Heritability of feed intake in grazing Merino ewes and the genetic relationships with production traits
N. M. Fogarty A D , E. Safari A , S. I. Mortimer B , J. C. Greeff C and S. Hatcher AA The Cooperative Research Centre for Sheep Industry Innovation, 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 Department of Agriculture and Food Western Australia, Great Southern Agricultural Research Institute, Katanning, WA 6317, Australia.
D Corresponding author. Email: neal.fogarty@dpi.nsw.gov.au
Animal Production Science 49(12) 1080-1085 https://doi.org/10.1071/AN09075
Submitted: 5 May 2009 Accepted: 4 July 2009 Published: 16 November 2009
Abstract
The feed intake of 1279 mature non-pregnant and non-lactating Merino ewes grazing pasture was estimated by faecal marker dilution methods using rumen controlled-release devices containing chromium sesquioxide capsules. The ewes were from two genetic resource flocks (QPLU$ flock at Trangie in NSW and a Western Australia flock at Katanning) that are representative of the major bloodlines and strains in the Australian Merino population. Pedigree information over several generations was used to genetically link other animals from the resource flocks that had additional production data to allow estimation of genetic correlations between feed intake and production traits with greater accuracy. Data were available for over 16 000 records for growth, wool and reproduction traits from the ewes and their relatives, together with carcass and meat quality traits from over 4000 rams that were slaughtered at ~18 months of age. Feed intake of the ewes was significantly affected by the reproductive status of the ewes at their previous lambing and feed intake, expressed as relative digestible dry matter intake (rDDMI), had an estimated heritability of 0.32 ± 0.08. The genetic correlations between rDDMI and growth traits were positive and larger than their standard error for birth (0.24 ± 0.12) and hogget (0.20 ± 0.09) weight, although inclusion of ewe liveweight as a covariate in the model reduced the correlations to close to zero. Generally, the genetic correlations between rDDMI and the wool, reproduction, carcass and meat quality traits were close to zero and smaller than their standard errors, with little effect of including ewe liveweight as a covariate. The results suggest that feed requirements of ewes could be reduced by selection, although ewe weight and growth would also decline unless accounted for in the model. Practical and cost effective methods of measurement of intake under grazing conditions need to be developed.
Additional keywords: carcass, growth, meat quality, reproduction, wool production.
Acknowledgements
The feed intake study was funded by the Australian Government through the Cooperative Research Centre for Sheep Industry Innovation, the NSW Department of Primary Industries and the Department of Agriculture and Food Western Australia. We thank Dr Greg Lee for advice in the implementation and Drs Arthur Gilmour and Kevin Atkins in the analysis of the study. Staff at Wollongbar Agricultural Institute are thanked for the chromium analyses of the faecal samples. The contributions of the many other scientists, technical and support staff of the NSW Department of Primary Industries and the Department of Agriculture and Food Western Australia who contributed to the management and data collection from the resource flocks over several years at the Agricultural Research Centre, Trangie and The Great Southern Agricultural Research Institute, Katanning are gratefully acknowledged. The support of Australian Wool Innovation Ltd in the establishment of the resource flocks and Meat and Livestock Australia in funding the carcass measurements at Trangie is also gratefully acknowledged.
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