Effects of dietary threonine supplementation on intestinal barrier function and gut microbiota of laying hens

Relationship between feed efficiency and gut microbiota in laying chickens under contrasting feeding conditions

The gut microbiota is known to play an important role in energy harvest and is likely to affect feed efficiency. In this study, we used 16S metabarcoding sequencing to analyse the caecal microbiota of laying hens from feed-efficient and non-efficient lines obtained by divergent selection for residual feed intake. The two lines were fed either a commercial wheat-soybean based diet (CTR) or a low-energy, high-fibre corn-sunflower diet (LE). The analysis revealed a significant line x diet interaction, highlighting distinct differences in microbial community composition between the two lines when hens were fed the CTR diet, and more muted differences when hens were fed the LE diet. Our results are consistent with the hypothesis that a richer and more diverse microbiota may play a role in enhancing feed efficiency, albeit in a diet-dependent manner. The taxonomic differences observed in the microbial composition seem to correlate with alterations in starch and fibre digestion as well as in the production of short-chain fatty acids. As a result, we hypothesise that efficient hens are able to optimise nutrient absorption through the activity of fibrolytic bacteria such as Alistipes or Anaerosporobacter, which, via their production of propionate, influence various aspects of host metabolism.

The Impact of Essential Amino Acids on the Gut Microbiota of Broiler Chickens

The research involving the beneficial aspects of amino acids being added to poultry feed pertaining to performance, growth, feed intake, and feed conversion ratio is extensive. Yet currently the effects of amino acids on the gut microbiota aren't fully understood nor have there been many studies executed in poultry to explain the relationship between amino acids and the gut microbiota. The overall outcome of health has been linked to bird gut health due to the functionality of gastrointestinal tract (GIT) for digestion/absorption of nutrients as well as immune response. These essential functions of the GI are greatly driven by the resident microbiota which produce metabolites such as butyrate, propionate, and acetate, providing the microbiota a suitable and thrive driven environment. Feed, age, the use of feed additives and pathogenic infections are the main factors that have an effect on the microbial community within the GIT. Changes in these factors may have potential effects on the gut microbiota in the chicken intestine which in turn may have an influence on health essentially affecting growth, feed intake, and feed conversion ratio. This review will highlight limited research studies that investigated the possible role of amino acids in the gut microbiota composition of poultry.

Gut microbiota bridges dietary nutrients and host immunity

Dietary nutrients and the gut microbiota are increasingly recognized to cross-regulate and entrain each other, and thus affect host health and immune-mediated diseases. Here, we systematically review the current understanding linking dietary nutrients to gut microbiota-host immune interactions, emphasizing how this axis might influence host immunity in health and diseases. Of relevance, we highlight that the implications of gut microbiota-targeted dietary intervention could be harnessed in orchestrating a spectrum of immune-associated diseases.

High amylose to amylopectin ratios in nitrogen-free diets decrease the ileal endogenous amino acid losses of broiler chickens

This study explored the variation of ileal endogenous amino acid (IEAA) losses and its influencing factors in chickens offered nitrogen-free diets (NFD) containing different ratios of amylose to amylopectin (AM/AP). A total of 252 broiler chickens at 28 d old were randomly allocated into 7 treatment groups for a 3-d trial. The dietary treatments included a basal diet (control), a NFD containing corn starch (CS), and 5 NFD with AM/AP ratios of 0.20, 0.40, 0.60, 0.80, and 1.00, respectively. As the AM/AP ratio increased, the IEAA losses of all AAs, starch digestibility and maltase activity linearly decreased (P < 0.05), but the DM digestibility linearly and quadratically decreased (P < 0.05). Compared with the control, the NFD increased the number of goblet cells and its regulatory genes mucin-2 and krüppel-like factor 4 (KLF-4) while decreasing serum glucagon and thyroxine concentrations, ileal villus height, and crypt depth (P < 0.05). Additionally, NFD with lower AM/AP ratios (0.20 and 0.40) decreased the ileal microbiota species richness (P < 0.05). In all NFD groups, the number of Proteobacteria increased whereas the abundance of Firmicutes dropped (P < 0.05). However, the broilers in the AM/AP 0.60 group were closer to the digestive physiological state of chickens fed the control diet, with no significant change in maltase activity and mucin-2 expression (P < 0.05). In conclusion, increasing AM/AP ratio in a NFD decreased the IEAA losses and the apparent ileal digestibility of starch but inevitably resulted in malnutrition and disruption of gut microbiota homeostasis. This study recommends AM/AP in NFD at 0.60 to measure IEAA of broiler chickens.

