Methionine Source and Level Modulate Gut pH, Amino Acid Transporters and Metabolism Related Genes in Broiler Chickens

This study determined the effects of two methionine (Met) sources at three total sulfur amino acids (TSAA) to lysine ratios (TSAA/Lys) on gut pH, digestive enzyme activity, amino acid transporter expression, and Met metabolism of broilers. The birds were randomly assigned to a 2 × 3 factorial arrangement with Met sources (dl-Met and dl-2-hydroxy-4-(methylthio)-butanoic acid (OH-Met)) and TSAA/Lys (0.58, 0.73, and 0.88) from 1 to 21 days. The results demonstrated that dl-Met and OH-Met supported the same growth performance, but high TSAA/Lys ratio reduced the feed intake and body weight (P < 0.05). OH-Met reduced the crop chyme pH and enhanced the jejunal lipase activity (P < 0.05). ATB0,+ expression decreased with increased dl-Met levels in the duodenum; the low TSAA/Lys ratio induced a stronger mRNA expression of basolateral Met transporters. OH-Met resulted in an increase of cystathionine β-synthase expression in the liver and a decrease in serum homocysteine levels at middle TSAA/Lys ratio compared with dl-Met treatment (P < 0.05). In conclusion, two Met sources support the same growth, but OH-Met acidified the crop chyme. The investigated transporter transcripts differed significantly along the small intestine. At the middle TSAA/Lys ratio, OH-Met showed a higher metabolic tendency of the trans-sulfuration pathway compared with dl-Met.

Metagenome-assembled genome reveals species and functional composition of Jianghan chicken gut microbiota and isolation of Pediococcus acidilactic with probiotic properties

BACKGROUND

Chickens are one of the most widely farmed animals worldwide and play a crucial role in meat and egg production. Gut microbiota is essential for chickens' health, disease, growth, and egg production. However, native chickens such as Jianghan chickens have better meat and egg production quality than centralized chickens, their intestinal microbial diversity is richer, and the potential gut microbial resources may bring health benefits to the host.

RESULTS

The bacterial species composition in the gut microbiota of Jianghan chickens is similar to that of other chicken breeds, with Phocaeicola and Bacteroides being the most abundant bacterial genera. The LEfSe analysis revealed significant differences in species composition and functional profiles between samples from Jingzhou and the other three groups. Functional annotation indicated that the gut microbiota of Jianghan chickens were dominated by metabolic genes, with the highest number of genes related to carbohydrate metabolism. Several antibiotic resistance genes (ARGs) were found, and the composition of ARGs was similar to that of factory-farmed chickens, suggesting that antibiotics were widely present in the gut microbiota of Jianghan chickens. The resistance genes of Jianghan chickens are mainly carried by microorganisms of the Bacteroidota and Bacillota phylum. In addition, more than 829 isolates were selected from the microbiota of Jianghan chickens. Following three rounds of acid and bile tolerance experiments performed on all the isolated strains, it was determined that six strains of Pediococcus acidilactici exhibited consistent tolerance. Further experiments confirmed that three of these strains (A4, B9, and C2) held substantial probiotic potential, with P. acidilactici B9 displaying the highest probiotic potential.

CONCLUSIONS

This study elucidates the composition of the intestinal microbiota and functional gene repertoire in Jianghan chickens. Despite the absence of antibiotic supplementation, the intestinal microbial community of Jianghan chickens still demonstrates a profile of antibiotic resistance genes similar to that of intensively reared chickens, suggesting resistance genes are prevalent in free-ranging poultry. Moreover, Jianghan and intensively reared chickens host major resistance genes differently, an aspect seldom explored between free-range and pastured chickens. Furthermore, among the 829 isolates, three strains of P. acidilatici exhibited strong probiotic potential. These findings provide insights into the unique gut microbiota of Jianghan chickens and highlight potential probiotic strains offering benefits to the host. Video Abstract.

MethylRAD Sequencing Technology Reveals DNA Methylation Characteristics of Apostichopus japonicus of Different Ages

The A. japonicus industry has expanded significantly, but no research has focused on determining the age of A. japonicus during farming. Correctly estimating the age of A. japonicus can provide a decision-making basis for the breeding process and data for the protection of A. japonicus aquatic germplasm resources. DNA methylation levels in the body wall of Apostichopus japonicus at 4 months, 1 year, 2 years, and 3 years old were determined using MethylRAD-Seq, and differentially methylated genes were screened. A total of 441 and 966 differentially methylated genes were detected at the CCGG and CCWGG sites, respectively. Aspartate aminotransferase, succinate semialdehyde dehydrogenase, isocitrate dehydrogenase, the histone H2AX, heat shock protein Hsp90, aminopeptidase N, cell division cycle CDC6, Ras GTPase activating protein (RasGAP), slit guidance ligand slit1, integrin-linked kinase ILK, mechanistic target of rapamycin kinase Mtor, protein kinase A Pka, and autophagy-related 3 atg3 genes may play key roles in the growth and aging process of A. japonicus. This study provides valuable information regarding age-related genes for future research, and these candidate genes can be used to create an "epigenetic clock".

Factors influencing the development of gastrointestinal tract and nutrient transporters' function during the embryonic life of chickens-A review

Intestinal morphology and regulation of nutrient transportation genes during the embryonic and early life of chicks influence their body weight and feed conversion ratio through the growing period. The intestine development can be monitored by measuring villus morphology and enzymatic activity and determining the expression of nutrient transporters genes. With the increasing importance of gut development and health in broiler production, considerable research has been directed towards factors affecting intestine development. Thus, this article reviews (1) intestinal development during embryogenesis, and (2) maternal factors, in ovo administration, and incubation conditions that influence intestinal development during embryogenesis. Conclusively, (1) chicks from heavier eggs may have a better-developed intestine than chicks from younger ones, (2) in ovo supplementation with amino acids, minerals, vitamins or a combination of several probiotics and prebiotics stimulates intestine development and increases the expression of intestine mucosal-related genes and (3) the long storage period, improper incubation temperature and imbalanced ventilation can negatively influence intestinal morphology and nutrient transporters gene expression. Finally, understanding the intestine development during embryonic life will enable us to enhance the productivity of broilers.

