Estimated Frequency of the RN− Allele in Swedish Hampshire Pigs and Comparison of Glycolytic Potential, Carcass Composition, and Technological Meat Quality Among Swedish Hampshire, Landrace, and Yorkshire Pigs1

The frequency of the dominant RN− allele (Rendement Napole) was estimated in purebred Swedish Hampshire pigs (n = 208) by using the estimated glycogen content in the longissimus muscle at slaughter (glycolytic potential; GP). Carriers (n = 177) and noncarriers (n = 31) of the RN− allele were compared with purebred Swedish Yorkshire (Y, n = 208) and Swedish Landrace (L, n = 114) pigs with respect to GP and carcass composition. Technological meat quality was compared between the RN phenotypes from the Hampshire breed and Yorkshire pigs. The distribution of GP deviated from a normal distribution in all three breeds. Hampshire pigs with GP ≥ 183 mmol lactate equivalents per gram wet weight were regarded as carriers of the RN− allele (RN−/RN−, or RN−/rn+) , and those constituted 85% of all Hampshire pigs evaluated, giving a frequency of .61 for the dominant allele (RN−) . The RN− carriers had higher GP than noncarriers, Landrace, and Yorkshire pigs, but noncarriers and Landrace did not differ regarding GP. The two RN phenotypes did not differ in carcass composition, but the carriers were leaner than Landrace and Yorkshire, with larger proportions of meat plus bone in ham and back. Noncarriers and Yorkshire did not differ in leanness, but both these groups were leaner than Landrace. The RN− carriers had lower Napole yield (cured cooked muscle) and higher drip loss than noncarriers and Yorkshire, but in comparison with noncarriers they also had lower shear force values. In conclusion, the frequency of the RN− allele is high in purebred Swedish Hampshire. Most of the effects of the allele on technological meat quality (i.e., ultimate pH, waterholding capacity, and technological yield) found in crossbred pigs seem also to be consistent for purebred pigs. However, the RN− allele exerted less influence on meat content in purebred pigs.