Interpretive Summary: Assessment of digestible lysine requirements in lipopolysaccharide-challenged pigs

By: Dr. Emily Taylor

Changes in metabolism due to immune system activation and the incidence of infectious disease can lead to differing dietary amino acid requirements for an animal. In addition, it is imperative to determine the nutritional requirements of animals under challenging conditions, so feed formulations are optimal to maximize growth rate and efficient use of nutrients. The objective of the current study published in the Journal of Animal Science was to model digestible lysine (Lys) requirements using a nitrogen balance assay in growing pigs challenged with E. coli lipopolysaccharide (LPS). The authors hypothesized that dietary Lys requirements used for LPS-challenged pigs would decrease relative to the control pigs' metabolic requirements for protein change. A 2x6 factorial design composed two immune activation states (control and LPS-challenged) and six dietary treatments where N levels varied and Lys was limiting. Nitrogen intake (NI), N excretion (NEX), and N deposition (ND) were evaluated. 

Stimulation of the inflammatory response through repeated injections of E. coli LPS altered protein metabolism. Therefore, N intake and deposition were reduced while N excretions increased. A nonlinear model adjustment of the equation used to establish protein requirements associated with the nitrogen balance was made, allowing an estimation of specific model parameters (NMR, NRmaxT) for growing pigs challenged with E. coli LPS. The authors concluded that differences in nutrient requirements of challenged animals must be considered to determine feeding programs. The current modeling approach used in this study allows the calculation of requirements for the first limiting amino acid for pigs challenged in similar conditions as presented in this paper.

This is available in the Journal of Animal Science.