Quercetin Alleviates Inflammation and Energy Deficiency Induced by Lipopolysaccharide in Chicken Embryos

Energy deficiency causes multiple organ dysfunctions after LPS induction. Quercetin is a phenolic compound found in herbal medicines. However, the effects of quercetin in alleviating LPS-induced energy deficiency remain unclear. In the present study, an in vivo LPS-induced inflammation model was established in chicken embryos. Specific pathogen-free chicken embryos (n = 120) were allocated to control, PBS with or without ethanol, quercetin (10, 20, or 40 nmol, respectively), and LPS (125 ng/egg) with or without quercetin groups. Fifteen day old embryonated eggs were injected with the abovementioned solutions via the allantoic cavity. On embryonic day 19, the tissues of the embryos were collected for histopathological examination using frozen oil red O staining, RNA extraction, real-time quantitative polymerase chain reaction, and immunohistochemical investigations. The glycogen and lipid contents in the liver increased after LPS stimulation as compared with the PBS group, whereas quercetin decreased the accumulation as compared with the LPS group. The mRNA expressions of AMPKα1 and AMPKα2 in the duodena, ceca, and livers were upregulated after LPS induction as compared with the PBS group, while quercetin could downregulate these expressions as compared with the LPS group. The immunopositivity of AMPKα2 in the villus, crypt, lamina propria, tunica muscularis, and myenteric plexus in the duodena and in the cytoplasms of hepatocytes significantly increased after LPS induction when compared with the PBS group (p < 0.01), whereas the immunopositivity to AMPKα2 in the quercetin treatment group significantly decreased when compared with the LPS group (p < 0.01 or p < 0.05). The LPS-induced high expressions of transcription factor PPARα and glucose transporter (SGLT1) were blocked by quercetin in the duodena, ceca, and livers. Quercetin treatment improved the LPS-induced decrease in APOA4 in the duodena, ceca, and livers. The mRNA expression of PEPT1 in the duodena and ceca increased after LPS challenge, whereas quercetin could downregulate PEPT1 gene expression. These data demonstrate that quercetin improved the energy deficiency induced by LPS in chicken embryos. The LPS-induced inflammation model was established to avoid the effect of LPS exposure from the environment and intestinal flora. The results form the basis the administration of quercetin pretreatment (in ovo infection) to improve the energy state of chicken embryos and improve the inflammation response.

Metagenomic analysis reveals the microbiome and antibiotic resistance genes in indigenous Chinese yellow-feathered chickens

Yellow-feathered chickens have great nutritional value and are widely and traditionally used in China, on an industrial scale as broilers. The presence of intestinal microbes has been shown to correlate with poultry performance and serves as an essential reservoir of antibiotic resistance genes (ARGs). Antibiotic resistance is a major public health concern. Here, we investigated functional characteristics of the gut microbiome of indigenous Chinese yellow-feathered chickens (the Huiyang Bearded, Xinghua, Huaixiang, Zhongshan Shanlan, Qingyuan Partridge, and Yangshan chickens) through metagenomic sequencing and reconstructed 409 draft genomes, including 60 novel species and 6 novel genera. Furthermore, we assessed the functions of the intestinal microbial communities and examined the ARGs within them. The results showed that the microbial populations of yellow-feathered broilers were primarily dominated by Bacteroidetes and Firmicutes at the phylum level and Bacteroides at the genus level. Furthermore, the Qingyuan Partridge chicken showed a significantly higher abundance of Prevotella than the other five breeds of chicken. Principal coordinates analysis indicated significant differences in the structures of microbial communities and ARGs, based on the binary Jaccard distance, among the six chicken breeds. Moreover, 989 ARGs conferring tetracycline, multidrug, and aminoglycoside resistance were identified, which represented more than 80% of the faecal resistomes; the most abundant gene in the yellow-feathered chickens was tet(Q). In addition, we found the greatest abundance of resistance genes in Xinghua chickens, indicating that Xinghua chickens are highly resistant to antibiotics. Overall, our findings revealed differences in the gut microbial community structure of indigenous Chinese yellow-feathered broiler breeds and the composition and characteristics of ARGs and antibiotic resistance that enabled us to reconstruct the yellow-feathered chicken gut microbial community genomes. The current data significantly improves our knowledge of the gut microbiome and antibiotic resistance of popular broiler breeds in China.

Characterization of the cecal microbiome composition of Nigerian indigenous chickens

Poultry cecum microbes are dynamic and complex. They play important roles in disease prevention, detoxification of harmful substances, nutrient processing, and ingestion harvesting. It may be possible to increase poultry productivity by better understanding and controlling the microbial population. We analyzed the composition and function of Nigerian hens' cecal microbiota using high-throughput sequencing methods. Using high-throughput sequencing of the 16S rRNA genes (V1-V9) hypervariable regions, the cecal microbiota of three Nigerian indigenous chicken genotypes (Naked neck, Frizzle, and Normal feather) was described and compared. A total of two phyla were represented among the three genotypes (Firmicutes and Proteobacteria). Microbiological diversity was found in the community, with naked neck having the most evenness, followed by normal feather, which had the least. There were a lot of similarities between the naked neck and frizzle feather chicken groups when it came to genetic diversity between them. For example, the bacterial cecal microbiota of the naked neck chickens was more diverse, with a higher concentration of motility proteins, two-component systems, bacterial secretion systems, and the formation and breakdown of secondary metabolites. More understanding on gut microbiota roles and interactions will help Nigerian poultry farmers improve their methods and give valuable data for the study of bacteria in the chicken gut.

