Development and application of a multi-step porcine in vitro system to evaluate feedstuffs and feed additives for their efficacy in nutrient digestion, digesta characteristics, and intestinal immune responses

In vitro model provides alternatives to the use of live animals in research. In pig nutrition, there has been a tremendous increase in in vivo research over the decades. Proper utilization of in vitro models could provide a screening tool to reduce the needs of in vivo studies, research duration, cost, and the use of animals and feeds. This study aimed to develop a multi-step porcine in vitro system to simulate nutrient digestion and intestinal epithelial immune responses affected by feedstuffs and feed additives. Seven feedstuffs (corn, corn distillers dried grains with solubles [corn DDGS], barley, wheat, soybean meal, soy protein concentrates, and Corynebacterium glutamicum cell mass [CGCM]), feed enzymes (xylanase and phytase), and supplemental amino acids (arginine, methionine, and tryptophan), were used in this in vitro evaluation for their efficacy on digestibility, digesta characteristics, and intestinal health compared with the results from previously published in vivo studies. All in vitro evaluations were triplicated. Data were analyzed using Mixed procedure of SAS9.4. Evaluations included (1) nutrient digestibility of feedstuffs, (2) the effects of feed enzymes, xylanase and phytase, on digestibility of feedstuffs and specific substrates, and (3) the effects of amino acids, arginine, tryptophan, and methionine, on anti-inflammatory, anti-oxidative, and anti-heat stress statuses showing their effects (P < 0.05) on the measured items. Differences in dry matter and crude protein digestibility among the feedstuffs as well as effects of xylanase and phytase were detected (P < 0.05), including xylo-oligosaccharide profiles and phosphorus release from phytate. Supplementation of arginine, tryptophan, and methionine modulated (P < 0.05) cellular inflammatory and oxidative stress responses. The use of this in vitro model allowed the use of 3 experimental replications providing sufficient statistical power at P < 0.05. This indicates in vitro models can have increased precision and consistency compared with in vivo animal studies.

Low crude protein formulation with supplemental amino acids for its impacts on intestinal health and growth performance of growing-finishing pigs

BACKGROUND

Low crude protein (CP) formulations with supplemental amino acids (AA) are used to enhance intestinal health, reduce costs, minimize environmental impact, and maintain growth performance of pigs. However, extensive reduction of dietary CP can compromise growth performance due to limited synthesis of non-essential AA and limited availability of bioactive compounds from protein supplements even when AA requirements are met. Moreover, implementing a low CP formulation can increase the net energy (NE) content in feeds causing excessive fat deposition. Additional supplementation of functional AA, coupled with low CP formulation could further enhance intestinal health and glucose metabolism, improving nitrogen utilization, and growth performance. Three experiments were conducted to evaluate the effects of low CP formulations with supplemental AA on the intestinal health and growth performance of growing-finishing pigs.

METHODS

In Exp. 1, 90 pigs (19.7 ± 1.1 kg, 45 barrows and 45 gilts) were assigned to 3 treatments: CON (18.0% CP, supplementing Lys, Met, and Thr), LCP (16.0% CP, supplementing Lys, Met, Thr, Trp, and Val), and LCPT (16.1% CP, LCP + 0.05% SID Trp). In Exp. 2, 72 pigs (34.2 ± 4.2 kg BW) were assigned to 3 treatments: CON (17.7% CP, meeting the requirements of Lys, Met, Thr, and Trp); LCP (15.0% CP, meeting Lys, Thr, Trp, Met, Val, Ile, and Phe); and VLCP (12.8% CP, meeting Lys, Thr, Trp, Met, Val, Ile, Phe, His, and Leu). In Exp. 3, 72 pigs (54.1 ± 5.9 kg BW) were assigned to 3 treatments and fed experimental diets for 3 phases (grower 2, finishing 1, and finishing 2). Treatments were CON (18.0%, 13.8%, 12.7% CP for 3 phases; meeting Lys, Met, Thr, and Trp); LCP (13.5%, 11.4%, 10.4% CP for 3 phases; meeting Lys, Thr, Trp, Met, Val, Ile, and Phe); and LCPG (14.1%, 12.8%, 11.1% CP for 3 phases; LCP + Glu to match SID Glu with CON). All diets had 2.6 Mcal/kg NE.

RESULTS

In Exp. 1, overall, the growth performance did not differ among treatments. The LCPT increased (P < 0.05) Claudin-1 expression in the duodenum and jejunum. The LCP and LCPT increased (P < 0.05) CAT-1, 4F2hc, and B0AT expressions in the jejunum. In Exp. 2, overall, the VLCP reduced (P < 0.05) G:F and BUN. The LCP and VLCP increased (P < 0.05) the backfat thickness (BFT). In Exp. 3, overall, growth performance and BFT did not differ among treatments. The LCPG reduced (P < 0.05) BUN, whereas increased the insulin in plasma. The LCP and LCPG reduced (P < 0.05) the abundance of Streptococcaceae, whereas the LCP reduced (P < 0.05) Erysipelotrichaceae, and the alpha diversity.

CONCLUSIONS

When implementing low CP formulation, CP can be reduced by supplementation of Lys, Thr, Met, Trp, Val, and Ile without affecting the growth performance of growing-finishing pigs when NE is adjusted to avoid increased fat deposition. Supplementation of Trp above the requirement or supplementation of Glu in low CP formulation seems to benefit intestinal health as well as improved nitrogen utilization and glucose metabolism.

Tryptophan improves antioxidant capability and meat quality by reducing responses to stress in nervous Hu sheep

In sheep, the effect of tryptophan (Trp) on behavioural traits that are associated with temperament and any effects on production traits is unknown. The hypothesis of this study is that the supplementation of Trp would improve temperament by enhancing serotonin production, which is beneficial to meat production subsequently in sheep. Twelve ewes that had the lowest and 12 ewes that had the highest behavioural responses to human contact were selected into the calm and the nervous groups respectively. Then, the ewes from each group were equally assigned into two treatments that were treated with the basal diet and the diet with extra 90 mg/kg/d Trp for 30 d. The temperament traits, the growth performance, the biochemicals that are related to health the slaughter performance and meat quality were measured at the end of feeding experiment. The findings in this study suggested the Hu sheep with calm temperament would experience less stress during production, resulting in less oxidative stress, better growth performance, slaughter traits and carcass traits, compared to the nervous sheep. Meanwhile, the dietary supplementation of Trp reduced stress responses by enhancing production of 5-HT in sheep from the nervous group which is beneficial to improve the production traits that mentioned above.

Standardized ileal digestible tryptophan and lysine affects the eating and sleeping behavior of 15-30 kg barrows

The objective of this study was to evaluate the effect of standardized ileal digestible (SID) tryptophan (Trp) and lysine (Lys) levels on eating and sleeping behavior and the respective feed intake of barrows. Sixty-four pigs, averaging 15.00 ± 1.63 kg of initial body weight, were used and distributed in a randomized blocks design, in a 4 × 4 factorial scheme, consisting of four levels of SID Trp (0.155, 0.185, 0.215, 0.245%) and four levels of SID Lys (0.972, 1.112, 1.252, and 1.392%). Behavior evaluation was performed by an instantaneous sampling using 10-min intervals during 24 h, at each 7 days (days 7, 14, and 21), and each day was divided into four times of 6 h each one (08:30-14:20, 14:30-20:20, 20:30-02:20, and 02:30-08:20 h), during all the experimental period, yielding a total of 3 × 24 h behavior recordings (72 h) × 6 10-min intervals, totalizing 432 observations per animal. Data were analyzed by classifying behavior into eating or sleeping. All these behaviors were measured in order to obtain the estimated frequency of the eating and sleeping behaviors. Changes were observed (P<0.05) for all the behavioral parameters during the starting phase. SID Trp and SID Lys showed an interactive positive effect on the estimated frequency of eating behavior, and mainly SID Trp increased the estimated frequency of the sleeping behavior of starting pigs in the nocturnal time. Pig diets with increasing levels of SID Trp and SID Lys until 0.245 and 1.392%, respectively, increased the average daily feed intake, and the interaction of the amino acids increased the estimated frequency of eating behavior during all the starting phase, and mainly the increasing levels of SID Trp increased the estimated frequency of sleeping behavior of pigs from the middle to the end of the starting phase, from 2:30 to 8:20 h.

Applications of Enteroendocrine Cells (EECs) Hormone: Applicability on Feed Intake and Nutrient Absorption in Chickens

This review focuses on the role of hormones derived from enteroendocrine cells (EECs) on appetite and nutrient absorption in chickens. In response to nutrient intake, EECs release hormones that act on many organs and body systems, including the brain, gallbladder, and pancreas. Gut hormones released from EECs play a critical role in the regulation of feed intake and the absorption of nutrients such as glucose, protein, and fat following feed ingestion. We could hypothesize that EECs are essential for the regulation of appetite and nutrient absorption because the malfunction of EECs causes severe diarrhea and digestion problems. The importance of EEC hormones has been recognized, and many studies have been carried out to elucidate their mechanisms for many years in other species. However, there is a lack of research on the regulation of appetite and nutrient absorption by EEC hormones in chickens. This review suggests the potential significance of EEC hormones on growth and health in chickens under stress conditions induced by diseases and high temperature, etc., by providing in-depth knowledge of EEC hormones and mechanisms on how these hormones regulate appetite and nutrient absorption in other species.