Dietary supplementation with Chinese herb ultrafine powder improves intestinal morphology and physical barrier function by altering jejunal microbiota in laying hens

Introduction

Chinese medicinal herbs play important roles in anti-inflammatory, antioxidant, and antibacterial activities. However, the effects of Chinese herb ultrafine powder (CHUP) on laying hens still need to be elucidated. Therefore, this study aimed to evaluate the effects of dietary CHUP supplementation on jejunal morphology, physical barrier function, and microbiota in laying hens.

Methods

A total of 576 Xinyang black-feather laying hens (300 days old) were randomly assigned into eight groups, with eight replicates per group and nine hens per replicate. The hens were fed a basal diet (control group) and a basal diet supplemented with 0.5% Leonuri herba (LH group), 0.25% Ligustri lucidi fructus (LF group), 0.25% Taraxaci herba (TH group), 0.5% LH + 0.25% LF (LH-LF group), 0.5% LH + 0.25% TH (LH-TH group), 0.25% LF + 0.25% TH (LF-TH group), and 0.5% LH + 0.25% LF + 0.25% TH (LH-LF-TH group), respectively, for 120 days.

Results

The results showed that dietary LH-LF and LH-LF-TH supplementation increased (p < 0.05) the jejunal villus height to crypt depth ratio of laying hens. Dietary LF-TH supplementation up-regulated jejunal claudin-5 expression, while LH supplementation up-regulated jejunal claudin-1 expression and increased the jejunal abundances of potentially beneficial bacteria related to short-chain fatty acids and bacteriocins production, such as Blautia, Carnobacterium, Clostridiales, and Erysipelotrichales (p < 0.05). In addition, dietary LH supplementation enriched (p < 0.05) the tetracycline biosynthesis, butirosin/neomycin biosynthesis, and D-arginine/D-ornithine metabolism, whereas steroid biosynthesis and limonene/pinene degradation were enriched (p < 0.05) in the LH-LF and LH-LF-TH groups. Moreover, Spearman's correlation analysis revealed the potential correlation between the abundance of the jejunal microbiota and jejunal morphology and the physical barrier function of laying hens.

Discussion

Collectively, these findings suggest that dietary CHUP supplementation could enhance the beneficial bacteria abundance, physical barrier function, and metabolic function associated with short-chain fatty acids and bacteriocins production. Moreover, combined supplementation of dietary CHUP showed better effects than the sole CHUP supplementation.

Dietary threonine and lysophospholipid supplement in broiler chickens: effect on productive performance, carcass variables, cecal microbiota activity, and jejunal morphology

The objective of this experiment was to investigate the efficacy of lysophospholipid (LPL) in combination with different levels of threonine (Thr) on productive performance, jejunal morphometric variables, cecal microbial population, and carcass characteristics of male broiler chickens. Four hundred 1-day-old male broiler chicks were distributed into eight experimental groups with five replicates, each of ten birds. Factors were two levels of 0 or 0.1% Lipidol as LPL supplement and four inclusion amount of Thr (100, 105, 110, or 115% of requirements) in the diets. During 1 to 35 days, inclusion of LPL supplementation in diets improved the body weight gain (BWG) and feed conversion ratio (FCR) of broilers (P < 0.05). Besides, FCR was significantly greater in the birds fed with 100% Thr compared to the other inclusion rates of Thr (P < 0.05). The jejuna villus length (VL) and crypt depth (CD) were greater in the birds fed with LPL-supplemented diets (P < 0.05) while the greatest VH/CD and villus surface was observed in the birds fed with 105% of dietary Thr (P < 0.05). In cecal microbiota composition, Lactobacillus population was lower in broilers which received diet containing 100% Thr compared to the other group receiving more than 100% Thr (P < 0.05). In conclusion, inclusion of LPL supplements and amounts greater than Thr requirement in diet improved productive performance and jejunal morphology of male broiler chickens.

Effects of protease enzyme supplementation and varying levels of amino acid inclusion on productive performance, egg quality, and amino acid digestibility in laying hens from 30 to 50 weeks of age

