Effects of protein sources and levels in antibiotic-free diets on diarrhea, intestinal morphology, and expression of tight junctions in weaned piglets

Nutrition strategies to control post-weaning diarrhea of piglets: From the perspective of feeds

Post-weaning diarrhea (PWD) is a globally significant threat to the swine industry. Historically, antibiotics as well as high doses of zinc oxide and copper sulfate have been commonly used to control PWD. However, the development of bacterial resistance and environmental pollution have created an interest in alternative strategies. In recent years, the research surrounding these alternative strategies and the mechanisms of piglet diarrhea has been continually updated. Mechanically, diarrhea in piglets is a result of an imbalance in intestinal fluid and electrolyte absorption and secretion. In general, enterotoxigenic Escherichia coli (ETEC) and diarrheal viruses are known to cause an imbalance in the absorption and secretion of intestinal fluids and electrolytes in piglets, resulting in diarrhea when Cl- secretion-driven fluid secretion surpasses absorptive capacity. From a perspective of feedstuffs, factors that contribute to imbalances in fluid absorption and secretion in the intestines of weaned piglets include high levels of crude protein (CP), stimulation by certain antigenic proteins, high acid-binding capacity (ABC), and contamination with deoxynivalenol (DON) in the diet. In response, efforts to reduce CP levels in diets, select feedstuffs with lower ABC values, and process feedstuffs using physical, chemical, and biological approaches are important strategies for alleviating PWD in piglets. Additionally, the diet supplementation with additives such as vitamins and natural products can also play a role in reducing the diarrhea incidence in weaned piglets. Here, we examine the mechanisms of absorption and secretion of intestinal fluids and electrolytes in piglets, summarize nutritional strategies to control PWD in piglets from the perspective of feeds, and provide new insights towards future research directions.

Low-protein diet supplemented with 1% L-glutamine improves growth performance, serum biochemistry, redox status, plasma amino acids, and alters fecal microbiota in weaned piglets

Glutamine, one of the most abundant amino acids in the body, has been shown to exert various beneficial effects in pigs. However, knowledge regarding the role of dietary glutamine in low-protein diet-fed piglets remains scarce. The present study aimed to investigate the effects of different levels of L-glutamine on growth performance, serum biochemistry parameters, redox status, amino acids, and fecal microbiota in low-protein diet-fed piglets. A total of 128 healthy crossbred piglets (Landrace × Yorkshire) were randomly allocated into 4 groups of 4 replicate pens, with 8 piglets per pen. Piglets in the 4 groups were fed with corn and soybean meal-based low-protein diets (crude protein level, 17%) that contained 0%, 1%, 2%, and 3% L-glutamine, respectively, for 28 d. Pigs administered 1% L-glutamine had greater body weight on d 28 and average daily gain (ADG, P < 0.01), whereas a lower feed to gain ratio (F:G) from d 1 to 28 (P < 0.01), compared to the other three groups. Besides, lower body weight on d 14 and 28, ADG, average daily feed intake, and higher F:G from d 15 to 28 and d 1 to 28 were observed in response to 2% and 3% L-glutamine treatments than 0% and 1% L-glutamine treatments (P < 0.01). Moreover, 1% L-glutamine reduced serum glucose, malondialdehyde, hydrogen peroxide concentrations and inhibited aspartate aminotransferase, alanine aminotransferase, myeloperoxidase activities in low-protein diet-fed piglets on d 14, with concomitantly upregulated catalase, total superoxide dismutase activities and glutathione level (P < 0.05). However, dietary 3% L-glutamine enhanced blood urea nitrogen content in pigs on d 14 (P < 0.05). Further investigation revealed that 1% L-glutamine upregulated the serum glutamine, lysine, methionine, tyrosine, and reduced plasma valine content (P < 0.05). Additionally, 1% L-glutamine upregulated the abundance of p_75_a5, Clostridium, Lactobacillus, Prevotellaceae_Prevotella, and Gemmiger in the stool of piglets on d 14, with the Streptococcus level being concomitantly reduced (P < 0.05). Collectively, dietary 1% L-glutamine enhances the growth performance and improves serum physiochemical parameters and antioxidative capacity in low-protein diet-fed piglets at an early age, which are associated with an increased synthesis of glutathione by modulating amino acid levels, and the optimization of gut microbiota.

Intestinal health of squab pigeons responded to parental dietary protein levels during breeding period

The objective of this study was to determine the effects of dietary crude protein (CP) levels on intestinal antioxidant status, tight junction proteins expression, and amino acids transporters levels in squabs. A total of 180 pairs of White King parent pigeons approximately 10 mo old were randomly assigned to 5 groups with 6 replications of 6 pairs of parental pigeons each, and were fed with 14, 15, 16, 17, and 18% CP diets for 46 d, respectively. Dietary increasing CP levels increased final body weight (linear and quadratic, P < 0.05), serum urea nitrogen (linear, P<0.05) and triglyceride levels (quadratic, P < 0.05), and reduced kidney relative weight (quadratic, P < 0.05) in squabs. Final body weight of squabs in the 18% CP diet group was higher than that of the 14, 15, and 16% CP diet groups (P < 0.05) but was similar to that of the 17% CP diet group (P > 0.05). Increasing dietary CP levels reduced intestinal malondialdehyde contents (linear and quadratic, P < 0.05) and jejunal total superoxide dismutase (T-SOD) activity (linear, P < 0.05), and enhanced (linear and quadratic, P<0.05) ileal catalase and T-SOD activities in squabs, and these effects were more prominent in the 17% CP diet group. Graded CP levels up-regulated the mRNA expression of intestinal zonula occludens 1 (linear, P < 0.05), solute carrier family 7 members 9 (linear, P < 0.05) and claudin 1 (CLDN1, linear and quadratic, P < 0.05), ileal CLDN3 and solute carrier family 6 members 14 (linear, P < 0.05) but lowered jejunal solute carrier family 6 member 14 (quadratic, P<0.05) mRNA expression in squabs. The effects of dietary CP levels on intestinal tight junction proteins expression were more apparent when its supplemental levels were 18%. These results suggested that increasing parental dietary CP levels ranged from 14 to 18% during breeding period improved growth and intestinal function of squabs, with its recommended level being 17%.

Blended-protein changes body weight gain and intestinal tissue morphology in rats by regulating arachidonic acid metabolism and secondary bile acid biosynthesis induced by gut microbiota

PURPOSE

The impact of dietary nutrients on body growth performance and the composition of gut microbes and metabolites is well-established. In this study, we aimed to determine whether dietary protein can regulate the physiological indexes and changes the intestinal tissue morphology in rats, and if dietary protein was a crucial regulatory factor for the composition, function, and metabolic pathways of the gut microbiota.

METHOD

A total of thirty male Sprague Dawley (SD) rats (inbred strain, weighted 110 ± 10 g) were randomly assigned to receive diets containing animal-based protein (whey protein, WP), plant-based protein (soybean protein, SP), or a blended protein (soybean-whey proteins, S-WP) for a duration of 8 weeks. To investigate the effects of various protein supplement sources on gut microbiota and metabolites, we performed a high throughput 16S rDNA sequencing association study and fecal metabolomics profiling on the SD rats. Additionally, we performed analyses of growth indexes, serum biochemical indexes, and intestinal morphology.

RESULTS

The rats in S-WP and WP group exhibited a significantly higher body weight and digestibility of dietary protein compared to the SP group (P < 0.05). The serum total protein content of rats in the WP and S-WP groups was significantly higher (P < 0.05) than that in SP group, and the SP group exhibited significantly lower (P < 0.05) serum blood glucose levels compared to the other two groups. The morphological data showed the rats in the S-WP group exhibited significantly longer villus height and shallower crypt depth (P < 0.05) than the SP group. The gut microbial diversity of the SP and S-WP groups exhibited a higher level than that of the WP group, and the microbiomes of the WP and S-WP groups are more similar compared to those of the SP group. The Arachidonic acid metabolism pathway is the most significant KEGG pathway when comparing the WP group and the SP group, as well as when comparing the SP group and the S-WP group.

CONCLUSION

The type of dietary proteins exerted a significant impact on the physiological indices of SD rats. Intake of S-WP diet can enhance energy provision, improve the body's digestion and absorption of nutrients, as well as promote intestinal tissue morphology. In addition, dietary protein plays a crucial role in modulating fecal metabolites by regulating the composition of the gut microbiota. Metabolomics analysis revealed that the changes in the levels of arachidonic acid metabolites and secondary bile acid metabolite induced by Clostridium_sensu_stricto_1 and [Eubacterium]_coprostanoligenes_group maybe the primarily causes of intestinal morphological differences.

