Dietary fat and high energy density diet: Influence on intestinal health, oxidative stress and performance of weaned piglets

The utilization of dietary components to support gut function and the health of young animals is an important factor for improved performance. The influence of high dietary fat levels in a low or high energy density diet on the performance of weaned piglets in relation to intestinal absorptive function, amino acid utilization, oxidative stress, and microbial metabolites was assessed in this study. The study examined the effect of two different diets containing either a low energy density/high-fat level or a high energy density/high-fat level. A total of 16 healthy weaners (9.60 ± 0.13 kg) were allocated to one of the two dietary treatments. There were eight weaners per treatment. Results showed that feed intake and body weight gain of weaners were increased by the diet of high energy density/high-fat level (p < 0.05), but the feed efficiency showed an increased tendency of significance (p = 0.05). In the duodenum, the villus height (VH) and VH/crypt depth (CD) ratio (VH:CD) were increased by dietary high energy density/high fat. In the jejunum and ileum, the CD was increased by low energy density/high-fat diet, while the goblet cell count and VH:CD were increased by dietary high energy density/high-fat level. Methionine, lysine and phenylalanine concentrations were increased by high energy density/high-fat diet while low energy density/high-fat diet showed an increased tendency to increase citrulline and ornithine concentrations in the piglet. Oxidative stress marker, lactase enzyme activity and serum calcium concentration were increased by a high energy density/high-fat diet. Increased dietary fat in all diets induced diarrhoea in the weaners (p < 0.01). It was concluded that a dietary high energy density/high-fat diet seems to positively modulate gut absorptive function, serum amino acid (methionine and lysine), calcium levels and increased oxidative stress markers in the weaned piglets.

Effect of low-nutrient-density diet with probiotic mixture (Bacillus subtilis ms1, B. licheniformis SF5-1, and Saccharomyces cerevisiae) supplementation on performance of weaner pigs

A total of one hundred and forty, 28 day-old weaner pigs [Duroc × (Yorkshire × Landrace)] with an initial body weight (BW) of 6.56 ± 1.25 kg were used in a six-week treatment (7 replicate pens per treatment; barrows, and 2 gilts/pen) to evaluate the effect of low-nutrient-density diet supplement with probiotic mixture supplementation on the growth performance, nutrient digestibility, faecal microbial and gas emission of weaner pigs. Pigs fed low-density diet with probiotic mixture supplementation had linearly increased (p = 0.028, 0.014) the body weight (BW) at weeks 3, and 6. Moreover, average daily gain (ADG) was linearly improved (p = 0.018, 0.014, 0.014) at weeks 3, 6 and the overall experiment. However, there were no interactive effects found on the nutrient digestibility of dry matter (DM), nitrogen (N) and energy (E) throughout the experiment. Dietary inclusion of a low-density diet with probiotic mixture supplementation has improved the faecal lactobacillus counts linearly, but E. coli was unaffected during the trial. On day 42, Ammonium gas emission was significantly decreased in pigs fed a low-density diet with probiotic mixture supplementation. However, H₂ S, acetic acid and CO₂ were not significantly affected by the probiotic mixture supplementation diet. Low-density diet with probiotic mixture supplementation had positively affected the growth performance, faecal microbial and faecal gas emission on weaner pigs.

Increasing dietary tryptophan in conjunction with decreasing other large neutral amino acids increases weight gain and feed intake in weaner pigs regardless of experimental infection with enterotoxigenic Escherichia coli

