Methods of ranking two-tooth rams for fat-free carcass growth
rate
A.M. Nicol, A.C. Parratt
Department of Animal Science, Lincoln College, Canterbury
Proceedings of the New Zealand Society of Animal Production.
1984, 44: 253-256
Twenty eight Border Leicester 2-tooth rams (mean live weight 70
kg) were scored for fatness on a 10-point scale by 6 drafters and back
fat thickness was measured by ultrasonic probe (UFD). Chemical fat
percentage (mean 33.9%) was determined on a half-carcass of each ram.
Mean carcass weight, measurement C and GR were 38.0 kg, 12 mm and 28 mm
respectively. Mean drafters' fat score was more highly correlated with
% carcass fat (+0.83) than UFD (+0.67). The prediction of fat-free
carcass weight (FFCW) from live weight plus UFD (R2=0.72, RDS 1.24 kg)
or drafters' fat score (R2=0.76, RSD 1.14 kg) was superior to prediction
from live weight alone (R@=0.59, RSD 1.49 kg). The inclusion of UFD o9r
drafters' fat score increased the efficiency with which rams were ranked
for fat-free carcass weight. Selection of the top 10% of rams ranked on
the prediction of FFCW from live weight achieved 75% of the potential
selection differential. Inclusion of either UFD or drafters' score
improved the potential to 95%.
Keywords: NZSAPAB;
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