Effects of dietary protein level on intestinal function and inflammation in nursery pigs

High crude protein (CP; 21% to 26%) diets fed during the first 21 to 28 d postweaning are viewed negatively because of a perceived increase in the incidence rates of diarrhea due to increased intestinal protein fermentation and/or augmented enteric pathogen burden. This is thought to antagonize nursery pig health and growth performance. Therefore, our objective was to evaluate the impact of low vs. high dietary CP on 21-day postweaned pig intestinal function. Analyzed parameters included ex vivo intestinal barrier integrity (ileum and colon), ileal nutrient transport, tissue inflammation, and fecal DM. One hundred and twenty gilts and barrows (average body weight) were randomly assigned to one of two diets postweaning. Diets were fed for 21 d, in two phases. Phase 1 diets: low CP (17%) with a 1.4% standardized ileal digestible (SID) Lys (LCP), or high CP (24%) with a 1.4% SID Lysine (HCP). Phase 2: LCP (17%) and a 1.35% SID lysine, or HCP (24%) formulated to a 1.35% SID lysine. Pig growth rates, feed intakes, and fecal consistency did not differ (P > 0.05) due to dietary treatment. Six animals per treatment were euthanized for additional analyses. There were no differences in colonic epithelial barrier function as measured by transepithelial electrical resistance (TER) and fluorescein isothiocyanate (FITC)-dextran transport between treatments (P > 0.05). Interleukins (IL)-1α, IL-1β, IL-1ra, IL-2 IL-4, IL-6, and IL-12 were not different between treatments (P > 0.05). However, IL-8 and IL-18 were higher in HCP- vs. LCP-fed pigs (P < 0.05). There were no differences in fecal dry matter (DM; P > 0.05) between treatments. In the ileum, there was a tendency (P = 0.06) for TER to be higher in HCP-fed pigs, suggesting a more robust barrier. Interestingly, glucose and glutamine transport were decreased in HCP- vs. LCP-fed pigs (P < 0.05). FITC-dextran transport was not different between treatments (P > 0.05). There were also no differences in ileal cytokine concentrations between diets (P > 0.05). Taken together, the data show that low CP does not negatively impact colonic barrier function, fecal DM, or inflammation. In contrast, ileal barrier function and nutrient transport were altered, suggesting a regional effect of diet on overall intestinal function.

Gastro-intestinal lesions are not relatable to diarrhoea or specific pathogens in post-weaning diarrhoea (PWD) in pigs

BACKGROUND

Post-weaning diarrhoea (PWD) is a multifactorial condition and the most well documented infectious cause is enterotoxigenic Escherichia coli. The objective of the study was to investigate possible associations between pathological manifestations and pathogens in pigs with and without PWD. The study was conducted as a case-control study and included a total of 173 pigs from 9 different commercial intensive indoor production herds in eastern Denmark.

RESULTS

Based on clinical examination, a total of 89 piglets with PWD (cases) and 84 piglets without PWD (controls) were included. Most of the pigs (n = 105/173) presented gastric lesions, which were more frequently observed in the control group. The odds of gastric ulcers were lower among pigs with PWD compared to pigs without PWD with an odds ratio (OR) of 0.2 (0.0; 0.7). Abnormal content in the colon was associated with PWD, with an OR of 6.5 (3.2; 14.3). No apparent association was found between lesions and the various pathogens or a combination of these. The odds of neutrophilic granulocyte infiltration were lower in the jejunum among pigs with PWD (OR 0.3 [0.1; 0.6]) compared to pigs without PWD. The association between neutrophilic granulocyte infiltration in jejunum and PWD differed between the herds (P = 0.03). Furthermore, the associations between PWD and hyperleukocytosis (P = 0.04) or infiltration of eosinophilic granulocytes (P = 0.04) in ileum were also herd dependent. Histopathology revealed several lesions not relatable to PWD.

CONCLUSION

The association between lesions and specific pathogens or PWD is more complex than anticipated.

Dietary inclusion of methanotrophic microbial cell-derived protein in the early post-weaning period sustains growth performance and intestinal health of weaner piglets

The global demand for sustainably produced protein feeds for animal production is increasing. Methanotrophic bacteria grow on methane and convert it into microbial cell protein (MCP) that has been shown to have high nutritive value for growing pigs. The present aimed to investigate how increasing amounts of MCP in diets fed during the first 15 days after weaning affect the growth performance of piglets from weaning until day 43 postweaning. Furthermore, the effect of MCP on intestinal morphology and histopathology was assessed on day 15 after weaning. During seven consecutive weeks, approximately 480 piglets were recruited for the experiment per batch. The piglets were divided into four groups and housed in eight double pens with 60 piglets per pen. The piglets were fed one of four experimental diets with 0, 3, 6, or 10% of MCP included at the expense of fishmeal and subsequently potato protein for the first 15 days postweaning. Thereafter, all pigs were fed commercial weaner diets in two phases (days 16-30 and days 31-43) until day 43 postweaning. All diets were without medicinal zinc. Feed intake and growth were registered on double pen level during all three phases. On day 15 after weaning, 10 piglets per treatment were randomly selected, autopsied, and sampled for intestinal morphology and histopathology. Daily gain during the first 15 days postweaning tended (P = 0.09) to be affected by the inclusion of MCP in the weaning diet being lowest in the group fed 10% MCP. Treatment did not affect daily feed intake; however, Feed Conversion Ratio (FCR) was significantly affected (P = 0.003) showing the highest FCR in piglets fed 10% MCP. Growth performance was not affected by the experimental treatment during the following phases. In the small intestine, villous height tended (P = 0.09) to show a quadratic response to level of MCP in the diet with the longest villi observed after feeding 6% MCP. Dietary treatment did not affect crypt depth. The villous height to crypt depth (VC) ratio showed a quadratic response to increased dietary inclusion of MCP (P = 0.02) with piglets fed 6% MCP having the highest VC ratio. In conclusion, this study demonstrated that MCP could constitute 6% of diets as-fed (22% of total CP), at the expense of fishmeal and potato protein, for newly weaned piglets without negative effects on growth rates and FCR. The inclusion of MCP in diets for newly weaned piglets could be part of improving the sustainability of pig production.

Effects of Different Combinations of Sodium Butyrate, Medium-Chain Fatty Acids and Omega-3 Polyunsaturated Fatty Acids on the Reproductive Performance of Sows and Biochemical Parameters, Oxidative Status and Intestinal Health of Their Offspring

The aim of the study was to investigate the comparative effects of different combinations of sodium butyrate (SB), medium-chain fatty acids (MCFAs), and omega-3 polyunsaturated fatty acids (n-3 PUFAs) on the reproductive performances of sows, as well as on the biochemical parameters, oxidative statuses, and intestinal health of the sucking piglets. A total of 30 sows were randomly allocated to five treatments: (1) control diet (CON); (2) CON with 1 g/kg of coated SB and 7.75 g/kg of coated MCFAs (SM); (3) CON with 1 g/kg of coated SB and 68.2 g/kg of coated n-3 PUFAs (SP); (4) CON with 7.75 g/kg of coated MCFAs and 68.2 g/kg of coated n-3 PUFAs (MP); (5) CON with 1 g/kg of coated SB, 7.75 g/kg of coated MCFAs and 68.2 g/kg of coated n-3 PUFA (SMP). The results showed that sows fed the SP, MP, and SMP diets had shorter weaning-to-estrus intervals than those fed the CON diet (p < 0.01). The piglets in the SM, SP, and MP groups showed higher increases in the plasma catalase and glutathione peroxidase activities than those of the CON group (p < 0.01). The diarrhea incidence of piglets in the SM, SP and SMP groups was lower than that of piglets in the CON group (p < 0.01). Additionally, the addition of SM, SP, MP, and SMP to the sow diets increased the contents of immunoglobulin A, immunoglobulin G, fat, and proteins in the colostrum (p < 0.01), as well as the plasma total superoxide dismutase activities (p < 0.01) in the suckling piglets, whereas it decreased the mRNA expressions of tumor necrosis factor-α, interleukin-1β, and toll-like receptor 4 in the jejunum mucosa of the piglets. The relative abundances of Prevotella, Coprococcus, and Blautia in the colonic digesta of the piglets were increased in the SM group (p < 0.05), and the relative abundances of Faecalibacterium increased in the SMP group (p < 0.05), compared with the CON group. The relative abundances of Collinsella, Blautia, and Bulleidia in the MP group were higher than those in the CON group (p < 0.05). Collectively, dietary combinations of fatty acids with different chain lengths have positive effects on the growth performances and intestinal health of suckling piglets.

Effects of different dietary protein levels on intestinal aquaporins in weaned piglets

This study was conducted to investigate the relationship between changes in intestinal aquaporins (AQPs) in piglets fed diets with different protein levels and nutritional diarrhoea in piglets. Briefly, 96 weaned piglets were randomly divided into four groups fed diets with crude protein (CP) levels of 18%, 20%, 22% and 24%. The small intestines and colons of the weaned piglets were collected, and several experiments were conducted. In the small intestine, AQP4 protein expression was higher in weaned piglets fed the higher-CP diets (22% and 24% CP) than in those fed the 20% CP diet except at 72 h (p < 0.01). At 72 h, the AQP4 protein expression in the small intestine was lower in the 18% group than in the other three groups (p < 0.01). Under 20% CP feeding, AQP2, AQP4 and AQP9 protein expression in the colons of piglets peaked at certain time points. The AQP2 and AQP4 mRNA levels in the colon and the AQP4 and AQP4 mRNA levels in the distal colon were approximately consistent with the protein expression levels. However, the AQP9 mRNA content in the colon was highest in the 18% group, and the AQP2 mRNA content in the distal colon was significantly higher in the 24% group than in the 20% group. AQP2 and AQP4 were expressed mainly around columnar cells in the upper part of the smooth colonic intestinal villi, and AQP9 was expressed mainly on columnar cells and goblet cells in the colonic mucosa. In conclusion, 20% CP is beneficial to the normal expression of AQP4 in the small intestine, AQP2, AQP4 and AQP9 in the colon of weaned piglets, which in turn maintains the balance of intestinal water absorption and secretion in piglets.

