0
Reducing crude protein in nursery pig diets can improve environmental sustainability and gut health by lowering nitrogen excretion and diarrhea risk, but it often compromises growth performance due to limitations in essential and functional amino acids.
Objective: This study explored how lowering crude protein levels in piglet diets, with or without supplementation of arginine and glutamine–glutamate, affects growth, gut health, metabolism, and nitrogen use during the nursery phase.
Methods: A total of 200 piglets weaned at 20 days of age were assigned to five different diets. These included four levels of crude protein (22.5%, 21.0%, 19.5%, and 18.0%) and one low-protein diet (18.0%) supplemented with arginine and glutamine–glutamate. The feeding trial lasted 24 days and was divided into two phases, covering early and later nursery periods.
Results: Lowering dietary protein reduced growth efficiency, meaning pigs needed more feed to gain weight. This effect was most pronounced in pigs fed the lowest protein diet supplemented with arginine and glutamine–glutamate. Moreover, markers in blood reflected these dietary changes. Higher protein diets were associated with increased levels of urea nitrogen and certain liver-related enzymes, suggesting greater protein metabolism. Supplementation with arginine and glutamine–glutamate increased circulating levels of arginine and its related compounds. Some amino acids, such as methionine, threonine, and valine, were more abundant in pigs fed low-protein diets, while others like phenylalanine and tyrosine decreased as protein levels were reduced. From a gut health perspective, pigs fed higher protein diets showed more frequent diarrhea and poorer fecal consistency. In fact, each increase in dietary protein was associated with a noticeable rise in diarrhea incidence. Higher protein diets resulted in higher nitrogen excretion in feces. Reducing dietary protein from 22.5% to 18.0% comes with clear trade-offs. While lower protein diets can improve gut health and reduce nitrogen waste, they also impair growth performance and nutrient digestibility, even when supplemented with key amino acids like arginine and glutamine–glutamate.
Conclusion: Overall, these findings highlight the challenge of balancing animal performance, intestinal health, and environmental impact in pig nutrition.
Teixeira LM, Genova JL, Abranches FF, Rocha GC. The effects of reduced protein diet supplemented with arginine plus glutamine–glutamate on growth performance, diarrhea incidence, blood metabolites, nutrient digestibility, and nitrogen utilization in nursery pigs. Animal Bioscience. 2025; 39(3): 250702. https://doi.org/10.5713/ab.250702