|Freking, Bradley - Brad|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/1999
Publication Date: N/A
Interpretive Summary: The impact on meat quality traits of a gene with large favorable effects on lean and fat development of sheep was investigated. This gene was named callipyge and sheep with specific forms of the gene had extreme values for carcass leanness. However, these lean sheep also produced loin chops that were less tender than desired. The means and variation of meat quality traits for each of the four combinations of gene forms was reported. It was discovered that sheep with two copies of the mutant form of the gene produced less tender loin chops without increased carcass leanness. Identification of the specific pathways which the callipyge gene influences lean and fat development while altering meat quality would improve understanding of biological events affecting muscle growth and meat tenderness.
Technical Abstract: A resource flock of 362 F2 lambs provided phenotypic and genotypic data to estimate effects of callipyge (CLPG) 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. Warner-Bratzler shear force and subjective evaluation of marbling were collected during both years from longissimus. Calpastatin activity was collected on longissimus from the 1994 group and ELISA quantification of calpastatin protein obtained from the 1995 group. Significant additive and paternal polar overdominance effects on meat quality traits were detected. This is in contrast to previous research that detected only polar overdominance effects on slaughter and carcass traits in this population. 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 in shear force between homozygous genotypes (additive effect) was supported by calpastatin activity data. Calpastatin ELISA data exhibited a paternal polar overdominance effect exclusively (P < .001). Additive and paternal polar overdominance effects on marbling were significant (P < .01). Consequences of increased longissimus shear force must be addressed if the advantages of CN lambs for dressing percentage and carcass composition are to be realized. Further research is needed to establish if selection targeted at changing the background genome can mitigate the negative effects of the C allele on meat tenderness.