Advances, Implications, and Limitations of Low-Crude-Protein Diets in Pig Production

Currently, five crystalline essential amino acids (Lys, Met, Thr, Trp, and Val) are generally used, allowing formulation of low-crude-protein (CP) diets. Moreover, Ile may also be used depending on its economic value and the specific feeding program. Experimentally, it has been shown that further reduced CP levels can be achieved by supplemental His, Leu, and Phe to the diets. However, decreasing the dietary CP level while maintaining optimal ratios of amino acids has shown contradictory effects on pigs' growth performance. Due to the divergence in the literature and the importance for practical formulation strategies in the swine industry, a literature review and a meta-analysis were performed to estimate the minimum CP level that would not compromise pig performance. Based on the present review, there is a minimum CP level after which the growth performance of pigs can be compromised, even though diets are balanced for essential amino acids. Considering average daily gain and gain to feed, respectively, these levels were estimated to be 18.4% CP (95% confidence interval [CI]: 16.3 to 18.4) and 18.3% CP (95% CI: 17.4 to 19.2) for nursery, 16.1% CP (95% CI: 16.0 to 16.2) and 16.3% CP (95% CI: 14.5 to 18.0) for growing, and 11.6% CP (95% CI: 10.8 to 12.3) and 11.4% CP (95% CI: 10.3 to 12.5) for finishing pigs.

Dietary Crude Protein Levels Alter Diarrhea Incidence, Immunity, and Intestinal Barrier Function of Huanjiang Mini-Pigs During Different Growth Stages

Huanjiang mini-pig is an indigenous pig breed in China; however, the optimal dietary crude protein (CP) levels for this pig breed during different growth stages has not been standardized yet. This study investigated the effects of different CP levels on diarrhea incidence, immunity, and intestinal barrier function in pigs. A total of 360 Huanjiang mini-pigs were assigned to three independent trials and fed the following CP diets: 5−10 kg stage, 14, 16, 18, 20, and 22%; 10−20 kg stage, 12, 14, 16, 18, and 20% and 20−30 kg stage, 10, 12, 14, 16, and 18%. In the 5−10 kg stage, the 22%; diet increased the plasma IL-1β, IL-6, IL-8, and TNF-α concentrations compared to the 14−20% diets and decreased IL-10 and TGF-β; however, these results were fluctuated in the later stages, including the decrease of IL-1β and IL-8 in the 20% group, TNF-α in the 18−20% groups, and the increase of IFN-γ in the 20% group at the 10−20 kg stage and the decrease of TNF-α in the 16% group at the 20−30 kg stage. The 20% diet increased the jejunal and ileal IL-10 concentration compared to the 14% diet at the 5−10 kg stage, as well as in the 16% diet compared to the 12% diet at the 10−20 kg stage. In addition, ileal IL-10 concentration was increased in the 16% diet compared to the 10, 12, and 18% diets at the 20−30 kg stage. Furthermore, the 18% diet at the 5−10 kg stage and the 16% diet at the 10−20 kg stage decreased jejunal IL-6 expression, whereas the 20% diet increased the TNF-α and IFN-γ at the 5−10 kg stage. The 20% diet increased the Claudin, Occludin, ZO-1, ZO-2, Mucin-1, and Mucin-20 expressions at the 5−10 kg stage, as well as TLR-2, TLR-4, and NF-κB in the 22 and 20% diets at the 5−10 and 10−20 kg stages, respectively. Collectively, these findings suggest optimal dietary CP levels of 16, 14, and 12% for Huanjiang mini-pigs during the 5−10, 10−20, and 20−30 kg growth stages, respectively; and provide the guiding significance of dietary CP levels for Huanjiang mini-pigs during different growth stages.

Effects of the increased protein level in small intestine on the colonic microbiota, inflammation and barrier function in growing pigs

Background

An increased level of the dietary protein alters the colonic microbial community and metabolic profile of pigs, but it remains unclear whether this leads to colonic inflammation and impairs barrier function in growing pigs.

Results

Sixteen pigs (35.2 ± 0.3 kg) were infused with sterile saline (control) or soy protein hydrolysate (SPH) (70 g/day) through a duodenal fistula twice daily during a 15-day experimental period. The SPH treatment did not affect their average daily feed intake and daily weight gain (P > 0.05), but reduced colon index and length (P < 0.05). Illumina MiSeq sequencing revealed that species richness was increased following SPH intervention (P < 0.05). Furthermore, SPH reduced the abundance of butyrate- and propionate-producing bacteria—such as Lachnospiraceae NK4A136 group, Lachnospiraceae_uncultured, Coprococcus 3, Lachnospiraceae UCG-002, and Anaerovibrio—and increased the abundance of potentially pathogenic bacteria and protein-fermenting bacteria, such as Escherichia-Shigella, Dialister, Veillonella, Prevotella, Candidatus Saccharimonas, Erysipelotrichaceae UCG-006, Prevotellaceae_uncultured, and Prevotellaceae UCG-003 (P < 0.05). In addition, a lower content of total short-chain fatty acids, propionate, and butyrate and a higher concentration of cadaverine, putrescine, total biogenic amines, ammonia, and isovalerate were observed following SPH infusion (P < 0.05). Further analysis revealed that SPH increased the concentration of tumour necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-8 in the colonic mucosa (P < 0.05). Interestingly, SPH intervention increased the expression of occludin, zonula occludens (ZO)-1, and claudin-1 in colonic mucosa (P < 0.05). Correlation analysis showed that different genera were significantly related to the production of metabolites and the concentrations of pro-inflammatory cytokines.

Conclusion

An increased soy protein level in the small intestine altered the colonic microbial composition and metabolic profile, which resulted in the secretion of colonic proinflammatory cytokines and the increased expression of tight junction proteins.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02498-x.

Effects of dietary protein level on small intestinal morphology, occludin protein, and bacterial diversity in weaned piglets

Due to the physiological characteristics of piglets, the morphological structure and function of the small intestinal mucosa change after weaning, which easily leads to diarrhea in piglets. The aim of this study was to investigate effects of crude protein (CP) levels on small intestinal morphology, occludin protein expression, and intestinal bacteria diversity in weaned piglets. Ninety‐six weaned piglets (25 days of age) were randomly divided into four groups and fed diets containing 18%, 20%, 22%, and 24% protein. At 6, 24, 48, 72, and 96 h, changes in mucosal morphological structure, occludin mRNA, and protein expression and in the localization of occludin in jejunal and ileal tissues were evaluated. At 6, 24, and 72 h, changes in bacterial diversity and number of the ileal and colonic contents were analyzed. Results showed that structures of the jejunum and the ileum of piglets in the 20% CP group were intact. The expression of occludin mRNA and protein in the small intestine of piglets in the 20% CP group were significantly higher than those in the other groups. As the CP level increased, the number of pathogens, such as Clostridium difficile and Escherichia coli, in the intestine increased, while the number of beneficial bacteria, such as Lactobacillus, Bifidobacterium, and Roseburia, decreased. It is concluded that maintaining the CP level at 20% is beneficial to maintaining the small intestinal mucosal barrier and its absorption function, reducing the occurrence of diarrhea, and facilitating the growth and development of piglets.

Glutamine, glutamate, and aspartate differently modulate energy homeostasis of small intestine under normal or low energy status in piglets

Weaning stress may cause reduced energy intake for maintenance of mucosal structure. Gln, Glu, and Asp are major energy sources for the small intestine. This study investigated whether Gln, Glu, and Asp improve the intestinal morphology via regulating the energy metabolism in weaning piglets. A total of 198 weaned piglets were assigned to 3 treatments: Control (Basal diet + 1.59% L-Ala); T1 (Basal diet + 1% L-Gln + 0.5% L-Glu + 0.1% L-Asp); T2 (Low energy diet + 1% L-Gln + 0.5% L-Glu + 0.1% L-Asp). Jejunum and ileum were obtained on d 5 or 21 post-weaning. T1 enhanced growth performance. T1 and T2 treatments improved small intestinal morphology by increasing villus height, goblet cell number and decreasing crypt depth. Days post-weaning affected the efficacy of T2, but not T1, on energy metabolism. At normal energy supplementation, Gln, Glu, and Asp restored small intestinal energy homeostasis via replenishing the Krebs' cycle and down-regulating the AMPK (adenosine monophosphate activated protein kinase) pathway. As these are not sufficient to maintain the intestinal energy-balance of piglets fed with a low energy diet on d 5 post-weaning, the AMPK, glycolysis, beta-oxidation, and mitochondrial biogenesis are activated to meet the high energy demand of enterocytes. These data indicated that Gln, Glu, and Asp could restore the energy homeostasis of intestinal mucosa of weaning piglets under normal energy fed. Low energy feeding may increase the susceptibility of piglets to stress, which may decrease the efficacy of Gln, Glu, and Asp on the restoration of energy balance. These findings provide new information on nutritional intervention for insufficient energy intake in weaning piglets.

