The value of ultrasound in assessing the leg muscling of lambs
B.G. Ward, R.W. Purchas, A.Y. Abdullah
John Read Agricultural Consultancy, PO Box 217, Palmerston
North, New Zealand
Proceedings of the New Zealand Society of Animal Production.
1992, 52: 33-36
Rib-eye muscle (M. longissimus lumborum) area (REA) and depth
(B) at the 12th rib were ultrasonically measured on 89 ram lambs from 3
sire breeds. The lambs were then slaughtered and these live measures
plus carcass weight were evaluated as predictors of the corresponding
carcass measures and the following two measures of muscling, based on
four muscles surrounding the femur bone and the femur itself: 1.
Muscle:Bone ratio (M:B), and 2: Muscularity (MUSC), defined as an index
of muscle depth (square root of the weight of the four muscles per unit
femur bone length) relative to a skeletal dimension (femur length).
Prediction of carcass REA and B from ultrasonic REA and B, after
adjusting for carcass weight, was more effective for B (partial r=0.40)
than REA (partial r=0.18). The main problems with prediction arose with
higher values (B>33mm), when ultrasonic values underestimated actual
carcass values. REA and B (ultrasonic live and direct carcass)
significantly (p<0.001) improved the prediction of MUSC or M:B over
carcass weight alone, but did not account for the highly significant
(P<0.001) breed effect on these traits. It is concluded that ultrasonic
and carcass measures of REA and B provide useful but limited information
on lamb leg muscularity.
Keywords: NZSAPAB;
Ultrasound; carcass muscularity; lambs; sheep selection; breed
differences
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Last Updated 25-01-1997