In ovo threonine supplementation affects ileal gene expression of nutrient transporters in broilers inoculated post-hatch with Salmonella Enteritidis

The effect of in ovo threonine (Thr) supplementation on the ileal expression of glucose, peptide and amino acid transporters was assessed in Salmonella Enteritidis-challenged broiler chicks. At 17.5 days of incubation, fertile eggs were supplemented in the amniotic fluid with sterile saline or 3.5% threonine. Hatchlings were individually weighed, and Salmonella Enteritidis negative status was confirmed. At 2 days of age, half of the birds of each group were inoculated with sterile nutrient broth or Salmonella Enteritidis inoculum. Relative expression of sodium-dependent glucose transporter 1 (SGLT1), glucose transporter 2 (GLUT2), di- and tri-peptide transporter 1 (PepT1) and alanine, serine, cysteine, threonine transporter (ASCT1) was assessed at hatch, 2 and 9 days of age, i.e., before inoculation and 7 days post-inoculation (dpi). At 9 days of age (7dpi), threonine increased SGLT1 and GLUT2 expression, whereas GLUT2 expression decreased in Salmonella-challenged birds. There was a significant interaction between threonine and Salmonella for PepT1 and ASCT1. Threonine increased PepT1 expression only in non-challenged birds. In addition, in ovo supplementation increased expression of ASCT1 regardless of post-hatch inoculation; Salmonella inoculation resulted in decreased expression of ASCT1 only in supplemented birds. The results suggest that while intra-amniotic threonine administration in broiler embryos increases the expression of genes related to the absorption of monosaccharides and amino acids, Salmonella challenge may negatively affect the expression of protein related transporters in the ileum of broilers.

Expression of genes associated with nutrient uptake in intestines of chickens with different growth potentials show temporal changes but are not correlated with growth

The study was designed to compare the expression of genes that encode proteins located at either the brush border (BB) or basolateral (BL) of the gut epithelium among fast and slow-growing broilers.Six lines of chicks with different growth capacities were used: Ross 708, Hubbard H1 (HH1), Cobb 500, Longnecker's Heritage (LHR), Red-Bro, and the Athens Canadian Randombred Control (ACRB). Birds were sampled between embryonic day (ED) 19 and day 35 post-hatch (PH).Performance parameters indicated that Ross 708, HH1, and Cobb 500 had the highest body weights (BW) while ACRBs had the lowest.Quantitative RT-PCR was performed on 13 genes encoding proteins associated with nutrient processing and uptake. Statistical analysis was carried out (ANOVA) for eight BB genes: Aminopeptidase N (APN), four amino acid transporters, (ATB^o,+, B^oAT, b^o,+AT, EAAT3) a di- and tri- peptide transporter (PepT1), and two sugar transporters (GLUT5 and SGLT1). Analysis of four amino acid transporters (CAT1, CAT2, LAT1, and γ⁺LAT1), and a single sugar transporter (GLUT2) associated with BL was carried out.Four BB associated genes (APN, EAAT3, B^oAT, and b^0,+AT) in the small intestine were negatively correlated with growth.In most cases, genes encoding BB proteins increased in expression over time (P<0.05) in the small intestine, while, in the caeca, the expression decreased (P<0.05). The mRNA of BL-associated proteins showed decreased (P<0.05) expression over time in all gut segments, with exception of GLUT2, which increased in expression in the small intestine.The temporal changes in gene expression were consistent among bird lines and BB associated genes tended to increase over time, while BL associated genes tended to decrease over time. Correlation analysis indicated that mRNA expression of nutrient transporter genes may not be a good predictor of growth potential.

Effect of dipeptide on intestinal peptide transporter 1 gene expression: An evaluation using primary cultured chicken intestinal epithelial cells

Peptide transporter 1 (PepT1) is a transporter responsible for absorbing dipeptide and tripeptide in enterocytes and is upregulated by dipeptide in mammals. It has not been certain whether intestinal PepT1 expression is responsive to dipeptides in chickens because of the lack of in vitro study using the cultured enterocytes. This study established a primary culture model of chicken intestinal epithelial cells (IECs) in two‐dimensional monolayer culture using collagen gel by which the response of chicken PepT1 gene expression to dipeptide stimuli was evaluated. The cultured chicken IECs showed the epithelial‐like morphology attached in a patch‐manner and exhibited positive expression of cytokeratin and epithelial cadherin, specific marker proteins of epithelial cells. Moreover, the chicken IECs exhibited the gene expression of intestinal cell type‐specific marker, villin1, mucin 2, and chromogranin A, suggesting that the cultured IECs were composed of enterocytes as well as goblet and enteroendocrine cells. PepT1 gene expression was significantly upregulated by synthetic dipeptide, glycyl‐l‐glutamine, in the cultured IECs. From the results, we herein suggested that dipeptide is a factor upregulating PepT1 gene expression in chicken IECs.

The effect of delayed feeding post-hatch on caeca development in broiler chickens

1. Broiler chicks are frequently deprived of food up to 72 h due to uneven hatching rates, management procedures and transportation to farms. Little is known about the effect of delayed feeding due to extended hatching times on the early neonatal development of the caeca. Therefore, the objective of this study was to investigate the developmental changes and effects of a 48-h delay in feed access immediately post-hatch (PH) on the caeca.2. After hatch, birds (Ross 708) were randomly divided into two treatment groups (n = 6 battery pen/treatment). One group (early fed; EF) received feed and water immediately after hatch, while the second group (late fed; LF) had access to water but had delayed access to feed for 48 h. Contents averaging across all regions of the caeca were collected for mRNA expression as well as for histological analysis at -48, 0, 4 h PH and then at 1, 2, 3, 4, 6, 8, 10, 12 and 14 days PH.3. Expression of MCT-1 (a nutrient transporter), Cox7A2 (related to mitochondrial function) IgA, pIgR, and ChIL-8 (immune function) genes was affected by delayed access to feed that was dependent by the time PH. Expression of immune and gut barrier function-related genes (LEAP2 and MUC2, respectively) was increased in LF group. There was no effect of feed delay on expression of genes related to mitochondrial functions in the caeca, although developmental changes were observed (ATP5F1B, Cox4|1). Caecal mucus and muscle thickness were affected by delayed access to feed during caeca development.4. The data suggested a limited effect of delayed feed access PH on the developmental changes in caecal functions. However, the caeca seemed to be relatively resistant to delayed access to feed early PH, with only a few genes affected.

