The Heritability and the Economic Importance of Nipple Numbers in Swine at the University of Ibadan.

Abstract

For the study, data were obtained from the Landrace and the Large White maintained separately as closed herds at the University of Ibadan. By subdividing each herd into three groups for rotational incrossing, close inbreeding was avoided. There was, in each herd, selection of a mild intensity for litter size and litter weaning weight in the females and for feed efficiency in the males. Piglets were creepfed from their two weeks of age and were weaned at 35 days of age. Thereafter they were fed weaners followed by growers rations which were both mixed on the farm and fed ad libitum. For the determination of heritability estimate of nipple numbers and of phenotypic and genetic correlation estimates, data were obtained from the whole or part of 20 sires, 67 dams and 345 female piglets of Landrace and 11 sires, 35 dams and 208 female piglets of Large White. There were unequal numbers of offspring to dam and of dam to sire in each breed. Heritability estimates by sib-analysis and by regression of daughter on dam, phenotypic and genetic correlation were derived in accordance with Becker (1963). The sibanalysis was based on the following model.