Skip to main content Accessibility help
×
Home

Growth and carcass characteristics in wether lambs of a crossbred dam line

  • A.M. van Heelsum (a1), R.M. Lewis (a1), M.H. Davies (a2) and W. Haresign (a3)

Abstract

While crossing of specialized sire and dam breeds can be biologically efficient overall, a by-product is produced in the form of (crossbred) males of the dam line that are unwanted for breeding. In the UK sheep industry, most commercial females are first crosses between males of ‘longwool’ crossing sire breeds, predominantly the Bluefaced Leicester, and females of hill breeds. Genetic improvement of carcass quality in longwool breeds would benefit the surplus F1 males as well as filter through to the terminal sire cross lambs produced by the F1 ewes. As a first step, this paper aims to describe the growth and carcass characteristics of crossbred ‘Mule’ wether offspring of Bluefaced Leicester sires and Scottish Blackface and Hardy Speckled Face dams, and relate the crossbred performance to the ‘lean’ index and live conformation score of the sires and the breed of the dams. In each of 3 years, 1500 hill ewes divided over three sites were mated to 15 ram lambs, selected using an elliptical design to best represent the full spectrum of lean index (designed to improve muscle and decrease fat content while keeping live weight unchanged) and live conformation score present in the Penglas Bluefaced Leicester Group Breeding Scheme. Full growth and slaughter records were available on 2192 Mule wether lambs slaughtered after reaching finished condition, defined as the borderline between MLC fat class 2 and 3L. Measurements included live weight, ultrasonic muscle and fat depth, live conformation score, carcass hot and cold weight, MLC fat score (on the standard seven-point scale) and conformation score (EUROP and 15-point scale) and a visual estimation of subcutaneous fat cover. Nearly 800 carcasses were dissected; 20% had a full side and 80% a shoulder dissection. In part-dissected carcasses, shoulder dissection results were used to predict the fat and lean content of the other joints. Fat and lean percentages and absolute weights were then regressed on the lean index and the residual live conformation score of the sire. At the same finished condition, Scottish Blackface offspring were heavier, older, and had less fat and more lean based both on ultrasound and on carcass dissection measurements compared with Hardy Speckled Face offspring. The index score of the sire had a positive effect on the lean content and a negative effect on fat content of all joints. Conformation of the sire did not have a significant effect on any of the carcass composition measurements, but most conformation traits measured on the animal itself (live or on the carcass) were positively related to fat and negatively to lean content in the carcass. When taking into account differences in visually assessed subcutaneous fat percentage, the carcass conformation traits persisted only in having a positive effect on carcass fat content; none of the conformation traits had an effect on carcass lean content. The results show that selection of sires on lean index is an effective way to improve carcass composition in Mule wethers, but selection on conformation is ineffective.

Copyright

Corresponding author

References

Hide All
Cameron, N.D. and Thompson, R. 1986. Design of multivariate selection experiments to estimate genetic parameters. Theoretical and Applied Genetics 72: 466476.
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 Production 67: 299309.
Conniffe, D. and Moran, M.A. 1972. Double sampling with regression in comparative studies of carcass composition. Biometrics 28: 10111023.
Cook, G.L., Jones, D.W. and Kempster, A.J. 1983. A note on a simple criterion for choosing among sample joints for use in double sampling. Animal Production 36: 493495.
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, pp. 113122.
Dickerson, G.E. 1978. Animal size and efficiency: basic concepts. Animal Production 27: 367379.
Heelsum, A.M. van, 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: 113127.
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: 553561.
Kempster, A.J., Cook, G.L. and Grantley-Smith, M. 1986. National estimates of the body composition of British cattle, sheep and pigs with special reference to trends in fatness. A review. Meat Science 17: 107138.
Kempster, A.J., Croston, D. and Jones, D.W. 1981. Value of conformation as an indicator of sheep carcass composition within and between breeds. Animal Production 33: 3949.
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: 133142.
Meat and Livestock Commission. 2000. Sheep yearbook. MLC, Milton Keynes, UK.
Simm, G. and Murphy, S.V. 1996. The effects of selection for lean growth in Suffolk sires on the saleable meat yield of their crossbred progeny. Animal Science 62: 255263.
Smith, C. 1964. The use of specialized sire and dam lines in selection for meat production. Animal Production 6: 337344.

Keywords

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed