Genetic Progress Of American Yorkshire Swine
North Carolina State University Swine Genetics Research from 2001. Performance records collected by the American Yorkshire Club from 1988 to present were evaluated to report annual genetic progress. Since 1988, the average breeding value for number of pigs born alive, number of pigs weaned and litter weight at 21 days has improved .36 pigs, .10 pigs and 3.6 kg, respectively. The Sow Productivity Index and the Maternal Line Index have increased 5 and 17 index points, respectively. Regression coefficients indicating average annual improvements in breeding values for backfat depth, loin muscle area, days to 144 kg and kg of lean in an 84 kg carcass were -.06 cm, .43 cm2, -.45 days, and .21 kg, respectively. These results would indicate that genetic improvement has been achieved simultaneously for both reproductive and postweaning traits.