Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 1998
Publication Date: N/A
Technical Abstract: Genotypic and phenotypic data collected from flocks segregating at the CLPG locus were used to estimate genotypic effects on growth, carcass, and female reproduction traits. The grandparent generation consisted of nine Dorset rams of callipyge phenotype (CN genotype) exposed to 255 Romanov ewes (NN genotype). The parent generation involved inter se matings of eight F1 rams of callipyge phenotype with 152 phenotypically normal and callipyge F1 ewes. F2 ewe and wether lambs (n=362) from two years of inter se matings were serially slaughtered to obtain carcass data. The statistical model for F2 data fitted effects of year, sex, sire, regressions on polar overdominance (PO) contrast of genotypic probabilities, and the interaction of PO with linear and quadratic regressions on carcass weight. Growth traits were similar among genotypes. When tested at 25.6 kg carcass weight, PO was highly significant (P<.001) for carcass traits except carcass ash. Least-squares means of CN genotype expressed as a percent of combined normal genotypes were: live weight, 94; pelt weight, 90; liver weight, 88; kidney-pelvic fat, 71; 12th-rib fat depth, 62; carcass length, 96; shoulder width, 102; rump width, 104; longissimus area, 133; and weight of carcass water, protein, fat, and ash, 111, 112, 77, and 98, respectively. CN genotype carcasses consisted of 24.3% fat and 71.3% fat-free lean compared to 31.5% and 64.0% for normal genotypes. Data collected on F2 ewes at slaughter indicated CN genotypes produced .2 corpora lutea less (P>.05) than normal genotypes at 215 d age. Callipyge genotypes can be used in structured mating systems to make improvements in dressing percentage, lean growth rate, muscle shape, and carcass composition.