Non-genetic factors affecting growth performance and carcass characteristics of two South African pig breeds

A study was conducted to establish non-genetic factors affecting growth and carcass traits in Large White and Landrace pigs. This study was based on 20 079 and 12 169 growth and 5 406 and 2 533 carcass data collected on performance tested pigs between 1990 and 2008 from Large White and Landrace breeds respectively. The traits analyzed were backfat thickness (BFAT), test period gain (TPG), lifetime gain (LTG), feed conversion ratio (FCR), age at slaughter (AGES), lean percentage (LEAN), drip-free lean percentage (DLEAN), drip loss (DRIP), dressing percentage (DRESS), carcass length (CRLTH) and eye muscle area (AREA). Significant effects were determined using PROC GLM of SAS. Herd of origin, year of testing and their interaction significantly affected all traits. Most traits were not affected by season of testing in both breeds, while all traits in both breeds were significantly affected by sex. Testing environment (station, farm) affected all growth traits except for LTG. Backfat thickness and AGES increased with increasing total feed intake, while other traits decreased as total feed intake increased. Improved test centre management did not compensate for pre-test underperformance. Castrates produced higher carcass yields of lower quality than females, while performance testing showed the best results when done at testing centres. This study showed the importance of adjusting for fixed effects when performing genetic evaluations in the two pig populations.