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Title: Genetics of growth, development and carcass quality in meat sheep and the use of CT scanning as a tool for selection
Author: Macfarlane, J. M.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2006
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Abstract:
This work aimed to (i) explore the consequences of some breed and feed choices on lamb growth and carcass composition, (ii) examine changes in carcass quality traits during growth in meat sheep, (iii) identify ways in which CT scanning information can be used to measure carcass quality traits in meat sheep, and (iv) optimise two stage selection strategies for incorporating CT scanning into breeding programmes for meat sheep. Consequences of some breed and feed choices on lamb growth and carcass composition were explored using experimental data where growth rate and carcass composition had been measured at various stages of maturity in lambs of different genotypes (Suffolk and Scottish Blackface and their cross) in different nutritional environments (different dried, pelleted forages indoors and different swards outdoors). Lambs fed indoors on dried Ryegrass or dried Lucerne showed no genotype of diet effects on carcass composition. However, lambs on Ryegrass had lower intakes (0.878 as great) and slower growth (0.851 as fast) than those on Lucerne. Genotype effects on geed intake and growth rate were related to mature size differences. When lambs were grazing different swards outdoors, sward type did not affect carcass composition at any stage of maturity. At 0.30 mature weight, genotype differences in carcass composition were small but by 0.45 mature weight, Scottish Blackface lambs had less fat (0.749 as much), more lean (1.065 as much) and more bone (1.055) as much) than did Suffolk lambs. Genotype by sward interactions existed for growth rate, Suffolk lambs having higher growth rates than Scottish Blackface lambs on Clover but not on Rye grass. Growth rate declined to a greater extent in Suffolk than Scottish Blackface lambs as nutritional environment became worse; that is, Suffolk lambs expressing greater environmental sensitivity than the Scottish Blackface. Carcass composition, tissue distribution and fat partitioning, and the way in which these attributes changed with growth in live weight, were studied in three breeds of terminal sire sheep. Data used were from 160 lambs from a serial slaughter and dissection trial. Texel lambs, at similar live weights, were leaner than Suffolk or Charollais lambs but any differences in tissue distribution and fat partitioning were small. Proportion of carcass weight and lean contained in the higher priced joints declined while intramuscular fat content increased with growth in live weight. Lambs became fatter overall, with partitioning of carcass fat tending more towards the subcutaneous depot, with growth in live weight.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.654237  DOI: Not available
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