An experiment was conducted to evaluate the effects of protease supplementation and reduced digestible amino acid (dAA)/ crude protein (CP) level on productive performance, AA digestibility, and egg quality parameters in Hy-Line W-36 laying hen from 30 to 50 wk of age. A total of 768 hens (12 replicates of 8 hens per treatment) were equally and randomly allocated into 8 experimental diets in a 4 × 2 factorial arrangement of dAA/CP level (100, 95, 90, and 85% of breeder recommendation) and protease (exclusion or inclusion). Protease was added at 60 g/metric ton of feed in the inclusion group. Hens were housed in raised-wire cages with a stocking density of 870 cm²/bird. The adequate (100%) diet was based on corn and soybean meal and formulated based on the digestible (d) Lys and dAAs (dMet, dThr, dTrp, dTSAA, dIle, and dVal) to meet 100% of the current management guide recommendation. Variations in dAA/CP (95, 90, and 85% diets) were accomplished by reducing the 100% dAA by 5, 10, and 15%, respectively. All diets were supplemented with phytase at 500 phytase units (FTU)/kg. Data were analyzed using PROC GLM of SAS 9.4. There was a main effect of dAA/CP level on 85% diet where it had a lower mean hen-day egg production (HDEP, P < 0.01), egg mass (EM, P < 0.01), and higher feed conversion ratio (FCR, P < 0.001). Higher egg weight (P < 0.01) was observed in 95 and 100% dAA/CP level diets. However, Haugh unit (P < 0.01) and albumen height (P < 0.01) were higher in 85 and 90% diets. The inclusion of protease reduced the feed consumption (P = 0.0247), FCR for dozens of eggs (P = 0.0049) from 30 to 49 wk of age without affecting the HDEP or EM. Protease supplementation and dAA/CP level had an effect on the apparent ileal digestibility (AID) of CP (P = 0.019), Lys (P < 0.01), Thr (P < 0.01), Trp (P = 0.017), and Val (P < 0.01). Addition of protease significantly increased egg income (P = 0.033) and return on investment (P = 0.00223) from 30 to 37 wk of age. At 38 to 50 wk of age, dAA/CP level had a significant effect on egg income (P < 0.001), feed cost (P < 0.001), and return on investment (P < 0.001). This experiment indicates that the inclusion of protease in 90 and 95% lower dAA/CP diets could help improve the digestibility of CP, and key amino acids and maintain productive performance of corn and soybean meal-based diets in Hy-Line W-36 laying hen from 30 to 50 wk of age.

Nutritional supplements for the control of avian coccidiosis

Coccidiosis is acclaimed as the most prevalent enteric parasitic ailment of poultry. It is caused by an apicomplexan protozoon of the genus Eimeria, which resides in chicken intestinal epithelium leading to intestinal damage. As a result, bloody droppings are there, feed efficiency is reduced, the growth rate is impaired, and egg production is temporarily decreased. Treatment and prevention of coccidiosis are primarily accomplished by inoculating live vaccines and administering anticoccidial drugs. Due to anticoccidials’ continuous and excessive use, the mounting issue is drug resistant Eimeria strains. The poultry industry has managed resistance-related issues by suggesting shuttle and rotation schemes. Furthermore, new drugs have also been developed and introduced, but it takes a long time and causes cost inflation in the poultry industry. Moreover, government disallows growth promoters and drugs at sub-therapeutic doses in poultry due to increased concerns about the drug residues in poultry products. These constraints have motivated scientists to work on alternative ways to control coccidiosis effectively, safely, and sustainably. Using nutritional supplements is a novel way to solve the constraints mentioned above. The intriguing aspects of using dietary supplements against coccidiosis are that they reduce the risk of drug-resistant pathogen strains, ensure healthy, nutritious poultry products, have less reliance on synthetic drugs, and are typically considered environmentally safe. Furthermore, they improve productivity, enhance nonspecific immunity, preventing oxidation of fats (acting as antioxidants) and inflammation (acting as an anti-inflammatory). The present manuscript focuses on the efficacy, possible mechanism of action, applications, and different facets of nutrition supplements (such as organic acids, minerals, vitamins, probiotics, essential oils, amino acids, dietary nucleotides, feed enzymes, and yeast derivatives) as feed additive for treating poultry coccidiosis.

Dietary and phytogenic inclusion effects on the broiler chicken cecal ecosystem

Dietary modulation in broilers is crucial for the establishment of beneficial microbiota and, subsequently, the promotion of intestinal health. In this trial, a 2 × 2 factorial design was used with two different specifications with respect to dietary metabolizable energy (ME) and crude protein (CP) levels (i.e., 95% and 100% of recommendations) and phytogenic levels (0 and 150 mg/kg). Levels of total bacteria, Bacteroides spp., Lactobacillus spp., and Clostridium cluster XIVa attached to the cecal mucosa and in the cecal digesta were lower in broilers fed the 95% ME and CP specification diets, as was the molar ratio of butyric acid. In addition, the relative activity of autoinducers-2 (AI-2) and the expression levels of TLR4 and AvBD6 were increased. Phytogenic supplementation reduced cecal digesta levels of Escherichia coli and Clostridium cluster I levels, and increased Clostridium cluster IV levels. Moreover, the butyric acid molar ratio and the relative activity of AI-2 were increased, whereas the concentration of branched VFAs and the expression of AvBD6 and LEAP2 were reduced by phytogenic administration. Dietary specifications and phytogenic interactions were shown for the cecal-attached microbiota composition, metabolic activity of digesta microbiota, relative expression of autoinducers-2, and relative expression of toll-like signaling molecules and host antimicrobial peptides. In conclusion, it has been shown that ME and CP dietary specifications, combined or not with phytogenics, modulate multilevel gut biomarkers ranging from microbiota composition and metabolic activity to microbial communications and host signaling, inflammation, and defense.

