Effects of Methionine Supplementation Levels in Normal or Reduced Protein Diets on the Body Composition and Femur Bone Characteristics of Broilers Challenged with Coccidia.

This study investigated the effects of dietary methionine (Met) levels on the bone quality of broilers challenged with coccidia. A total of 600 fourteen-day-old male Cobb500 broilers were gavaged with mixed Eimeria spp. and randomly allocated into 10 treatment groups by a 2 × 5 factorial arrangement. Birds received normal protein diets (NCP) or reduced-protein diets (LCP), containing 2.8, 4.4, 6.0, 7.6, and 9.2 g/kg of Met. Data were analyzed via two-way ANOVA and orthogonal polynomial contrast. At 9 days post-inoculation (DPI), whole body bone mineral density (BMD) and bone mineral content (BMC) linearly decreased as Met levels increased (p < 0.05). For the femoral metaphysis bone quality at 9 DPI, BMD linearly decreased, and porosity linearly increased as Met levels increased (p < 0.05) in the cortical bone. The increased Met levels linearly improved trabecular bone quality in LCP groups (p < 0.05) while not in NCP groups. For the femoral diaphysis cortical bone at 6 DPI, LCP groups had higher BMD and BMC than NCP groups (p < 0.05). Bone volume linearly increased as Met levels increased in LCP groups (p < 0.05) while not in NCP groups. In summary, the results suggested that increased Met levels decreased the cortical bone quality. However, in the context of reduced-protein diets, the increased Met levels improved trabecular bone quality.

Effects of phytase supplementation on broilers fed with calcium and phosphorus-reduced diets, challenged with Eimeria maxima and Eimeria acervulina: influence on growth performance, body composition, bone health, and intestinal integrity.

An experiment was conducted to evaluate the effects of phytase in calcium (Ca) and available phosphorous (avP)-reduced diet on growth performance, body composition, bone health, and intestinal integrity of broilers challenged with Eimeria maxima and Eimeria acervulina. A total of 672 14-day-old male broilers were allocated to a 2 × 4 factorial arrangement with 6 replicates per treatment and 14 birds per replicate. Two factors were Eimeria challenge and 4 dietary treatments: 1) a positive control (PC; 0.84% Ca and 0.42% avP); 2) a negative control (NC; 0.74% Ca and 0.27% avP); 3) NC + 500 FTU/Kg of phytase (NC + 500PHY); and 4) NC + 1,500 FTU/Kg of phytase (NC + 1500PHY). On d 14, birds in the Eimeria-challenged groups received a solution containing 15,000 sporulated oocysts of E. maxima and 75,000 sporulated oocysts of E. acervulina via oral gavage. At 5 d postinoculation (DPI), the challenged birds showed a higher (P < 0.01) FITC-d level than the unchallenged birds. While the permeability of the NC group did not differ from the PC group, the phytase supplementation groups (NC + 500PHY and NC + 1500PHY) showed lower (P < 0.05) serum FITC-d levels compared to the NC group. Interaction effects (P < 0.05) of Eimeria challenge and dietary treatments on feed intake (FI), mucin-2 (MUC2) gene expression, bone ash concentration, and mineral apposition rate (MAR) were observed. On 0 to 6 and 0 to 9 DPI, Eimeria challenge decreased (P < 0.01) body weight (BW), body weight gain (BWG), FI, bone mineral density (BMD), bone mineral content (BMC), bone area, fat free bone weight (FFBW), bone ash weight, bone ash percentage and bone ash concentration; and it showed a higher FCR (P < 0.01) compared to the unchallenged group. The reduction Ca and avP in the diet (NC) did not exert adverse effects on all parameters in birds, and supplementing phytase at levels of 500 or 1,500 FTU/Kg improved body composition, bone mineralization, and intestinal permeability, with the higher dose of 1,500 FTU/Kg showing more pronounced enhancements. There was an observed increase in FI (P < 0.01) when phytase was supplemented at 1,500 FTU/Kg during 0 to 6 DPI. In conclusion, results from the current study suggest that dietary nutrients, such as Ca and avP, can be moderately reduced with the supplementation of phytase, particularly in birds infected with Eimeria spp., which has the potential to save feed cost without compromising growth performance, bone health, and intestinal integrity of broilers.

Nutritional Strategies to Improve Meat Quality and Composition in the Challenging Conditions of Broiler Production: A Review.

Poultry meat is becoming one of the most important animal protein sources for human beings in terms of health benefits, cost, and production efficiency. Effective genetic selection and nutritional programs have dramatically increased meat yield and broiler production efficiency. However, modern practices in broiler production result in unfavorable meat quality and body composition due to a diverse range of challenging conditions, including bacterial and parasitic infection, heat stress, and the consumption of mycotoxin and oxidized oils. Numerous studies have demonstrated that appropriate nutritional interventions have improved the meat quality and body composition of broiler chickens. Modulating nutritional composition [e.g., energy and crude protein (CP) levels] and amino acids (AA) levels has altered the meat quality and body composition of broiler chickens. The supplementation of bioactive compounds, such as vitamins, probiotics, prebiotics, exogenous enzymes, plant polyphenol compounds, and organic acids, has improved meat quality and changed the body composition of broiler chickens.

Effects of levels of methionine supplementations in forms of L- or DL-methionine on the performance, intestinal development, immune response, and antioxidant system in broilers challenged with Eimeria spp.

The study was conducted to investigate the effects of 2 isoforms of methionine on growth performance and intestinal health induced by methionine (Met) deficiency and Eimeria infection in broilers. A total of 720 one-day old male chicks (Cobb500) were randomly allocated to 10 groups in a 2 × 5 factorial arrangement (6 reps/group, 12 birds/cage) with diets and Eimeria challenge as the main factors. Hundred percent DL-Met, 100% L-Met, 80% DL-Met, and 80% L-Met diets were formulated to meet approximately 100 or 80% of the total sulfur amino acid (TSAA) requirement with DL-Met or L-Met as Met supplementation sources. The 60% TSAA basal diet (60% Met) was formulated without Met supplementation. At d14, the challenge groups were gavaged with mixed Eimeria spp. Growth performance was recorded on d7, 14, 20 (6-day postinfection [DPI]), and 26 (12 DPI). The gut permeability was measured on 5 and 11 DPI. Antioxidant status and gene expression of immune cytokines and tight junction proteins were measured on 6 and 12 DPI. Data were analyzed by 1-way and 2-way ANOVA before and after the challenge, respectively. Orthogonal polynomial contrasts were used for post hoc comparison. Overall, the Eimeria challenge and 60% Met diet significantly reduced growth performance, antioxidant status, and mRNA expression of tight junction genes and immune cytokines. For other Met treatments, the L-Met groups had significantly higher BWG and lower FCR than the DL-Met group from d 1 to 20. The L-Met groups had less gut permeability than the DL-Met groups on 5 DPI. Compared to the 80% Met groups, the 100% Met groups reduced gut permeability. At 6 DPI, the 80% Met groups showed higher ZO1 expression than the 100% Met groups. The challenge groups had higher Muc2 expression and GSH/GSSG compared to the nonchallenge groups, and SOD activity was lower in the L-Met groups compared to the DL-Met groups at 6 DPI. The 100% Met groups had higher GPx activity than the 80% Met groups at 12 DPI. In conclusion, during coccidiosis, the 100% Met groups had better gut integrity and antioxidant status. Met supplementation in the form of L-Met improved growth performance in the starter phase and gut permeability in the challenge phase.

Comparative effects of dietary methionine and cysteine supplementation on redox status and intestinal integrity in immunologically challenged-weaned pigs.

Sulfur-containing amino acids such as methionine and cysteine play critical roles in immune system and redox status. A body of evidence shows that metabolic aspects of supplemented Met and Cys may differ in the body. Therefore, the study aimed to investigate the effects of dietary Met and Cys supplementation in immunologically challenged weaned pigs. Forty weaned piglets (6.5 ± 0.3 kg) were randomly allocated to five treatment groups. The treatment included: (1) sham-challenged control (SCC), (2) challenged control (CC), (3) MET (CC + 0.1% DL-Met), (4) CYS (CC + 0.1% L-Cys), and (5) MET + CYS (CC + 0.1% DL-Met + 0.1% L-Cys). On day 7, all pigs were intramuscularly injected with either Escherichia coli O55:B5 lipopolysaccharides (LPS) or phosphate-buffered saline. Blood, liver, and jejunum samples were analyzed for immune response and redox status. The CC group had lower (P < 0.05) villus surface area and higher (P < 0.05) flux of 4-kDa fluorescein isothiocyanate dextran (FD4) than the SCC group. A lower (P < 0.05) glutathione (GSH) concentration was observed in the jejunum of pigs in the CC group than those in the SCC group. Dietary Cys supplementation increased (P < 0.05) villus surface area, GSH levels, and reduced (P < 0.05) the flux of FD4 in the jejunum of LPS-challenged pigs. Dietary Met supplementation enhanced (P < 0.05) hepatic GSH content. Pigs challenged with LPS in the MET group had lower serum IL-8 concentration than those in the CC group. There was a Met × Cys interaction (P < 0.05) in serum IL-4 and IL-8 concentrations, and Trolox equivalent antioxidant capacity. Dietary L-Cys supplementation restored intestinal integrity and GSH levels that were damaged by lipopolysaccharides administration. Dietary DL-Met supplementation improved hepatic GSH and reduced systemic inflammatory response, but antagonistic interaction with dietary L-Cys supplementation was observed in the inflammatory response and redox status.

Effects of supplemental tannic acid on growth performance, gut health, microbiota, and fat accumulation and optimal dosages of tannic acid in broilers.

This study was conducted to investigate the effects of different dosages of tannic acid (TA) on growth performance, nutrient digestibility, gut health, immune system, oxidative status, microbial composition, volatile fatty acids (VFA), bone mineral density, and fat digestion and accumulation in broilers and to find optimal dosages of TA for efficient growth and gut health in broilers. A total of 320 male Cobb500 broilers were randomly distributed to 4 treatments with 8 replicates including 1) tannic acid 0 (TA0): basal diet without TA; 2) tannic acid 0.5 (TA0.5): basal diet with 0.5 g/kg TA; 3) tannic acid 1.5 (TA1.5); and 4) tannic acid 2.5 (TA2.5). Supplemental TA at levels greater than 972 mg/kg tended to reduce BW on D 21 (p = 0.05). The TA2.5 had significantly lower apparent ileal digestibility (AID) of crude protein compared to the TA0 group. The AID of ether extract tended to be reduced by TA at levels greater than 525 mg/kg (p = 0.08). The jejunal lipase activities tended to be reduced by TA at levels less than 595.3 mg/kg (p = 0.09). TA linearly decreased goblet cell density in the crypts of the jejunum (p < 0.05) and reduced mRNA expression of mucin two at levels less than 784.9 mg/kg and zonula occludens two at levels less than 892.6 mg/kg (p < 0.05). The TA0.5 group had higher activities of liver superoxide dismutase compared to the TA0 group (p < 0.05). Bone mineral density and contents tended to be linearly decreased by TA (p = 0.05), and the ratio of lean to fat was linearly decreased (p < 0.01). Total cecal VFA production tended to be linearly reduced by TA at levels greater than 850.9 mg/kg (p = 0.07). Supplemental TA tended to increase the relative abundance of the phylum Bacteroidetes (p = 0.1) and decrease the relative abundance of the phylum Proteobacteria (p = 0.1). The relative abundance of the family Rikenellaceae was the lowest at 500 mg/kg TA, and the relative abundance of the family Bacillaceae was the highest at 1,045 mg/kg TA. Collectively, these results indicate that the optimum level of supplemental TA would range between 500 and 900 mg/kg; this range of TA supplementation would improve gut health without negatively affecting growth performance in broilers under antibiotic-free conditions.

Antimicrobial and immunomodulatory effects of tannic acid supplementation in broilers infected with Salmonella Typhimurium.

Infection by Salmonella Typhimurium, a food-borne pathogen, can reduce the poultry production efficiency. The objective of this study was to investigate the effects of tannic acid (TA) supplementation on growth performance, Salmonella colonization, gut barrier integrity, serum endotoxin levels, antioxidant capacity, gut health, and immune function in broilers infected with the Salmonella enterica serovar Typhimurium nalidixic acid resistant strain (STNR). A total of 546 one-day-old broilers were arbitrarily allocated into 6 treatments including 1) Sham-challenged control (SCC; birds fed a basal diet and administrated peptone water); 2) Challenged control (CC; birds fed a basal diet and inoculated with 108 STNR); 3) Tannic acid 0.25 (TA0.25; CC + 0.25 g/kg TA); 4) TA0.5 (CC + 0.5 g/kg TA); 5) TA1 (CC + 1 g/kg TA); and 6) TA2 (CC + 2 g/kg TA). On D 7, supplemental TA linearly reduced STNR colonization in the ceca (P < 0.01), and TA1 and TA2 group had significantly lower reduced STNR colonization in the ceca (P < 0.01). On D 7 to 21, average daily gain tended to be linearly increased by supplemental TA (P = 0.097). The serum endotoxin levels were quadratically decreased by supplemental TA on D 21 (P < 0.05). Supplemental TA quadratically increased ileal villus height (VH; P < 0.05), and the TA0.25 group had higher ileal VH compared to the CC group (P < 0.05). Supplemental TA linearly increased percentage of peripheral blood CD8+ T cells on D 18 (P < 0.01). The TA0.5 group had significantly lower lymphocyte numbers compared to the CC groups (P < 0.05). The abundance of monocytes linearly increased with TA supplementation (P < 0.01). Therefore, broilers fed TA had reduced STNR colonization, increased growth performance, decreased serum endotoxin levels, enhanced gut health in the broilers, and stimulated the immune system in broilers infected with STNR. Supplementation of TA (1-2 g/kg) enhanced growth performance and gut health via antimicrobial and immunostimulatory effects in broilers infected with STNR.

Effects of tannic acid supplementation on growth performance, gut health, and meat production and quality of broiler chickens raised in floor pens for 42 days.

A study was conducted to investigate the effects of tannic acid (TA) supplementation on growth performance, gut health, antioxidant capacity, gut microbiota, and meat yield and quality in broilers raised for 42 days. A total of 700 one-day-old male broiler chickens (Cobb500) were allocated into 5 treatments with 7 replicates of 20 birds per pen. There were five treatments: 1) tannic acid 0 (TA0: basal diet without TA); 2) tannic acid 0.25 (TA0.25: basal diet+0.25 g/kg TA); 3) tannic acid 0.5 (TA0.5: basal diet+0.5 g/kg TA); 4) tannic acid 1 (TA1: basal diet+1 g/kg TA); and 5) tannic acid 2 (TA2: basal diet+2 g/kg TA). The dietary phases included starter (D 0 to 18; crumble feed), grower (D 18 to 28; pellet feed), and finisher (D 28 to 42; pellet feed). On D 18, the supplementation of TA linearly reduced body weight (BW) and average daily feed intake (ADFI) (p < 0.05), and on D 28, the supplementation of TA linearly reduced BW, average daily gain (ADG), and feed conversion ratio (FCR) (p < 0.05). Relative mRNA expression of genes related to mucin production (MUC2), tight junction proteins (CLDN2 and JAM2), and nutrient transporters (B0AT1 and SGLT1) was linearly increased by the supplementation of TA (p < 0.05). The supplementation of TA tended to linearly increase the relative abundance of the family Enterobacteriaceae (p = 0.08) and quadratically increased the relative abundance of the families Lachnospiraceae and Ruminococcaceae in the cecal microbial communities (p < 0.05). On D 36, the ratio of the phyla Firmicutes and Bacteroidetes was quadratically reduced by the supplementation of TA (p < 0.05). On D 42, bone mineral density and the lean to fat ratio were linearly decreased by the supplementation of TA (p < 0.05). On D 43, total chilled carcass weight was linearly reduced (p < 0.05), and proportion of leg weight was increased by supplementation of TA (p < 0.05). The supplementation of TA linearly reduced pH of the breast meat (p < 0.05) and linearly increased redness (a*) (p < 0.05). Although the supplementation of TA positively influenced gut health and gut microbiota in the starter/grower phases, it negatively affected overall growth performance, bone health, and meat production in broilers on D 42.

Effects of low-crude protein diets supplemented with arginine, glutamine, threonine, and methionine on regulating nutrient absorption, intestinal health, and growth performance of Eimeria-infected chickens.

The study was conducted to evaluate the effects of low crude protein diets supplemented with arginine, glutamine, methionine, and/or threonine on apparent ileal digestibility of amino acids, intestinal morphology, intestinal permeability, gene expression of nutrient transporters, and tight junction proteins of broiler chickens challenged with mixed Eimeria spp. A total of five hundred seventy-six, 12-day-old male broiler chickens were allocated into 8 treatments, and 6 replicate cages of 12 chickens per cage. This experiment included a nonchallenged control (NC) fed regular corn-soybean meal-based diet (Regular diet, 19% crude protein), an Eimeria-challenged control (CC) fed Regular diet, an Eimeria challenge group fed low-crude protein diet (LCP, 16% crude protein), 4 Eimeria challenge groups fed low-crude protein diet supplemented with 0.75% arginine, glutamine, methionine, and threonine, respectively (ARG, GLN, MET, and THR), and an Eimeria challenge group fed low-crude protein diet with 0.75% supplemented arginine, glutamine, methionine, and threonine collectively as a combination group (COMB). On d 14, birds in the challenge groups were gavaged with a mixed Eimeria spp. solution containing 12,500 oocysts of E. maxima, 12,500 oocysts of E. tenella, and 62,500 oocysts of E. acervulina. The results showed that the Eimeria challenge reduced overall growth performance, but the LCP had no adverse impacts on intestinal health and growth of Eimeria-infected birds compared to the CC. Additionally, supplementation of crystalline arginine, glutamine, methionine, and threonine improved the apparent ileal digestibility of these specific amino acids on 6 dpi. Moreover, the THR treatment increased villus height in the duodenum. The ARG treatment decreased intestinal permeability and gene expression of amino acid transporters, whereas the GLN and THR treatments both reversed adverse effects of coccidiosis on gene expression of tight junction protein (claudin 1). However, the MET and COMB treatments exacerbated infection severity of coccidiosis. In summary, adding 0.75% of arginine, glutamine, or threonine in a low crude protein diet can improve the intestinal health of birds challenged with a mild coccidia infection.

Effects of antibiotic growth promoter and dietary protease on growth performance, apparent ileal digestibility, intestinal morphology, meat quality, and intestinal gene expression in broiler chickens: a comparison.

This study aimed to evaluate the effects of supplementing broiler diets with a dietary protease on growth performance, digestive function, intestinal morphology, and meat quality as compared with feeding diets with or without an antibiotic growth promoter (AGP). A total of 240 1-day-old male chicks (Cobb 500, 48.3 ± 3.3 g) were distributed to three treatments with eight replicates (10 birds per replicate). Three treatments were: 1) corn-soybean meal basal diets (CTRL), 2) basal diets with 0.003% avilamycin (AB), and 3) basal diets with 0.0125% protease (PRT). The diets were provided as mash form, and birds were fed ad libitum during the whole experimental period. On day 45, birds were euthanized, and tissue and digesta samples were collected. On day 46, the remaining birds were processed in a commercial slaughterhouse, and breast muscle samples were collected. Despite a trend for a decreased feed conversion ratio (FCR) in the AB group during the whole phase (P = 0.071), no significant differences in growth performance parameters and relative weights of organs were observed (P > 0.05) among the groups. The AB and PRT groups showed significantly greater apparent ileal digestibility of amino acids (AA) compared with the CTRL group (P < 0.05). The PRT group significantly improved the morphology of duodenum and jejunum (P < 0.05). No differences were detected for meat quality, white striping, and woody breast among the groups (P > 0.05). For the gene expressions, the AB group showed a greater level of B0-system neutral amino acid co-transporter 1 and excitatory amino acid transporter 1 mRNA abundance compared with PRT group, while a significantly lesser level of cationic amino acid transporter 1 mRNA abundance was observed in the AB group compared with CTRL group (P < 0.05). The PRT group had a lesser level of peptide transporter 1 mRNA abundance in the jejunum than the CTRL group (P < 0.05). The highest mRNA abundances of zonula occludens-1 and cadherin 1 were observed in the CTRL group (P < 0.05). In conclusion, supplementation of avilamycin tended to reduce FCR and significantly improved AA utilization, and supplementation of dietary protease significantly enhanced intestinal morphology and AA utilization in broilers. In that respect, exogenous protease use appears to be an interesting tool to be considered in AGP reduction strategies.

Effects of a microencapsulated formula of organic acids and essential oils on nutrient absorption, immunity, gut barrier function, and abundance of enterotoxigenic Escherichia coli F4 in weaned piglets challenged with E. coli F4.

The objective was to study the effects of microencapsulated organic acids (OA) and essential oils (EO) on growth performance, immune system, gut barrier function, nutrient digestion and absorption, and abundance of enterotoxigenic Escherichia coli F4 (ETEC F4) in the weaned piglets challenged with ETEC F4. Twenty-four ETEC F4 susceptible weaned piglets were randomly distributed to 4 treatments including (1) sham-challenged control (SSC; piglets fed a control diet and challenged with phosphate-buffered saline (PBS)); (2) challenged control (CC; piglets fed a control diet and challenged with ETEC F4); (3) antibiotic growth promoters (AGP; CC + 55 mg·kg-1 of Aureomycin); and (4) microencapsulated OA and EO [P(OA+EO); (CC + 2 g·kg-1 of microencapsulated OA and EO]. The ETEC F4 infection significantly induced diarrhea at 8, 28, 34, and 40 hr postinoculation (hpi) (P < 0.05) in the CC piglets. At 28 d postinoculation (dpi), piglets fed P(OA+EO) had a lower (P < 0.05) diarrhea score compared with those fed CC, but the P(OA+EO) piglets had a lower (P < 0.05) diarrhea score compared with those fed the AGP diets at 40 dpi. The ETEC F4 infection tended to increase in vivo gut permeability measured by the oral gavaging fluorescein isothiocyanate-dextran 70 kDa (FITC-D70) assay in the CC piglets compared with the SCC piglets (P = 0.09). The AGP piglets had higher FITC-D70 flux than P(OA+EO) piglets (P < 0.05). The ETEC F4 infection decreased mid-jejunal VH in the CC piglets compared with the SCC piglets (P < 0.05). The P(OA+EO) piglets had higher (P < 0.05) VH in the mid-jejunum than the CC piglets. The relative mRNA abundance of Na+-glucose cotransporter and B0AT1 was reduced (P < 0.05) by ETEC F4 inoculation when compared with the SCC piglets. The AGP piglets had a greater relative mRNA abundance of B0AT1 than the CC piglets (P < 0.05). The ETEC F4 inoculation increased the protein abundance of OCLN (P < 0.05), and the AGP piglets had the lowest relative protein abundance of OCLN among the challenged groups (P < 0.05). The supplementation of microencapsulated OA and EO enhanced intestinal morphology and showed anti-diarrhea effects in weaned piglets challenged with ETEC F4. Even if more future studies can be required for further validation, this study brings evidence that microencapsulated OA and EO combination can be useful within the tools to be implemented in strategies for alternatives to antibiotics in swine production.

Diet complexity and l-threonine supplementation: effects on growth performance, immune response, intestinal barrier function, and microbial metabolites in nursery pigs.

The aim of this study was to investigate the effects of diet complexity and l-Thr supplementation level on the growth performance, immune response, intestinal barrier function, and microbial metabolites in nursery pigs. Thirty-two weaned pigs (body weight 7.23 ± 0.48 kg) were randomly assigned to dietary treatments in a 2 × 2 factorial arrangement based on diet complexity (complex or simple) and dietary Thr content. The complex diet contained fish meal, plasma protein, and dried whey to mimic a conventional nursery diet. The simple diet was formulated with corn, wheat, and soybean meal and did not contain any animal products. l-Thr was supplemented to each diet to supply either 100% (STD Thr) or 115% (SUP Thr) of the NRC (2012) requirement for standardized ileal digestible Thr. Pigs were individually housed and fed experimental diets ad libitum for 14 d. Diet complexity, dietary Thr content, and their interactions were considered the main effects. Pigs fed the simple diet had greater (P < 0.05) plasma interleukin (IL)-10 and IL-6 concentrations compared with those fed the complex diet on days 7 and 14, respectively. Simple diet-fed pigs tended to show greater (P < 0.10) expression of genes encoding for tumor necrosis factor-α, claudin-1, and zonula occludens-1 in the jejunum compared with complex diet-fed pigs. The simple diet-fed pigs had greater (P < 0.05) concentrations of NH3-N in the jejunum digesta than did complex diet-fed pigs. The SUP Thr increased (P < 0.05) villus height and goblet cell (GC) density in villi and crypts in the jejunum and deepened (P < 0.05) crypts in the proximal colon. The SUP Thr resulted in the upregulation (P < 0.05) of occludin gene expression and a tendency toward the downregulation (P = 0.10) of IL-6 gene expression in the jejunum. Interactions (P < 0.05) between diet complexity and l-Thr supplementation level were observed in GC density in the crypt, NH3-N concentration in the jejunum, and the contents of acetate, propionate, and total volatile fatty acids in the colon. In conclusion, feeding a simple diet to nursery pigs resulted in systemic and intestinal inflammation. The SUP Thr diet did not normalize the simple diet-induced inflammation but improved gut integrity. SUP Thr seems to have greater benefits with a simple diet than with a complex diet. Therefore, SUP Thr in a simple diet could be a beneficial nutritional strategy for enhancing gut health.