The fat thickness over the 12th rib was measured ultrasonically on 41 Coopworth ram lambs (7 months of age, 34 to 57 kg live weight). Four of the 7 fattest and 4 of the 7 leanest were selected on the basis of their deviations from the overall fat thickness - live-weight relationship. Ten to 12 male progeny of each of these rams generated from Perendale ewes were slaughtered at 4 to 7 months of age and 4 parameters of carcass fatness measured. The difference between the progeny of the 4 lean sires and that of the 4 fat sires was significant for 2 fat measurements, namely C (P<0.05) the backfat thickness over the 12th rib, and S2 (P<0.01) a fat depth in the shoulder region. Differences in GR and total chemical fat failed to reach significance. The data indicate that selection of sires on the basis of backfat thickness could be an effective means of reducing carcass fat thickness in lambs.

GN, Hinch, and CJ Thwaites

Proceedings of the New Zealand Society of Animal Production, Volume 42, , 131-132, 1982
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