Coated Zinc Oxide Improves Growth Performance of Weaned Piglets via Gut Microbiota

Weaned piglets stayed in transitional stages of internal organ development and external environment change. The dual stresses commonly caused intestinal disorders followed by damaged growth performance and severe diarrhea. High dose of zinc oxide could improve production efficiency and alleviate disease status whereas caused serious environmental pollution. This research investigated if coated ZnO (C_ZnO) in low dose could replace the traditional dose of ZnO to improve the growth performance, intestinal function, and gut microbiota structures in the weaned piglets. A total of 126 cross-bred piglets (7.0 ± 0.5 kg body weight) were randomly allocated into three groups and fed a basal diet or a basal diet supplemented with ZnO (2,000 mg Zn/kg) or C_ZnO (500 mg Zn/kg), respectively. The test lasted for 6 weeks. C_ZnO improved average daily gain (ADG) and feed efficiency, alleviated diarrhea, decreased the lactulose/mannitol ratio (L/M) in the urine, increased the ileal villus height, and upregulated the expression of Occludin in the ileal tissue and the effect was even better than a high concentration of ZnO. Importantly, C_ZnO also regulated the intestinal flora, enriching Streptococcus and Lactobacillus and removing Bacillus and intestinal disease-associated pathogens, including Clostridium_sensu_stricto_1 and Cronobacter in the ileal lumen. Although, colonic microbiota remained relatively stable, the marked rise of Blautia, a potential probiotic related to body health, could still be found. In addition, C_ZnO also led to a significant increase of acetate and propionate in both foregut and hindgut. Collectively, a low concentration of C_ZnO could effectively promote growth performance and reduce diarrhea through improving small intestinal morphology and permeability, enhancing the barrier function, adjusting the structure of gut microbiota, and raising the concentration of short-chain fatty acids (SCFAs) in the weaned piglets.

Tea Tree Oil Terpinen-4-ol Protects Gut Barrier Integrity by Upregulation of Tight Junction Proteins via the ERK1/2-Signaling Pathway

Tea tree oil (TTO) exhibits a potent antioxidant, antibacterial, and anti-inflammatory activity and is commonly used in skincare products. However, it is not clear whether TTO can protect gut barrier damage in inflammatory bowel disease (IBD) patients. Herein, we report the impact of terpinen-4-ol (TER, the primary constituent of TTO), on lipopolysaccharide (LPS)-induced intestinal epithelial cell barrier function impairment in intestinal porcine epithelial cell lines (IPEC-J2) and dextran sulfate sodium (DSS)-induced IBD in mice. TER protected against LPS-induced damage in IPEC-J2 cells in vitro and attenuated DSS-induced colitis in vivo. Added TER promoted the tight junction (TJ) proteins expressing in vitro and in vivo and attenuated the LPS-induced upregulation of ERK phosphorylation in IPEC-J2 cells. However, when an inhibitor of ERK phosphorylation was added, TER did not promote the expression of TJ protein, denoting that the ERK signaling pathway mediates the upregulation of TJ proteins. Our data may propose the potential application of TER in treating IBD.

Dietary Hermetia illucens Larvae Replacement Alleviates Diarrhea and Improves Intestinal Barrier Function in Weaned Piglets Challenged With Enterotoxigenic Escherichia coli K88

A high-quality protein substitute, Hermetia illucens (black soldier fly) larvae powder, is rich in protein and often used in animal feed. This study aimed to investigate the feasibility and optimal ratio of replacing fish meal with H. illucens larvae in weaned piglets and to demonstrate the effects on piglets' growth performance, intestinal microflora and immune performance. Forty-eight female weaned piglets were randomly classified into three groups. Each group consisted of eight pens (replicates), with two piglets per pen. Three groups containing different proportions of H. illucens larvae (0, 4, and 8%) were referred to as C, HI4, and HI8. We first designed a 28-day feeding experiment to detect growth performance; after that, the piglets were induced with oral gavage of enterotoxigenic Escherichia coli K88 (ETEC K88) and recording diarrhea on day 29 of the experiment. Samples were taken on the 32nd day to detect the effect of H. illucens larvae on the immune performance of the weaned piglets. H. illucens larvae replacement did not cause any obvious change in the growth performance nether in HI4 nor in HI8 of weaned piglets with 28 d feeding stage. H. illucens larvae could improve the intestinal health of weaned piglets by increasing the content of Lactobacillus and reducing the content of Streptococcus. Compared with C+K88 group, the diarrhea rate was attenuated for the H. illucens supplemented group. The integrity of ileum villi in HI4+K88 and HI8+K88 groups was better than that in C+K88 group, and the villi in C+K88 group were severely damaged. The expression of IL-10, Occludin and Claudin-3 in the intestinal mucosa of the HI4+K88 group and HI8+K88 group were significantly increased (P < 0.05), and the expression of TNF-α was significantly decreased (P < 0.05) compared with the C+K88 group. The results of immunoblotting also validated that the same ETEC K88 treatment of weaned piglets enhanced the expression of tight junction protein in the intestinal mucosa of the H. illucens addition group. ETEC-induced diarrhea will be reduced by the diet of weaned piglets containing H. illucens larvae, ameliorating the immune performance of piglets. Our results indicates that the optimal dosage of H. illucens replacement in weaned piglets is 4%.

Dietary high protein-induced diarrhea and intestinal inflammation by activation of NF-κB signaling in piglets

The present study aimed to investigate whether inflammation-associated responses in piglets are induced by high protein (HP) through activating nuclear factor kappa B (NF-κB) signaling. Sixteen piglets (35 d of age, Duroc × [Landrace × Yorkshire], weaned at d 21, initial BW = 9.70 ± 0.11 kg) were allocated to 18% and 26% CP (HP group) at random, comprising 8 replicate pens per treatment. The piglets were slaughtered to collect intestinal tissues when apparent, persistent, and stable diarrhea syndromes happened (on d 12). No significant differences were observed in their growth performance (P > 0.05), but reduction by 19.11%, 25.31%, 23.64% of ADFI, ADG, and G:F, respectively was detected in the HP group. The HP group had greater (P = 0.002) diarrhea rates. Furthermore, dietary HP had lower ileal villus height (VH; P = 0.048), ratio of villus height to crypt depth (VH/CD ratio; P = 0.016), and colonic CD (P = 0.034), as well as had the trend (P = 0.075) to reduce the ileal villus absorptive area. Moreover, HP diets significantly elevated the goblet cell numbers in the ileal villi (P = 0.016) and colonic crypts (P < 0.001) and up-regulated (P = 0.012) the mRNA expression of mucin2 (Muc2) in the ileum. In addition, HP diets increased the myeloperoxidase concentration in the ileum (P = 0.002) and colon (P = 0.007) of piglets. Dietary HP significantly down-regulated the mRNA expression of tumor necrosis factor-α (TNF-α; P < 0.001) in the ileum, induced nitric oxide synthase (iNOS; P = 0.040) and interleukin-22 (IL-22; P = 0.008) in the colon, and inclined to down-regulate interleukin-1β (IL-1β; P = 0.076) expression in the colon. The relative protein abundance of Galectin-3 (P = 0.046) in the colon and the ratio of phosphorylation NF-κB to NF-κB (p-NF-κB/NF-κB ratio) in the ileum of HP piglets were also greater (P = 0.038). These results suggest that dietary HP may cause diarrhea in piglets by activating NF-κB signaling induced intestinal inflammation.

Effects of Replacing Medical Zinc Oxide with Different Ratios of Inorganic: Organic Zinc or Reducing Crude Protein Diet with Mixed Feed Additives in Weaned Piglet Diets

One hundred twenty weaned piglets (9.34 ± 0.74 kg) were used in a four-week experiment to investigate the effects of replacing medical ZnO with a different ratio of inorganic and organic zinc (IZ:OZ) or a low-crude-protein diet (LP) with mixed feed additives (MFAs) in the weaned piglets' diet. The dietary treatments included a control (CON), T1 (T1; ZnO 1000 mg/kg), T2 (IZ:OZ 850:150), T3 (IZ:OZ 700:300), T4 (IZ:OZ, 500:500), and T5 (LP with MFAs (0.1% essential oils + 0.08% protease + 0.02% xylanase)). The growth performance was decreased (p < 0.05) in the CON treatment compared with the T4 treatment. The diarrhea incidence was decreased (p < 0.05) in the T4 and the T5 treatment compared with the CON and the T1 treatments. The apparent total tract digestibility (ATTD) of nutrients were increased (p < 0.05) in the T4 and T5 treatments compared with the CON, T1, and T2 treatments. The T4 treatment had a higher (p < 0.05) ATTD of zinc than the T1, T2, and T3 treatments. The fecal microflora was improved (p < 0.05) in the T5 treatment compared with the CON and T3 treatments. In conclusion, IZ:OZ 500:500 could improve growth performance, nutrient digestibility, and zinc utilization while reducing diarrhea incidence in weaned piglets. Moreover, LP with MFA could replace medical ZnO.

Research progress on diarrhoea and its mechanism in weaned piglets fed a high-protein diet

In order to pursue faster growth and development of weaned piglets, increased dietary protein (CP) levels were favoured by the pig industry and the feed industry. The digestive organs of piglets were not fully developed at weaning, and the digestive absorption capacity of protein was limited. High-protein diets can cause allergic reactions in piglets, destroy intestinal structural integrity, reduce immunity, and cause intestinal flora imbalance. Undigested proteins were prone to produce toxic substances, such as ammonia and biogenic amines, after fermentation in the hindgut, which negatively affects the health of the intestine and eventually causes reduced growth performance and diarrhoea in piglets. This review revealed the mechanism of diarrhoea caused by high-protein diets in weaned piglets and provided ideas for preventing diarrhoea in weaned piglets.

