Genetic relationship between growth and carcass traits in Large White pigs

Genetic relationships between growth and carcass traits in South African Large White pigs were estimated. Genetic parameters for growth and carcass traits were generated using a maternal effects model in ASREML. Data analysed were on 13 703 pigs from 28 herds tested between 1990 and 2007, and 4 128 carcasses from 21 herds evaluated between 1993 and 2007. The traits included in the study were backfat thickness (BFAT), test period weight gain (TPG), lifetime weight gain (LTG), test period feed conversion ratio (FCR), age at slaughter (AGES), lean percentage (LEAN), drip-free lean percentage (DLEAN), drip loss percentage (DRIP), carcass length (CRLTH), dressing percentage (DRESS), eye muscle area (AREA) and carcass fat (CFAT). Heritability estimates for growth traits ranged from 0.24 +/- 0.03 for FCR to 0.45 +/- 0.04 for BFAT, while those for carcass traits ranged from 0.14 +/- 0.06 for DRIP to 0.55 +/- 0.0.08 for AREA. Maternal genetic effects were significant in most traits, and were negatively correlated with direct heritabilities. Genetic correlations among growth traits ranged from -0.14 +/- 0.08 between BFAT and LTG to -0.99 +/- 0.01 between TPG and FCR, and LTG and AGES. For carcass traits, genetic correlations ranged from -0.02 +/- 0.20 between DRIP and CRLTH to 0.99 +/- 0.01 between LEAN and DLEAN. There is substantial genetic variation in growth and carcass traits; hence faster genetic improvement may be achieved through selection. Growth performance and carcass characteristics can be improved through selection for reduced backfat thickness and increased daily weight gain.