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Title: Methods of incorporating market signals and measures of carcass shape into genetic selection indices for terminal sire breeds of sheep
Author: Jones, Huw Euros
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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Abstract:
The price obtained for lamb carcass has a direct effect on the profitability of a sheep and hence market requirements should be directly reflected in the objective of any breeding program for sheep. Despite their importance, market requirements are often assumed rather than known and market prices are not always used to form the objective. Moreover, although carcass shape affects commercial value, it has not been directly considered in current breeding programs. The aims of this study were (i) to establish the requirements of the current and likely future markets for lamb (ii) to develop methods of incorporating measures of carcass shape into selection programs and (iii) to develop methods for calculating economic values for selection objectives. A case study was conducted to establish current and likely future markets for lamb. Questionnaires were sent to the largest lamb retailers and abattoirs in the UK. Current markets generally required a carcass of weight 16-21kg, conformation E-R and fat score 2 or 3L. The forecast for future requirements was not clear, although both abattoirs and retailers desired carcasses that fitted a narrower range of quality specifications and foresaw increasing demand for heavier carcasses (above 21kg) to supply bone -less products. This suggests that a two market scenario, one for medium sized lambs to supply bone-in cuts, and the other for heavier, lean carcasses to supply bone-less lamb, could develop in the long term. Carcass shape is quantified commercially using a conformation score. However, the assessment is subjective and confounded with fatness and hence an objective assessment of muscularity is undoubtedly preferable. five measures of muscularity (three for the M. longissimus thoracis et lumborum (LTL) muscle, one for the hind leg and one for the whole carcass) were derived from carcass dissection data for 100 Suffolk, 40 Texel and 20 Charollais lambs. Changes with growth, relationships with tissue composition and lean distribution, as well as the relationships between the different muscularity measures were investigated. Higher muscularity at a given live weight was generally associated with higher lean to bone ratio and carcass lean content. Associations with fat content were either non-significant or negative. Relationships with lean distribution were also non-significant. Correlations between muscularity measures in different regions were low in Suffolk and Charollais lambs but higher for the Texels. This suggested that more than one measure would be required, particularly for Suffolk and Charollais lambs, if the muscularity of a carcass was to be described effectively. The results of this study provide the information needed to develop new selection indices that include measures of carcass shape and are well suited to produce sires with progeny that will meet the requirements of current markets for lamb, and those likely in the future.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.653138  DOI: Not available
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