Comparative effects of enzymatic soybean, fish meal and milk powder in diets on growth performance, immunological parameters, SCFAs production and gut microbiome of weaned piglets

Background

The objective of this study was to evaluate the replacement effects of milk powder (MK) and fish meal (FM) by enzymatic soybean (ESB) in diets on growth performance, immunological parameters, SCFAs production and gut microbiome of weaned piglets.

Methods

A total of 128 piglets with initial body weight at 6.95 ± 0.46 kg, were randomly assigned into 4 dietary treatments with 8 replicates per treatment and 4 piglets per replicate for a period of 14 d. Piglets were offered iso-nitrogenous and iso-energetic diets as follows: CON diet with MK and FM as high quality protein sources, ESB plus FM diet with ESB replacing MK, ESB plus MK diet with ESB replacing FM, and ESB diet with ESB replacing both MK and FM.

Results

No significant differences were observed in growth performance among all treatments (P > 0.05). However, piglets fed ESB plus FM or ESB diet had increased diarrhea index (P<0.01), and lower digestibility of dry matter (DM), gross energy (GE) or crude protein (CP), relative to piglets fed CON diet (P <  0.01). Moreover, the inclusion of ESB in diet markedly decreased the plasma concentration of HPT and fecal concentration of butyric acid (BA) (P<0.01). The High-throughput sequencing of 16S rRNA gene V3−V4 region of gut microbiome revealed that the inclusion of ESB in diet increased the alpha diversity, and the linear discriminant analysis effect size (LEfSe) showed that piglets fed with ESB plus FM or ESB diet contained more gut pathogenic bacteria, such as g_Peptococcus, g_Veillonella and g_Helicobacter.

Conclusion

The inclusion of ESB in diet did not markedly affect growth performance of piglets, but the replacement of MK or both MK and FM by ESB increased diarrhea index, which could be associated with lower nutrients digestibility and more gut pathogenic bacteria. However, piglets fed diet using ESB to replace FM did not markedly affect gut health-related parameters, indicating the potential for replacing FM with ESB in weaning diet.

Low crude protein diets supplemented with casein hydrolysate enhance the intestinal barrier function and decrease the pro-inflammatory cytokine expression in the small intestine of pigs

To reduce nitrogen excretion and lower feeding costs, low crude protein (CP) diets are sometimes proposed, however, a great reduction of dietary CP concentration (>4% reduction vs. recommended concentration), even supplemented with essential and nonessential amino acids (AA) can detrimentally affect small intestinal barrier function and immunity, possibly due to the excessive lack of peptides. Here we hypothesize that with an extremely low CP concentration diet, protein-derived peptides, rather than AA supplementation, can improve intestinal barrier development and health. To test this hypothesis, 21 growing pigs (19.90 ± 1.00 kg body weight) were randomly assigned to 3 treatments with control diet (16% CP), or low CP diets (13% CP) supplemented with AA (LCPA) or casein hydrolysate (LCPC) for 28 days. In comparison with the control diet, the LCPA diet decreased the protein expression level of jejunal barrier factor zonula occludens-1 (ZO-1) and stem cell proliferation factor leucine-rich repeat-containing G-protein-coupled receptor-5, whereas the LCPC diet enhanced intestinal barrier function by increasing the protein expression level of jejunal occludin and ZO-1 and ileal mucin-2. The LCPA diet reduced Lactobacillus counts, whereas the LCPC diet increased Lactobacillus counts and reduced Escherichia coli counts in the ileum. The LCPA diet also increased protein expression levels of pro-inflammatory cytokine interleukin-6 (IL-6) and IL-22, whereas the LCPC diet decreased protein expression levels of pro-inflammatory IL-1β, IL-17A and tumor necrosis factor-α in the ileum. Collectively, the casein hydrolysate supplementation of low CP diets showed beneficial effects on the small intestinal barrier, bacterial community, and immunity in pigs, pointing to the important role of protein-derived peptides in small intestinal health in cases of low crude protein diets.

Dietary Copper Improves Intestinal Morphology via Modulating Intestinal Stem Cell Activity in Pigs

Simple Summary

Copper (Cu) is one of the essential trace elements for animal growth. Piglet intestinal epithelium undergoes a complete renewal driven by intestinal stem cells located at the crypt base. However, whether Cu improves intestinal morphology and development via modulating intestinal stem cell activity in pigs remains unclear. This study aimed to investigate the effects of dietary Cu during the weaning period on the intestinal morphology and development of weaned and finished pigs and explored the potential mechanism by culturing the intestinal organoids and treated them with Cu in vitro. The results indicated that Cu supplementation during the weaning period improves the intestinal morphology in finishing pigs by modulating the activity of intestinal stem cells.

Abstract

Copper (Cu) is an essential micronutrient for animals. Many studies have been conducted on the effects of dietary Cu on growth performance, intestinal morphology, and function of piglets. However, the underlying mechanism remains to be explored. Intestinal stem cells (ISC) drive the development and constant renewal of intestinal epithelium. Therefore, we hypothesized that dietary Cu affects piglets’ intestinal development via modulating ISC activity. A total of eighty-five 21-day-old piglets were randomly assigned to five groups, where 25, 50, 75, 100, and 125 mg CuSO₄/kg on a dry matter basis were supplemented to the basal diet at phase 1 (day 0 to 21). Increasing the dietary Cu concentration decreased (p < 0.05) villus width but increased (p < 0.001) the number of Ki67-positive cells. At phase 2 (day 22 to 163), the other 45 pigs were offered the same diets. Villus height in the 125 mg/kg Cu group was greater (p < 0.001) than in the other groups. Moreover, the effects of Cu on ISC activity in vitro were tested to explore the underlying mechanism. Compared to the control group, 10 μmol/L CuSO₄·5H₂O increased (p < 0.001) the organoid budding efficiency, crypt depth, and crypts per organoid. Dietary Cu improved the intestinal morphology of finishing pigs via promoting cell proliferation and modulating ISC activity.

Etiology of Colitis-Complex Diarrhea in Growing Pigs: A Review

Simple Summary

Diarrhea in growing pigs is a challenge for the pig industry since it is associated with reduced animal welfare, retarded growth, increased feed conversion ratio, and is often treated with antibiotics. One of the major causes of diarrhea in the growing period is large intestinal inflammation, often referred to as colitis. The exact causes of colitis-complex diarrhea are still to be understood, but dietary factors and/or pathogens have been recognized as the major factors in developing colitis-complex diarrhea. In this review, a thorough picture of pathogens, dietary factors, and a number of possible biomarkers related to colitis-complex diarrhea is presented.

Abstract

Colitis-complex diarrhea (CCD) in pigs can be defined as a type of diarrhea, which is associated with colonic inflammation and disrupted colonic gut barrier functionality in growing pigs (4–16 weeks post-weaning). It is a challenge for the pig industry as it is associated with the high use of antibiotics, reduced animal welfare, and depressed growth rate. The exact etiology of CCD is still unclear; however, pathogens including Brachyspira (B.) hyodysenteriae, B. pilosicoli, and swine whipworms such as Trichuris (T.) suis have been involved in specific colitis (SC). In the absence of specific pathogens, dietary factors, such as high levels of protein, pelleted feedstuffs, and lack of sufficient antioxidants, can result in non-specific colitis (NSC). On the other hand, supplement of polyunsaturated fatty acids (PUFA) and polyphenols, sufficient supply of essential amino acids (e.g., threonine, cysteine, and proline), short-chain fatty acids (SCFA; especially butyrate), and resistant starch have shown to confer preventing/ameliorating effects on CCD. Different putative biomarkers associated with CCD have been presented. It is anticipated that a comprehensive picture of the possible causes of CCD and potential dietary interventions could cast light on the direction of future studies aimed at developing preventive and curative strategies against CCD in growing pigs.

Supplementation of protease to low amino acid diets containing superdose level of phytase for wean-to-finish pigs: effects on performance, postweaning intestinal health and carcass characteristics

This experiment investigated the effects of protease supplementation to low amino acid (AA) diets containing phytase on pig growth performance, postweaning intestinal health and carcass characteristics. A total of 936 weaned pigs (21 d of age, initial BW 5.87 ± 0.31 kg) were used in a 2 × 2 factorial design comparing the main effects of AA supply [standard feeding program: balanced for all nutrients with adjustment of Ca and P due to inclusion of phytase (2,500 FTU/kg in Phase 1 to 4; 500 FTU/kg in Phase 5 to 9) vs. low AA feeding program: 15% lower standardized ileal digestible lysine with relative reduction of all other essential AA] and protease level (0 vs. 0.0125%). Pens were assigned to dietary treatment according to a randomized complete block design with 26 pigs per pen and nine replicates per dietary treatment. Feed and water were provided on an ad libitum basis for all phases throughout the wean-to-finish period. Feed intake and body weight were determined every 2 wk during nursery period and monthly in the grow-finish period. Intestinal health in the first 17 d was assessed based on lactulose:mannitol ratio (L:M), serum IgA, and pen diarrhea assessment. Overall, pigs fed standard wean-to-finish diets had greater (P < 0.05) ADG and G:F than pigs fed low AA diets. Pig growth performance was not different throughout the wean-to-finish period with or without protease supplementation and with no interaction between AA supply and protease supplementation. There were no differences among dietary treatments for carcass characteristics. No difference was observed for urinary L:M and serum IgA; however, the L:M ratio was approximately 32% lower in pigs fed low AA diets + protease compared with pigs fed standard and low AA diets at d 5 and d 17 postweaning. Pigs fed protease supplemented diets had lower incidence of diarrhea (χ² < 0.05) compared with pigs fed diets without protease. Results of the experiment indicate that dietary protease supplementation benefits intestinal health of nursery pigs.

