Evaluation of Pig Genotype, Strategic Use of Antibiotics and Grow-Finish Management Effects on Lean Growth Rate and Carcass Characteristics

Purdue University 2000 Swine Research Report. Commercial swine production presents many challenges for producers because their pigs are often subject to environmental stressors that can limit their potential for growth. The stress level a pig experiences is a combination of physical stress (pen density, temperature and diet), social stress (mixing), and disease stress (health status and immune system activation) that is present in a herd. While physical and social stressors have been investigated extensively (Hyun et al., 1998), emphasis has only recently been focused on the effect that the health status of an animal has on its performance. Pigs reared in a commercial environment expressed only about 70% of the performance of those in unrestricted environments (Holck et al., 1998). Pigs with a high level of immune system activation had reduced feed intake and body weight gain, and different dietary amino acid requirements than those with a low level of immune system activation (Williams et al., 1997). It is well established that pigs from different genetic populations are variable in their growth performance and carcass characteristics (Schinckel and de Lange, 1996), but also in their response to different rearing environments (Kendall et al., 1999). Feed grade antibiotics have been utilized as an effective means of improving growth rate and efficiency of growth in commercial environments. However, medicated diets have also been shown to have only modest or limited effect on growth rate in clean environments (Hays and Speer, 1960). The objectives of this study are to determine if differences exist in lean growth rate for pigs reared in different health status environments, and the effect that strategic antibiotic use has on performance in these two different health status environments.