Testing for the RN(-) gene in retail pork chops

A random sample of pork chops were purchased from local retail outlets to determine if the frequency of the RN(-) phenotype could be roughly estimated by GP measurements in fresh raw pork products or by genotyping for the nearest DNA microsatellite markers. Glycolytic potential (GP) is the estimated sum of glycogen, the intermediate metabolites of glycogenolysis, and the end product, lactate. GP has been used to identify a genetic mutation known as the RN(-) or Hampshire gene. Currently, there is no genetic test for the RN(-) allele and flanking DNA microsatellite markers were not useful at predicting the RN(-) phenotype in the random samples. Excessively high GP was found in 25% of the samples which correlated with a significant (P>0.05) drop in pH (5.8 to 5.7), a paler (L* value; 54.1 to 57.5) more yellowish (b* value; 9.6 to 11.6) color, and an increased cooking loss (9 to 18%), typical of the RN(-) phenotype. A genetic test for skin colour in swine proved that the majority (79%) of high GP pork sampled were from phenotypically white pigs. Analysis of glucose levels in post-rigor samples may be useful in progeny testing for the RN gene until a true genetic marker can be identified.