Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 6/10/1996
Publication Date: N/A
Technical Abstract: A resource population was produced to provide genotypic and phenotypic data for detection of chromosomal segments affecting traits recorded on sheep. The grandparent generation consisted of nine Dorset rams of callipyge phenotype exposed to 255 Romanov ewes. The parent generation involved inter se matings of six F1 rams of callipyge phenotype with 152 phenotypically normal and callipgye F1 ewes. F2 ewe and wether lambs were serially slaughtered in six groups at 3-wk intervals beginning at 23 wk of age. Leg conformation scores (range 9-17), assigned to carcasses, formed the basis for classification as normal (9-12) and callipyge (14-17) phenotypes. The present objective is to estimate effects of phenotypic class on various carcass traits. Data collected on 120 normal and 67 callipyge carcasses were analyzed. The statistical model fit effects of sex, class, sex x class, and class-specific linear regressions on carcass weight. When tested at 24.5 kg of carcass weight, effects of class were detected (P<.0001) for all reported traits except carcass ash (P<.25). The least-squares means of callipyge carcasses, expressed as a percent of normal carcasses, were: carcass length, 96; femur length, 97; shoulder width, 103; rump width, 104; longissimus area, 130; kidney-pelvic fat, 72; 12th-rib fat depth, 62; and carcass water, protein, fat, and ash, 111, 111, 77, and 98, respectively. Adverse effects of the callipyge phenotype on meat quality were detected as marbling score decreased 37%, postmortem calpastatin activity at d 0 and 7 increased 51 and 85%, respectively, and shear force increased 52%. Despite the beneficial effect of the callipyge phenotype on carcass leanness, the detrimental effect on meat tenderness must be circumvented before the callipyge allele can be exploited.