Dietary tryptophan (Trp) is a precursor for serotonin, a neuromediator involved in stress responses. Tryptophan competes with other large neutral amino acids (LNAA: tyrosine, isoleucine, leucine, valine, and phenylalanine) to cross the blood-brain barrier; therefore, the regulation of circulating LNAA can influence Trp availability in the cortex and serotonin biosynthesis. The hypothesis examined in this study was that increased supplementation of dietary Trp and a reduction in LNAA for weaned pigs experimentally infected with enterotoxigenic Escherichia coli (ETEC; F4) will increase Trp availability in plasma and reduce indices of the stress response, which will translate to reduced production losses. At 21 ± 3 d of age (mean ± SEM), 96 male pigs (Large White × Landrace) weighing 6.3 ± 0.98 kg (mean ± SEM) were individually penned and allocated to a 4 × 2 factorial arrangement of treatments, with respective factors being 1) four dietary standardized ileal digestible (SID) Trp and LNAA contents, being HTrpHLNAA (Low Trp-High LNAA; 0.24% SID Trp: 5.4% SID LNAA), HTrpHLNAA (Low Trp-Low LNAA; 0.24% SID Trp: 4.6% SID LNAA), HTrpHLNAA (High Trp-High LNAA; 0.34% SID Trp: 5.4% SID LNAA), and HTrpHLNAA (High Trp-Low LNAA; 0.34% SID Trp: 4.6% SID LNAA), and 2) without/with ETEC infection. Pigs were orally infected with 0.8 mL (3.6 × 109 CFU/mL) ETEC at days 7 and 8 after weaning. Pigs fed diets high in Trp irrespective of the level of LNAA (HTrpHLNAA and HTrpLLNAA) had higher plasma Trp concentrations (P < 0.001) and a Trp:LNAA ratio (P < 0.001) before infection and 6 d after infection. Following infection, noninfected pigs had higher plasma Trp (P = 0.03) and a Trp:LNAA ratio (P = 0.004) compared with pigs infected with ETEC. Plasma cortisol levels after infection were higher in ETEC-infected pigs (P = 0.05) and altering dietary Trp and LNAA concentrations did not influence (P > 0.05) plasma cortisol. Pigs fed diet HTrpLLNAA had higher serum serotonin levels 24 h after infection (P = 0.02) compared with pigs fed diets LTrpLLNAA and HTrpHLNAA. Similarly, pigs fed diet HTrpLLNAA had a higher (P = 0.02) average daily gain during the 3-wk study. Overall, average daily feed intake tended to be higher in pigs fed an HTrpLLNAA diet compared with the other diets (P = 0.08). These results suggest that the increased supplementation of dietary Trp with reduced LNAA increased circulating Trp levels that, in turn, likely caused higher serum serotonin levels, irrespective of infection with ETEC, and improved aspects of post-weaning performance.

Analysis of temporal fecal microbiota dynamics in weaner pigs with and without exposure to enterotoxigenic Escherichia coli1,2

The primary aim of this work was to study potential effects of subclinical enterotoxigenic Escherichia coli (ETEC) exposure on porcine fecal microbiota composition, with a secondary aim of profiling temporal shifts in bacterial communities over the weaning transition period. 16S rRNA gene metabarcoding and quantitative PCR (qPCR) were used to profile the fecal microbiota and quantify ETEC excretion in the feces, respectively. Temporal shifts in fecal microbiota structure and stability were observed across the immediate postweaning period (P < 0.05), including significant shifts in the relative levels of specific bacterial phylotypes (P < 0.05). ETEC exposure did not change the fecal microbiota structure (P > 0.05), but significant variations in fecal community structure and stability were linked to variations in ETEC excretion level at particular time points (P < 0.05). In this study, marked temporal changes in microbiota structure and stability were evident over the short weaning transition period, with a relationship between ETEC excretion level and fecal microbiota composition being observed. This study has provided a detailed analysis of fecal microbiota dynamics in the pig, which should help to inform the development of novel management strategies for enteric disorders based on an improved understanding of microbial populations during the challenging postweaning period.

Technical note: novel delivery methods for an enterotoxigenic Escherichia coli infection model in MUC4-locus sequenced weaner pigs1