Effects of Dietary Oregano Essential Oil on Cecal Microorganisms and Muscle Fatty Acids of Luhua Chickens

This experiment was conducted to investigate the effects of oregano essential oil on the cecal microorganisms and muscle fatty acids of Luhua chickens. One hundred and twenty 49-day-old healthy dewormed Luhua chickens were randomly divided into four groups with three replicates per group and ten chickens per replicate. The corn−quinoa and soybean meal diets were supplemented with 0 (Q8 group), 50 (QO50 group), 100 (QO100 group) and 150 mg·kg−1 (QO150 group) of oregano essential oil, respectively, and the experiment lasted for 75 days. The composition of intestinal flora was detected by Illumina sequencing of the 16S rRNA V4 region, and the composition and content of fatty acids in the muscles were analyzed by gas chromatography. The results showed that dietary oregano essential oil can effectively increase the contents of elaidic acid (C18:ln9t), polyunsaturated fatty acids (PUFAs) and n-3 polyunsaturated fatty acids (n-3 PUFAs) in breast muscle tissues. However, the fatty acid composition and PUFA content in leg muscle tissues were not significantly improved. According to a 16S rRNA high-throughput sequencing analysis, dietary oregano essential oil supplementation with a certain concentration can change the cecal microbial community composition of broilers. At the phylum level, Elusimicrobia in the QO150 group was significantly lower than that in Q8 group (p < 0.05). At the genus level, Phascolarctobacterium, Parasutterella and Bilophila in the experimental groups (QO50, QO100 and QO150) were significantly lower than those in the Q8 group (p < 0.05). An enrichment analysis of the microbial function found that the amino acid metabolism, energy metabolism, metabolism, signal transduction and genetic information processing were mainly enriched in the experimental groups, which promoted the digestion and absorption of nutrients and enhanced intestinal barrier functioning. An analysis of the association between fatty acids and microbes found that the abundance of microbiota was significantly correlated with partially saturated fatty acids (SFAs) and unsaturated fatty acids (UFAs) (p < 0.05). In conclusion, the dietary addition of oregano essential oil can effectively improve cecal microbial community composition, promote the digestion and absorption of nutrients, and enhance intestinal barrier functioning. It can significantly improve the content of some fatty acids, and there was a certain correlation between caecum microorganisms and fatty acid deposition in muscles.

Sodium humate alters the intestinal microbiome, short-chain fatty acids, eggshell ultrastructure, and egg performance of old laying hens

This study investigated the effect of sodium humate supplementation on changes in the intestinal microbiome, intestinal short-chain fatty acids production, and trace element absorption in older laying hens, with consequent effects on egg performance and shell quality. We used the same hens as their own control; a total of 720 laying hens aged 422 days were randomly divided into three replicates, with the CON group fed a commercial diet at 422–441 days of age and the HANa group fed a commercial diet supplemented with 0.05% sodium humate at 442–461 days of age. Compared with the CON group, in the HANa group, Bacteroidetes and Actinobacteria were significantly increased, whereas, Firmicutes was significantly decreased. Further, Veillonella, Enterococcus, Lactobacillus, and Turricibacter significantly decreased, and Peptoniphilus, Helcococcus, GW-34, Psychrobacter, Anaerococcus, Corynebacterium, Facklamia, Trichococcus, Gallicola, Clostridium, and Oscillospira were significantly increased. The results showed that sodium humate significantly altered the alpha and beta diversity and changed the structure of the intestinal microbiome. Acetic acid, isovaleric acid, and isobutyric acid, among short-chain fatty acids were significantly increased in the HANa group, whereas trace elements such as Mn, Zn, and Fe were significantly reduced. The eggshell strength and ultrastructure were significantly altered. In this study, sodium humate was found to alter the intestinal microbiome structure of aged hens, change the production of short-chain fatty acids, and promote the absorption of trace elements to keep aged hens from experiencing a decrease in egg production performance.

