GENETIC-VARIATION IN MEASURES OF FOOD EFFICIENCY IN PIGS AND THEIR GENETIC-RELATIONSHIPS WITH GROWTH-RATE AND BACKFAT

Data on 3783 Yorkshire, 2842 Landrace and 937 Duroc littermate pairs o f boars, station tested between 1976 and 1989, were used to measure ge netic parameters of average daily gain (ADG) from 30 to 90 kg, live ba ckfat at 90 kg (BF), estimated lean growth rate (LGR), average daily f ood intake, food conversion ratio (FCR) and lean food conversion ratio (LFCR), as well as measures of residual daily food intakes over and a bove requirements for growth and lean growth. A method was developed t o obtain restricted maximum likelihood estimates of genetic variances and covariances under an animal model when observations are on the mea ns of sib pairs. Heritabilities of ADG, BF, LGR, FCR and LFCR were 0.4 3, 0.59, 0.39, 0.28 and 0.34, respectively. Heritability of daily food intake was 0.45, and heritability of measures of residual daily food intake ranged from 0.30 to 0.38. About half of the variation in daily food intake was residual (0.48 to 0.56). Genetic correlations of ADG w ith daily food intake, FCR and LFCR were 0.80, -0.28 and -0.09, respec tively, and were small and positive (0.18 to 0.34) with measures of re sidual daily food intake. Backfat had genetic correlations of 0.42, 0. 24 and 0.52 with daily food intake, FCR and LFCR, respectively, and ge netic correlations between backfat and measures of residual daily food intake ranged from 0.15 to 0.61. Selection against residual food inta ke may be a useful means of improving efficiency of food utilization.