Frequency of the Rendement Napole RN super(-) allele in a population of American Hampshire pigs

A total of 204 purebred Hampshire pigs were obtained from 23 breeders. These animals were the progeny of 41 sires and 123 dams. A sample of purebred Yorkshire (n = 24) pigs were also used in the study. Animals were classified by glycolytic potential determined on a live-animal longissimus muscle biopsy sample. Hampshire pigs (n = 176) with glycolytic potential greater than 185 mu mol/g (mean = 238.8 mu mol/g; SD = 29.54) were classified as heterozygous or homozygous for the dominant RN super(-) allele (RN super(-)rn super(+) or RN super(-)RN super(-), respectively), whereas cohorts (n = 28) with glycolytic potential less than 185 mu mol/g (mean = 141.3 mu mol/g; SD = 24.48) were considered as homozygous normal (rn super(+)rn super(+)). All Yorkshire pigs (n = 24) had a mean glycolytic potential level of 146.1 mu mol/g (SD = 20.18) and were considered as homozygous normal (rn super(+)rn super(+)). The Hardy-Weinberg equilibrium yielded frequencies of .630 and .370 for the dominant RN super(-) allele and normal rn super(+) alleles in the Hampshire population, respectively, and genotypic frequencies of .397 (RN super(-)RN super(-)), .466 (RN super(-)rn super(+)), and .137 (rn super(+)rn super(+)). Hampshires with glycolytic potential is more than or equal to 185 mu mol/g had significantly lower longissimus muscle ultimate pH, intramuscular fat, subjective marbling scores, and percentage of protein (P < .001) and had greater longissimus muscle percentage of moisture (P < .001), drip loss (P < .01), and cooking loss (P < .001) than rn super(+)rn super(+) Hampshires and Yorkshires. These data suggest the RN super(-) allele exists at a high frequency within the American Hampshire breed. Higher glycolytic potential levels, which accompany the allele, may cause decreased meat quality. Implications: The high frequency of the RN super(-) allele and its negative effects on water-holding capacity is of concern because of the widespread use of the Hampshire breed in the United States. Selection against the allele is likely to have a positive impact on the water-holding capacity of the muscle and consequently on processing and curing yields.