Excessive dietary L-tryptophan regulated amino acids metabolism and serotonin signaling in the colon of weaning piglets with acetate-induced gut inflammation

L-Tryptophan (Trp) was shown to improve the gut barrier and growth of weaning piglets. However, whether excessive dietary Trp regulates amino acids (AAs) metabolism and gut serotonin (5-HT) homeostasis in piglets with gut inflammation is not clear yet. We hypothesize that excessive dietary Trp alleviates acetate-induced colonic inflammation and gut barrier damage in weaning piglets partially through the regulation of colonic AAs metabolism and 5-HT signaling. Fifty-four 21-day-old weaned piglets were divided into six groups: control, acetate, 0.2%Trp, 0.2%Trp + acetate, 0.4% Trp, and 0.4%Trp + acetate. Piglets were fed a basal diet supplemented with 0%, 0.2%, or 0.4% of Trp throughout the 12-day experiment. During days 0-7, all piglets had free access to diet and drinking water. On day 8, piglets were intrarectal administered with 10 mL of 10% acetate saline solution or 0.9% saline. During days 8-12, all piglets were pair-fed the same amount of feed per kg bodyweight. Results showed that excessive dietary Trp alleviated acetate-induced reductions in daily weight gain and increase in feed/gain ratio. Trp restored (P < 0.05) acetate-induced increase in concentrations of free aspartate, glutamate/glutamine, glycine, 5-HT, and 3-methylindole in the colon, downregulation of zonula occludens-1 and 5-HT reuptake transporter (SERT) expression and upregulation of IL-1β, IL-8, TLR4, and 5-HT receptor 2A (HTR2A) expression, and the increase in ratios of p-STAT3/ STAT3 and p-p65/p65 in the colon. The above findings suggested that excessive dietary Trp in the proper amount regulated colonic AAs metabolism, 5-HT homeostasis, and signaling that may contribute as important regulators of gut inflammation during the weaning transition.

The effects of standardized ileal digestible His to Lys ratio on growth performance, intestinal health, and mobilization of histidine-containing proteins in pigs at 7 to 11 kg body weight

The objectives were to evaluate the effects of standardized ileal digestible (SID) His:Lys ratio above the current NRC requirement on growth performance, intestinal health, and mobilization of His-containing proteins, including hemoglobin, carnosine, and trypsinogen, in nursery pigs from 7 to 11 kg body weight (BW). Forty pigs (26 d of age; initial BW of 7.1 ± 0.5 kg) were allotted to 5 dietary treatments based on a randomized complete block design with sex and initial BW as blocks. Dietary treatments were supplemented with varying SID His to Lys ratios of 26%, 32%, 38%, 43%, and 49% and fed to pigs for 14 d (SID Lys = 1.22%). Feed intake and BW were recorded at d 0, 7, and 14 to measure growth performance. Blood samples were collected on d 12. Pigs were euthanized on d 14 to collect pancreas, longissimus dorsi muscles, mid-jejunum, and jejunal mucosa. Data were analyzed using the Proc Mixed of SAS. Growth performance was not affected, whereas varying SID His to Lys ratio affected hemoglobin (P < 0.05, max: 12 g/dL at 36%), immunoglobulin A (IgA, P < 0.05, min: 1.25 μg/mg at 35%) in jejunal mucosa, villus height (P = 0.065, max: 536 μm at 40%) in jejunum, trypsinogen (P = 0.083, max: 242 pg/mg at 41%) in pancreas, and carnosine (P = 0.051, max: 4.7 ng/mg at 38%) in muscles. Varying SID His to Lys ratios linearly increased (P < 0.05, from 1.95 to 2.80 nmol/mg) protein carbonyl in muscles and decreased (P < 0.05, from 29.1% to 26.9%) enterocyte proliferation. In conclusion, SID His to Lys ratio between 35% and 41% in diets fed to nursery pigs at 7 to 11 kg enhanced intestinal health and maximized concentrations of His-containing proteins, indicating that His-containing proteins are effective response criteria when determining His requirement.

Effects of branched-chain amino acids to lysine ratios in corn distillers dried grains with solubles containing diets on growth performance, plasma nitrogen profile, carcass traits, and economic analysis in growing-finishing pigs

A study was conducted to identify the effects of standardized ileal digestible (SID) branched-chain amino acids (BCAA):lysine (Lys) ratios on the growth performance, plasma nitrogen (N) profile, carcass traits, and economic analysis of growing-finishing pigs fed diets with high corn distillers dried grains with solubles (cDDGS) inclusions. A total of 1,140 pigs (initial body weight [BW] = 28.7 ± 2.0 kg) were housed in 45 pens of 25 or 26 pigs and fed one of five diets in a randomized complete block design. Experimental diets were fed in four phases based on BW. Dietary treatments were a corn-soybean meal (SBM) based diet (PC), a corn-SBM-cDDGS-based diet (NC) with SID BCAA:Lys ratio of PIC (2020) recommendation and NC diets with SID BCAA:Lys ratios targeted for the 73% SID Val:Lys, 60% SID Ile:Lys, and 144% SID Leu:Lys during the growing phases (25 to 80 kg, Grow), targeted for the 78% SID Val:Lys, 70% SID Ile:Lys, and 160% to 170% SID Leu:Lys during the finishing phases (80 to 120 kg, finish), and both during the growing and finishing phases (Grow-Finish). One pig from each pen was bled at the end of 7 and 13 wk. After the 11-wk-feeding trial, pigs were sent to a commercial abattoir to investigate carcass traits. Pigs fed the Finish diet had a greater overall average daily gain (P < 0.05) than pigs fed the other cDDGS diets. Dietary treatments did not affect the hot carcass weight. However, feeding the Finish diet increased (P < 0.05) the iodine value of pork belly samples and decreased (P < 0.05) carcass yield. The plasma urea nitrogen (PUN) concentration at the end of the growing phase and plasma concentrations of Leu and Val were greater (P < 0.05) in pigs fed the Finish diet compared to the other cDDGS diets. Feeding pigs the cDDGS diets with different BCAA:Lys ratios had no difference in income over feed cost and income over feed and facility costs compared to the corn-SBM diet. Therefore, feeding pigs cDDGS diets with SID BCAA:Lys ratios adjusted for the previously determined finishing phase (from 80 to 120 kg of BW) recommendations by SBM inclusion supported growth performance and economic benefits equal to the corn-SBM diet.

Integrated transcriptome analysis for the hepatic and jejunal mucosa tissues of broiler chickens raised under heat stress conditions

Background

Heat stress (HS) is one of the most important threats for the current poultry industry. Therefore, many efforts have been made to ameliorate the adverse effect of HS on poultry production; however, physiological and molecular mechanisms pertaining to HS are still limited in poultry. Therefore, the objective of the current study was to investigate functional alterations based on individual and integrated transcriptomes in the liver and jejunal mucosa tissues of broiler chickens exposed to HS conditions.

Results

Broiler chickens exposed to HS showed decreased growth performance and increased corticosterone concentrations in the feather. In the transcriptome analysis, the number of differentially expressed genes (DEGs) were identified in the liver and jejunal mucosa by HS conditions. In the liver, genes related to amino acid oxidation, tryptophan metabolism, lipid metabolism, oxidative phosphorylation, and immune responses were altered by HS, which support the reason why heat-stressed poultry had decreased productive performance. In the jejunal mucosa, genes related to defense systems, glutathione metabolism, detoxification of xenobiotics, and immune responses were differently expressed by HS conditions. The integrated transcriptome analysis with DEGs found in the liver and jejunal mucosa showed a considerable connectivity between the core nodes in the constructed networks, which includes glutathione metabolism, xenobiotic metabolism, carbon metabolism, and several amino acid metabolisms.

Conclusions

The core network analysis may indicate that increased requirement of energy and amino acids in the jejunal mucosa of broiler chickens exposed to HS conditions is likely compromised by increased oxidation and synthesis of amino acids in the liver. Therefore, our results may provide comprehensive insights for molecular and metabolic alterations of broiler chickens raised under HS conditions, which can aid in the development of the novel strategies to ameliorate the negative effect of HS on poultry productivity and health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00734-y.