Critical transporters of methionine and methionine hydroxyl analogue supplements across the intestine: What we know so far and what can be learned to advance animal nutrition

DL-methionine (DL-Met) and its analogue DL-2-hydroxy-4-(methylthio) butanoic acid (DL-methionine hydroxyl analogue or DL-MHA) have been used as nutritional supplements in the diets of farmed raised animals. Knowledge of the intestinal transport mechanisms involved in these products is important for developing dietary strategies. This review provides updated information of the expression, function, and transport kinetics in the intestine of known Met-linked transporters along with putative MHA-linked transporters. As a neutral amino acid (AA), the transport of DL-Met is facilitated by multiple apical sodium-dependent/-independent high-/low-affinity transporters such as ASCT2, B⁰AT1 and rBAT/b^0,+AT. The basolateral transport largely relies on the rate-limiting uniporter LAT4, while the presence of the basolateral antiporter y⁺LAT1 is probably necessary for exchanging intracellular cationic AAs and Met in the blood. In contrast, the intestinal transport kinetics of DL-MHA have been scarcely studied. DL-MHA transport is generally accepted to be mediated simply by the proton-dependent monocarboxylate transporter MCT1. However, in-depth mechanistic studies have indicated that DL-MHA transport is also achieved through apical sodium monocarboxylate transporters (SMCTs). In any case, reliance on either a proton or sodium gradient would thus require energy input for both Met and MHA transport. This expanding knowledge of the specific transporters involved now allows us to assess the effect of dietary ingredients on the expression and function of these transporters. Potentially, the resulting information could be furthered with selective breeding to reduce overall feed costs.

It's All About Timing: Early Feeding Promotes Intestinal Maturation by Shifting the Ratios of Specialized Epithelial Cells in Chicks

The small intestine (SI) of chicks (Gallus gallus) matures rapidly during the initial post-hatch period and acquires digestive, absorptive, and secretive capabilities. The effects of the timing of first feeding on the quantities and distribution of specialized epithelial cells, which generate and maintain SI morphology and functionality, have not yet been examined. In this study, we identified specialized SI epithelial cell sub-types, including stem, progenitor, proliferating, and differentiated cells within crypts and villi of chicks during the first 10 days post-hatch, by in situ hybridization (ISH), immunofluorescence (IF), and histochemical staining. We then examined their quantities and ratios between day of hatch and d10 in chicks that were fed upon hatch [early feeding (EF)], compared to chicks that were fed 24 h post-hatch [delayed feeding (DF)]. Results showed that EF increased total cell quantities in the crypts and villi at days 1, 3, 7, and 10, compared to DF (p < 0.0001). At d3, EF, in comparison to DF, decreased crypt stem cell proportions (p < 0.0001), increased crypt proliferating (p < 0.01) and differentiated (p < 0.05) cell proportions, and increased villus enterocyte proportions (p < 0.01). By d10, EF increased both the quantities and proportions of villus enterocytes and goblet cells, compared to DF. We conclude that feeding upon hatch, compared to 24 h-delayed feeding, enhanced SI maturation and functionality by increasing the quantities and proportions of proliferating and differentiated cells, thus expanding the digestive, absorptive, and secretive cell populations throughout the initial post-hatch period.

Effects of in ovo feeding of N-acetyl-L-glutamate on early intestinal development and growth performance in broiler chickens

The present study determined the effects of in ovo feeding (IOF) of N-acetyl-L-glutamate (NAG) on early intestinal development and growth performance of broilers. A total of 702 fertile broiler eggs were randomly divided into 3 treatments: 1) non-punctured control group, 2) saline-injected control group, and 3) NAG solution-injected group (1.5 mg/egg). At 17.5 D of incubation, 300 μL of each solution was injected into each egg of injected groups. Results indicated that the hatchability and healthy chicken rate were not affected by NAG injection (P > 0.05). Chicks from NAG solution-injected group had significantly decreased average daily feed intake and feed conversion ratio during 1-14 D than those in the non-punctured control group (P < 0.05). Compared with the non-punctured control group, IOF of NAG significantly increased the density of goblet cells in jejunum at hatch, duodenum at 7 D, and ileum at 14 D; decreased crypt depth in jejunum at hatch; and increased villus height in duodenum and jejunum and villus height:crypt depth ratio in duodenum at 7 D (P < 0.05). The intestinal mRNA expression of Na⁺-dependent neutral amino acid transporter, peptide transporter, and excitatory amino acid transporter 3 did not differ between groups at 7 or 14 D. However, the mRNA expression level of rBAT in jejunum significantly increased in the NAG solution-injected group than in the non-punctured control group at 7 D (P < 0.05). In conclusion, IOF of NAG (1.5 mg/egg) accelerated the early intestinal development by enhancing intestinal immune and absorption function, thereby positively affecting the feed efficiency for the first 2 wk post-hatch.

Effects of encapsulated essential oils and organic acids on laying performance, egg quality, intestinal morphology, barrier function, and microflora count of hens during the early laying period

The objective of this study was to investigate the effect of encapsulated essential oils and organic acids (EOA) on the growth performance, egg quality, intestinal morphology and functions, and microbial count of laying hens from week 21 to 30. A total of five hundred and four 21-wk-old layers were randomly allotted into 4 groups consisting of 7 replicates with 18 birds per replicate. The birds were fed a basic diet (CON) or diets with EOA at 150 mg/kg, 300 mg/kg, and 450 mg/kg in the other 3 groups, respectively. Compared to the CON group, the addition of 150 mg/kg EOA significantly increased laying rate (P < 0.05) of hens from week 21 to 25. A linear increasing (linear, P < 0.01) in ileal villus height of laying hens fed EOA from 150 to 300 mg/kg was observed at week 30. At week 25, the supplementation of 300 mg/kg EOA significantly increased (P < 0.05) mRNA relative expression of aminopeptidase, sodium-glucose cotransporter 1, and Na+-independent neutral amino acid transporter in duodenum and glucose transporter 2 in jejunum of laying hens compared to the CON groups. Meanwhile, the relative expression of glucose transporter 2 mRNA in the jejunum was upregulated with increasing concentration of EOA in diets (linear, P < 0.05). Hens in EOA 300 group had higher mRNA relative expression of mucin-2 in ileum (P < 0.05) than hens in CON group. Additionally, the secretory immunoglobulin in ileum A were linear decreased (linear, P < 0.01) with the increasing supplement of EOA. Dietary supplementation with EOA tended to increase (P = 0.083) the counts of Bifidobacterium in cecal digesta at week 25 and 30. In conclusion, dietary with EOA may maintain intestinal tract morphology and promote digestive and absorptive capacities and barrier function, especially at 300 mg/kg. This study provided evidence of using EOA as a potential feed additive for laying hens.

