The number of ribs and vertebrae in a Pietrain cross: variation, heritability and effects on performance traits

In a three-generation experiment with five purebred Pietrain boars and one Landrace, one Large White and 12 Landrace x Large White crossbred sows as founder animals the number of ribs and presacral vertebrae was determined. These numbers were recorded for 111 F-1-animals and for 2711 F-2-animals. The number of ribs varied from 13 to 17 and the number of presacral vertebrae ranged from 26 to 30. Means of 15.5 for the number of ribs and 28.6 for the number of vertebrae with a standard deviation of 0.6 for both were calculated. Bayesian heritability estimates were 0.51 for the rib number and 0.62 for the vertebrae number. A phenotypic correlation of 0.76 and a genetic correlation of 0.97 indicated a close relationship of both traits. In additional analyses possible direct or linked effects of rib and vertebrae number on different growth and carcass traits were investigated. Significant effects were found for several traits related to growth, fatness, muscularity and meat quality. Genes for the presacral vertebrae number or linked quantitative trait loci (QTL) accounted for 11.5% of the phenotypic variation in carcass length and for 2.4% of the phenotypic variation in ham weight.