Effect of supplemental threonine above requirement on growth performance of Salmonella typhimurium challenged pigs fed high-fiber diets1

Abstract

It was shown previously that high dietary fiber (DF) and immune system stimulation (ISS) with systemic Escherichia coli lipopolysaccharide independently increased the threonine (Thr) requirement to maximize growth performance and protein deposition (PD). However, no additive effects on the Thr requirement were observed when both DF and ISS were present. The objective of the present study was to investigate whether supplementing Thr to meet previously estimated requirements for high DF and systemic immune challenge would maintain performance of pigs exposed to an enteric immune challenge when fed high DF. A total of 128 pigs (22.6 ± SD = 1.6 kg initial BW) were assigned to 1 of 4 dietary treatments in a 2 × 2 factorial arrangement in a randomized complete block design (n = 8 pens/treatment and 4 pigs/pen) for 28 d. Treatments were a low-fiber (LF; 13% total DF) or high-fiber (HF; 20% total DF) diet with either a standard (STD; 0.65% SID) or supplemental (SUP; 0.78% SID) Thr level. After a 7-d adaptation, pigs were orally inoculated with 2 mL (2.3 × 109 CFU/mL) of Salmonella typhimurium (ST). Blood samples and rectal swabs were obtained and rectal temperature recorded to determine clinical responses and ST shedding. On day 7 postinoculation, 1 pig/pen was euthanized and mesenteric lymph nodes, spleen, and digesta (ileum, cecum, and colon) were sampled to assess ST colonization and translocation. Body weight and feed intake were recorded on day 0, 7, and 21 postinoculation to calculate ADG, ADFI, and G:F. Rectal temperature increased (P < 0.05) 24 h postinoculation and remained elevated at day 6. Serum albumin concentration decreased (P < 0.05), whereas haptoglobin concentration increased (P < 0.05) postinoculation. There was no fiber or Thr effect (P > 0.05) on ST counts in the ileum and cecum, but a fiber × Thr interaction (P < 0.05) was observed in the colon. Supplemental Thr improved (P < 0.05) growth performance in LF- and HF-fed challenged pigs. However, performance of supplemented HF challenged pigs was less than (P < 0.05) supplemented LF challenged pigs. These results suggest that Thr supplemented to meet requirements for high DF and systemic immune challenge was not sufficient to maintain growth performance of pigs fed HF diets and challenged with an enteric pathogen.

Effect of dietary fiber and threonine content on intestinal barrier function in pigs challenged with either systemic E. coli lipopolysaccharide or enteric Salmonella Typhimurium

“…Unlike in experiment 1, we observed an increase in fecal mucin output with Salmonella inoculation as compared with systemic LPS administration suggesting significant direct effects of enteric pathogen on intestinal mucin production, which likely reduced the expected effects of high DF on mucin production. As previously reported [24], supplemental Thr improved growth performance in Salmonella-challenged pigs, regardless of DF content, however, this increase was less with high DF. In addition, in the current study we observed a fiber by Thr interaction on fecal mucin output, in which supplemental Thr increased fecal mucin output in HF but not LF-fed pigs.…”

“…This contrasts the lack of fecal mucin output response in LPS challenged pigs reported here. As outlined in our previous work [24], Salmonella Typhimurium challenge induced an immune response in pigs, as indicated by clinical response data (rectal temperature, acute phase proteins, and Salmonella shedding), without any mitigating effect of high DF. Unlike in experiment 1, we observed an increase in fecal mucin output with Salmonella inoculation as compared with systemic LPS administration suggesting significant direct effects of enteric pathogen on intestinal mucin production, which likely reduced the expected effects of high DF on mucin production.…”

“…As previously reported by Wellington et al [24], a total of 128 pigs (Camborough Plus × C3378; PIC Canada Ltd.) of 22.6 ± 1.6 kg initial BW were housed in groups of 4 pigs/pen on solid floors lined with rubber mats in a temperature-controlled room (22 ± 1°C). Briefly, pens were randomly assigned to 1 of 4 dietary treatments based on the previous study [22] and consisted of an LF (13% TDF) or HF (20% TDF) diet with either a standard (STD; 0.65% SID) or supplemental (SUP; 0.78% SID) Thr level.…”

Intestinal Health and Threonine Requirement of Growing Pigs Fed Diets Containing High Dietary Fibre and Fermentable Protein

“…Mechanisms for these effects include reduced nutrient availability and microbial metabolite production [1,2] modulation of gut microbiome [3], and changes in intestinal morphology [4]. For example, DF can reduce nutrient digestibility [5,6] and increase endogenous AA losses [7], resulting in greater threonine (Thr) requirement for protein deposition (PD) and growth [2,8,9].…”

“…Metabolites of protein fermentation (e.g., ammonia, amines, phenolic and indole compounds) have been associated with a negative impact on gut health and predisposition to post-weaning diarrhea following enterotoxigenic E. coli challenge [12]. Although feeding high DF increases endogenous Thr losses [13] and increases dietary Thr requirement for growth and PD [2,9], the inclusion of DF in swine diets has been suggested as a potential mechanism to mitigate the negative effects of protein fermentation [14] by providing gut microbes a preferential fermentation substrate. For example, inclusion of DF has been reported to reduce ammonia and putrescine levels in pigs fed a diet containing highly fermentable protein [14].…”