Effects of Protein Restriction and Subsequent Realimentation on Body Composition, Gut Microbiota and Metabolite Profiles in Weaned Piglets

Simple Summary

Protein restriction strategies are often used in weaned piglets to reduce the incidence of intestinal disorders that are sensitive to dietary protein supply, but may lead to a decline in production performance. Subsequent protein realimentation can alleviate the detrimental effects of reduced dietary protein on growth. However, the effects of protein realimentation on the body composition, gut microbiota and metabolite profiles of piglets are poorly understood. The present study, combining comparative slaughter methods, microbiome and metabolome analyses, demonstrated that protein restriction and subsequent realimentation lead to compensatory growth and compensatory protein deposition in piglets, and contribute to animal intestinal health by altering the gut microbiota and metabolite profiles.

Abstract

The objective of this study was to evaluate the effects of protein restriction and subsequent protein realimentation on the body composition, gut microbiota and metabolite profiles of piglets. Fifty weaned piglets were randomly assigned to two treatments: a normal protein (NP) group (20% crude protein (CP)) or a low protein (LP) group (16% CP) with five animals per pen and five pens per group. Treatment diets were fed for 14 d during the protein restriction phase, and then all pigs were fed the same nursery diets with a normal CP level (19% CP) during the protein realimentation phase until they reached an average target body weight (BW) of 25 ± 0.15 kg. At day 14 and the end of the experiment, one piglet close to the average BW of each pen was slaughtered to determine body composition, microbial composition and microbial metabolites. Results showed that there was no difference (p > 0.05) in the experimental days to reach target BW between the LP and NP groups. The average daily gain (ADG) and gain:feed ratio (G:F) during the protein restriction phase as well as BW at day 14, were significantly decreased (p < 0.05) in the LP group compared with the NP group. However, there were no significant differences (p > 0.05) during the protein realimentation phase and the overall experiment. Similarly, piglets in the LP group showed a significantly decreased body protein content (p < 0.05) at day 14, but not (p > 0.05) at the end of the experiment. The relative abundance of Parabacteroides, Butyricicoccus, Olsenella, Succinivibrio and Pseudoramibacter were significantly increased (p < 0.05), while the relative abundance of Alloprevotella and Faecalicoccus were significantly decreased (p < 0.05) in the LP group at day 14. At the end of the experiment, the piglets in the LP group showed a higher (p < 0.05) colonic relative abundances of Parabacteroides, unidentified Christensenellaceae and Caproiciproducens, and a lower (p < 0.05) relative abundance of unidentified Prevotellaceae, Haemophilus, Marvinbryantia, Faecalibaculum, Neisseria and Dubosiella than those in the NP group. Metabolomics analyses indicated that tryptophan metabolism and vitamin metabolism were enriched in the LP group at day 14, and glycerophospholipid metabolism and fatty acid esters of hydroxy fatty acid metabolism were enriched at the end of the experiment. Moreover, Spearman’s correlation analysis demonstrated that the microbial composition was highly correlated with changes in colonic metabolites. Collectively, these results indicated that protein restriction and subsequent realimentation lead to compensatory growth and compensatory protein deposition in piglets and contribute to animal intestinal health by altering the gut microbiota and its metabolites.

A reduced CP level without medicinal zinc oxide does not alter the intestinal morphology in weaned pigs 24 days post-weaning

The use of medicinal zinc oxide (ZnO) to prevent diarrhoea post-weaning will be banned in the EU from 2022. Therefore, new alternatives are needed to avoid an increase in diarrhoea and higher antibiotic use. A low dietary CP level has shown to lower the frequency of diarrhoea in pigs, due to lower microbial protein fermentation in the colon as well as improved conditions in the small intestine after weaning. The objective of this study was to examine the effect of decreased CP levels post-weaning as an alternative to medicinal ZnO on gut morphology and histopathology. Five hundred and sixty pigs were randomly assigned into one of six groups receiving a two-phase diet from 5.5 to 15 kg: positive control group (PC) with medicinal ZnO and standard levels of protein (19.1-18.4% CP), negative control group (NC) without medicinal ZnO and standard levels of protein (19.1-18.4% CP). The remaining four low protein groups were a low-standard (LS) CP level (16.6-18.4% CP), a low-low (LL) CP level (16.6-16.2% CP), a very low-high (VLH) CP level (14-19.3% CP) and a very low-medium (VLM) CP level (14-17.4% CP). Individual BW was recorded at day 0, 10 and 24 post-weaning, and all antibiotic treatments were recorded. Tissue samples from the small intestine (mid-jejunum) for morphological and histopathologic analysis, organ weights, blood and urine samples were collected at day 10 and 24 post-weaning from a total of 90 sacrificed weaners. The results demonstrated no differences in intestinal morphology between groups, but the histopathology showed a damaged brush border score in VLM and VLH pigs . In addition, a lower blood urea nitrogen in VLM pigs at 24 days was found. The LL and VLM pigs had a significantly decreased average daily gain in the overall trial period compared to PC and NC pigs. Conclusively, intestinal brush border was damaged by the very low protein diet at 24 days post-weaning, but intestinal morphology was unaffected by dietary strategy.

Effects of crude protein and lactose levels in diets on growth performance, intestinal morphology, and expression of genes related to intestinal integrity and immune system in weaned piglets

To evaluate the effects of crude protein (CP) and lactose (LAC) for weaned piglets on performance, intestinal morphology, and expression of genes related to intestinal integrity and immune system, 144 piglets with initial weight 7.17 ± 0.97 kg were allotted in a randomized design, in a 2 × 3 factorial arrangement (20.0% and 24.0% CP and 8.0%, 12.0%, and 16.0% LAC) with eight replicates. Piglets fed 20.0% CP had greater weight gain and feed intake. Including 12.0% LAC in the 20.0% CP diet provided higher villous height in the duodenum than 8.0% LAC, and 12.0% or 16.0% LAC in the 24.0% CP diet resulted in higher villous height in the jejunum and ileum, and higher villi/crypt ratio in the ileum than 8.0% LAC. No effects of CP and LAC on interleukin-1β and tumor necrosis factor-α mRNA were observed. The 16.0% LAC diet provided higher gene expression of transforming-β1 growth factor. Feeding 20.0% CP resulted in better performance than 24.0% CP. The 12.0% LAC diet promoted greater genetic expression of occludin and zonula occludens. Including 12.0% LAC in the diet may improve intestinal epithelial morphology and integrity, and these improvements are more evident when piglets are fed diets with 24.0% CP.

Effects of hydrolyzed yeast supplementation on growth performance, immunity, antioxidant capacity, and microbial shedding in weaning pigs

Background and Aim

Weaning pigs normally suffer from many stressors which have impaired growth performance and immunity. Hydrolyzed yeast has been proposed as an alternative feed additive. The aim of this study was to investigate the effects of various levels of hydrolyzed yeast (HY) supplementation in the feed of weaning pigs on growth performance, diarrhea incidence, immunity, antioxidant capacity, and microbial populations.

Materials and Methods

A total of 144 crossbred weaning pigs (Duroc × Landrace × Large White) with a mean body weight (BW) of 7.46 kg were randomly assigned to one of four treatments during a 5-week feeding trial. Treatments consisted of a basal diet without HY inclusion (control), or the basal diet supplemented with HY at 0.5, 1.0, and 1.5 g/kg of diet, respectively.

Results

Piglets fed with 1.0 or 1.5 g/kg HY presented significantly increased BW (p=0.009) and decreased incidence of diarrhea (p=0.001). The final BW (p=0.012), average daily gain (p=0.094), and average daily feed intake (p=0.091) showed a linear improvement with the level of HY inclusion. However, the gain-to-feed ratio was unaffected by dietary treatments. Linear responses to the HY supplementation levels were also observed for blood urea nitrogen (p=0.030), total protein (p=0.017), lymphocyte percentage (p=0.064), catalase activity (p=0.089), malondialdehyde (MDA) level (p=0.001), Salmonella spp. (p=0.024), Escherichia coli (p=0.021), and Lactobacillus spp. (p=0.048). Dietary inclusion of HY at 1.0 and 1.5 g/kg resulted in increased immunoglobulin A and G secretions (p=0.042 and p=0.022, respectively) and decreased MDA concentration (p<0.01) and Salmonella spp. (p=0.026) and E. coli (p=0.050).

Conclusion

It was concluded that HY inclusion at 1.0 and 1.5 g/kg in the diet of weaning pigs improve BW, immunoglobulin secretion, and antioxidant enzyme activity, whereas it lowers diarrhea occurrence, lipid peroxidation, and pathogenic bacteria in weaning pigs.

