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Growth and carcase parameters of lams sired by extreme muscle density lambs at differing end points

Price, E.M., Roden, J.A., Haresign, W., Finch, J.A., Gardner, G.E. and Scollan, N.D. (2013) Growth and carcase parameters of lams sired by extreme muscle density lambs at differing end points. In: 64th Annual Meeting of the European Federation of Animal Science, 26 - 30 August, Nantes, France.


In vivo measures of carcase quality can aid selection. Muscle density, (measured by computer tomography) has strong negative genetic and phenotypic correlations with intramuscular fat. The aim of this study was to evaluate growth and carcase parameters of lambs, sired by five high and low muscle density Terminal sire rams, using three different covariates. Progeny (n=394) were recorded for live weight at: birth; 8 weeks, 16 weeks and immediately pre-slaughter. Ultrasonic measurements were made at the third lumbar vertebrae, pre-slaughter. Carcase records include carcase weights, EUROP classification scores for fatness and conformation. Data were analysed using GENSTAT 15, using a sire nested within muscle density ANOVA design model, fitting sex; dam age (slaughter batch for carcase traits); birth/rear type and MyoMaxTM carrier status. The model was adjusted for the covariates, age at measurement (age): live weight at slaughter (Slwt); or slaughter fat grade (fat). Low muscle density sired lambs were heavier at 8 weeks (age P=0.022; Slwt P=0.043: fat P=0.04) and 16 weeks (age 0.014; Slwt P=0.05; fat P=0.036). However high muscle density sired lambs had increased ultrasonic muscle depth (age 0.0 19: Slwt P=0.017; and fat P=0.017), heavier hot carcase weight (age P=0.004; Slwt P<0.001; fat P=0.004), 48 h cold carcase weight (age P=0.027; Slwt P<0.001: fat P=0.013), higher killing out percentages (age, Slwt and fat P<0.001), and improved carcase conformation (age, Slwt and fat P<0.001). It is proposed that when compared at the same end point, high muscle density sired lambs have increased lean tissue which is expressed as higher carcase weight rather than live weight. Further data analysis is underway to investigate primal yields, waste data and eating quality.

Publication Type: Conference Item
Murdoch Affiliation: School of Veterinary and Life Sciences
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