Effect of l-theanine on growth performance, intestinal development and health, and peptide and amino acid transporters expression of broilers

BACKGROUND

l-Theanine has multiple beneficial biological activities. However, there is little information about the use of l-theanine in broiler production. Therefore, this study investigated the effect of l-theanine on growth performance, intestinal development and health, and the mRNA levels of intestinal peptide and amino acid (AA) transporters of broilers.

RESULTS

Body weight and average daily gain were increased by l-theanine, whereas feed to gain ratio was decreased (quadratic, P < 0.05). Notably, the relative weight of duodenum, jejunum and ileum, villus height, villus height to crypt depth ratio, the jejunal activities of glutathione peroxidase, total antioxidant capacity, catalase and total superoxide dismutase were increased linearly and/or quadratically by l-theanine (P < 0.05), whereas crypt depth, serum d-lactic acid, and jejunal protein carbonyls and malondialdehyde content were decreased linearly and/or quadratically (P < 0.05). Moreover, l-theanine enhanced the jejunal mRNA levels of occludin, claudin-1, E-cadherin, zona occludens-1, di- and tripeptide transporter, excitatory AA transporter 3, Na⁺ -independent cationic AA transporter 1, Na⁺ -independent cationic and zwitterionic AA transporter, Na⁺ - and Cl^- -dependent neutral and cationic AA transporter, Na⁺ -independent cationic and Na⁺ -dependent neutral AA transporter (y+LAT) 1, y+LAT2, Na⁺ -independent branched-chain and aromatic AA transporter, and heavy chain corresponding to the b°^,+ transport system (linear and/or quadratic, P < 0.05).

CONCLUSIONS

l-Theanine beneficially affected the growth performance of broilers by improving intestinal development and health, and the intestinal mRNA levels of AA and peptide transporters. Therefore, l-theanine has the potential to be a promising feed additive for broilers. © 2020 Society of Chemical Industry.

Effect of early neonatal development and delayed feeding post-hatch on jejunal and ileal calcium and phosphorus transporter genes expression in broiler chickens

Calcium (Ca) and phosphorus (P) are essential minerals involved in many biological processes including bone development and mineralization. Plasma concentration of both minerals is tightly regulated, and Ca and P homeostasis is maintained via intestinal absorption, bone storage and exchange, and renal reabsorption. In the current broiler production systems, chicks are deprived of food and water for up to 72 h due to uneven hatching, hatchery procedures, and transportation time to farms. Post-hatch (PH) feed delay results in lower body and organ weight, higher feed conversion ratio and mortality, and delayed PH growth and GIT development. Little is known about the effects of early neonatal development and delayed or immediate feeding PH on Ca and P transporters. Therefore, the aim of the present study was to characterize expression patterns of Ca and P transporter genes in small intestine during the first 2 wk PH in chickens fed immediately after hatch (FED) or subjected to 48 h delayed feeding (NOTFED). Expression of all Ca and P transporters in jejunum and ileum was significantly (P < 0.05) affected by age. Among Ca transporter genes, only mRNA expression of Calbidin D28k in jejunum and Ca sensing receptor (CaSR) in ileum were significantly (P < 0.05) affected by delay in feed access. For P transporter genes' expression, only P transporter type III (PIT1) mRNA was significantly affected by age, delay in feed access, and their interaction (P < 0.05). In summary, we have shown, for the first time, early developmental changes of Ca and P transporter genes in broiler chickens. Results suggest that an increase in gene expression of some of the transporters corresponds with the switch from yolk to high starch diet. Overall, our results can be helpful in better understanding of Ca and P homeostasis in broilers.

Culture and characterization of chicken small intestinal crypts

The integrity and normal function of the small intestinal epithelium depends critically on the rapid renewal of epithelial cells from basal stem cells. The intensive proliferation that fuels this self-renewal process is confined to the intestinal crypts. Establishment of suitable protocols for crypt isolation and culture is pivotal for the studies of intestinal self-renewal mechanisms. In this study, chicken small intestinal crypts were isolated, purified, and further cultured in a Matrigel 3-D culture system. The growth factor concentration assay on the fourth d of culture showed that Group C (50 ng/mL epidermal growth factor (EGF), 100 ng/mL Noggin, and 500 ng/mL R-spondin 1) supplement in culture medium could significantly enlarge the diameter of organoids when compared with Group A (5 ng/mL EGF, 10 ng/mL Noggin, 50 ng/mL, and R-spondin 1) and Group B (10 ng/mL EGF, 20 ng/mL Noggin, and 100 ng/mL R-spondin 1) by 188.4% (P = 0.026) and 176.9% (P = 0.034), respectively. Transmission electron microscopy, neutral red staining, and 5-ethynyl-2΄-deoxyuridine incorporation demonstrated the integrated structure, high viability, and proliferative activity in cultured chicken intestinal organoids. In addition, intestinal stem cell marker genes (Olfm4, Znrf3, Hopx, and Lgr5) also could be detected in cultured intestinal organoids. Furthermore, CHIR99021 (a glycogen synthase kinase 3β inhibitor) could enhance the expression of Olfm4, Znrf3, Hopx, and Lgr5 by 750% (P = 0.001), 467% (P < 0.001), 450% (P < 0.001), and 333% (P = 0.008), respectively, indicating the responsiveness of the cultured chicken intestinal organoids to exogenous stimulus. This study modified a murine culture model and optimized it to provide a chicken intestinal organoid model for use as a physiological or pathological research platform in vitro.

