Grant: Discovery Grants Program - Individual

Current essential amino acid (EAA) requirements are based on the ideal protein concept, assuming a proper balance of EAA is required to maximize growth and amino acid (AA) or nitrogen (N) utilization. However, little attention is given to the importance of non-essential amino acids (NEAA) or N on EAA requirements, nutrient utilisation, and growth performance. The EAA-N:NEAA-N (E:T) ratio has been suggested as a means to determine NEAA or N sufficiency in diets for multiple species.  Our previous research has shown that N-retention was increased when an additional source of N was supplied, either as intact protein or as non-protein N (NPN), resulting in a higher lysine requirement. The results of these studies suggest that it may be possible to replace some dietary protein/AA with a source of NPN to maintain growth performance, reducing our reliance on traditional protein sources in livestock feed. We have also shown that immune system stimulation (ISS) alters nutrient metabolism, including AA. Adoption of the E:T ratio has the potential to change the way diets are formulated to meet both EAA and NEAA requirements in the pig, increasing lean gain and performance and improving sustainability of pork production. However, there are a number of factors that need to be examined in order to allow the accurate use of E:T and ensure adequate nutrient supply. Our main hypothesis is that utilization of EAA for N retention will be affected by the dietary N content (as indicated by the E:T ratio) and that this effect will be dependent on the specific EAA, N source, and immune status of the pig. Specific objectives are (1) to determine the E:T ratio for maximum N retention and utilization in growing pigs, (2) to determine the effect of EAA inclusion on optimal E:T ratio, (3) to determine the effect of adjusting E:T ratio with intact protein on EAA requirements, (4) to determine the effect of adjusting E:T ratio with NPN on EAA requirements, (5) to determine the effect of ISS on E:T ratio, utilization of N, and EAA requirements in growing pigs, and (6) to validate the optimum E:T ratio and EAA content on growth performance and body composition in growing pigs. To address these objectives, a PDF, 4 MSc students, and a BSc honours thesis student will be recruited to complete a series of animal experiments in pigs, an agricultural important animal species.  A combination of N-balance, AA analysis, ISS, and growth performance techniques will be used.  The proposed research will result in improved knowledge of the metabolism of N in the non-ruminant animal and will allow for the development of feeding programs aimed at improving N utilization. The objectives of this research program will benefit our long-term research objective to characterize the interaction of dietary nutrient composition and animal physiology in order to better understand the impact of these factors on nutrient utilization for animal growth and health.