Effects of reducing dietary crude protein concentration and supplementation with laminarin or zinc oxide on the faecal scores and colonic microbiota in newly weaned pigs

A 2 × 3 factorial design experiment was conducted to examine the effects of reducing dietary crude protein (CP) concentration and/or supplementation with zinc oxide (ZnO) or laminarin on faecal scores (FS) and the large intestinal microbiota post-weaning (PW). One hundred and forty-four pigs were assigned to (T1) 21% standard CP diet (SCP); (T2) SCP + ZnO (SCP ZnO); (T3) SCP + laminarin (SCP LAM); (T4) 18% low CP diet (LCP); (T5) LCP + ZnO (LCP ZnO); and (T6) LCP + laminarin (LCP LAM; n = 8 replicates/treatment). The LCP diet had no effect on FS (p > .05), it increased two measures of alpha diversity, reduced Bacteroidetes and increased Enterobacteriaceae and Helicobacteraceae in the colon relative to the SCP diet (p < .05). ZnO supplementation reduced FS and increased Ruminococcaceae compared with unsupplemented pigs (p < .05). ZnO supplementation increased the genera Frisingicoccus (p < .001), Lachnoclostridium (p < .05) and Peptoclostridium (p < .05) in the colon and reduced total caecal volatile fatty acids (VFA) concentrations compared with the unsupplemented and laminarin-supplemented pigs. Laminarin supplementation reduced FS compared with unsupplemented pigs but had no major effect on the microbiota compared with the unsupplemented pigs. There were CP concentration × additive interactions on both Firmicutes and Proteobacteria. Firmicutes were increased in the LCP ZnO group compared with the LCP group, but there was no difference between the SCP groups. Proteobacteria were reduced in the LCP ZnO group compared with the LCP and LCP LAM groups (p < .05), but there was no difference between the SCP groups. In conclusion, reducing CP did not improve FS; it increased the relative abundance of Enterobacteriaceae; however, it also increased bacterial diversity. Supplementation with ZnO and laminarin improved FS, although all groups had scores within the healthy range. ZnO altered the large intestinal microbiota and VFA concentrations; however, laminarin did not enhance these parameters, suggesting these compounds have differing modes of action.

Protein Level and Infantile Diarrhea in a Postweaning Piglet Model

Infantile diarrhea is a serious public health problem around worldwide and results in millions of deaths each year. The levels and sources of dietary protein are potential sources of diarrhea, but the relationship between the pathogenesis causes of infantile diarrhea and protein intake remains poorly understood. Many studies have indicated that the key to understanding the relationship between the protein in the diet and the postweaning diarrhea of piglets is to explore the influences of protein sources and levels on the mammalian digestion system. The current study was designed to control diarrhea control by choosing different protein levels in the diet and aimed at providing efficient regulatory measures for infantile diarrhea by controlling the protein levels in diets using a postweaning piglets model. To avoid influences from other protein sources, casein was used as the only protein source in this study. Fourteen piglets (7.98 ± 0.14 kg, weaned at 28 d) were randomly allotted to two dietary treatments: a control group (Cont, containing 17% casein) and a high protein group (HP, containing 30% casein). The experiment lasted for two weeks and all animals were free to eat and drink water ad libitum. The diarrhea score (1 = normal; 3 = watery diarrhea) and growth performance were recorded daily. The results showed that the piglets in HP group had persistent diarrhea during the whole study, while no diarrhea was noticed in the control groups. Also, the feed intake and body weights were reduced in the HP groups compared with the other group (P < 0.05). The diarrhea-related mRNA abundances were analyzed by real-time PCR; the results showed that HP treatment markedly decreased the expression of aquaporin (AQP, P < 0.05) and the tight junction protein (P<0.05), but increased inflammatory cytokines (P < 0.01) than those in control group. In addition, the Adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway (P < 0.01) was inhibited in the HP group. Intestinal microbiota was tested by 16S sequencing, and we found that the HP group had a low diversity compared the other group. In conclusion, despite being highly digestible, a high casein diet induced postweaning diarrhea and reduced the growth performance of the postweaning piglets. Meanwhile, AQP, tight junction protein, and intestinal immune were compromised. Thus, the mechanism of how a highly digestible protein diet induces diarrhea might be associated with the AMPK signaling pathway and intestinal microbiome.

The effects of dietary sodium butyrate supplementation on the growth performance, carcass traits and intestinal microbiota of growing-finishing pigs

AIM

This study was carried out to investigate the effects of dietary sodium butyrate supplementation on growth performance, carcass traits and intestinal of growing-finishing pigs.

METHODS AND RESULTS

Thirty pigs (27·4 ± 0·4 kg) were randomly assigned to receive one of three diets: basal diet (negative control group), basal diet + 40 ppm zinc bacitracin (positive control group) and basal diet + 0·2% sodium butyrate (sodium butyrate group), respectively. The experiment lasted for 69 days, including 3 days for diet and housing condition adaptation. On day 70, five piglets from each diet group were slaughtered for collecting blood and tissue samples. When compared to the control group, final body weight, daily body weight gain and daily feed intake of pigs in the sodium butyrate group were increased (P < 0·05) and feed intake/body weight gain ratio was decreased (P < 0·05). Carcass weight of pigs in the sodium butyrate group was higher than that of pigs in the negative and positive groups (P < 0·05); backfat thickness of pigs in the positive group was higher than that of pigs in the negative group and sodium butyrate group (P < 0·001). When compared to the negative and positive groups, pigs fed diet supplemented with sodium butyrate showed a increased relative abundance of bacteroidetes in the caecum and a decreased relative abundance of fiemicutes and proteobacteria in the caecum (P < 0·05).

CONCLUSION

The results indicated that dietary sodium butyrate supplementation increased growth performance of growing-finishing pigs and improved the carcass traits and intestinal health.

SIGNIFICANCE AND IMPACT OF THE STUDY

Antibiotic-free feed has become an inevitable worldwide trend. This study showed that dietary sodium butyrate supplementation improved the growth performance and intestinal health of growing-finishing pigs. Thus, sodium butyrate can be applied in growing-finishing pig feed as an alternative of antibiotics.

What Is the Impact of Diet on Nutritional Diarrhea Associated with Gut Microbiota in Weaning Piglets: A System Review

Piglets experience severe growth challenges and diarrhea after weaning due to nutritional, social, psychological, environmental, and physiological changes. Among these changes, the nutritional factor plays a key role in postweaning health. Dietary protein, fibre, starch, and electrolyte levels are highly associated with postweaning nutrition diarrhea (PWND). In this review, we mainly discuss the high protein, fibre, resistant starch, and electrolyte imbalance in diets that induce PWND, with a focus on potential mechanisms in weaned piglets.

Effects of Soybean Meal Fermented by Lactobacillus Species and Clostridium butyricum on Growth Performance, Diarrhea Incidence, and Fecal Bacteria in Weaning Piglets

Fermented soybean meal (FSBM) has been widely investigated as a nutritional strategy for reducing the use of fish meal (FM) and antibiotic growth promoters. Microbial fermentation by using bacteria can increase the bioavailability of nutrients and reduce the levels of antinutritional factors in soybean meal (SBM). In this study, we evaluated whether FSBM produced from Lactobacillus species and Clostridium butyricum improves growth performance, diarrhea incidence, and fecal bacteria in weaning piglets. Eighty-four crossbred male piglets with an average initial body weight of 8.36±0.63 kg were randomly allotted to 3 dietary treatments consisting of 7 replicate stalls with 4 piglets each. The dietary treatments were: (1) 3% FM in the diet; (2) 5% FSBM in the diet; and (3) 3% FM in the diet plus 4 mg/kg antibiotic growth promoters (AGP). We determined that growth performance was unaffected in FSBM-fed weaning piglets compared with a FM group. Similar to the AGP group, FSBM supplementation significantly reduced diarrhea incidence in weaning piglets. The number of fecal Lactobacillus species significantly increased in 28-day-old FSBM-fed weaning piglets compared with the other groups. Compared with AGP, FSBM has the highest inhibitory effect on the number of fecal Enterobacteriaceae at 28 d old. Furthermore, serum immunoglobulin G and immunoglobulin A levels in FSBM-fed weaning piglets significantly increased at the same age. These results together indicate that FSBM can replace FM in the diets of weaning piglets without affecting growth performance. Furthermore, similar to AGP, FSBM could improve diarrhea incidence, fecal bacteria, and immunoglobulin levels in weaning piglets. Therefore, SBM fermented by Lactobacillus species and C. butyricum demonstrated high potential for development as swine feed ingredients.