Dietary supplementation with fermented plant product modulates production performance, egg quality, intestinal mucosal barrier, and cecal microbiota in laying hens

Fermented plant product (FPP) is a kind of functional complex containing probiotics and a variety of bioactive substances, which has multiple physiological functions. However, there is no systematic appraisal of FPP as a feed additive for laying hens. This study was conducted to evaluate the utilization of FPP in laying hens. A total of 120 healthy 34-week-old Xianju layers with similar body weight and egg production were randomly allocated into two dietary treatments with four replicates per treatment and 15 birds per replicate for 8 weeks. The dietary treatments included the basal diet without FPP (CON group) and CON diet supplemented with 500 mg/kg of FPP (FPP group). Compared with the CON group, the egg production and egg mass were significantly increased in the FPP group from 38 to 42 and 34 to 42 weeks of age (P < 0.05). Birds fed with the diet containing 500 mg/kg FPP had higher albumen height (P < 0.01) and Haugh unit (P < 0.05) than those of the controls. FPP supplementation significantly increased the villus height (VH) and crypt depth (CD) in the jejunum of laying hens (P < 0.01), as well as the ratio of VH to CD (P < 0.05). The mRNA expression of tight junctions showed that dietary supplementation with FPP significantly increased the expression levels of Occludin (P < 0.01) and ZO-1 (P < 0.05) in jejunum of hens compared to the control group. In addition, dietary supplementation with FPP influenced cecal microbiota of laying hens, which was characterized by the changes in the microbial community composition, including the increased abundances of Firmicutes, Faecalibacterium, Oscillospira, Clostridium, Ruminococcus, and Coprococcus, along with the decreased abundance of Bacteroidetes, Proteobacteria, Phascolarctobacterium, Odoribacter, Desulfovibrio, and Mucispirillum. Spearman's correlation analysis revealed that bacteria such as Faecalibacterium, Ruminococcus, Coprococcus, and Blautia were significantly and positively correlated with the intestinal barrier markers (P < 0.05), with extremely significant correlations between Ruminococcus and ZO-1, and Coprococcus and Occludin (P < 0.01), whereas Desulfovibrio had a negative correlation with the expression of Occludin (P < 0.05). As it can be concluded, FPP supplementation increased the egg production, egg mass, albumen height, and Haugh unit of laying hens, and improved intestinal health by ameliorating intestinal barrier function, which may be partially attributed to the regulation of cecal microbiota. Our findings suggest that FPP has the potential to be used as a feed additive to promote the performance of layers.

Influence of Eimeria maxima coccidia infection on gut microbiome diversity and composition of the jejunum and cecum of indigenous chicken

Coccidiosis is an economically significant protozoan disease and an intracellular parasite that significantly impacts poultry production. The gastrointestinal tract microbiota plays a central role in host health and metabolism, and these microbes enhance chickens’ immune systems and nutrient absorption. In this study, we analyzed the abundance and diversity of microbiota of the jejunum and cecum of a dual-purpose indigenous Horro chicken following Eimeria maxima infection. We compared microbial abundance, composition, and diversity at the 4- and 7- days post-infection using 16S rRNA gene sequencing. We obtained, on average, 147,742 and 132,986 high-quality sequences per sample for jejunum and cecum content, respectively. Firmicutes, Proteobacteria, Campilobacterota and Bacteroidota were the major microbial phylum detected in the jejunum content. Firmicutes were the dominant phylum for 4- and 7-days jejunum control groups accounting for (>60% of the sequences). In the infected group Campilobacterota was the dominant phylum in the jejunum (> 24% of sequences) at 4-and 7-days post-infection groups, while Proteobacteria was predominant at 4- and 7-days post-infection of the cecum (> 40% of the sequences). The microbial genus Lactobacillus and Helicobacter were found in the jejunum, while Alistipes, Barnesiella and Faecalibacterium were detected in the cecum. In the jejunum, Helicobacter was dominant at 4 -and-7 days post-infection (≥24%), and Lactobacillus was dominant at 4 -and 7- days in the control group (> 50%). In 4- and 7-days post-infection, Alistipes genus was the more prevalent (> 38%) in the cecum. Thus, clear differences were observed in the bacterial microbiota distribution and abundance between the jejunum and cecum, as well as between infected and control groups for both tissues. The results indicate that chicken intestinal microbial imbalance (dysbiosis) is associated with Eimeria parasite infection and will likely affect the host-microbial non-pathogenic and pathogenic molecular interactions.

