Effects of a second mutant allele (V199I) at the PRKAG3 (RN) locus on carcass composition in pigs
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The effect of a second mutant allele (V199I, here denoted rn*) at the PRKAG3 (RN) locus on carcass composition was determined in 334 pigs, entire males and females, from crosses between Swedish Hampshire (H) and Finnish Landrace (L) (H LH; LH H; LH LH). Pigs were classified according to DNA test into the following PRKAG3 genotypes: RN -/RN- (23%), RN-/rn+ (24%), RN -/rn* (33%), rn+/rn+ (8%), rn +/rn* (9%) and rn*/rn* (2%). The pigs were slaughtered at a commercial slaughterhouse and assessed 24 h postmortem. Right sides were fabricated into primary wholesale cuts, then further processed into defatted hams and loins, and a subset of hams (n = 122) was dissected into the five major individual muscles. The genotype frequencies for the subsample were RN-/RN- (27%), RN-/rn+ (20%), RN-/rn* (35%), rn+/rn+ (9%), rn +/rn* (8%) and rn*/rn* (1%). Weights were recorded for meat and bone in ham and loin, fat in ham, back and shoulder and the individual dissected muscles. The genotype effect was significant (P < 0.05) for estimated lean meat content and the proportions of meat and bone and fat in ham and loin (of carcass weight). Also, the content of meat and bone in ham and loin, in proportion of whole ham and loin, respectively, differed significantly (P < 0.01) between genotypes. Estimated lean meat content was highest for RN-/RN- (63.0%) and RN-/rn+ (63.1%) and lowest in the combined group rn*/- (rn+/ rn* and rn*/rn*, 61.7%); RN-/rn* (62.5%) and rn+/rn+(62.1%) were intermediate. The same results were found for meat and bone in ham and loin, as a proportion of whole ham and loin, respectively. RN-/RN- and RN-/rn+ did not differ in any trait; however, they produced carcasses with the lowest proportions of fat within loin and the major wholesale cuts (ham, loin and shoulder). The carcass percentage of meat and bone in ham was higher in the three RN-/ genotypes (RN-/RN-, RN -/rn+ and RN-/rn*, P < 0.05) than in the rn*/- group, whereas rn+/rn+ did not (P > 0.05) differ from any of the other genotypes. RN-/rn + and RN-/rn* had higher (P < 0.05) proportion of meat and bone in loin compared to the rn*/- group. We conclude that the second mutant allele found at the PRKAG3 (RN) locus, rn*, decreased the lean meat content compared with the two other alleles (RN -, rn+). The RN-/RN- and RN -/rn+ genotypes were leanest, followed by RN -/rn* and rn+/rn+, and rn +/rn* and rn*/rn* were the fattest. 2005 Elsevier B.V. All rights reserved.
