title: Restricted maximum likelihood estimation of variance components from field data for number of pigs born alive.
abstract: Variance components for number of pigs born alive (NBA) were estimated from sow productivity field records collected by purebred breed associations. Data sets analyzed were as follows: Hampshire (n = 13,537), Landrace (n = 10,822), and Spotted (n = 3,949). Variance components for service sire, sire of sow, dam of sow, and residual effects on NBA (adjusted for parity) were estimated. The single-trait model included relationships between service sires, sires of sows, and dams of sows. The model was implemented using an expectation maximization (EM) REML algorithm. A sparse-matrix solver was also used. Heritability estimates for NBA were .13, .13, and .12 for Hampshire, Spotted, and Landrace, respectively. Estimates of maternal genetic (co)variances (m2) expressed as a proportion of the phenotypic variance were .05, .01, and .03 for Hampshire, Spotted, and Landrace, respectively. Results indicated that service sires account for 1 to 2% of the total variation for NBA. Genetic effects influencing NBA seem to be small in these data sets, but selection for increased NBA should be effective.
authors.affiliation: Animal and Dairy Science Department, University of Georgia, Athens 30602-2771.
authors.forename: M T
authors.initials: MT
authors.lastname: See
authors.forename: J W
authors.initials: JW
authors.lastname: Mabry
authors.forename: J K
authors.initials: JK
authors.lastname: Bertrand
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001947:Breeding; D005260:Female; D014644:Genetic Variation; D016013:Likelihood Functions; D008098:Litter Size / Q000235:genetics*; D008297:Male; D008957:Models, Genetic; D012641:Selection, Genetic; D013552:Swine / Q000235:genetics* / Q000502:physiology