PSI-14 Enteric Challenge Increases Amino Acids and Energetic Costs in Growing Pigs

Abstract

Abstract Supplementing tryptophan (Trp), threonine (Thr), and methionine (Met) above the requirements might support immune system energetic and protein costs during a sanitary challenge. This study aimed to evaluate the correlation between protein deposition (PD) and immune response in challenged pigs. Twenty gilts per treatment (25.4 kg, ± 3.7 of body weight [BW]) were group-housed for 28 d in a poor sanitary condition characterized by oral inoculation with 2×109 CFU of Salmonella typhimurium, fresh manure spreading from a commercial pig farm on the barn floor and no daily cleaning. Pigs were distributed in a complete randomized block design in two treatments: control (CN) or supplemented (AA+) diet with Trp, Thr, and Met:Lysine 20% above the requirements recommended by NRC (2012). Serum samples were collected at 7 days post-challenge (dpc) for immunoglobulins (IgG and IgA) quantification. Body composition was estimated by dual-energy X-ray densitometry at d -1 and 28 dpc to obtain protein (PM, % of BW) and lipid (LM, % of BW) masses. Pigs were individually fed through automatic feeding stations throughout the trial. The percentual feed intake (FI) decrease was calculated relative to individual FI of pigs before the challenge (d -4 dpc). Pearson correlations (Figure 1) were performed using the ggpubr package of R Software, and means were compared using a mixed model. Initial PM, LM, and treatment had no influence (P > 0.05) on the average FI reduction during 7 dpc, which was on average 20% less for both treatments (Table 1). However, PM was 8%, and PD was 15% greater (P < 0.05) AA+ than CN pigs, without changes in lipid deposition. Although the IgG and IgA serum concentrations were not influenced by the initial PM and LM (P > 0.05), pigs with increased IgG concentration at 7 dpc presented lower PD for both AA+ (r = -0.64; P < 0.01) and CN (r = -0.58; P < 0.01) treatments. The Pearson correlation indicates that less IgG was synthesized per unit of protein deposited in AA+ pigs, suggesting that AA+ diet might have impaired the systemic immune response and improved PD. The concentration of IgA in blood at 7 dpc had no correlation (r = -0.27; P > 0.05) with PD in CN fed pigs, whereas increased IgA at d 7 resulted in decreased PD at d 28 for AA+ pigs (r = -0.68; P < 0.01). Likely because IgA has a greater Thr content in its composition, the AA+ diet provided a better AA profile for its synthesis. Additionally, LD decreased proportionally to PD, suggesting increases in energetic costs not linked to FI, but rather to the immune system energetic expenses during the enteric challenge. Increasing Trp, Thr and Met ratio attenuates the inflammatory response and improves nutrient utilization and PD in challenged pigs.