Genetic by Environmental Interactions for Pig Growth
Purdue University 1999 Swine Research Report. The pork industry is driven by consumer demand for consistent quality, lean pork products. To meet consumer demand, the pork industry must continue to improve the efficiency of lean pork production. The two primary approaches for improving the efficiency of pork production are through genetic and environmental-management changes. Each commercial producer must first decide which genetics should be used in their production facility. After making the key genetic decisions, each pork producer must consider cost-effective management changes to optimize the expression of the genetic potential of their pigs. A number of alternative management decisions must be evaluated which are influenced by production costs (i.e., feed, facilities, labor and interest costs) and the relative rate of payment for carcass lean versus fat in the marketing system. Substantial differences in performance exist between different environments and health management strategies. Environmental factors including disease exposure, social stress, and less than optimal stocking density limit growth, such that pigs managed under commercial conditions are unlikely to express their maximum potential protein accretion, even when allowed ad libitum access to a high quality, nutrient dense diet. In a past trial, pigs with minimal diseases via segregated early weaning (SEW), which were fed a series of non-limiting diets, achieved 230 lb at 136 days of age and 264 lb at 151 days of age (Schinckel et al., 1995). Pigs raised on the original commercial farm, conventionally weaned with all-in, all-out production, required 184 days to attain 230 lb live weight. In a second trial, pigs moved to a research building with 3 pigs per pen and 24 ft2 per pig grew 42% faster than pigs reared on the commercial farm (Holck et al., 1998). These types of observations are prompting producers to make health management changes. To produce quality lean pork more efficiently, the direct effects and interactions between genetic potential for lean growth and health-management level must be understood. Producers need to have some expectations as to the magnitude of performance changes as a result of both genetic and health status changes. Therefore, three genotype by environmental interaction trials were completed. The objectives of these studies were to evaluate possible interactions between genetic potential for lean growth, sex, antibiotic treatment, and health status environments on lean gain and pork quality.