SLAUGHTER AND CARCASS CHARACTERISTICS OF 3 FAT-TAILED SHEEP BREEDS AND THEIR CROSSES WITH CORRIEDALE AND TARGHEE RAMS

Intact ram lambs (n = 119) of three fat-tailed Iranian breeds: Karakul, Mehraban and Baluchi, and their crosses with Corriedale and Targhee rams were kept in feedlot for 100 days after weaning and slaughtered at 175 days of age. Offal items, internal fat, and carcass cuts were individually weighed, backfat thickness and rib-eye muscle dimensions were recorded. Mehraban lambs had heaviest and Baluchi lightest (P < 0.05) slaughter and carcass weights among the three breeds. Measures of body fat and carcass fat were major sources of differences among the breeds. The small-size Baluchi, which is well adapted to sub-desert conditions, was fattest and had highest proportions of kidney and tail fat. Karakul had highest omental and mesenteric fat, while Mehraban had the thickest subcutaneous fat cover. Averages of crossbreds exceeded averages of purebreds by 11% (P < 0.01) in slaughter and tail-free carcass weight, but only by 6.0% (P = 0.06) in carcass weight. Crossbreds had markedly higher percentages of non-carcass components, carried 18.3% more fat in the body cavity, and had 64% less fat in the tail region compared with the fat-tailed purebreds. Tail-free carcasses of purebred and crossbred lambs were similar in proportional weight of wholesale cuts, but crossbreds had larger rib-eye muscle dimensions and thicker subcutaneous fat cover than purebreds. Corriedale and Targhee rams had similar effects on almost all traits studied. It was concluded that crossbreeding improved slaughter and carcass traits of fat-tailed breeds mainly by reducing total body fat, and extent of reduction was directly proportional to body fat content of fat-tailed breeds.