Functional amino acids (FAA) attenuate the effects of Salmonella challenge in pigs. However, this may be affected by protein source (PS). The objective of the present study was to determine the effects of nursery dietary PS and FAA supplementation on growth performance and immune status of pigs subsequently challenged with Salmonella Typhimurium (ST). Thirty-two weanling pigs (8.7 ± 0.23 kg) were assigned to a feeding program for 31 d in a 2 × 2 factorial arrangement. Factors were dietary PS (plant-based [PB] vs. animal-based [AB]) and FAA profile (basal [FAA-] or supplemented [FAA+; Thr, Met, and Trp at 120% of requirements]). Pigs were subsequently placed on a common grower diet and, after a 7-d adaptation, were inoculated with ST and monitored for 7 d postinoculation. Growth performance, rectal temperature, fecal score, gut health, ST shedding score, intestinal colonization and translocation, and blood parameters of acute-phase response and antioxidant balance were measured pre- and postinoculation. Data were analyzed with a 2 (AB vs. PB) × 2 (FAA- vs. FAA+) factorial arrangement of treatments and differences between means were considered significant at P ≤ 0.05. Postinoculation fecal score was worse, ST shedding, cecal myeloperoxidase, and cecal and colonic ST colonization were greater in PB compared to AB pigs (P < 0.05). Translocation of ST to spleen was decreased by FAA+ (P < 0.05), regardless of dietary PS. Postinoculation, AB pigs had greater average daily gain compared to PB-FAA- (P < 0.05). Pigs fed AB-FAA- showed increased average daily feed intake compared to PB-FAA- pigs (P < 0.05) and feed efficiency was increased in AB-FAA+ compared to PB-FAA- pigs (P < 0.05). Feeding PB ingredients in nursery diets seems to increase susceptibility of pigs to Salmonella. Moreover, FAA supplementation partially attenuated the negative effects of PB diets on the response of pigs to ST challenge.
Keywords: Salmonella Typhimurium; functional amino acids; immune status; protein source; swine.
While long-term growth performance of weaned pigs is not negatively affected by feeding nursery diets containing only plant-based protein sources, these pigs may be more susceptible to subsequent disease challenges. It has been previously shown that supplementation with key functional amino acids improves growth performance and the immune status of pigs during intestinal pathogen challenge. A study was performed to determine the effect of feeding nursery diets containing only plant-based protein sources or including animal-based protein sources with or without supplementation with a blend of functional amino acids (methionine, threonine, and tryptophan) on growth and immune status during a subsequent Salmonella challenge. Pigs fed diets containing animal-based protein sources had improved growth performance and immune status compared to pigs fed plant-based diets, regardless of the inclusion of functional amino acids. Pigs fed plant-based diets were more susceptible to the disease challenge, however, this was partially mitigated by the inclusion of functional amino acids. The inclusion of animal-based protein sources may be necessary to optimize pig health and performance, however, functional amino acid inclusion may be beneficial when plant-based diets are fed.
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