Tryptophan Supplementation Enhances Intestinal Health by Improving Gut Barrier Function, Alleviating Inflammation, and Modulating Intestinal Microbiome in Lipopolysaccharide-Challenged Piglets

Tryptophan (Trp) can modify the gut microbiota. However, there is no information about the effect of Trp on intestinal microbiota after lipopolysaccharide (LPS) challenge. This study aimed to investigate the effect of Trp on intestinal barrier function, inflammation, antioxidant status, and microbiota in LPS-challenged piglets. A total of 18 weaned castrated piglets were randomly divided into three treatments with 6 replicate per treatment, namely, (i) non-challenged control (CON); (ii) LPS-challenged control (LPS-CON); and (iii) LPS + 0.2% Trp (LPS-Trp). After feeding with control or 0.2% tryptophan-supplemented diets for 35 days, pigs were intraperitoneally injected with LPS (100 μg/kg body weight) or saline. At 4 h post-challenge, all pigs were slaughtered, and colonic samples were collected. The samples were analyzed for gut microbiota, fatty acids, antioxidant parameters, and the expression of mRNA and protein. The community bar chart showed that Trp supplementation to LPS-challenged pigs increased the relative abundance of Anaerostipes (P < 0.05) and tended to increase the relative abundance of V9D2013_group (P = 0.09), while decreased the relative abundance of Corynebacterium (P < 0.05) and unclassified_c__Bacteroidia (P < 0.01). Gas chromatography showed that Trp increased the concentrations of acetate, propionate, butyrate, and isovalerate in the colonic digesta (P < 0.05). Trp reduced the mRNA level of pro-inflammatory cytokines (P < 0.01), and increased mRNA level of aryl hydrocarbon receptor, cytochrome P450 (CYP) 1A1 and CYP1B1 (P < 0.05). Correlation analysis results showed that acetate, propionate, and butyrate concentrations were positively correlated with mRNA level of occludin and CYP1B1 (P < 0.05), and were negatively correlated with pro-inflammatory cytokines gene expression (P < 0.05). Isovalerate concentration was positively correlated with catalase activity (P < 0.05), and was negatively correlated with pro-inflammatory cytokines gene expression (P < 0.05). Furthermore, Trp enhanced the antioxidant activities (P < 0.01), and increased mRNA and protein expressions of claudin-1, occludin, and zonula occludens-1 (P < 0.01) after LPS challenge. These results suggest that Trp enhanced intestinal health by a modulated intestinal microbiota composition, improved the short chain fatty acids synthesis, reduced inflammation, increased antioxidant capacity, and improved intestinal barrier function.

Tryptophan and the innate intestinal immunity: Crosstalk between metabolites, host innate immune cells and microbiota

The intestinal mucosal barrier is critical for the absorption of nutrients and the health of both humans and animals. Recent publications from clinical and experimental studies have shown the importanceof the nutrients-bacteria-host interaction for the intestinal homeostasis. Dysfunction of these interactions has been reported to be associated with metabolic disorders and development of intestinal diseases, such as the irritable bowel syndrome and inflammatory bowel diseases. Tryptophan and its metabolites, including kynurenine, kynurenic acid, and 5-hydroxytrptamine, can influence the proliferation of enterocytes, intestinal integrity and immune response, as well as intestinal microbiota, therefore regulating and contributing to the intestinal health. In this review, we highlight recent findings on the effect of tryptophan and its metabolites on the mucosal barrier and intestinal homeostasis and its regulation of innate immune response. Moreover, we present the signaling pathways related to Trp metabolism, such as mammalian target of rapamycin, aryl hydrocarbon receptor, and pregnane X receptor, that contribute to the intestinal homeostasis and discuss future perspectives on spontaneous interference in host tryptophan metabolism as potential clinical strategies of intestinal diseases. This article is protected by copyright. All rights reserved.

Effects of dietary leucine and tryptophan on serotonin metabolism and growth performance of growing pigs

An experiment was conducted to test the hypothesis that increased dietary Trp is needed in high-Leu diets for growing pigs to prevent a drop in plasma serotonin and hypothalamic serotonin concentrations and to maintain growth performance of animals. A total of 144 growing pigs (initial weight: 28.2 ± 1.9 kg) were assigned to 9 treatments in a randomized complete block design with 2 blocks, 2 pigs per pen, and 8 replicate pens per treatment. The 9 diets were formulated in a 3 × 3 factorial with 3 levels of dietary Leu (101, 200, or 299% standardized ileal digestible [SID] Leu:Lys), and 3 levels of dietary Trp (18, 23, or 28% SID Trp:Lys). A basal diet that met requirements for SID Leu and SID Trp was formulated and 8 additional diets were formulated by adding crystalline L-Leu and (or) L-Trp to the basal diet. Individual pig weights were recorded at the beginning of the experiment and at the conclusion of the 21-d experiment. On the last day of the experiment, one pig per pen was sacrificed, and blood and hypothalamus samples were collected to measure plasma urea N, plasma serotonin, and hypothalamic serotonin concentrations. Results indicated that increasing dietary Trp increased (P < 0.05) hypothalamic serotonin, whereas increases (P < 0.05) in average daily gain (ADG) and average daily feed intake (ADFI) were observed only in pigs fed diets containing excess Leu. Increasing dietary Leu reduced (P < 0.05) ADG, ADFI, and hypothalamic serotonin. However, the increase in ADG and ADFI caused by dietary Trp was greater if 299% SID Leu:Lys was provided than if 101% SID Leu:Lys was provided (interaction, P < 0.05). Plasma Leu concentration was positively affected by dietary Leu and negatively affected by dietary Trp, but the negative effect of Trp was greater if 299% SID Leu:Lys was provided than if 101% SID Leu:Lys was provided (interaction, P < 0.05). Plasma concentration of Trp was positively affected by increased dietary Trp and increased dietary Leu, but the increase in plasma concentration of Trp was greater if Leu level was at 101 % SID Leu:Lys ratio than at 299% SID Leu:Lys ratio (interaction, P < 0.05). In conclusion, increased dietary Leu reduced ADG, ADFI, and hypothalamic serotonin concentration, and influenced metabolism of several indispensable amino acids, but Trp supplementation partly overcame the negative effect of excess Leu. This demonstrates the importance of Trp in regulation of hypothalamic serotonin, and therefore, feed intake of pigs.

Impacts of weaning age on dietary needs of whey permeate for pigs at 7 to 11 kg body weight

Background

Whey permeate is an effective lactose source for nursery pigs and the most benefits are obtained when pigs are at 7 to 11 kg BW. Altering weaning ages could cause different length of early-weaner phases until 7 kg BW and thus it would influence the dietary need of whey permeate during 7 to 11 kg BW of pigs. This study aimed to evaluate if weaning ages would affect the dietary needs of whey permeate for optimum growth performance of pigs at 7 to 11 kg BW.

Methods

A total of 1,632 pigs were weaned at d 21 (d 21.2 ± 1.3) or d 25 (d 24.6 ± 1.1) after birth. All pigs had a common early-weaner feeds until they reached 7 kg BW. When pigs reached 7 kg BW within a weaning age group, they were allotted in a randomized complete block design (2 × 4 factorial). Two factors were weaning age groups (21 and 25 d of age) and varying whey permeate levels (7.50%, 11.25%, 15.00%, and 18.75%). Data were analyzed using the GLM and NLIN procedures of SAS for slope-ratio and broken-line analyses to determine the growth response to whey permeate and optimal daily whey permeate intake for the growth of the pigs weaned at different ages.

Results

Pigs weaned at 21 d of age had a common diet for 11 d to reach 7 kg BW whereas pigs weaned at 25 d of age needed 2 d. The G:F of pigs weaned at 25 d of age responded to increased daily whey permeate intake greater (P < 0.05) than pigs weaned at 21 d of age. Breakpoints were obtained (P < 0.05) at 88 and 60 g/d daily whey permeate intake or 17.0% and 14.4% of whey permeate for G:F of pigs weaned at 21 and 25 d of age, respectively.

Conclusion

Pigs weaned at an older age with a short early-weaner phase had a greater growth response to whey permeate intake compared with pigs weaned at a younger age with a long early-weaner phase. Altering weaning ages affected dietary needs of whey permeate for optimum growth performance of pigs from 7 to 11 kg BW.

Effects of dairy and plant protein on growth and growth biomarkers in a piglet model

The increasing world population with improved living conditions has increased the demand for food protein. This has intensified the search for sustainable alternative plant-derived high-quality protein sources for human nutrition. To study the effect of plant and milk proteins on growth in weaned pigs as a model for humans, 96 weaned pigs were divided into 48 pens and fed one of 4 different diets for 3 weeks. The dietary protein originated from either 50% rice + 50% 00-rapeseed protein (RICE + RAPE), 50% milk protein (MPC) + 50% 00-rapeseed protein (MPC + RAPE), 50% milk + 50% rice protein (MPC + RICE), or 100% MPC, and were supplemented with crystalline amino acids to meet the amino acid requirements. Weekly feed intake and body weights were recorded and after 3 weeks, a blood sample was taken 1 hour after a fixed meal, while organ weights were measured, and liver- and muscle tissue, and bone samples were collected at euthanasia. All pigs had a high daily gain and a low feed-to-gain ratio (F : G, feed intake per kg weight gain), but feed intake and daily gain was lowest and F : G highest in the RICE + RAPE diet. Metacarpal bones were longer and heavier in MPC + RICE and MPC fed pigs compared to pigs fed diet RICE + RAPE (P < 0.05), and intermediate in MPC + RAPE fed pigs, with no differences in bone thickness (P > 0.05). Plasma levels of all essential amino acids except Cys and Lys decreased markedly when fed a diet containing only plant protein. The differences were not associated with differences in plasma insulin or IGF-1, nor in the abundance of mRNA related to growth in liver and longissimus dorsi muscle. In conclusion, the growth of piglets fed a combination of milk and rice protein did not differ from the pure dairy-based diet, whereas the pure plant-based diet consisting of rice and rapeseed protein led to reduced growth. This was most likely caused by a lower feed intake and a lower than expected amino acid digestibility of the 00-rapeseed protein. There were no indications that the milk protein, beyond a favourable amino acid composition and high digestibility, specifically stimulated growth factors or other biomarkers of growth via the IGF-1 and insulin signalling pathways.

