Preventive-curative functional amino acid-supplemented diet improves health, growth performance, and resilience of growing pigs under an immune challenge.

Immune system stimulation (ISS) alters the metabolic demand for amino acids (AA), and amino acid-based nutritional strategies may mitigate performance reduction in pigs subjected to sanitary challenge conditions. This study aimed to evaluate the effect of extra supplementation of a combination of functional AA (FAA, +20% threonine, methionine, and tryptophan) preventively (pre-ISS), curatively (during-ISS) or both on the performance of growing pigs challenged with Salmonella Typhimurium (ST) and poor housing conditions. Fifty-two entire male pigs (21.7 ± 4.6 kg) were allocated to four dietary treatments, with a control AA profile diet fed throughout the experimental period (Control; NRC, 2012) or a FAA supplemented diet (FAA+; supplied +20% Trp: Lys, Thr: Lys, and Met+Cys: Lys above Control) fed only before the ISS (FAA Preventive), during the ISS (FAA Curative), or before and during the ISS-period (FAA Continuous). On day 0, after a 7-d pre-ISS-period (day -7 to -1, pre-ISS), all pigs were inoculated with ST (2 × 109 CFU/mL). Additionally, manure from a commercial pig farm was spread on the solid concrete floor, and the room was not cleaned during the ISS-period for 4 wk (0 to 28 d). Thereafter, all pigs received the same standard diet for 9 wk (days 29 to 91), and the facilities were cleaned daily. Pigs were group-housed and fed using five electronic precision feeders during pre-ISS and ISS-period (-7 to 28 d). There was no effect of providing additional FAA before the ISS-period on growth performance (P > 0.10), indicating that the control diet met at least the requirements under non-challenged conditions. Rectal temperature increased by 1.25 °C on day 1 of the ISS-period (P < 0.05) and remained higher than pre-ISS during days 2 to 7 of the ISS-period (P < 0.05). Control group had higher rectal temperature than the FAA Preventive (P < 0.05). Serum haptoglobin was higher on day 7 and 28 (P < 0.05), while albumin was lower on day 28 (P < 0.05), with lower concentrations in the control group compared with the FAA curative (P < 0.05). Higher final BW (P < 0.05), ADG (P < 0.05), and G:F (P < 0.05) were observed in the FAA Continuous compared to the Control. On day 28, FAA curative pigs showed higher total body protein content than FAA preventive pigs (P < 0.10). Nitrogen utilization efficiency improved by 32.6% (P < 0.05) for the FAA Curative compared with the Control. There were no remaining effects of treatments on BW or body composition on day 91 (P > 0.10). In conclusion, the combination of short-term preventive and curative strategies with FAA dietary supplementation modulated the immune response and improved the growth performance of growing pigs under chronic immune system stimulation.