The effect of preventive and curative functional amino acid supplementation on health, growth performance, and resilience of growing pigs under an immune challenge

Immune system stimulation (ISS) increases amino acid (AA) requirements, and amino acid-based strategies may reduce performance losses under sanitary challenges.

Objective: 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 and poor housing conditions.

Methods: Fifty-two entire male pigs (21.7 ± 4.6 kg) were assigned to four dietary treatments, with a control AA diet (CT) or a FAA supplemented diet (FAA+, supplied +20% Trp:Lys, Thr:Lys, and Met+Cys:Lys above CT) fed only before (FAA-Pre), during (FAA-Cur), or before and during the ISS-period (FAA-Con). On day 0, after a 7-day pre-ISS-period, all pigs were inoculated with Salmonella Typhimurium (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 weeks. Thereafter, all pigs received the same standard diet for 9 weeks, and the facilities were cleaned daily. Growth performance, temperature, blood and nitrogen balance were measured.

Results: There was no effect of providing additional FAA before the ISS-period on growth performance, indicating that the CT diet met at least the requirements under non-challenged conditions. Rectal temperature increased by 1.25 °C on day 1 and remained elevated throughout days 2–7 of ISS. CT group had higher rectal temperature than the FAA-Pre. Serum haptoglobin was higher on day 7 and 28, while albumin was lower on day 28, with lower concentrations in the CT group compared with the FAA-Cur. Higher final body weight, average daily gain, and gain-to-feed ratio were observed in FAA-Con compared with CT. On day 28, FAA-Cur improved total body protein compared with FAA-Pre and nitrogen utilization by 32.6% vs CT. There were no remaining effects of treatments on body weight or body composition on day 91.

Conclusion: The combination of preventive and curative strategies with functional AA supplementation modulated the immune response and improved the growth performance of growing pigs under chronic immune system stimulation.