Branched-chain amino acids partially recover the reduced growth of pigs fed with protein-restricted diets through both central and peripheral factors

The objective of this study was to assess the growth efficiency of pigs fed with protein-restricted diets supplemented with branched-chain amino acids (BCAA) and limiting amino acids (LAA) above the recommended levels. Following 2 weeks of adaptation, 48 young barrows were weight matched and randomly assigned to 6 treatments (8 pigs/treatment) for 4 weeks: positive control (PC) with standard protein, negative control (NC) with very low protein containing LAA (i.e., Lys, Met, Thr and Trp) at recommended levels, and NC containing LAA 25% (L25), LAA 50% (L50), LAA+BCAA (i.e., Leu, Ile and Val) 25% (LB25) and LAA+BCAA 50% (LB50) more than recommendations. Feed intake (FI) and body weight (BW) were measured daily and weekly, respectively. At week 6, blood samples were collected, all pigs euthanized and tissue samples collected. The data were analyzed by univariate GLM or mixed procedure (SPSS) and the means were separated using paired Student's t-test followed by Benjamini-Hochberg correction. Relative to PC, NC had decreased FI, BW, unsupplemented plasma essential amino acids, serum insulin-like growth factor-I (IGF-I) and hypothalamic neuropeptide Y (NPY) (P < 0.01). Compared to NC, L25 or L50, LB50 had increased BW and serum IGF-I and decreased plasma serotonin and both LB25 and LB50 had higher FI, plasma BCAA, hypothalamic 5-hydroxytryptamine-receptor 2A and NPY and jejunal 5-hydroxytryptamine-receptor 7 (P < 0.01). Overall, supplementation of protein-restricted diets with increased levels of dietary BCAA partially recovered the negative effects of these diets on growth through improved IGF-I concentration and FI, which was associated with changed expression of serotonin receptors, blood AA and hypothalamic NPY.

Physiological Effects of Deoxynivalenol from Naturally Contaminated Corn on Cerebral Tryptophan Metabolism, Behavioral Response, Gastrointestinal Immune Status and Health in Pigs Following a Pair-Feeding Model

This study investigated the impact of deoxynivalenol (DON) from naturally contaminated feed on pig growth, immune status, organ health, brain serotonin (5-Hydroxytryptamine, 5-HT) and behavior. Sixteen individually housed pigs (25.57 ± 0.98 kg, age 9 weeks) were randomly allotted to two dietary treatments: without DON (CON) or with 3.8 mg/kg of DON (MT). Pigs were pair-fed to eliminate differences in feed intake (equal tryptophan (Trp) intake). Pigs fed CON received a daily ration based on the ad libitum feed consumption of their MT pair-mate. Performance was determined over 21 days and blood collected for immunological and oxidative stress parameters. Behavior was recorded for 12 h on days 0, 7, 14 and 21. After 21 days, pigs were euthanized to collect tissues for immune parameters, gut morphology and brain serotonin levels. Overall, pigs fed MT had greater weight gain compared with CON. Immunological and oxidative stress parameters were unaffected, but pigs fed MT had reduced villus height, crypt depth and villus-to-crypt ratio in the jejunum. Pigs consuming MT had reduced concentration of 5-HT and increased 5-HT turnover in the hypothalamus. Mycotoxin-fed pigs spent more time lying and sitting, and less time standing and drinking. In conclusion, consumption of DON impacted gastrointestinal tract structure, altered behavior and changed Trp metabolism through increasing 5-HT turnover in hypothalamus.

Functional Amino Acids in Pigs and Chickens: Implication for Gut Health

In pigs and broiler chickens, the gastrointestinal tract or gut is subjected to many challenges which alter performance, animal health, welfare and livability. Preventive strategies are needed to mitigate the impacts of these challenges on gut health while reducing the need to use antimicrobials. In the first part of the review, we propose a common definition of gut health for pig and chickens relying on four pillars, which correspond to the main functions of the digestive tract: (i) epithelial barrier and digestion, (ii) immune fitness, (iii) microbiota balance and (iv) oxidative stress homeostasis. For each pillar, we describe the most commonly associated indicators. In the second part of the review, we present the potential of functional amino acid supplementation to preserve and improve gut health in piglets and chickens. We highlight that amino acid supplementation strategies, based on their roles as precursors of energy and functional molecules, as signaling molecules and as microbiota modulators can positively contribute to gut health by supporting or restoring its four intertwined pillars. Additional work is still needed in order to determine the effective dose of supplementation and mode of administration that ensure the full benefits of amino acids. For this purpose, synergy between amino acids, effects of amino acid-derived metabolites and differences in the metabolic fate between free and protein-bound amino acids are research topics that need to be furtherly investigated.

Invited Review: Maintain or Improve Piglet Gut Health around Weanling: The Fundamental Effects of Dietary Amino Acids

Gut health has significant implications for swine nutrient utilization and overall health. The basic gut morphology and its luminal microbiota play determinant roles for maintaining gut health and functions. Amino acids (AA), a group of essential nutrients for pigs, are not only obligatory for maintaining gut mucosal mass and integrity, but also for supporting the growth of luminal microbiota. This review summarized the up-to-date knowledge concerning the effects of dietary AA supplementation on the gut health of weanling piglets. For instance, threonine, arginine, glutamine, methionine and cysteine are beneficial to gut mucosal immunity and barrier function. Glutamine, arginine, threonine, methionine and cysteine can also assist with relieving the post-weaning stress of young piglets by improving gut immunological functions, antioxidant capacity, and/or anti-inflammatory ability. Glutamine, glutamate, glycine and cysteine can assist to reconstruct the gut structure after its damage and reverse its dysfunction. Furthermore, methionine, lysine, threonine, and glutamate play key roles in affecting bacteria growth in the lumen. Overall, the previous studies with different AA showed both similar and different effects on the gut health, but how to take advantages of all these effects for field application is not clear. It is uncertain whether these AA effects are synergetic or antagonistic. The interactions between the effects of non-nutrient feed additives and the fundamental effects of AA warrant further investigation. Considering the global push to minimize the antibiotics and ZnO usage in swine production, a primary effort at present may be made to explore the specific effects of individual AA, and then the concert effects of multiple AA, on the profile and functions of gut microbiota in young pigs.

Dietary Tryptophan Levels Impact Growth Performance and Intestinal Microbial Ecology in Weaned Piglets via Tryptophan Metabolites and Intestinal Antimicrobial Peptides

Tryptophan (Trp) plays an important role in piglet growth. However, the effect of dietary Trp on microbial flora is still poorly understood. A total of 40 28-d weaned piglets were allocated to four groups with 10 barrows per group and one pig per replicate. Piglets were fed a corn and soybean meal-based diet with 0.14%, 0.21%, 0.28%, or 0.35% Trp for four weeks. Five piglets from each diet group were euthanized, and blood and tissue samples were collected. The average daily body weight gain, average daily feed intake, feed conversion ratio, spleen index, pancreas index, longissimus dorsi muscle index, plasma insulin, 5-hydroxytryptamine, kynurenine, and Trp concentrations of weaned piglets increased in a dose-dependent manner (p < 0.05). Compared with the 0.14% Trp diet, the adequate-Trp diets (0.21%, 0.28%, or 0.35%) down-regulated the relative abundances of 12 genera including Turicibacter, Prevotella, Mitsuokella, Anaerovibrio, Megasphaera, Succinivibrio, Sutterella, Desulfovibrio, and Methanobrevibacter (p < 0.05); up-regulated the abundances of Ruminococcaceae, Lactobacillus, and Muribaculaceae in the colon (p < 0.05); and augmented the mRNA level and concentration of porcine β-defensin 2 in the small intestinal mucosa (p < 0.05). Moreover, Trp-adequate diets increased the abundances of Trp hydroxylase, indoleamine 2,3-dioxygenase, porcine β-defensin 2, phosphorylated mammalian target of rapamycin, and phosphorylated protein kinase B in the small intestinal mucosa (p < 0.05). We noted that a corn and soybean meal-based diet with 0.35% Trp may be a nutritional strategy to improve growth performance, intestinal mucosal barrier integrity, and intestinal microbial ecology in weaned piglets.

