The influence of RN genotype, including the new V199I allele, on the eating quality of pork loin

The eating quality of M. longissimus dorsi (LD) from RN- homozygotes, RN- heterozygotes and RN- non-carriers was investigated in a Swedish Hampshire x Finnish Landrace pig population. The recently identified new allele (V1991, here denoted rn*) at the RN locus was also detected among the pigs selected and included in the sensory evaluation. The number of animals varied from 10 to 15 in the five genotype groups; RN-/RN-, RN-/rn+, RN-/rn*, rn+/rn+ and rn+/rn* (in total 59 pigs). In addition, one pig was determined to be rn*/rn* but was excluded from the analysis. The three genotypes in which the RN allele was represented (RN-/RN-, RN-/rn+ and RN-/rn*) had higher glycogen and lower protein contents as well as lower ultimate pH (measured 48 h post-mortem) in LD than the non-carriers (rn+/rn+ and rn + rn*). Of the sensory parameters evaluated (tenderness, chewing time, chewing residual, juiciness, meat flavour and acidity), the five RN genotypes only affected acidity significantly; the RN- allele contributing to a more acid taste in LD. The influence of the rn* allele resembled that of rn + on the sensory parameters. When the material was divided into three groups (homo-Zygous, heterozygous and non-carriers of the RN- allele) the juiciness was found to be significantly influenced by RN genotype, and LD from animals that were homozygous and heterozygous with respect to the RN- allele exhibited a higher juiciness than LD from non-carriers. The RN- allele also tended to contribute to greater tenderness, which was significantly higher in LD from heterozygous carriers than from non-carriers of the RN- allele. A more rapid decline in pH (measured as pH at 45 min and 3 It postmortem) contributed to a greater tenderness in LD (according to a trained panel and Warner-Bratzler shear force). In addition to the RN genotype, the decline in pH was influenced by carcass weight, which varied between 71 and 97 kg, and by stunning procedure, which changed during the course of the study from individual to group stunning with CO, The individual stunning procedure contributed to a lower pH in the initial post-mortem phase (pH(45)), whereas a higher carcass weight and the RN- allele lowered the pH in the mid-post-mortem region (pH(3h) and pH(24h)), significantly (P less than or equal to 0.05). The pH continued to decline after 24 h post-mortem and the ultimate pH was not reached until 48 h post-mortem. The cooking loss, juiciness and acidity were related to the specific characteristics of the RN- carriers, such as higher glycogen content, lower protein content and lower ultimate pH (pH(48h)) (C) 2003 Elsevier Ltd. All rights reserved

A second mutant allele (V199I) at the PRKAG3 (RN) locus - II. Effect on colour characteristics of pork loin

Three alleles at the PRKAG3 (RN) locus that influence the glycogen content of pork were found to be segregating in Hampshire x Landrace crossbred pigs, RN-, rn(+) as well as second mutant allele V 1991 (here denoted rn*). The effect of these three alleles on ultimate pH, pigment content, internal reflectance (FOP), surface colour measured by tristimulus colorimetry (L*, a*, b*) and fractions of deoxymyoglobin (Mb), oxymyoglobin (MbO(2)) and metmyoglobin (MetMb) of pork loin was studied. Moreover, the effect of sex, entire male versus female pigs, on these traits was also analysed. The three PRKAG3 alleles affected ultimate pH, internal reflectance, colour and distribution of myoglobin derivatives of pork loin, while the pigment content was not influenced. Ultimate pH values of loins from the three genotypes were found to be in the order RN-/- genotypes < rn(+)/rn(+) genotype < rn(+)/ genotype rn(+)/rn(+) genotype. The internal reflectance in the loin was found to be in the order RN-/- genotypes <rn(+/)rn(+) genotype = rn(+)/rn(+) genotype = rn(+)/rn(+) genotype. The RN- allele was dominant resulting in higher redness (a* value) and yellowness (b* value), while the rn* allele tended to result in lower redness and yellowness compared with the rn* allele. The RN- allele was dominant over the rn* allele in lightness (L* value) giving a lighter colour. Surface colour differences were mainly explained by differences in the distribution of the myoglobin derivatives. Finally, surface lightness was higher and pigment content, redness and fraction of MbO(2) lower in loin from entire males compared with females. (C) 2003 Elsevier Ltd. All rights reserved

Effects of a second mutant allele (V199I) at the PRKAG3 (RN) locus on carcass composition in pigs

The effect of a second mutant allele (V1991, 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 x LH; LH x H; LH x LH). Pigs were classified according to DNA test into the following PRKAG3 genotypes: RN-IRN- (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* (M). 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) 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. (c) 2005 Elsevier B.V All rights reserved

A second mutant allele (V199I) at the PRKAG3 (RN) locus - I. Effect on technological meat quality of pork loin

The effect of three alleles (RN-, rn(+) and a second mutant allele V1991, denoted rn*) at the PRKAG3 (RN) locus on such meat quality traits as pH, internal reflectance (FOP), Warner-Bratzler shear force, water-holding capacity and cooking loss were studied. M. longissimus dorsi (LD) from a total of 334 crossbreed pigs, entire males and females, Hampshire (H) and Finnish Landrace (L) of three combinations H x LH, LH x H and LH x LH, were used. The PRKAG3 alleles were identified with a DNA test and all possible RN genotypes, RN-/RN- (23%), RA(-)/rn(+) (24%), RN-/rn* (33%), rn(+)/rn(+) (8%), rn(+)/rn* (9%) and rn*/rn* (2%), were found. Water, intramuscular fat, protein and glycogen contents were determined. All the three alleles at the RN locus affected the studied technological meat quality traits of pork loin, except for the internal reflectance 24 h post mortem and the shear force. The RN- allele was dominant over the other two alleles, rn(+) and rn*, in LD with regard to ultimate pH, water-holding capacity and cooking loss, giving lower ultimate pH and water-holding capacity and higher cooking loss. The rn* allele affected ultimate pH in LD of non-carriers of the RN- allele, giving higher ultimate pH. The RN- allele was also dominant over the other two alleles in residual glycogen content in entire male pigs, but not in female pigs, where the rn* allele had a glycogen-lowering effect. The water content was higher and the protein content lower in LD of all RN-/- animals compared with the other genotypes, while no significant differences were found with regard to IMF content. Water-holding capacity, cooking loss and shear force were higher in LD of entire males compared with females. (C) 2003 Elsevier Ltd. All rights reserved