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A Genetic Analysis of Feed Conversion Efficiency and Associated Traits in Swine

U.S. Department of Agriculture³, Beltsville, MD 20705

Abstract

Performance records were analyzed for 1,869 purebred Duroc and Yorkshire gilts tested in littermate groups of two to four pigs in 703 pens. Traits studied were average daily gain during a standard test period from 56 d of age to 90.7 kg (ADG), average daily feed consumption during the test period (ADF), average backfat thickness (ABF) measured from polaroid photos of ultrasonic scans at 90.7 kg and efficiency of feed conversion for the whole test period (feed conversion efficiency, FCE). The main objectives were: 1) to estimate pertinent genetic and phenotypic parameters and 2) to discuss applications of the findings to the swine industry in the United States. A balanced 16% crude protein diet in pelleted form was provided ad libitum during the entire test period. Nested analyses of variance were computed with both the individual and pen mean records. Sire components of variance and covariance, adjusted for level of inbreeding, were used to estimate heritabilities and genetic and phenotypic variances, covariances and correlations. Heritabilities estimated from individual records were .098 for ADG and .423 for ABF. Estimates from pen means were .105 for ADF and .061 for FCE. Genetic correlations of FCE with ADG, ADF and ABF were estimated as -.520, -.520 and .694, respectively, while phenotypic correlations for the same traits were -.240, .570 and .212, respectively, all from pen means. Genetic and phenotypic correlations of ADG with ABF from individual records were .176 and .254, respectively. Implications for swine testing programs were discussed, including a proposal that would include FCE indirectly in an index with ADG and ABF, based on genetic covariances of FCE with ADG and ABF, thereby removing the need to measure FCE directly.

¹ USDA, Agr. Res. Serv., Beltsville Agr. Res. Center, Anim. Sci. Inst., Nonruminant Anim. Nutr. Lab., Beltsville, MD 20705.

² The author acknowledges with appreciation the contributions of R. L. Figulski and D. L. Parsons, Animal Caretaker Leaders, for managing the swine herd and collecting and recording the necessary data; the cooperation of W. H. Peters, Head, Animal Operations; and the contributions of Bonnie Morgan, Statistical Assistant.

³ Mention of trade names, proprietary product or vendor does not constitute a guarantee or warranty of the product by USDA or imply its approval to the exclusion of other products or vendors that may also be suitable.