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Genetic relationships among objectively and subjectively assessed traits measured on crossbred (Mule) lambs

Published online by Cambridge University Press:  09 March 2007

A. M. van Heelsum ,
R. M. Lewis ,
M. H. Davies  and
W. Haresign
A. M. van Heelsum
Affiliation:
Sustainable Livestock Systems Group, Scottish Agricultural College, West Mains Road, Edinburgh, EH9 3JG, UK
R. M. Lewis
Affiliation:
Sustainable Livestock Systems Group, Scottish Agricultural College, West Mains Road, Edinburgh, EH9 3JG, UK Department of Animal and Poultry Sciences (0306), Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
M. H. Davies
Affiliation:
ADAS Rosemaund, Preston Wynne, Hereford, HR1 3PG, UK
W. Haresign
Affiliation:
Institute of Rural Sciences, Llanbadarn Campus, University of Wales, Aberystwyth, SY23 3AL, UK
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Abstract

Sheep farming in the UK is characterized by a crossbreeding system where ‘Longwool’ sire breeds are mated with hill dam breeds, with the crossbred (F1) ewe lambs retained for mating to terminal sires. The F1 wether and terminal-sire cross lambs are marketed for meat. At selection, F1 females are typically assessed visually for type traits relevant to dam lines, and these traits could be considered as goal traits. Their offspring and their male sibs derive their value from carcass traits. This study investigated the genetic relationships between type (subjective) and carcass (objective) traits in F1 lambs, and their potential impact on genetic improvement within this production system. Bluefaced Leicester rams were crossed with Scottish Blackface and Hardy Speckled Face ewes to produce F1 (‘Mule’) lambs. The wether lambs (no.=2197) were selected for slaughter at a target condition (a carcass fat score of 2/3L) and a number of live and carcass traits were measured. Carcass dissection data were collected on approximately one-third of these wether lambs. The ewe lambs (no.=2423) were measured for similar live traits but at a fixed age (195±5·5 days). In addition, they were subjectively assessed for a number of functional and type traits. Genetic parameters among these traits were then estimated. Heritabilities for the ewe traits were generally moderate (0·18 to 0·31) and genetic correlations between the traits were variable, with some moderate to high correlations (favourable in direction) of growth/carcass traits with overall type traits. Live weight at slaughter in wethers was highly correlated to live weight at constant age in ewes (r=0·72). In the wethers, live, cold carcass and lean weight had moderately high heritabilities (between 0·26 and 0·46), and were positively correlated with slaughter age (≥0·79). However, age at slaughter in wethers was highly negatively correlated with growth/carcass and overall type traits in ewes (between −0·45 and −0·97), perhaps reflecting differences in maturity in lambs measured at a target fatness versus age. The correlations of most other type traits in ewes with wether traits were non-significant. These results show that the subjectively assessed type traits (at least as measured in this study) will not deteriorate, and some will in fact be improved, in a selection programme aiming to improve carcass merit.

Keywords

carcass compositioncrossbreedinglambstype score
Type
Research Article
Information
Animal Science , Volume 82 , Issue 2 , April 2006 , pp. 141 - 149
Copyright
Copyright © British Society of Animal Science 2006

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References

Brown, D. J., Ball, A., Mortimer, R. and Oppenheimer, M. 2002. Incorporating subjectively assessed sheep and wool traits into genetic evaluations for merino sheep. 2. Phenotypic and genetic correlations. Wool Technology and Sheep Breeding 50: 378–382.Google Scholar
Cameron, N. D. and Thompson, R. 1986. Design of multivariate selection experiments to estimate genetic parameters. Theoretical and Applied Genetics 72: 466–476.CrossRefGoogle ScholarPubMed
Cuthbertson, A., Harrington, G. and Smith, R. J. 1972. Tissue separation–to assess beef and lamb variation. In Symposium on aspects of carcass evaluation. Proceedings of the British Society of Animal Production, 1972, pp. 113–122Google Scholar
Fisher, A. V. 1990. New approaches to measuring fat in the carcasses of meat animals. In Reducing fat in meat animals (ed. Wood, J. D. and Fisher, A. V.), pp. 255–343. Elsevier Applied Science, London.Google Scholar
Gilmour, A. R., Cullis, B. R., Welham, S. J. and Thompson, R. 1998. Asreml user guide. NSW Agriculture, Orange, Australia.Google Scholar
Jones, H. E., Simm, G., Dingwall, W. S. and Lewis, R. M. 1999. Genetic relationships between visual and objective measures of carcass composition in crossbred lambs. Animal Science 69: 533–561.Google Scholar
Krause, E., Yamada, Y. and Bell, A. E. 1965. Genetic parameters in two populations of chickens under reciprocal recurrent selection. British Poultry Science 6: 197–206.CrossRefGoogle ScholarPubMed
Lewer, R. P., Woolaston, R. R. and Howe, R. R. 1995. Studies on Western-Australian Merino sheep. 3. Genetic and phenotypic parameter estimates for subjectively assessed and objectively measured traits in ewe hoggets. Australian Journal of Agricultural Research 46: 379–388.Google Scholar
Pollott, G. E., Guy, D. R. and Croston, D. 1994. Genetic parameters of lamb carcass characteristics at three end-points: fat level, age and weight. Animal Production 58: 65–75.Google Scholar
Smith, C. 1964. The use of specialised sire and dam lines in selection for meat production. Animal Production 6: 337–344.Google Scholar
Snyman, M. A. and Olivier, W. J. 2002. Correlations of subjectively assessed fleece and conformation traits with production and reproduction in Afrino sheep. South African Journal of Animal Science 32: 88–96.Google Scholar
Van Heelsum, A. M., Lewis, R. M., Haresign, W., Williams, S. P. and Davies, M. H. 2001. Non-normality in carcass quality measurements and effects on the genetic evaluation of sheep. Livestock Production Science 69: 113–127.CrossRefGoogle Scholar
Van Heelsum, A. M., Lewis, R. M., Davies, M. H. and Haresign, W. 2003. Growth and carcass characteristics in wether lambs of a crossbred dam line. Animal Science 76: 43–53.CrossRefGoogle Scholar