Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 1999
Publication Date: N/A
Technical Abstract: A resource flock of 362 F2 lambs provided phenotypic and genotypic data to estimate effects of four callipyge genotypes (NN, NC, CN, and CC) on meat quality traits. The mutant allele is represented as C, the normal allele(s) as N, and the paternal allele of a genotype is given first. Lambs of each genotype born in 1994 and 1995 were serially slaughtered in six groups at 3-wk intervals starting at 23 wk of age. Significant additive and paternal polar overdominance (PO) effects on meat quality traits were detected. The magnitude of genotypic effects on shear force differed significantly between years; however, additive (P<.01), PO (P<.001), and maternal dominance (P<.01) effects adjusted for variation in carcass weight were detected within each year. Shear force data adjusted to the mean slaughter age or carcass weight indicated that the means and variances of CN and CC genotypes were greater than values of NC and NN. Shear force values were greatest for CN and were intermediate for CC. The difference between homozygous genotypes was supported by calpastatin activity data with 2-df F tests of 3.66 (P<.05) and 11.84 (P<.001) at d 0 and d 7 postmortem, respectively. Corresponding values for the PO effect on calpastatin activity were 53.80 (P<.001) and 87.43 (P<.001). Calpastatin ELISA data exhibited a PO effect exclusively with a 2-df F test of 57.63 (P<.001). Additive and PO effects on marbling had F tests of 6.41 (P<.01) and 93.29 (P<.001), respectively. Further research is needed to establish if selection targeted at changing the background genome can ameliorate the negative effects of the C allele on tenderness of the longissimus and maintain favorable muscle growth.