The post-weaning period is a critical time in the pig’s life with both short- and long-term consequences for both productivity and health. Nutrition plays a vital role in this transition period and, as with swine production as a whole, the focus is largely on maximizing growth performance. However, feeding programs also need to account for immature and developing gastrointestinal and immune systems in the newly-weaned pig. In examining the impact of nutrition on gastrointestinal and immune health, it has become evident that protein and amino acids play a vital role. While protein and amino acids are needed in order to meet requirements for growth, excess protein can predispose pigs to post-weaning diarrhea, thought to be the result of fermentation of undigested protein and proliferation of enteric pathogens. In addition, the source of protein may also have a significant impact on performance and health of nursery pigs. Traditionally, amino acid requirements, and thus dietary inclusion, have been based on maximizing growth performance. It has become evident that the requirements of some amino acids may differ when based on development of the gastrointestinal tract and during times of immune stimulation, such as during disease challenge.
The inclusion of some amino acids, such as methionine, threonine, and tryptophan, above the requirements for growth have been shown to improve performance, intestinal health, and immune status in weaned pigs under enteric pathogen challenge. Nursery diet formulations should account for the role of nutrients not only on maximizing growth performance but optimizing gastrointestinal health and immune status including adjustments to protein content and source and amino acid requirements.