Increased arginine, lysine, and methionine levels can improve the performance, gut integrity and immune status of turkeys but the effect is interactive and depends on challenge conditions

Arginine (Arg), lysine (Lys), and methionine (Met) can be used to support the health status of turkeys. The present study investigated selected performance, gut integrity, and immunological parameters in turkeys reared in optimal or challenge conditions. The experiment lasted for 28 days, and it had a completely randomized 2 × 3 factorial design with two levels of dietary Arg, Lys and Met (high or low) and challenge with Clostridium perfringens (C. perfringens), Escherichia coli lipopolysaccharide (LPS) or no challenge (placebo). Increased dietary levels of Arg, Lys and Met had a beneficial effect on turkey performance and immunological parameters, and it improved selected indicators responsible for maintaining gut integrity in different challenge conditions. Under optimal conditions (with no challenge), high ArgLysMet diets did not compromise bird performance and they improved selected performance parameters in challenged birds. The immune system of turkeys was not excessively stimulated by high ArgLysMet diets, which did not disrupt the redox balance and had no negative effect on gut integrity. High ArgLysMet diets increased the expression levels of selected genes encoding nutrient transporters and tight junction proteins. However, the influence exerted by different dietary inclusion levels of Arg, Lys and Met on gut integrity was largely determined by the stressor (C. perfringens vs. LPS). Further studies are required to investigate the role of Arg, Lys and Met levels in the diet on the immune response, gut function and performance of turkeys in different challenge conditions.

Dietary Supplementation of Chitosan Oligosaccharide–Clostridium butyricum Synbiotic Relieved Early-Weaned Stress by Improving Intestinal Health on Pigeon Squabs (Columba livia)

According to a previous study, we had found that early weaning causes harm to growth performance, intestinal morphology, activity of digestive enzymes, and antioxidant status in pigeon squabs (Columba livia). Chitosan oligosaccharides (COS) and Clostridium butyricum have been reported to have great potential to improve the growth performance and intestinal health of early-weaned animals. Therefore, the aim of this study is to explore whether dietary supplementation with COS-C. butyricum synbiotic could relieve early-weaned stress by evaluating its effects on growth performance and intestinal health in pigeon squabs. A total of 160 squabs (weaned at 7 days of age) were randomly divided into 5 groups: the control group, fed with artificial crop milk; the COS supplementation group, fed with artificial crop milk + 150 mg/kg COS; and three synbiotic supplementation groups, fed with artificial crop milk + 150 mg/kg COS + 200, 300, and 400 mg/kg C. butyricum. The results showed that a diet supplemented with COS-C. butyricum synbiotic benefitted the growth performance of early-weaned squabs; even so the differences were not significant among the five groups (p > 0.05). In addition, dietary supplementation of 150 mg/kg COS + 300~400 mg/kg C. butyricum significantly improved the intestinal morphology (especially villus surface area and the ratio of villus height to crypt depth), the activity of digestive enzymes (lipase, trypsin, and leucine aminopeptidase) in duodenum contents, and the production of total short-chain fatty acids and acetic acid in ileum content (p < 0.05). Additionally, dietary supplementation of 150 mg/kg COS + 400 mg/kg C. butyricum benefitted gut health by improving the antioxidant capacity (glutathione peroxidase and total antioxidant capacity) and cytokine status (IL-4 and IL-10) (p < 0.05), as well as by improving the intestinal microbiota diversity. In conclusion, our results revealed that dietary supplementation with synbiotic (150 mg/kg COS + 300~400 mg/kg C. butyricum) could relieve early-weaned stress by maintaining intestinal health in pigeon squabs.

Natural Products of Plants and Animal Origin Improve Albumen Quality of Chicken Eggs

Albumen quality is recognized as one of the major yardsticks in measuring egg quality. The elasticity of thick albumen, a strong bond in the ovomucin-lysozyme complex, and excellent biological properties are indicators of high-quality albumen. The albumen quality prior to egg storage contribute to enhance egg’s shelf life and economic value. Evidence suggests that albumen quality can deteriorate due to changes in albumen structure, such as the degradation of β-ovomucin subunit and O-glyosidic bonds, the collapse of the ovomucin-lysozyme complex, and a decrease in albumen protein-protein interaction. Using organic minerals, natural plants and animal products with antioxidant and antimicrobial properties, high biological value, no residue effect and toxicity risk could improve albumen quality. These natural products (e.g., tea polyphenols, marigold extract, magnolol, essential oils, Upro (small peptide), yeast cell wall, Bacillus species, a purified amino acid from animal blood, and pumpkin seed meal) are bio-fortified into eggs, thus enhancing the biological and technological function of the albumen. Multiple strategies to meeting laying hens’ metabolic requirements and improvement in albumen quality are described in this review, including the use of amino acids, vitamins, minerals, essential oils, prebiotics, probiotics, organic trace elements, and phytogenic as feed additives. From this analysis, natural products can improve animal health and consequently albumen quality. Future research should focus on effects of these natural products in extending shelf life of the albumen during storage and at different storage conditions. Research in that direction may provide insight into albumen quality and its biological value in fresh and stored eggs.