Dose-response and functional role of whey permeate as a source of lactose and milk oligosaccharides on intestinal health and growth of nursery pigs

Two experiments were conducted to evaluate dose-response and supplemental effects of whey permeate on growth performance and intestinal health of nursery pigs. In experiment (exp.) 1, 1,080 pigs weaned at 6.24 kg body weight (BW) were allotted to five treatments (eight pens/treatment) with increasing levels of whey permeate in three phases (from 10% to 30%, 3% to 23%, and 0% to 9% for phase 1, 2, and 3, respectively) fed until 11 kg BW and then fed a common phase 4 diet (0% whey permeate) until 25 kg BW in a 48-d feeding trial. Feed intake and BW were measured at the end of each phase. In exp. 2, 1,200 nursery pigs at 7.50 kg BW were allotted to six treatments (10 pens/treatment) with increasing levels of whey permeate from 0% to 18.75% fed until 11 kg BW. Feed intake and BW were measured during 11 d. Six pigs per treatment (1 per pens) were euthanized to collect the jejunum to evaluate tumor necrosis factor-alpha, interleukin-8 (IL-8), transforming growth factor-beta 1, mucin 2, histomorphology, digestive enzyme activity, crypt cell proliferation rate, and jejunal mucosa-associated microbiota. Data were analyzed using contrasts in the MIXED procedure and a broken-line analysis using the NLIN procedure of SAS. In exp. 1, increasing whey permeate had a quadratic effect (P < 0.05) on feed efficiency (G:F; maximum: 1.35 at 18.3%) in phase 1. Increasing whey permeate linearly increased (P < 0.05) average daily gain (ADG; 292 to 327 g/d) and G:F (0.96 to 1.04) of pigs in phase 2. In exp. 2, increasing whey permeate linearly increased (P < 0.05) ADG (349 to 414 g/d) and G:F (0.78 to 0.85) and linearly increased (P < 0.05) crypt cell proliferation rate (27.8% to 37.0%). The breakpoint from a broken-line analysis was obtained at 13.6% whey permeate for maximal G:F. Increasing whey permeate tended to change IL-8 (quadratic, P = 0.052; maximum: 223 pg/mg at 10.9%), to decrease Firmicutes:Bacteroidetes (P = 0.073, 1.59 to 1.13), to increase (P = 0.089) Bifidobacteriaceae (0.73% to 1.11%), and to decrease Enterobacteriaceae (P = 0.091, 1.04% to 0.52%) and Streptococcaceae (P = 0.094, 1.50% to 0.71%) in the jejunal mucosa. In conclusion, dietary inclusion of whey permeate increased the growth of nursery pigs from 7 to 11 kg BW. Pigs grew most efficiently with 13.6% whey permeate. Improvement in growth performance is partly attributed to stimulating intestinal immune response and enterocyte proliferation with positive changes in jejunal mucosa-associated microbiota in nursery pigs.

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

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

Effects of supplemental xylanase on health of the small intestine in nursery pigs fed diets with corn distillers' dried grains with solubles

Forty pigs [10.7 ± 1.2 kg initial body weight (BW) at 6 wk of age] were used in a 21-d study to evaluate the effects of supplemental xylanase (Hostazym X 100, Huvepharma, Inc., Peachtree City, GA) in nursery diets on digesta viscosity, nutrient digestibility, health of the small intestine, and growth performance when supplemented with corn distillers' dried grains with solubles (DDGS). Pigs were individually housed and randomly allotted to four treatments in a 2 × 2 factorial arrangement (n = 20/factor, 0% or 30% DDGS and 0 or 1,500 endo-pentosanase unit/kg xylanase as two factors) based on sex and initial BW. Feed intake and BW were recorded weekly. On day 15 of the study, TiO2 in diets (0.3%) was used as an indigestible marker to calculate apparent ileal digestibility (AID). Plasma samples were collected on day 19 to measure tumor necrosis factor-alpha (TNF-α), malondialdehyde, and peptide YY. On day 21, all pigs were euthanized to collect tissues from duodenum, jejunum, and colon to measure morphology, TNF-α, and malondialdehyde concentrations. Distal jejunal digesta were collected to measure viscosity. Ileum digesta were collected to measure AID of nutrients. During the entire period, supplemental xylanase increased (P < 0.05) average daily gain (ADG; 616 to 660 g/d) of nursery pigs, whereas DDGS (0 or 30%) did not affect ADG. On week 3, average daily feed intake (ADFI) was increased (P < 0.05) when fed DDGS (1,141 to 1,267 g/d) and there was an interaction (P < 0.05) between two factors indicating that supplemental xylanase decreased ADFI when DDGS was used in a diet. Use of DDGS increased (P < 0.05) viscosity [1.86 to 2.38 centipoise (cP)], whereas supplemental xylanase reduced (P < 0.05) viscosity (2.27 to 1.96 cP) of jejunal digesta. The AID of dry matter (DM) and gross energy (GE) were improved (P < 0.05) by supplemental xylanase. Plasma TNF-α was decreased (P < 0.05, 108.5 to 69.9 pg/mL) by supplemental xylanase. Use of DDGS reduced (P < 0.05) villus height:crypt depth ratio (1.46 to 1.27), whereas supplemental xylanase increased (P < 0.05) the crypt depth (360 to 404 µm) in duodenum. In conclusion, feeding a diet with 30% DDGS to nursery pigs for 3 wk had no negative effect on growth performance, whereas reduced AID of DM and GE, increased TNF-α level in colon tissue, and reduced the ratio of villus height to crypt depth. Dietary supplementation of xylanase reduced digesta viscosity improving AID of nutrients, reduced inflammatory response, and altered intestinal morphology, collectively improving ADG of nursery pigs regardless of the use of DDGS in a diet.

Effects of tryptophan and probiotic supplementation on growth and behavior in quail

In laying hens, a diet supplemented with tryptophan (Trp) has been shown to affect their pecking behavior. However, unlike this positive effect, Trp is also involved in negative effects on behavior and stress through indolic pathways. Indole production can be reduced by probiotics (Pro), thus we hypothesized that Pro may prevent negative effects of Trp and increase beneficial effects on behavior in birds. Combined effects of Pro and Trp were also expected. To investigate the effects on behavior in birds of supplementing with a high level of Trp with or without Pro, Japanese quail were used because their behavior can be influenced by Pediococcus acidilactici, and they can be highly aggressive. Quails (n = 120) were assigned to 4 groups in a 2 × 2 factorial design for 55 d: C-C (control diet with usual Trp level, 0.3%; without Pro; n = 30), Trp-C (Trp: 2%; without Pro; n = 30), C-Pro (control diet; with Pro: 1 x 10⁹ CFU/L P. acidilactici in drinking water; n = 30), and Trp-Pro (Trp 2%; with Pro; n = 30). Body weight was measured every week, and different tests were conducted to investigate behavioral characteristics of each quail. Contrary to our hypothesis, there was almost no interaction between Trp and Pro treatments. Tryptophan supplementation significantly (P < 0.05) reduced live weight up to 27 d, whereas Pro treatment had no effect. There was no significant difference between groups for tonic immobility variables (P > 0.05). The birds fed the high Trp diet spent significantly less time in the periphery of the open field than those fed the control diet and moved less in the arena during the social isolation test. Interindividual distances were significantly lower in males fed with Trp 2% than with the control diet, whereas Trp and Pro supplements interacted in females. The treatments did not affect sexual motivation in males. These results indicate that a high level of Trp reduced growth and appeared to enhance emotional reactivity in quails and that supplementing with Pro did not reduce these effects. In conclusion, feeding high Trp for 55 d cannot be recommended as a strategy to improve social behavior unlike effects observed in laying hens.

Evaluating the potential role of tryptophan in calf milk replacers to facilitate weaning

Tryptophan is a precursor of serotonin, a neurotransmitter that participates in the control of the affective state of an animal. We hypothesized that Trp supplementation could help dairy calves to cope with weaning stress. Twenty-seven Holstein male calves (48 ± 0.8 d old; 82 ± 2.6 kg of body weight) were used to evaluate the effects of Trp supplementation at a rate of 4.5 g/d via milk replacer (MR) on performance and behavioral parameters around weaning. All calves received the same feeding program (6 L/d at 15% dry matter from d 1 to 7, 4 L/d at 15% dry matter from d 8 to 14, and 2 L/d at 15% dry matter in one feeding until d 21 of study) and were completely weaned 22 d after the beginning of the study (around 70 d of life). Calves were fed a starter feed (19.3% crude protein and 16.2% neutral detergent fiber, on a dry matter basis) and chopped straw ad libitum. Animals were weighed weekly, dry matter intakes were recorded daily, lying behavior was recorded using accelerometers throughout the study, and scan sampling was performed twice a week, 1 h after the morning feeding, to record behavioral activity (nonnutritive oral behaviors, suckling a neighbor calf, standing, resting, rumination, vocalizations, eating, and drinking). Tryptophan supplementation did not affect calf performance or concentrate and MR intake, but straw intake tended to be greater in nonsupplemented compared with Trp-supplemented calves (153 vs. 129 ± 9.0 g/d, respectively). Lying time, lying bouts, and lying duration decreased when changes in the MR feeding program occurred, independent of treatment. Similarly, differences in behavioral observations occurred along days of study, with no effect of Trp supplementation. The main changes observed in calf behavior were an increase in vocalizations and standing time 1 h after the morning feeding at weaning, but again these changes were independent of treatment. Parameters measured in serum and plasma indicated an increase in Trp, kynurenine, and the kynurenine/Trp ratio after feeding in the Trp calves. A tendency for lower plasma glucose concentration after feeding was observed in the Trp group. No changes in stress markers such as cortisol and haptoglobin in serum were detected. In conclusion, supplementing 4.5 g/d of Trp via MR between 48 and 62 d of life had no effect on performance or behavior in calves around weaning.

Metabolic maturation in the first 2 years of life in resource-constrained settings and its association with postnatal growths

Malnutrition continues to affect the growth and development of millions of children worldwide, and chronic undernutrition has proven to be largely refractory to interventions. Improved understanding of metabolic development in infancy and how it differs in growth-constrained children may provide insights to inform more timely, targeted, and effective interventions. Here, the metabolome of healthy infants was compared to that of growth-constrained infants from three continents over the first 2 years of life to identify metabolic signatures of aging. Predictive models demonstrated that growth-constrained children lag in their metabolic maturity relative to their healthier peers and that metabolic maturity can predict growth 6 months into the future. Our results provide a metabolic framework from which future nutritional programs may be more precisely constructed and evaluated.