Melatonin Improves Laying Performance by Enhancing Intestinal Amino Acids Transport in Hens

The high concentration of melatonin (MEL) in the intestinal mucosa suggests that it has a special physiological function in intestine. In hens, previous studies have shown that MEL treatment promoted egg-laying performance. Considering the importance of amino acids (AA) for egg formation, we hypothesized that MEL may enhance the intestinal absorption of AA from the feed, thus promoting egg laying performance. In this study, we supplemented the hens with MEL for two consecutive weeks. The results showed that, compared with control group, feeding with 0.625 mg MEL/kg diets gave rise to higher egg laying rate (by 4.3%, P = 0.016), increased eggshell thickness (by 16.9%, P < 0.01) and albumen height (by 4.5%, P = 0.042). Meanwhile, feeding with 0.625 and 2.5 mg MEL/kg diets could significantly increase serum levels of aspartic acid, threonine, serine, glutamic acid, glycine, alanine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine, arginine, and proline. Furthermore, a 0.625 mg MEL/kg diets could significantly increase the expression of PepT1 (by 3949.9%), B⁰AT (by 6045.9%), b^{0, +}AT (by 603.5%), and EAAT3 (by 412.7%) in the jejunum. Additionally, in the cultured intestinal crypt "organoids," treatment with 0.5 μM MEL could significantly enhance the expression of PepT1, b^{0, +}AT and EAAT3 mRNAs by 35.4%, 110.0%, and 160.1%, respectively. Detection of MEL concentration in serum and intestinal fluid suggested that lower dosage of MEL feeding was mainly acted on intestine locally, and further increased intestinal antioxidases (GPx-3, SOD-1 or PRDX-3) mRNA expression. Taken together, we demonstrated that MEL feeding in laying hens could locally promote the expression and function of AA transporter in small intestine by up-regulating antioxidases expression, and finally elevate laying performance.

Phylogenetic and functional characterization of the distal intestinal microbiome of rainbow trout Oncorhynchus mykiss from both farm and aquarium settings

AIMS

This study focused on comparing the phylogenetic composition and functional potential of the intestinal microbiome of rainbow trout sourced from both farm and aquarium settings.

METHODS AND RESULTS

Samples of distal intestinal contents were collected from fish and subjected to high throughput 16S rRNA sequencing, to accurately determine the composition of the intestinal microbiome. The predominant phyla identified from both groups were Tenericutes, Firmicutes, Proteobacteria, Spirochaetae and Bacteroidetes. A novel metagenomic tool, PICRUSt, was used to determine the functional potential of the bacterial communities present in the rainbow trout intestine. Pathways concerning membrane transport activity were dominant in the intestinal microbiome of all fish samples. Furthermore, this analysis revealed that gene pathways relating to metabolism, and in particular amino acid and carbohydrate metabolism, were upregulated in the rainbow trout intestinal microbiome.

CONCLUSIONS

The results suggest that the structure of the intestinal microbiome in farmed rainbow trout may be similar regardless of where the fish are located and hence could be shaped by host factors. Differences were, however, noted in the microbial community membership within the intestine of both fish populations, suggesting that more sporadic taxa could be unique to each environment and may have the ability to colonize the rainbow trout gastrointestinal tract. Finally, the functional analysis provides evidence that the microbiome of rainbow trout contains genes that could contribute to the metabolism of dietary ingredients and therefore may actively influence the digestive process in these fish.

SIGNIFICANCE AND IMPACT OF THE STUDY

To better understand and exploit the intestinal microbiome and its impact on fish health, it is vital to determine its structure, diversity and potential functional capacity. This study improves our knowledge of these areas and suggests that the intestinal microbiome of rainbow trout may play an important role in the digestive physiology of these fish.

High-throughput sequencing technology to reveal the composition and function of cecal microbiota in Dagu chicken

BACKGROUND

The chicken gut microbiota is an important and complicated ecosystem for the host. They play an important role in converting food into nutrient and energy. The coding capacity of microbiome vastly surpasses that of the host's genome, encoding biochemical pathways that the host has not developed. An optimal gut microbiota can increase agricultural productivity. This study aims to explore the composition and function of cecal microbiota in Dagu chicken under two feeding modes, free-range (outdoor, OD) and cage (indoor, ID) raising.

RESULTS

Cecal samples were collected from 24 chickens across 4 groups (12-w OD, 12-w ID, 18-w OD, and 18-w ID). We performed high-throughput sequencing of the 16S rRNA genes V4 hypervariable regions to characterize the cecal microbiota of Dagu chicken and compare the difference of cecal microbiota between free-range and cage raising chickens. It was found that 34 special operational taxonomic units (OTUs) in OD groups and 4 special OTUs in ID groups. 24 phyla were shared by the 24 samples. Bacteroidetes was the most abundant phylum with the largest proportion, followed by Firmicutes and Proteobacteria. The OD groups showed a higher proportion of Bacteroidetes (>50 %) in cecum, but a lower Firmicutes/Bacteroidetes ratio in both 12-w old (0.42, 0.62) and 18-w old groups (0.37, 0.49) compared with the ID groups. Cecal microbiota in the OD groups have higher abundance of functions involved in amino acids and glycan metabolic pathway.

CONCLUSION

The composition and function of cecal microbiota in Dagu chicken under two feeding modes, free-range and cage raising are different. The cage raising mode showed a lower proportion of Bacteroidetes in cecum, but a higher Firmicutes/Bacteroidetes ratio compared with free-range mode. Cecal microbiota in free-range mode have higher abundance of functions involved in amino acids and glycan metabolic pathway.

