Sendros D. Mulugeta

Integrating economic parameters into genetic selection for Large White pigs.

The objective of the study was to integrate economic parameters into genetic selection for sow productivity, growth performance and carcass characteristics in South African Large White pigs. Simulation models for sow productivity and terminal production systems were performed based on a hypothetical 100-sow herd, to derive economic values for the economically relevant traits. The traits included in the study were number born alive (NBA), 21-day litter size (D21LS), 21-day litter weight (D21LWT), average daily gain (ADG), feed conversion ratio (FCR), age at slaughter (AGES), dressing percentage (DRESS), lean content (LEAN) and backfat thickness (BFAT). Growth of a pig was described by the Gompertz growth function, while feed intake was derived from the nutrient requirements of pigs at the respective ages. Partial budgeting and partial differentiation of the profit function were used to derive economic values, which were defined as the change in profit per unit genetic change in a given trait. The respective economic values (ZAR) were: 61.26, 38.02, 210.15, 33.34, -21.81, -68.18, 5.78, 4.69 and -1.48. These economic values indicated the direction and emphases of selection, and were sensitive to changes in feed prices and marketing prices for carcasses and maiden gilts. Economic values for NBA, D21LS, DRESS and LEAN decreased with increasing feed prices, suggesting a point where genetic improvement would be a loss, if feed prices continued to increase. The economic values for DRESS and LEAN increased as the marketing prices for carcasses increased, while the economic value for BFAT was not sensitive to changes in all prices. Reductions in economic values can be counterbalanced by simultaneous increases in marketing prices of carcasses and maiden gilts. Economic values facilitate genetic improvement by translating it to proportionate profitability. Breeders should, however, continually recalculate economic values to place the most appropriate emphases on the respective traits during genetic selection.

Evaluating Environmental Effects on Growth Performance and Carcass Characteristics of South African Large White Pigs

Abstract Genetic improvement of growth and carcass traits and animal management require proper identification and evaluation of non-genetic effects on these traits. Performance data were on 20079 Large White pigs from 29 herds, while carcass data comprised of 5406 records from 20 herds. The animals were tested between 1990 and 2008 and carcass evaluated between 1993 and 2007. 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). PROC REG and GLM were used to determine significant effects. Herd of origin, year of testing and their interaction significantly affected all traits. Most traits were not affected by season of testing, while all traits were significantly affected by sex. Testing environment affected all growth traits except for LTG. All traits decreased with increasing feed intake, while age at the start of the test was associated with decreases in most traits. On-test treatments do not compensate for pre-test underperformance. Castrates produce higher carcass yields of less quality than females, while performance testing has best results when done at the testing centres in summer. There is need to adjust for fixed effects when performing genetic evaluations in these pig populations.