Hostname: page-component-8448b6f56d-sxzjt Total loading time: 0 Render date: 2024-04-18T14:57:49.563Z Has data issue: false hasContentIssue false
  • English
  • Français

Testing selection indices for sustainable hill sheep production – lamb growth and carcass traits

Published online by Cambridge University Press:  09 March 2007

J. Conington ,
S. C. Bishop ,
N. R. Lambe ,
L. Bünger  and
G. Simm
J. Conington*
Affiliation:
Scottish Agricultural College, (SAC) West Mains Road, Edinburgh, EH9 3JG, UK
S. C. Bishop
Affiliation:
Roslin Institute (Edinburgh), Roslin, Midlothian, EH25 9PS, UK
N. R. Lambe
Affiliation:
Scottish Agricultural College, (SAC) West Mains Road, Edinburgh, EH9 3JG, UK
L. Bünger
Affiliation:
Scottish Agricultural College, (SAC) West Mains Road, Edinburgh, EH9 3JG, UK
G. Simm
Affiliation:
Scottish Agricultural College, (SAC) West Mains Road, Edinburgh, EH9 3JG, UK
*
† E-mail: jo.conington@sac.ac.uk
Get access

Abstract

Two selection indexes, one intended for lamb producers and finishers and one for store lamb producers, were derived using genetic parameters for carcass and maternal characteristics from Conington et al. (2001) and economic values from Conington et al. (2004). This paper summarizes responses to selection for lamb traits only, after 5 years of selection (1998 to 2003) on two farms using these selection indexes. The index for lamb producers and finishers, evaluated on farm 1, with a flock size of 680 ewes, includes economic weightings for maternal traits as well as carcass weight, fat and conformation grades, whereas the index for store lamb producers, evaluated on farm 2, with a flock size of 580 ewes, only includes economic values for maternal traits and lamb growth to weaning. Three selection lines of Scottish Blackface sheep per farm were created with the first lambs born to each line in 1999. These lines were selection (S), control (C) and industry (I); they were of equal size on each farm. Five top- and five average-performing ram lambs were selected each year for the S and C lines respectively using a multi-trait best linear unbiased prediction (BLUP) implementation of the indexes. The I-line used four mature rams bought from industry, selected on appearance only, i.e. adherence to breed ‘type’. Results showed that 5 years after the implementation of the index, the S line had significantly higher index scores than the C or I lines on both farms. The means (s.d.) for the average index scores in 2003 are 114 (328), 119 (371) and 451 (328) (farm 1), and −8 (146), −11 (130), and 250 (129) (farm 2) for the C, I and S lines, respectively, giving predicted net differences (S-C) of £3·38 (farm 1) and £2·58 (farm 2) per ewe. Phenotypic responses showed significant S v. C differences in weaning weight on both farms. As predicted from previous analyses, no changes in carcass quality traits were seen at farm 1 although S-line carcass weights tended to be heavier than those from the C or I lines. The results show that genetic improvement using multi-trait selection indices has been successful and it is a viable, long-term strategy to improve levels of production for hill sheep in extensive environments.

Keywords

carcassesgeneticsgrowthselection indexsheep
Type
Research Article
Information
Animal Science , Volume 82 , Issue 4 , August 2006 , pp. 445 - 453
Copyright
Copyright © British Society of Animal Science 2006

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Conington, J., Bishop, S. C., Waterhouse, A. and Simm, G. (1998) A comparison of growth and carcass traits in Scottish Blackface lambs sired by genetically lean or fat rams. Animal Science 67: 299–309.CrossRefGoogle Scholar
Conington, J., Bishop, S. C., Grundy, B., Waterhouse, A. and Simm, G. (2001) Multi-trait selection indexes for sustainable UK hill sheep production. Animal Science 73: 413–424.CrossRefGoogle Scholar
Conington, J., Bishop, S. C., Waterhouse, A. and Simm, G. (2004) A bio-economic approach to derive economic values for pasture-based sheep genetic improvement programs. Journal of Animal Science 82: 1290–1304.CrossRefGoogle Scholar
Defra. 2005. How to condition score ewes. www.defra.gov.uk/animalh/welfare/farmed/sheep/pb1875/SHEEP7a.htm.Google Scholar
Doney, J.M. and Smith, W. F. (1966) Fleece characteristics of the three strains of Scottish Blackface sheep. Animal Production 8: 313–320.Google Scholar
Eady, S.J., Woolaston, R.R. and Barger, I. A. (2003) Comparison of genetic and non genetic strategies for control of gastrointestinal nematodes in sheep. Livestock Production Science 81: 11–23.CrossRefGoogle Scholar
Groeneveld, E., Kovac, M. and Wang, T. (1990) PEST, a general purpose BLUP package for multivariate prediction and estimation. Proceedings of the fourth world congress on genetics applied to livestock production, Edinburgh, pp. 488–491.Google Scholar
Kempster, A.J., Cook, G. L. and Grantley-Smith, M. (1986) National estimates of body composition of British cattle, sheep and pigs with special reference to trends in fatness: a review. Meat Science 17: 107–138.CrossRefGoogle ScholarPubMed
Lambe, N.R., Conington, J., McLean, K.A., Navajas, E., Fisher, A.V. and Bünger, L. (2006) In-vivo prediction of internal fat weight in Scottish Blackface lambs, using computer tomography (CT). Journal of Animal Breeding and Genetics 123: 105–113.CrossRefGoogle Scholar
Lawes Agricultural Trust (1994) Genstat Statistical package. Genstat 7 release 2 Harpenden Rothamstead Experimental Station.Google Scholar
Lewis, R.M., Simm, G., Dingwall, W.S. and Murphy, S. V. (1996) Selection for lean growth in terminal sire sheep to produce leaner crossbred progeny. Animal Science 63: 133–142.CrossRefGoogle Scholar
McEwan, J.C., Morris, C.A., Fennessey, P.F., Greer, G. J., Bain, W.E. and Hickey, S.M. (2001) Selection for high or low backfat depth in Coopworth sheep: breeding ewe traits. Animal Science 73: 241–252.CrossRefGoogle Scholar
Rasch, D., Herrendörfer, G., Bock, J. and Busch, K. (1978) Verfahrensbibliothek Versuchsplanung und -auswertung - Band 2 VEB. Deutscher Landwirtschaftsverlag,Berlin.Google Scholar
Simm, G. and Dingwall, W.S. (1989) Selection indices for lean meat production in sheep. Livestock Production Science 21: 223–233.CrossRefGoogle Scholar
Woolaston, R.R. and Baker, R. L. (1996) Prospects of breeding small ruminants for resistance to internal parasites. International Journal of Parasitology 26: 845–855.CrossRefGoogle ScholarPubMed