Excess dietary leucine in diets for growing pigs reduces growth performance, biological value of protein, protein retention, and serotonin synthesis1

An experiment was conducted to test the hypothesis that excess dietary Leu affects metabolism of branched-chain amino acids (BCAA) in growing pigs. Forty barrows (initial body weight [BW]: 30.0 ± 2.7 kg) were housed individually in metabolism crates and allotted to 5 dietary treatments (8 replicates per treatment) in a randomized complete block design. The 5 diets were based on identical quantities of corn, soybean meal, wheat, and barley and designed to contain 100%, 150%, 200%, 250%, or 300% of the requirement for standardized ileal digestible Leu. Initial and final (day 15) BW of pigs were recorded. Daily feed consumption was also recorded. Urine and fecal samples were collected for 5 d following 7 d of adaptation to the diets. At the end of the experiment, blood and tissue samples were collected to analyze plasma urea N (PUN), plasma and hypothalamic serotonin, tissue BCAA, serum and tissue branched-chain α-keto acids, and messenger ribonucleic acid abundance of genes involved in BCAA metabolism. Results indicated that acid detergent fiber, average daily feed intake, and gain-to-feed ratio decreased (linear, P < 0.05) as dietary Leu increased. A trend (linear, P = 0.082) for decreased N retention and decreased (linear, P < 0.05) biological value of dietary protein was also observed, and PUN increased (linear, P < 0.05) as dietary Leu increased. A quadratic reduction (P < 0.05) in plasma serotonin and a linear reduction (P < 0.05) in hypothalamic serotonin were observed with increasing dietary Leu. Concentrations of BCAA in liver increased (linear, P < 0.001), whereas concentrations of BCAA in skeletal muscle decreased (linear, P < 0.05) as dietary Leu increased. Concentration of α-ketoisovalerate was reduced (linear and quadratic, P < 0.001) in liver, skeletal muscle, and serum, and α-keto-β-methylvalerate was reduced (linear, P < 0.001; quadratic, P < 0.001) in skeletal muscle and serum. In contrast, α-keto isocaproate increased (linear, P < 0.05) in liver and skeletal muscle and also in serum (linear and quadratic, P < 0.001) with increasing dietary Leu. Expression of mitochondrial BCAA transaminase and of the E1α subunit of branched-chain α-keto acid dehydrogenase increased (linear, P < 0.05) in skeletal muscle as dietary Leu increased. In conclusion, excess dietary Leu impaired growth performance and nitrogen retention, which is likely a result of increased catabolism of Ile and Val, which in turn reduces availability of these amino acids resulting in reduced protein retention, and excess dietary Leu also reduced hypothalamic serotonin synthesis.

Effect of stocking density and dietary tryptophan on growth performance and intestinal barrier function in broiler chickens

The objective of the present experiment was to investigate the effect of stocking density (SD) and dietary supplementation of crystalline tryptophan (Trp) on growth performance and intestinal barrier function in broiler chickens raised in a floor pen. The experiment was conducted using a completely randomized design with a 2 × 2 factorial arrangement consisting of 2 different SD and 2 supplemental levels of dietary Trp. A total of 1,140 Ross 308 broiler chickens at 21 d of age were allotted to 1 of 4 treatments with 5 replicates. Low SD (9 birds/m2) and high SD (18 birds/m2) were achieved by raising different number of birds per identical floor pen (2.0 m × 2.4 m). The basal diet was formulated with no supplemental Trp in diets to meet or exceed nutrient recommendation of the Ross 308 manual. The calculated concentrations of total Trp and digestible Trp in the basal diet were 0.19 and 0.16%, respectively. The other diet was prepared by adding 0.16% crystalline Trp to the basal diet. Diets were fed to birds for 21 d. At the end of the experiment, 2 birds per replicate were euthanized to collect tissue samples for further analyses. Results indicated that there were no interactions between SD and dietary Trp for all measurements. For the main effects, birds raised at a low SD had greater (P < 0.01) body weight gain, feed intake, and feed efficiency than those raised at a high SD. However, supplementation of dietary Trp had no effect on broiler performance. Furthermore, there were no main effects of SD and dietary Trp on intestinal barrier functions. In conclusion, broiler chickens raised in a floor pen with a high SD (18 birds/m2) have decreased growth performance with little changes in intestinal barrier functions. Supplementation of dietary Trp at 0.16% has no positive effect on broiler chickens raised in a floor pen with either a low or high SD.

Supplemental effects of dietary nucleotides on intestinal health and growth performance of newly weaned pigs

Intestinal challenges upon weaning would increase the needs of nucleotides for enterocyte proliferation, whereas de novo synthesis maybe insufficient. This study aimed to evaluate supplemental effects of dietary nucleotides on intestinal health and growth performance in newly weaned pigs. Fifty newly weaned pigs (19-d-old, 25 barrows and 25 gilts, 4.76 ± 0.42 kg BW) were individually housed and allotted to 5 treatments with increasing nucleotide supplementation (0, 50, 150, 250, and 500 mg/kg) based on a randomized complete block design with the initial BW and sex as blocks. Dietary nucleotides were provided from YT500 (Hinabiotech, Guangzhou, China). Pigs were fed for 21 d based on 2 phases (phase 1: 11 d and phase 2: 10 d) and experimental diets were formulated to meet or exceed nutrient requirements suggested by NRC (2012). Feed intake and BW were recorded. Titanium oxide (0.4%) was added as an indigestible marker from day 17. Plasma collected on day 18 was used to measure tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and malondialdehyde (MDA). Pigs were euthanized on day 21 to collect tissues to evaluate TNF-α, IL-6, MDA, morphology, and crypt cell proliferation rate in the jejunum. Ileal digesta were collected to measure ileal nutrient digestibility. Data were analyzed using contrasts in the MIXED procedure of SAS. Nucleotide supplementation increased (P < 0.05) ADFI in phase 1. Nucleotide supplementation at 50 and 150 mg/kg increased (P < 0.05) ADG in phase 1, whereas increased (P < 0.05) ADFI and tended to increase (P = 0.082) ADG in overall. Increasing nucleotide supplementation changed (quadratic, P < 0.05) villus height-crypt ratio (at 247 mg/kg) and decreased (linear, P < 0.05) crypt cell proliferation rate in the jejunum. Increasing nucleotide supplementation reduced (P < 0.05) jejunal IL-6 (at 50 and 150 mg/kg) and tended to change (quadratic, P = 0.074) plasma MDA (at 231 mg/kg). Nucleotide supplementation at 50 and 150 mg/kg increased (P < 0.05) ileal digestibility of energy and ether extract. In conclusion, nucleotide supplementation at a range of 50 to 250 mg/kg in the diets seems to be beneficial to newly weaned pigs by enhancing growth performance possibly due to reduced intestinal inflammation and oxidative stress as well as improved intestinal villi structure and energy digestibility.

L-tryptophan Enhances Intestinal Integrity in Diquat-Challenged Piglets Associated with Improvement of Redox Status and Mitochondrial Function

Simple Summary

In the present study, three groups of piglets were treated with diquat, a bipyridyl herbicide which can utilize molecular oxygen to generate superoxide anion radicals and is widely considered as an effective chemical agent for inducing oxidative stress. The three groups were fed a 0, 0.15%, and 0.30% tryptophan (Trp) supplemented diet, and one control group without diquat treatment was used to study the protective effects of supplemented Trp on growth performance and intestinal barrier function of piglets exposed to oxidative stress. The results showed that 0.15% Trp supplementation alleviated diquat-induced impaired growth performance, intestinal barrier injury, redox imbalance, and mitochondrial dysfunction. These findings from the current study suggest that piglets under the condition of stress might need more Trp to maintain intestinal integrity and optimal growth performance, but the proper dosage of Trp supplementation is needed to determine for different conditions or models.

Abstract

Tryptophan (Trp) supplementation has been shown to improve growth performance and enhance intestinal integrity in piglets. However, the effects of dietary Trp supplementation on the intestinal barrier function in piglets exposed to oxidative stress remain unknown. This study was conducted to evaluate whether dietary Trp supplementation can attenuate intestinal injury, oxidative stress, and mitochondrial dysfunction of piglets caused by diquat injection. Thirty-two piglets at 25 days of age were randomly allocated to four groups: (1) the non-challenged control; (2) diquat-challenged control; (3) 0.15% Trp-supplemented diet + diquat; (4) 0.30% Trp supplemented diet + diquat. On day seven, the piglets were injected intraperitoneally with sterilized saline or diquat (10 mg/kg body weight). The experiment lasted 21 days. Dietary supplementation with 0.15% Trp improved growth performance of diquat-challenged piglets from day 7 to 21. Diquat induced an increased intestinal permeability, impaired antioxidant capacity, and mitochondrial dysfunction. Although dietary supplementation with 0.15% Trp ameliorated these negative effects induced by diquat challenge that showed decreasing permeability of 4 kDa fluorescein isothiocyanate dextran, increasing antioxidant indexes, and enhancing mitochondrial biogenesis. Results indicated that dietary supplementation with 0.15% Trp enhanced intestinal integrity, restored the redox status, and improved the mitochondrial function of piglets challenged with diquat.