An infection model with enterotoxigenic Escherichia coli (ETEC) harboring the F4 fimbriae can be used to assess the impacts that various challenges associated with weaning (e.g., dietary, psychological, environmental) have on the expression of postweaning diarrhea. The objective of this study was to develop a novel inoculation method for administering an ETEC culture that would induce a higher proportion of ETEC-F4 diarrhea, in pigs that genetically showed ETEC-F4 susceptibility or resistance. The study was designed as a factorial arrangement of treatments with the factors being 1) partially susceptible or resistant to ETEC-F4 based on genetic testing, and 2) 4 challenge treatments, being a) a conventional liquid broth method using a drenching gun [Positive control (PC)], b) a Syringe method, c) a Capsule method, and d) Negative control [pigs not challenged (NC)]. At 21 ± 3 d of age (mean ± SEM), 48 male castrate pigs (Large White × Landrace) weighing approximately 7.0 ± 1.18 kg were allocated to 4 treatment groups in 2 replicate pens (6 pigs per pen). Initial ETEC-F4 susceptibility was based on a DNA marker test and each treatment group had 9 partially susceptible and 3 resistant pigs. On days 7 and 8 after weaning, pigs were challenged with ETEC (serotype O149:K88; toxins LT1, ST1, ST2, and EAST). On each inoculation day the PC pigs were orally dosed with 9 mL 7.12 × 109 colony-forming unit (CFU), the Syringe pigs with 0.8 mL 6.72 × 109 CFU, the Capsule pigs were orally administered 2 capsules containing 0.8 mL 3.28 × 109 CFU, and the NC pigs 1 mL of phosphate-buffered saline (PBS) solution. Approximately 72 h after infection, 44, 22, 78, and 0% of partially susceptible pigs in the PC, the Syringe, the Capsule, and the NC group had developed ETEC-F4 diarrhea (P = 0.007). Partially susceptible pigs had a higher diarrhea index (DI) compared to resistant pigs (31.5 vs. 4.8, P < 0.001). The NC group had a lower DI compared to the PC and Capsule pigs (3.9, 38.1, and 40.3, respectively, P < 0.005). Following infection, genetically resistant pigs in the Capsule group had a DI of zero and the partially susceptible pigs had a DI of 55.6 (P = 0.014). This study showed that genetically screening pigs and using a Capsule to deliver ETEC-F4 can increase cases of diarrhea and the efficiency of the challenge model. Taken together, these methods have the potential to reduce the number of pigs needed in future experimental infection studies.

Response of gastrointestinal fermentative activity and colonic microbiota to protected sodium butyrate and protected sodium heptanoate in weaned piglets challenged with ETEC F4. Arch Anim Nutr 2019;73:339-359. [PMID: 31342760 DOI: 10.1080/1745039x.2019.1641376]

This study aimed to evaluate the potential of two new fat-protected butyrate or heptanoate salts to improve gut health and control post-weaning colibacillosis in weaning piglets challenged with enterotoxigenic Escherichia coli (ETEC) F4⁺, particularly focusing on their impact on intestinal microbiota and fermentative activity along the gastrointestinal tract (GIT). Seventy-two 21-d-old pigs were fed a plain diet (CTR) or supplemented with sodium butyrate (BUT) or sodium heptanoate (HPT), both at 0.3%. After a week of adaptation, animals were orally challenged at days 8 and 9 with 5.8 · 10⁹ and 6.6 · 10¹⁰ cfu, respectively, and were euthanised on d 4 and d 8 post-inoculation (PI) (n = 8) to collect blood, digesta and tissue samples and characterise microbial groups, pathogen loads (qPCR), fermentation, ileal histomorphometry and immune markers. Colonic microbiota was analysed by 16S rRNA gene MiSeq sequencing. Supplementing both acid salts did not compensate clinical challenge effects nor performance impairments and neither histomorphometry nor serum biomarkers. Changes in the gastric fermentative activity were registered, BUT reducing lactic acid concentrations (day 8 PI), and with HPT fewer animals presenting detectable concentrations of propionic, butyric and valeric acids. At ileum BUT increased acetic acid concentration (day 8 PI), and both additives reduced short-chain fatty acids (SCFA) in the colon. Increases in enterobacteria and coliforms counts in ileal digesta (day 4 PI, p < 0.10) and mucosa scrapes (p < 0.05) were registered although E. coli F4 gene copies were unaffected. Regarding changes in the colonic microbiota (day 4 PI), Prevotellaceae and Prevotella were promoted with BUT supplementation whereas only minor groups were modified in HPT-treated animals. Summarising, although the pathogen loads or inflammatory mediators remained unresponsive, butyrate and heptanoate showed a significant impact on microbial fermentation along the whole GIT, being able to modify different bacterial groups at the colon. It could be hypothesised that these effects might be mediated by a carry-over effect of the changes observed in gastric fermentation, but possibly also to a better nutrient digestion in the foregut as a result of the reduced colonic SCFA concentrations.