Author : Pham Ngoc Hiep

Summary : A total of 1468 individual records from an NSDB-UPCA cooperative project, which was initiated in 1964 and is still in progress, were used to study the response to selection and to construct a selection index for sow productivity traits. Method of fitting constants was used to determine the effect of known sources of variation, year, season, breeding group, line, sire, and age of dam on traits studied. Since all these factors showed significant effects, data adjusted for age of dam were analyzed with the statistical model containing all these sources. A four-way nested classification was assumed and the variance-covariance components were computed from this model, using the analysis of variance and co-variance technique. Heritability estimates and environmental, phenotypic, and genetic correlation values were obtained from the sire and within-sire components of variance and covariance.