Growth Performance, Diarrhoea Incidence, and Nutrient Digestibility in Weaned Piglets Fed an Antibiotic-Free Diet with Dehydrated Porcine Plasma or Potato Protein Concentrate

Two experiments were conducted to test if dehydrated porcine plasma (DPP) and potato protein concentrate (PPC) could be used as an alternative to antibiotics in starter diets for piglets. Experiment one was conducted to test if DPP and PPC in an antibiotic-free diet affected pig performance, and faecal consistency. Eighty-four piglets weaned at 22 days and weighing 6.9 kg were used. Piglets were fed for two weeks with one of four diets: a positive control diet with antibiotics (C+); and three other diets without antibiotics added with DPP, PPC, or DPP and PPC (DPP+PPC) to measure the average daily feed intake (ADFI), average daily gain (ADG), feed efficiency (FE), and incidence and severity of diarrhoea (ID and ISD respectively). In experiment two, twenty-four piglets weaned at 17 days and weighing 5.7 kg, were implanted at 21 days of age with a T-cannula at the terminal ileum to measure the apparent ileal digestibility (AID) and the apparent total tract digestibility (ATTD) of nutrients. Piglets were fed one of four diets: a positive control diet with antibiotics (C+); a negative control diet without antibiotics (C–), and two diets without antibiotics added with DPP, or PPC. The results of experiment one showed that the DPP diet was the most consumed diet during the first week, and the ADG and FE were similar among treatments. During the second week and the total experimental period the ADFI, ADG, and FE were similar among diets. The ID was lower in the C+ diet than other diets. The ISD was lower in the C+ diet than DPP and DPP+PPC diets; piglets fed PPC diet were similar to piglets fed C+ and DPP and DPP+PPC diets. The results of digestibility showed that crude protein AID was higher in piglets fed C+ and PPC diets than C– and DPP diets. Dry matter ATTD and energy ATTD were higher for piglets fed PPC than other diets. Further, crude protein ATTD of DPP and PPC diets tended to have a similar digestibility to that of C+ diet. The results suggest that PPC is a potential controller of post-weaning diarrhoea.

Effects of dietary energy and crude protein levels on growth performance, blood profiles, and nutrient digestibility in weaning pigs

Objective

This experiment was conducted to investigate the effect of reducing dietary metabolic energy (ME) and crude protein (CP) levels on growth performance, blood profiles, and nutrient digestibility in weaning pigs.

Methods

A total of 240 crossbred pigs (Duroc×[Landrace×Yorkshire]) with an average body weight of 8.67±1.13 kg were used for a 6-week feeding trial. Experimental pigs were allotted to a 2×3 factorial arrangement using a randomized complete block design. The first factor was two levels of dietary ME density (low ME level, 13.40 MJ/kg or high ME level, 13.82 MJ/kg) and the second factor was three dietary CP levels based on subdivision of early and late weaning phases (low CP level, 19.7%/16.9%; middle CP level, 21.7%/18.9%; or high CP level, 23.7%/20.9%).

Results

Over the entire experimental period, there were no significant difference in body weight among groups, but a decrease in diet energy level was associated with an increase in average daily feed intake (p = 0.02) and decrease in gain-feed ratio (G:F) ratio (p<0.01). Decreased CP levels in the diet were associated with a linear increase in average daily gain (p< 0.05) and quadratic increase in G:F ratio (p<0.05). In the early weaning period, blood urea nitrogen concentration tended to increase when ME in the diet decreased and decrease when CP level in the diet decreased (p = 0.09, p<0.01, respectively). Total protein concentration tended to increase when CP level was reduced (p = 0.08). In the late weaning period, blood urea nitrogen concentration decreased linearly as CP level decreased (p<0.01). The CP and crude fat digestibility decreased when ME was decreased by 0.42 MJ/kg (p = 0.05, p = 0.01, respectively). The CP digestibility increased linearly as CP level decreased (p = 0.01).

Conclusion

A weaning pig diet containing high ME level (13.82 MJ/kg) and low CP level (19.7%/16.9%) can improve pig growth performance and nutrient digestibility.

Nigella sativa L. as an alternative antibiotic feed supplement and effect on growth performance in weanling pigs

BACKGROUND

Nigella sativa L. (NS) is a plant containing bioactive constituents such as thymoquinone. Extracts of NS improve performance and reduce enteropathogen colonization in poultry and small ruminants, but studies with swine are lacking. In two different studies oral administration of NS extracts at doses equivalent to 0, 1.5 and 4.5 g kg^-1 diet was assessed on piglet performance and intestinal carriage of wildtype Escherichia coli and Campylobacter, and Salmonella Typhimurium.

RESULTS

Wildtype E. coli populations in the jejunal and rectal content collected 9 days after treatment began were decreased (P ≤ 0.05). Populations recovered from pigs treated with extract at 1.5 and 4.5 g kg^-1 diet were 0.72-1.31 log₁₀ units lower than the controls (ranging from 6.05 to 6.61 log₁₀ CFU g^-1 ). Wildtype Campylobacter and Salmonella Typhimurium were unaffected by NS treatment. Feed efficiency over the 9 days improved linearly (P < 0.05) from 3.88 with 0 NS-treated pigs to 1.47 and 1.41 with pigs treated with NS at 1.5 and 4.5 g kg^-1 diet, respectively, possibly due to high glutamine/glutamic acid content of the NS extract.

CONCLUSION

NS supplementation of weanling pigs improved feed efficiency and helped control intestinal E. coli during this vulnerable production phase. © 2017 Society of Chemical Industry.

Effect of Dietary Protein Level on the Expression of Proteins in the Gastrointestinal Tract of Young Pigs

The objective of this research is to investigate the effect of protein level on proteins expression in the gastrointestinal tract of young pigs. Eighteen piglets (Duroc × Landrace × Yorkshire) were weaned at 28 days of age and randomly assigned to three diets with 20%, 17%, and 14% CP level, and four essential amino acids, Lys, Met, Thr, and Trp, in three diets met the requirements of weaned piglets. The experimental period lasted 45 days. Compared with the control (20% CP level), the average daily feed intake, the average daily gain, and gain feed ratio of the 17% CP group did not decrease ( P > 0.05), but those of 14% CP group decreased ( P < 0.05). The proteomics profiles result of three tissues (gastric antrum, duodenum, and jejunum) showed that, compared with the control, the immune system, protein digestion and absorption, lipid or carbon digestion and absorption, etc. were up-regulated in 17% CP group, while most of them were down-regulated in 14% CP group. Amino acids metabolism of gastric, pancreatic secretion of duodenum or steroid hormone biosynthesis of jejunum was down-regulated in the 17% CP group, but the lipid metabolism was up-regulated in the 14% CP group. Six proteins were selected for identification by Western-blot, and their changes had the same trend as the proteomics results. The protein level decreased from 20% to 17%, the growth performance was not affected, while the nutrient digestion and absorption or the immune function were improved, which implied that 17% protein level maybe benefit for nutrients absorption of pigs.

Immunomodulatory potential of dietary soybean-derived isoflavones and saponins in pigs

In this review, the potential for use of soy-derived bioactive compounds as immunomodulatory feed additives in pigs is discussed. Soy is a major component of the modern U.S. swine diet in today's commercial industry, providing the bulk of dietary AA necessary for growth and production. However, soy use has generally been limited in early growth phases, during which the risks of immunological insult and disease are among the highest. Improvements of soybean processing and development of soy protein products with little to no antinutritional factors have made soy more appropriate for use in young pigs but additional processing may affect bioactive compound levels in the feed. The bioactive compounds of interest for this review are soy isoflavones and soy saponins. Soy isoflavones are flavonoid compounds with a range of biological activity including moderate estrogenic effects at low biological concentrations. Although estrogenic effects are of more interest in human medical research, isoflavones are also known for their anti-inflammatory, antioxidative properties at cellular levels, engaging several receptors and pathways including inhibition of NF-κB activation and inducible-nitric oxide synthase enzymes, thereby ascribing antiviral properties. Saponins, amphipathic glycoside compounds, also engage anti-inflammatory pathways, though their biological activity in pigs has not been well investigated and seem to mainly be observed on the mucous membrane in the gastrointestinal tract. Regarding use as an immunomodulatory feed additive, supplemental soy isoflavones have been shown to improve immunological status of pigs and produce mild improvements of growth performance under certain disease challenges including porcine reproductive and respiratory syndrome virus. Although more in vivo research in pigs is needed to fully understand biological activity of these compounds in the live animal, soy-derived bioactive compounds show great potential as a health promoting feed additive for the modern swine industry.

Fecal scores and microbial metabolites in weaned piglets fed different protein sources and levels

This experiment studied the effects of dietary protein sources and levels on the gut health of piglets, pH value, and concentrations of microbial metabolites (ammonia-N, volatile fatty acids [VFA], and polyamines) in the distal colonic and proximal colonic digesta of piglets weaned at 21 d of age. A total of 150 early-weaned piglets were allotted randomly to 5 diets: 1) control diet (CT; 17% CP), 2) CT formulated with more soy protein concentrate (SPC19; 19% CP), 3) more fish meal (FM19; 19% CP), 4) CT formulated with more soy protein concentrate (SPC23; 23% CP), and 5) more fish meal (FM23; 23%CP). Results showed high protein level increased fecal score (P < 0.05), but different protein sources did not (P > 0.05). The pH value and ammonia-N concentration of digesta in the proximal and distal colon of FM23 were significantly higher (P < 0.05) than those of CT. Acetic acid, propionic acid, butyric acid and valeric acid concentrations in the proximal colon of FM23 exceeded those of CT, SPC19, and FM19 (P < 0.05); however, isobutyric acid and isovaleric acid were not affected (P > 0.05). Histamine and spermidine concentrations of FM23 were higher than those of other treatments (P < 0.05). Propionic acid and butyric acid concentrations in the distal colon were higher of FM23 than of FM19 (P < 0.05); putrescine, histamine and spermidine were higher of FM23 than of LP and FM19 (P < 0.05). It was concluded that high dietary CP content increased microbial metabolites (ammonia-N, histamine, putrescine) in colonic digesta and aggravated piglets' diarrhea.