Effect of Mucine 4 and Fucosyltransferase 1 genetic variants on gut homoeostasis of growing healthy pigs

Putative genetic markers have been associated with ETEC F4 (Mucine 4 [MUC4]; MUC4GG;CG as susceptible; MUC4CC as resistant) and F18 (Fucosyltransferase 1 [FUT1]; FUT1GG;AG as susceptible; FUT1AA as resistant) resistances respectively. In this study, 71 post-weaning pigs were followed from d0 (35 days old) to d42 (77 days of age) to investigate the effect of MUC4 or FUT1 genotypes on the mid-jejunal microbiota composition, pigs expression of genes related to inflammation (IL8, GPX2, REG3G, TFF3, CCL20 and LBPI) and glycomic binding pattern profile (Ulex europaeus agglutinin I [UEA] fucose-binding lectin and peanut agglutinin [PNA] galactose-specific), and on blood plasma targeted metabolomics profile, faecal score and performance parameters of growing healthy pigs. The MUC4 and FUT1 resistant genotypes improved the pigs' growth performance and had firmed faecal score susceptible genotypes in d0-d21 period. Pigs with MUC4GG genotype had a higher jejunal expression of genes relate to immune function (CCL20 and REG3G) than MUC4CG and MUC4CC pigs (p < 0.05). MUC4CG pigs had higher expression of TFF3 (implicated in mucosal integrity) than MUC4GG and MUC4CC (p < 0.05). FUT1 influenced the alpha- and beta-jejunal microbial indices. The FUT1AA group had a higher number of operational taxonomic units (OTUs) belonging to Lactobacillus genus, while FUT1GG group had a higher number of OTUs belonging to Veillonella genus. MUC4CC pigs had lower scores for UEA on brush borders and goblet cells in villi than MUC4GG (p < 0.05). FUT1AA pigs had lower UEA positivity and higher PNA positivity on brush borders and goblet cells than FUT1AG and FUT1GG (p < 0.05). Both FUT1 and MUC4 influenced the metabolic profile of healthy pigs. Results highlight the role of MUC4 and FUT1 on pig intestinal homoeostasis and improved the knowledge regarding the potential interaction between host genetics, gut microbiota composition and host metabolism in a healthy status.

Comparative Metabonomic Investigations of Schistosoma japonicum From SCID Mice and BALB/c Mice: Clues to Developmental Abnormality of Schistosome in the Immunodeficient Host

The growth and development of schistosome has been affected in the immunodeficient hosts. But it remains unresolved about the molecular mechanisms involved in the development and reproduction regulation of schistosomes. This study tested and compared the metabolic profiles of the male and female Schistosoma japonicum worms collected from SCID mice and BALB/c mice at 5 weeks post infection using liquid chromatography tandem mass spectrometry (LC-MS/MS) platform, in which the worms from SCID mice were the investigated organisms and the worms from BALB/c mice were used as the controls. There were 1015 ion features in ESI+ mode and 342 ion features in ESI- mode were identified after filtration by false discovery rate. Distinct metabolic profiles were found to clearly differentiate both male and female worms in SCID mice from those in BALB/c mice using multivariate modeling methods including the Principal Component Analysis (PCA), Partial Least Squares Discriminant Analysis (PLS-DA), and Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA). There were more differential metabolites in female worms than in male worms between SCID mice and BALB/c mice. And common and uniquely perturbed metabolites and pathways were identified among male and female worms from SCID mice when compared with BALB/c mice. The enriched metabolite sets of the differential metabolites in male worms between SCID mice and BALB/c mice included bile acid biosynthesis, taurine and hypotaurine metabolism, sphingolipid metabolism, retinol metabolism, purine metabolism, etc. And the enriched metabolite sets of differential metabolites in female worms included retinol metabolism, alpha linolenic acid and linoleic acid metabolism, purine metabolism, sphingolipid metabolism, glutamate metabolism, etc. Further detection and comparison in transcript abundance of genes of the perturbed retinol metabolism and its associated meiosis process in worms identified clues suggesting accumulated retinyl ester and perturbed meiotic process. These findings suggested an association between the schistosome with retarded growth and development in SCID mice and their perturbed metabolites and metabolic pathways, and provided a new insight into the growth and development regulation of S. japonicum worms from the metabolic level, which indicated great clues for discovery of drugs or vaccines against the parasites and disease with more researches.

Oral Administration of Lactobacillus delbrueckii during the Suckling Phase Improves Antioxidant Activities and Immune Responses after the Weaning Event in a Piglet Model

Early colonization in the gut by probiotics influences the progressive development and maturity of antioxidant and immune system functionality in the future. This study investigated the impact of orally administrated Lactobacillus delbrueckii (LAB) during the suckling phase on future antioxidant and immune responses of the host, using a piglet model. One hundred neonatal piglets received saline (CON) or LAB at the amounts of 1, 2, 3, and 4 mL at 1, 3, 7, and 14 d of age, respectively. The piglets were weaned at the age of 21 d and fed until the age of 49 d. Serum, liver, and intestinal samples were obtained at 21, 28, and 49 d of age. The results showed that LAB tended to decrease serum 8-hydroxy-2-deoxyguanosine concentration and decreased the concentration of serum and hepatic malondialdehyde, but increased the activity of hepatic glutathione peroxidase on days 21, 28, and 49. The concentrations of secretory immunoglobulin A and some inflammatory cytokines and chemokines were increased (P < 0.05) in the intestinal mucosa of LAB-treated piglets on days 21, 28, and 49 compared to that of CON piglets. Likewise, protein expression of cyclooxygenase 2 and inducible nitric oxide synthase in the intestine of LAB-treated piglets was increased (P < 0.05) during the whole period. These results indicate that administration of LAB to the suckling piglet could improve antioxidant capacity and stimulate intestinal immune response, and these long-lasting effects are also observed up to 4 weeks after weaning. A proper utilization of LAB to neonates would be beneficial to human and animal's future health.

Effects of supplemental L-methionine on growth performance and redox status of turkey poults compared with the use of DL-methionine

This study was conducted to test the effects of dietary supplementation of feed grade L-Met on growth performance and redox status of turkey poults compared with the use of conventional DL-Met. Three hundred and eighty five newly hatched turkey poults were weighed and allotted to 5 treatments in a completely randomized design and the birds were fed dietary treatments for 28 d, including a basal diet (BD), the BD + 0.17 or 0.33% DL-Met or L-Met (representing 60, 75, and 90% of the requirement by National Research Council (NRC) for S containing AA, respectively). Increasing Met supplementation from 0 to 0.33% increased (P < 0.05) weight gain (690 to 746 g) and feed intake (1,123 to 1,248 g) of turkey poults. Supplementing L-Met tended (P = 0.053) to reduce feed to gain ratio (1.70 to 1.63) compared with DL-Met. The relative bioavailability of L-Met to DL-Met was 160% based on a multilinear regression analysis of weight gain. Supplementing Met regardless of its sources decreased (P < 0.05) malondialdehyde (3.29 to 2.47 nmol/mg protein) in duodenal mucosa compared with birds in the BD. Supplementing L-Met tended (P = 0.094) to decrease malondialdehyde (1.27 to 1.16 nmol/mg protein) and increase glutathione (3.21 to 3.45 nmol/mg protein) in the liver compared with DL-Met. Total antioxidant capacity, protein carbonyl, and morphology of duodenum and jejunum were not affected by Met sources. In conclusion, dietary supplementation of 0.33% Met to a diet with S containing AA meeting 60% of the NRC requirement enhanced weight gain, feed intake, and redox status by reducing oxidative stress in the gut and liver of turkey poults during the first 28 d of age. Use of L-Met tended to enhance feed efficiency and was more effective in reducing oxidative stress and increasing glutathione in the liver compared with the use of DL-Met. The use of L-Met as a source of Met replacing DL-Met seems to be beneficial to turkey poults during the first 28 d of age.

Identification of activation of tryptophan-NAD+ pathway as a prominent metabolic response to thermally oxidized oil through metabolomics-guided biochemical analysis

Consumption of thermally oxidized oil is associated with metabolic disorders, but oxidized oil-elicited changes in the metabolome are not well defined. In this study, C57BL/6 mice were fed the diets containing either control soybean oil or heated soybean oil (HSO) for 4 weeks. HSO-responsive metabolic events were examined through untargeted metabolomics-guided biochemical analysis. HSO directly contributed to the presence of new HSO-derived metabolites in urine and the decrease of polyunsaturated fatty acid-containing phospholipids in serum and the liver. HSO disrupted redox balance by decreasing hepatic glutathione and ascorbic acid. HSO also activated peroxisome proliferator-activated receptors, leading to the decrease of serum triacylglycerols and the changes of cofactors and products in fatty acid oxidation pathways. Most importantly, multiple metabolic changes, including the decrease of tryptophan in serum; the increase of NAD⁺ in the liver; the increases of kynurenic acid, nicotinamide and nicotinamide N-oxide in urine; and the decreases of the metabolites from pyridine nucleotide degradation in the liver indicated that HSO activated tryptophan-NAD⁺ metabolic pathway, which was further confirmed by the upregulation of gene expression in this pathway. Because NAD⁺ and its metabolites are essential cofactors in many HSO-induced metabolic events, the activation of tryptophan-NAD⁺ pathway should be considered as a central metabolic response to the exposure of HSO.