Effects of L-valine in layer diets containing 0.72% isoleucine

In a previous study with LSL-LITE layers (-23 to 30-week-old), isoleucine at 0.72% and 0.84% produced values for FCR at 1.45 and 1.44, respectively and shared significance with 0.78% isoleucine (1.49). Considering that FCR is an important standard in the poultry industry due to the cost for adding feed ingredients such as synthetic amino acids and the low FCR of 1.45, 0.72% isoleucine was chosen for further study with LSL-LITE layers (n = 490 at 33- to 40-week-old) to determine effects on production and egg quality. The study included 7 diets (2730 Kcal kg metabolizable energy and constant isoleucine at 0.72%) containing varying quantities of valine [0.72 (Control), 0.75, 0.78, 0.81, 0.84, 0.87 or 0.90%] x 7 replicates x 10 hens/replicate. Significance at P ≤ 0.05 and P < 0.10 was determined. Level and week were significant for feed intake, egg production, and FCR; the interaction of level x week (L*W) was significant for feed intake and FCR. An isoleucine:valine of 1.233 corresponding to 0.72% isoleucine and 0.87% valine produced the lowest FCR of 1.30 (a 2.26% decrease compared to the Control at 1.33 ± 0.04). All measurements for external egg quality, except shape index and eggshell thickness, were significant for level. Week was significant for all parameters except shell thickness; L*W was significant for external quality measurements except shape index and shell thickness. Level, week, and L*W were significant for internal egg quality measurements. Serum protein and H1 titer were significant for level. Various production, egg quality, and biochemical measurements were significantly different from the control (0.72% isoleucine and 0.72% valine) at 0.81 to 0.87% valine. Findings of this study will aid researchers and commercial producers in narrowing the range of isoleucine, valine, and leucine needed for effects on particular parameters. Knowledge gained from this and others studies will eventually lead to an understanding of synergistic and antagonistic effects of branched chain amino acids in feed for various genetic types of layers throughout their productive lifetime.

Novel Insight Into Nutritional Regulation in Enhancement of Immune Status and Mediation of Inflammation Dynamics Integrated Study In Vivo and In Vitro of Teleost Grass Carp (Ctenopharyngodon idella): Administration of Threonine

This study aims to investigate the effects of threonine (Thr) on immunoregulation in vivo and in vitro of teleost grass carp (Ctenopharyngodon idella). Juveniles (9.53 ± 0.02 g) were reared for 8 weeks with respective Thr diet (3.99, 7.70, 10.72, 14.10, 17.96, and 21.66 g/kg) and then challenged with Aeromonas hydrophila for in vivo study. Macrophages isolated from head kidney were treated in vitro for 48 h with L-Thr (0, 0.5, 1.0, 2.0, 4.0, and 8.0 mM) after 6 h of lipopolysaccharide induction. The results showed that, compared with Thr deficiency (3.99 g/kg), the optimal dietary Thr (14.10g/kg) affected the immunocyte activation in the head kidney (HK) and spleen (SP) by downregulating the mRNA expressions of MHC-II and upregulating CD4 (not CD8), and it mediated the innate immune by enhancing the activities of lysozyme (LZ), acid phosphatase content of complement 3 (C3) and C4, increasing the mRNA abundances of hepcidin, liver expressed antimicrobial peptide-2A (LEAP-2A), LEAP-2B, β-defensin1, downregulating tumor necrosis factor α (TNF-α), IL-6, IL-1β, IL-12p35, IL-12p40, IL-17AF1, and IL-17D partly by attenuating RORγ1 transcriptional factor and nuclear factor kappa B p65 (NF-κBp65) signaling cascades [IKKβ/IκBα/NF-κBp65] and upregulating transforming growth factor β1 (TGF-β1), IL-4/13A, -4/13B, IL-10, and IL-22 partly by GATA-3. Besides these, the optimal dietary Thr regulated the adaptive immune by upregulating the mRNAs of immunoglobulin M (IgM) and IgZ (not IgD). Moreover, 2 mM Thr downregulated in vitro the mRNA abundances of colony stimulating factor-1, inducible nitric oxide synthase, mannose receptor 1, matrix metalloproteinase2 (MMP-2), and MMP-9 significantly (P < 0.05), indicating that Thr could attenuate the M1-type macrophages’ activation. Moreover, L-Thr downregulated the mRNA transcripts of TNF-α, IL-6, and IL-1β associated with impairing the SOCS1/STAT1 signaling and upregulated IL-10 and TGF-β1 partly by accentuating the SOCS3/STAT3 pathway. The above-mentioned observations suggested that Thr improved the immune status in the immune organs of fish by enhancing the immune defense and mediating the inflammation process. Finally, based on the immune indices of LZ activity in HK and C3 content in SP, the optimal Thr for immune enhancement in juvenile grass carp (9.53–53.43 g) was determined to be 15.70 g/kg diet (4.85 g/100 g protein) and 14.49 g/kg diet (4.47 g/100 g protein), respectively.