Di- and tripeptide transport in vertebrates: the contribution of teleost fish models

Solute Carrier 15 (SLC15) family, alias H⁺-coupled oligopeptide cotransporter family, is a group of membrane transporters known for their role in the cellular uptake of di- and tripeptides (di/tripeptides) and peptide-like molecules. Of its members, SLC15A1 (PEPT1) chiefly mediates intestinal absorption of luminal di/tripeptides from dietary protein digestion, while SLC15A2 (PEPT2) mainly allows renal tubular reabsorption of di/tripeptides from ultrafiltration, SLC15A3 (PHT2) and SLC15A4 (PHT1) possibly interact with di/tripeptides and histidine in certain immune cells, and SLC15A5 has unknown function. Our understanding of this family in vertebrates has steadily increased, also due to the surge of genomic-to-functional information from 'non-conventional' animal models, livestock, poultry, and aquaculture fish species. Here, we review the literature on the SLC15 transporters in teleost fish with emphasis on SLC15A1 (PEPT1), one of the solute carriers better studied amongst teleost fish because of its relevance in animal nutrition. We report on the operativity of the transporter, the molecular diversity, and multiplicity of structural-functional solutions of the teleost fish orthologs with respect to higher vertebrates, its relevance at the intersection of the alimentary and osmoregulative functions of the gut, its response under various physiological states and dietary solicitations, and its possible involvement in examples of total body plasticity, such as growth and compensatory growth. By a comparative approach, we also review the few studies in teleost fish on SLC15A2 (PEPT2), SLC15A4 (PHT1), and SLC15A3 (PHT2). By representing the contribution of teleost fish to the knowledge of the physiology of di/tripeptide transport and transporters, we aim to fill the gap between higher and lower vertebrates.

Growth of embryo and gene expression of nutrient transporters in the small intestine of the domestic pigeon (Columba livia)

The objective of this study was to investigate the relationship between gene expression of nutrient (amino acid, peptide, sodium and proton) transporters in the small intestine and embryonic growth in domestic pigeons (Columba livia). One hundred and twenty-five fertilized eggs were randomly assigned into five groups and were incubated under optimal conditions (temperature of 38.1 °C and relative humidity of 55%). Twenty embryos/birds from each group were sacrificed by cervical dislocation on embryonic day (E) 9, 11, 13, 15 and day of hatch (DOH). The eggs, embryos (without yolk sac), and organs (head, brain, heart, liver, lungs, kidney, gizzard, small intestine, legs, and thorax) were dissected, cleaned, and weighed. Small intestine samples were collected for RNA isolation. The mRNA abundance of intestinal nutrient transporters was evaluated by real-time reverse transcription-polymerase chain reaction (RT-PCR). We classified these ten organs into four types according to the changes in relative weight during embryonic development. In addition, the gene expression of nutrient transporters was differentially regulated by embryonic day. The mRNA abundances of b(0,+)AT, EAAT3, y(+)LAT2, PepT1, LAT4, NHE2, and NHE3 increased linearly with age, whereas mRNA abundances of CAT1, CAT2, LAT1, EAAT2, SNAT1, and SNAT2 were increased to higher levels on E9 or E11 and then decreased to lower levels until DOH. The results of correlation analysis showed that the gene expressions of b(0,+)AT, EAAT3, PepT1, LAT4, NHE2, NHE3, and y(+)LAT2 had positive correlations with body weight (0.71<correlation coefficient (CC)<0.82, P<0.0001), while CAT1, CAT2, EAAT2, SNAT1, and SNAT2 had negative correlations with body weight (-0.86<CC<-0.64, P<0.0001). The gene expressions of b(0,+)AT, EAAT3, LAT4, PepT1, NHE2, NHE3, and y(+)LAT2 showed positive correlations with intestinal weight (0.80<CC<0.91, P<0.0001), while CAT1, CAT2, and EAAT2 showed negative correlations with intestinal weight (-0.84<CC<-0.67, P<0.0001). It was concluded that the differences between growth trajectories of organs and gene expression of nutrient transporters in small intestine were due to their functional and physiological properties, which provided a comprehensive study of amino acid and peptide transporter mRNA in the small intestine during embryonic growth of pigeons.

Egg storage duration and hatch window affect gene expression of nutrient transporters and intestine morphological parameters of early hatched broiler chicks

In recent years, researchers have given emphasis on the differences in physiological parameters between early and late hatched chicks within a hatch window. Considering the importance of intestine development in newly hatched chicks, however, changes in gene expression of nutrient transporters in the jejunum of early hatched chicks within a hatch window have not been studied yet. This study was conducted to determine the effects of egg storage duration before incubation and hatch window on intestinal development and expression of PepT1 (H+-dependent peptide transporter) and SGLT1 (sodium-glucose co-transporter) genes in the jejunum of early hatched broiler chicks within a 30 h of hatch window. A total of 1218 eggs obtained from 38-week-old Ross 308 broiler breeder flocks were stored for 3 (ES3) or 14 days (ES14) and incubated at the same conditions. Eggs were checked between 475 and 480 h of incubation and 40 chicks from each egg storage duration were weighed; chick length and rectal temperature were measured. The chicks were sampled to evaluate morphological parameters and PepT1 and SGLT1 expression. The remaining chicks that hatched between 475 and 480 h were placed back in the incubator and the same measurements were conducted with those chicks at the end of hatch window at 510 h of incubation. Chick length, chick dry matter content, rectal temperature and weight of small intestine segments increased, whereas chick weight decreased during the hatch window. The increase in the jejunum length and villus width and area during the hatch window were higher for ES3 than ES14 chicks. PepT1 expression was higher for ES3 chicks compared with ES14. There was a 10.2 and 17.6-fold increase in PepT1 and SGLT1 expression of ES3 chicks at the end of hatch window, whereas it was only 2.3 and 3.3-fold, respectively, for ES14 chicks. These results suggested that egg storage duration affected development of early hatched chicks during 30 h of hatch window. It can be concluded that the ES14 chicks would be less efficiently adapted to absorption process for carbohydrates and protein than those from ES3 at the end of the hatch window.

mRNA expression of amino acid transporters, aminopeptidase, and the di- and tri-peptide transporter PepT1 in the intestine and liver of posthatch broiler chicks

