Introduction
The presence of the RN gene in swine of Hampshire descent and the impact of the gene upon fresh and processed pork quality attributes have been demonstrated by a number of European researchers (Le Roy et al., 1990; Lundstrom et al., 1996; Enfalt et al., 1997ab; Lundstrom et al., 1998; Lebret et al., 1999). Research has shown the dominant RN- allele frequency to be 0.61 (Enfalt et al., 1997a) in a Sweddirectional selection for or against the dominant RN allele difficult. Because the causative mutation for the RN gene is currently unknown, a biochemical test evaluating the GP of pork muscle is used to classify animals as carriers (RN-,RN- or RN-,rn+) or negative (rn+,rn+) for the RN gene.
This study was conducted in response to an industry need to characterize and study the impact of the RN gene in a typical U.S. Hampshire population raised and processed under typical U.S. swine production systems. The specific objectives of the research were 1) to estimate the RN allele frequencies in a sample of Hampshire AI sires, 2) assess the impact of the RN gene on performance, carcass composition, muscle quality and sensory characteristics of pigs and pork, and 3) to utilize available technology to genotype sires for the RN gene so that sire and family selection processes can be completed at the nucleus level.