Supplementation of functional amino acids above the requirement improves growth performance and immune status of weanling pigs challenged with Salmonella Typhimurium

The functional amino acids (FAA) Met, Thr, and Trp play an important role supporting the immune system and gut health. Two studies were designed to evaluate the supplementation of FAA above requirements during a Salmonella Typhimurium (ST) challenge. Experiment 1 was conducted for 14 d in a 2 × 2 × 2 factorial arrangement, consisting of 2 CP levels (16% or 20%), 2 FAA levels (Met, Thr, and Trp at 100% [FAA−] or 120% of requirements [FAA+]), and 2 challenge conditions (saline [CT] or ST inoculation). Pigs (initial BW = 13.9 kg; 8 pigs/treatment [Trt]) received the diets from d 0 to 14, and on d 7 pigs were inoculated. Pigs inoculated with ST had higher rectal temperature, serum haptoglobin, and activity of antioxidant systems, softer feces, and lower growth compared with CT pigs. Pigs challenged with ST and fed FAA+ diets had a less severe acute inflammatory response and greater growth compared with FAA− counterparts. Pigs fed 16% CP diets had lower cecal ST score compared with pigs fed 20% CP diets. Protein level did not affect growth and immune status. Experiment 2 was conducted for 21 d to evaluate whether providing an adaptation period of FAA+ is beneficial during health challenges. All pigs (initial BW = 11 kg, 8 pigs/trt) were inoculated with ST on d 14. Pigs were fed FAA− or FAA+ diets at different periods. The 4 treatments included (1) FAA−, only FAA−, (2) FAA+15, pigs received FAA− and from d 15 FAA+, (3) FAA+8, pigs received FAA− and from d 8 FAA+, and (4) FAA+, only FAA+. As in Exp. 1, pigs experienced an acute inflammatory response due to ST regardless of the treatments. Pigs fed FAA+ diets had lower levels of serum haptoglobin, activity of antioxidant systems, cecal ST score, and greater growth compared with FAA−. Pigs fed FAA+15 and FAA+8 had intermediate activity of antioxidant systems and growth compared with FAA− and FAA+. Both experiments demonstrated that pigs fed FAA+ are better equipped to counteract an ST infection while maintaining optimum growth, and the benefits are greater when pigs are fed FAA+ diets for a longer period.

Key Words: functional amino acids, pig, Salmonella.

Presented at the 9th Symposium on Gut Health in Production of Food Animals, St. Louis, USA, 2021. For information on the next edition, click here.