Amino acid (AA) transporter proteins are responsible for the movement of amino acids in and out of cells. Aminopeptidase cleaves AAs from the N-terminus of polypeptides making them available for transport, while PepT1 is a di- and tripeptide transporter. In the intestine, these proteins are present on the brush border and basolateral membranes of enterocytes, and are essential for the uptake of AAs into enterocytes and their release into circulation. The purpose of this study was to determine the level of transcription of these genes after hatch in 3 regions of the small intestine, the ceca, and liver. Heritage broiler chicks (n=5) were sampled at day after hatch and days 3, 5, 7, 10, 12, 14, 17, and 21 posthatch, and mRNA expression level was measured using absolute quantitation. The small intestine (duodenum, jejunum, and ileum) expressed the largest quantities of each gene tested. The expression in the ceca and liver was 1 to 3 orders of magnitude less than that of the small intestine. The expression of basolateral transporters in the small intestine was more constant over days posthatch than the expression of brush border transporters. In the ceca the expression of the brush border transporters decreased over the sampling period, while expression of basolateral genes was relatively constant. In the liver the expression of Na+ independent cationic and zwitterionic amino acid transporter (bo,+AT), Na+ independent cationic amino acid transporter 2 (CAT2), excitatory amino acid transporter 3 (EAAT3), and the heavy chain corresponding to the bo,+) system (rBAT) significantly decreased at 12 days posthatch; however, the expression of Na+ independent cationic and Na+ dependent neutral amino acid transporter 1 (y+LAT1), Na+ coupled neutral amino acid transporter 1; (SNAT1), and Na+ coupled neutral amino acid transporter 2 (SNAT2) significantly increased at day 5 posthatch compared to day 1 and these levels remained throughout the rest of the sampling period. The current results suggest that at 1 day posthatch chicks are capable of AA processing and transport in the intestine as well as the liver. Additionally the ability of the ceca in transporting AA from the lumen may decrease with age. The liver should be capable of amino acid transport, but its capabilities may be more specific since the expression of several transporters in this organ is either absent or very low.

Deciphering chicken gut microbial dynamics based on high-throughput 16S rRNA metagenomics analyses

Background

Chicken gut microbiota has paramount roles in host performance, health and immunity. Understanding the topological difference in gut microbial community composition is crucial to provide knowledge on the functions of each members of microbiota to the physiological maintenance of the host. The gut microbiota profiling of the chicken was commonly performed previously using culture-dependent and early culture-independent methods which had limited coverage and accuracy. Advances in technology based on next-generation sequencing (NGS), offers unparalleled coverage and depth in determining microbial gut dynamics. Thus, the aim of this study was to investigate the ileal and caecal microbiota development as chicken aged, which is important for future effective gut modulation.

Material and methods

Ileal and caecal contents of broiler chicken were extracted from 7, 14, 21 and 42-day old chicken. Genomic DNA was then extracted and amplified based on V3 hyper-variable region of 16S rRNA. Bioinformatics, ecological and statistical analyses such as Principal Coordinate Analysis (PCoA) was performed in mothur software and plotted using PRIMER 6. Additional analyses for predicted metagenomes were performed through PICRUSt and STAMP software package based on Greengenes databases.

Results

A distinctive difference in bacterial communities was observed between ilea and caeca as the chicken aged (P < 0.001). The microbial communities in the caeca were more diverse in comparison to the ilea communities. The potentially pathogenic bacteria such as Clostridium were elevated as the chicken aged and the population of beneficial microbe such as Lactobacillus was low at all intervals. On the other hand, based on predicted metagenomes analysed, clear distinction in functions and roles of gut microbiota such as gene pathways related to nutrient absorption (e.g. sugar and amino acid metabolism), and bacterial proliferation and colonization (e.g. bacterial motility proteins, two-component system and bacterial secretion system) were observed between ilea and caeca, respectively (P < 0.05).

Conclusions

The caeca microbial communities were more diverse in comparison to ilea. The main functional differences between the two sites were found to be related to nutrient absorption and bacterial colonization. Based on the composition of the microbial community, future gut modulation with beneficial bacteria such as probiotics may benefit the host.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-015-0051-7) contains supplementary material, which is available to authorized users.

Expression of digestive enzymes and nutrient transporters in Eimeria-challenged broilers

Avian coccidiosis is a disease caused by the intestinal protozoa Eimeria. The site of invasion and lesions in the intestine is species-specific, for example E. acervulina affects the duodenum, E. maxima the jejunum, and E. tenella the ceca. Lesions in the intestinal mucosa cause reduced feed efficiency and body weight gain. The growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to compare the expression of digestive enzymes, nutrient transporters and an antimicrobial peptide in broilers challenged with either E. acervulina, E. maxima or E. tenella. The genes examined included digestive enzymes (APN and SI), peptide and amino acid transporters (PepT1, ASCT1, b(0,+)AT/rBAT, B(0)AT, CAT1, CAT2, EAAT3, LAT1, y(+)LAT1 and y(+)LAT2), sugar transporters (GLUT1, GLUT2, GLUT5 and SGLT1), zinc transporter (ZnT1) and an antimicrobial peptide (LEAP2). Duodenum, jejunum, ileum and ceca were collected 7 days post challenge. E. acervulina challenge resulted in downregulation of various nutrient transporters or LEAP2 in the duodenum and ceca, but not the jejunum or ileum. E. maxima challenge produced both downregulation and upregulation of nutrient transporters and LEAP2 in all three segments of the small intestine and ceca. E. tenella challenge resulted in the downregulation and upregulation of nutrient transporters and LEAP2 in the jejunum, ileum and ceca, but not the duodenum. At the respective target tissue, E. acervulina, E. maxima and E. tenella infection caused common downregulation of APN, b(0,+)AT, rBAT, EAAT3, SI, GLUT2, GLUT5, ZnT1 and LEAP2. The downregulation of nutrient transporters would result in a decrease in the efficiency of protein and polysaccharide digestion and uptake, which may partially explain the weight loss. The downregulation of nutrient transporters may also be a cellular response to reduced expression of the host defense protein LEAP2, which would diminish intracellular pools of nutrients and inhibit pathogen replication.