The same gene also causes increased leanness and feed efficiency. It is uncertain whether, and if so to what degree, these heterozygotes also produce PSE meat. On the belief that heterozygotes show increased leanness but not PSE, it has been suggested that heterozygotes might have an economic advantage over normal homozygotes that carry no copies of the PSS gene. The HAL-1843 TM test was used to determine the PSS genotype of some 2900 pigs in the project based on DNA extracted from lean meat, fat and blood samples. Methods of statistical analysis of data are described in Appendix 3.
All estimates presented here are from reduced models with all non-significant effects removed.
In the following description of results, differences between heterozygotes and homozygotes are described as percentages of the homozygote performance. Results The numbers of pigs of each genotype for each breed are shown in Table 1. There was no statistical evidence of decline in frequency across the three years of the project, but it is known that many participants were using the test to eliminate the gene from their populations and we would expect much lower frequencies today. Estimates of the effect of the gene on growth and carcass characteristics are shown in Table 2. Although not statistically significant, changes in chemical fat and lean in belly and loin were consistent with changes in other measures of carcass leanness.