government through the Australian Sheep Industry Cooperative Research Centre. We also gratefully thank the many other scientists and technical and support staff who have contributed to the management of the flocks and collected the data over many years, from the Agricultural Research Centre, Trangie, and NSW Department of Primary Industries; CSIRO Livestock Industries, Armidale; Turretfield Research Centre and the South Australian Research and Development Institute; the Great Southern Agricultural Research Institute, Katanning, and the Department of Agriculture and Food Western Australia. Contributions of sheep breeders and industry funding bodies such as Australian Wool Innovation and Meat and Livestock Australia and their predecessors over many years to the various flocks are also gratefully acknowledged.
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