With new legislation eliminating the use of in-feed antibiotics for growth promotion in Canada and increasing consumer pressure to reduce antibiotic use in animal agriculture, it is critical that we develop alternatives to antibiotic use in order to maintain animal performance and health during immune challenge. An increased understanding of the interaction of nutrition and animal robustness (i.e., the ability to cope with an immune challenge), therefore, will be a key component in efforts to replace and/or reduce antibiotic use. Specifically, nutrition-based alternatives to antibiotic use need to be identified.
Pigs are continuously exposed to microbial pathogens and immune-stimulatory antigens that negatively impact animal productivity. Pigs exposed to immune challenge, without exhibiting any clinical signs of disease, show reduced appetite and growth and less efficient use of nutrients compared to healthy animals. Previous studies have estimated a reduction in lean growth of 20-35% and feed efficiency of 10-20% in growing pigs at sub-clinical levels of disease (Williams et al., 1997; Le Floc’h et al., 2009). This decrease in performance can have a substantial impact on profitability of producers. Stimulation of the immune system alters protein and amino acid metabolism and utilization, with amino acids redirected from growth towards supporting the immune response. Of the amino acids, glutamine, arginine, threonine, and aromatic and sulfur amino acids are of particular importance as precursors for synthesis of many critical components of the immune response (Reeds and Jahoor, 2001). It is thought that provision of these amino acids may be important for improving pig response and growth performance during times of stress and disease challenge.