Effects of dietary tryptophan levels on performance and biochemical variables of plasma and intestinal mucosa in yellow-feathered broiler breeders

The effects of dietary tryptophan (Trp) levels on performance and biochemical variables of plasma and intestinal mucosa in broiler breeder hens were investigated in this study. A total of 780 Lingnan yellow-feathered broiler breeder hens were randomly assigned in one of five dietary treatments with six replicates per treatment (26 birds per replicate). The breeder hens were fed either the basal diet (0.11% Trp) or the basal diet supplemented to 0.15%, 0.19%, 0.23% and 0.27% Trp, from 197 to 259 days of age. Graded levels of Trp from 0.11% to 0.27% in the diet produced quadratic (p < .05) responses in laying rate, average daily egg production, and feed conversion ratio, and quadratic (p < .01) responses in total large follicle weight and average large follicle weight. An increase in fertilization rate of total eggs was observed in breeders fed 0.27% Trp, and hatchability was higher in breeders fed 0.23% and 0.27% Trp than with 0.19% Trp (p < .05). The content of uric acid N decreased with 0.15% and 0.23% dietary Trp (p < .05). The content of GSH and the GSH-to-GSSG ratio in plasma were reduced by 0.15%, 0.19% and 0.27% Trp diets (p < .05). A higher activity of GST in plasma was observed with 0.15% Trp in relation to 0.23% and 0.27% Trp (p < .05). The activity of Na⁺ -K⁺ -ATPase of plasma in birds fed 0.27% Trp was lower than in those fed 0.15% Trp and the control birds (p < .05). There were significant influences of dietary Trp levels on S6K1, B⁰ AT1, Nrf2, TLR4, TNF-α and IL-6 transcripts of ileal mucosa (p < .05). The optimal dietary Trp level was 0.203% or 254 mg per hen per day, for Chinese yellow-feathered broiler breeder hens aged from 197 to 259 days.

Pigs experimentally infected with an enterotoxigenic strain of Escherichia coli have improved feed efficiency and indicators of inflammation with dietary supplementation of tryptophan and methionine in the immediate post-weaning period

This experiment tested the hypothesis that pigs challenged with an enterotoxigenic strain of E. coli (ETEC) will improve performance by dietary supplementation of sulfur amino acids (SAA) and tryptophan (Trp) above the current recommended levels in the immediate post-weaning period. Male pigs (n = 96) weighing 6.2 ± 0.78 kg (mean ± s.d.) and weaned at 21 days were stratified into one of four treatments based on weaning weight (n = 24). Four diets were formulated [11.2 MJ NE/kg; 20.1% crude protein, 1.25% standardised ileal digestible (SID) lysine (Lys)] according to a 2 × 2 factorial arrangement of treatments with two levels of SID SAA : Lys ratio (0.52 vs 0.60) and two levels of SID Trp : Lys ratio (0.16 vs 0.24). Diets did not contain any antimicrobial compounds. Pigs were individually housed and were fed diets for 14 days after weaning. Pigs were infected with ETEC (3.44 × 108 CFU/mL, serotype O149 : K91 : K88) on Days 5, 6, and 7 after weaning. Pigs were bled on Days 5, 8 and 14 and subsequently analysed for plasma levels of acute-phase proteins, urea, cytokines (Days 5 and 8 only) and amino acids (Days 5 and 8 only). Increasing Trp (P = 0.036) and SAA (P = 0.028) improved feed conversion ratio, and combined supplementation of SAA and Trp further improved FCR than individual supplementation of either SAA or Trp (P = 0.092). Dietary treatments had no impact on the incidence of post-weaning diarrhoea (P > 0.05). Increasing SAA increased shedding of ETEC on Days 12 and 14 after weaning (P < 0.019). Increasing dietary Trp reduced the intensity of inflammation (as measured by APP Index = [(C-reactive protein × PigMAP)/apolipoprotein A1]) immediately after infection with ETEC (P < 0.05), while increasing dietary SAA reduced the APP index on 24 h and 7 days after ETEC infection (P < 0.05). Increasing dietary SAA reduced plasma levels of interferon-gamma regardless of dietary Trp or day of sampling (P = 0.043). Increasing dietary SAA decreased plasma urea (PU) levels on Days 5, 8 and 14 (P < 0.05). These data indicate that Trp supplementation reduced the intensity of inflammation and SAA supplementation decreased the pro-inflammatory interferon-gamma response and improved protein utilisation, as measured by PU, whereas supplementation with both Trp and SAA improved feed conversion ratio.

Effects of different dietary tryptophan : lysine ratios and sanitary conditions on growth performance, plasma urea nitrogen, serum haptoglobin and ileal histomorphology of weaned pigs

A total of 180 mixed-sex pigs (Duroc × (Yorkshire × Landrace); average initial body weight of 7.36 ± 0.2 kg) weaned at 21 ± 1 days were fed corn-soybean meal-wheat-based diets to determine the optimal standardized ileal digestible (SID) tryptophan to lysine ratio (Trp : Lys) in a 2 × 5 factorial arrangement (two sanitary conditions: clean (CL) and unclean (UCL), and five dietary treatments (SID Trp : Lys (16, 18, 20, 22 and 24%)). In each sanitary condition, blood was collected on days 0 and 14 to determine plasma urea nitrogen and on day 14, ileal tissue (one pig per pen) was collected for the measurement of gut morphology. Pigs kept under UCL conditions had lower growth rate (P < 0.05) than under CL conditions. Under CL conditions, the estimated optimal SID Trp : Lys for average daily gain (ADG) was 19.7% whereas under UCL conditions these values were 20.5% and 19.0% for ADG and gain-to-feed ratio, respectively. Under CL conditions, increasing SID Trp : Lys reduced (linear, P = 0.05) plasma urea nitrogen concentration but had no effect (P > 0.10) on villous height (VH), crypt depth ( CD) and VH : CD. In conclusion, an SID Trp : Lys to optimize ADG for pigs raised under UCL conditions was higher (4%) than CL conditions.

Deconstructing the pig sex metabolome: Targeted metabolomics in heavy pigs revealed sexual dimorphisms in plasma biomarkers and metabolic pathways

Metabolomics has opened new possibilities to investigate metabolic differences among animals. In this study, we applied a targeted metabolomic approach to deconstruct the pig sex metabolome as defined by castrated males and entire gilts. Plasma from 545 performance-tested Italian Large White pigs (172 castrated males and 373 females) sampled at about 160 kg live weight were analyzed for 186 metabolites using the Biocrates AbsoluteIDQ p180 Kit. After filtering, 132 metabolites (20 AA, 11 biogenic amines, 1 hexose, 13 acylcarnitines, 11 sphingomyelins, 67 phosphatidylcholines, and 9 lysophosphatidylcholines) were retained for further analyses. The multivariate approach of the sparse partial least squares discriminant analysis was applied, together with a specifically designed statistical pipeline, that included a permutation test and a 10 cross-fold validation procedure that produced stability and effect size statistics for each metabolite. Using this approach, we identified 85 biomarkers (with metabolites from all analyzed chemical families) that contributed to the differences between the 2 groups of pigs ( < 0.05 at the stability statistic test). All acylcarnitines and almost all biogenic amines were higher in castrated males than in gilts. Metabolites involved in tryptophan catabolism had the largest differences (i.e., delta = 20% for serotonin) between castrated males (higher) and gilts (lower). The level of several AA (Ala, Arg, Gly, His, Lys, Ser, Thr, and Trp) was higher in gilts (delta was from approximately 1.0 to approximately 4.8%) whereas products of AA catabolism (taurine, 2-aminoadipic acid, and methionine sulfoxide) were higher in castrated males (delta was approximately 5.0-6.0%), suggesting a metabolic shift in castrated males toward energy storage and lipid production. Similar general patterns were observed for most sphingomyelins, phosphatidylcholines, and lysophosphatidylcholines. Metabolomic pathway analysis and pathway enrichment identified several differences between the 2 sexes. This metabolomic overview opened new clues on the biochemical mechanisms underlying sexual dimorphism that, on one hand, might explain differences in terms of economic traits between castrated male pigs and entire gilts and, on the other hand, could strengthen the pig as a model to define metabolic mechanisms related to fat deposition.

Effect of High Dietary Tryptophan on Intestinal Morphology and Tight Junction Protein of Weaned Pig

Tryptophan (Trp) plays an essential role in pig behavior and growth performances. However, little is known about Trp's effects on tight junction barrier and intestinal health in weaned pigs. In the present study, twenty-four (24) weaned pigs were randomly assigned to one of the three treatments with 8 piglets/treatments. The piglets were fed different amounts of L-tryptophan (L-Trp) as follows: 0.0%, 0.15, and 0.75%, respectively, named zero Trp (ZTS), low Trp (LTS), and high Trp (HTS), respectively. No significant differences were observed in average daily gain (ADG), average daily feed intake (ADFI), and gain: feed (G/F) ratio between the groups. After 21 days of the feeding trial, results showed that dietary Trp significantly increased (P < 0.05) crypt depth and significantly decreased (P < 0.05) villus height to crypt depth ratio (VH/CD) in the jejunum of pig fed HTS. In addition, pig fed HTS had higher (P < 0.05) serum diamine oxidase (DAO) and D-lactate. Furthermore, pig fed HTS significantly decreased mRNA expression of tight junction proteins occludin and ZO-1 but not claudin-1 in the jejunum. The number of intraepithelial lymphocytes and goblet cells were not significantly different (P > 0.05) between the groups. Collectively, these data suggest that dietary Trp supplementation at a certain level (0.75%) may negatively affect the small intestinal structure in weaned pig.