Enhancement of protein production using synthetic brewery wastewater by Haematococcus pluvialis

Microalgae is a sustainable protein source that has been widely applied in animal feeds, functional foods, pharmaceutical, and cosmeceutical industries. Waste products could be a potential cost-saving and nutrient-rich substrate in the cultivation of microalgae for protein production. This study aims to investigate the cultivation condition of Haematococcus pluvialis for protein synthesis using synthetic brewery wastewater (BW). H. pluvialis was cultivated in the Bold's Basal Medium (BBM) mixed with synthetic BW at different concentrations. Various cultivation conditions including brewer's spent grain hydrolysate (BSGH) concentrations, pH, and light sources were studied. The molecular weight, amino acids profile and antioxidant activity of synthesized protein were determined. Fed-batch cultivation using different percentages of fresh medium replacement for enhancing protein production was investigated. The 20% fed-batch cultivation reached 27 ×10⁵ ± 0.42 cells/mL, and 4-fold of the protein content of 64.93 ± 5.30% of dry weight was recorded on day-13. Seven essential amino acids (lysine, threonine, histidine, phenylalanine, isoleucine, leucine, methionine) were produced in fed-batch cultivation. Red LED obtained the highest DPPH radical scavenging activity of 27.47 ± 0.98%. The findings suggested that BW is a promising substrate in the cultivation of H. pluvialis to commercially produce protein for numerous industrial applications.

Pine (Pinus massoniana Lamb.) Needle Extract Supplementation Improves Performance, Egg Quality, Serum Parameters, and the Gut Microbiome in Laying Hens

The effects of Masson pine (Pinus massoniana Lamb.) needle extract (PNE) on gastrointestinal disorders and oxidative stress have been widely investigated using experimental models; however, the functions and mechanisms of these effects in chicken models remain unknown. We investigated the effects of Masson PNE supplementation on performance, egg quality, serum parameters, and the gut microbiome in laying hens. A total of 60 healthy 50-week-old Peking Pink laying hens with similar body conditions and egg production were randomly divided into the control (CON) (0 mg/kg PNE), PNE100 (100 mg/kg PNE), PNE200 (200 mg/kg PNE), and PNE400 (400 mg/kg PNE) groups, with fifteen replicates per treatment and one hen per replicate. Compared with the CON group, egg mass, feed conversion ratios, and yolk weight were significantly increased (p < 0.01) in the PNE100 group. Dietary supplementation of 100 mg/kg PNE increased the serum total protein, albumin, and glucose concentrations (p < 0.01) and decreased the alanine aminotransferase activity (p < 0.05) compared with those of the CONs. Hens in the PNE100 group had reduced serum malondialdehyde levels (p < 0.05) and increased catalase, superoxide dismutase, and glutathione peroxidase activities (p < 0.01) compared with those of the CON group. Serum proinflammatory cytokine concentrations of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α were lower (p < 0.01) and the IL-10 level was higher (p < 0.01) in the PNE100 group than in the CON group. Serum immunoglobulin (Ig)A, IgG, and IgM concentrations were increased in the PNE100 group (p < 0.01). The relative abundance of Bacteroidetes was increased, while the relative abundances of Firmicutes and Proteobacteria were decreased in the PNE100 group. The relative abundances of Vibrio, Shewanella, and Lactobacillus were decreased, while the relative abundances of unclassified_o_Bacteroidales, Rikenellaceae_RC9_gut_group, unclassified_f_Rikenellaceae, and Butyricicoccaceae were increased in the PNE100 group compared with those of the CON group. PNE supplementation at 100 mg/kg improved the diversity and structure of the gut microbial composition, production performance, egg quality, and serum parameters of laying hens. The laying hens in this study had good production performance when supplemented with 100 mg/kg PNE.

Florfenicol Enhances Colonization of a Salmonella enterica Serovar Enteritidis floR Mutant with Major Alterations to the Intestinal Microbiota and Metabolome in Neonatal Chickens

Florfenicol is an important antibiotic commonly used in poultry production to prevent and treat Salmonella infection. However, oral administration of florfenicol may alter the animals' natural microbiota and metabolome, thereby reducing intestinal colonization resistance and increasing susceptibility to Salmonella infection. In this study, we determined the effect of florfenicol (30 mg/kg of body weight) on gut colonization of neonatal chickens challenged with Salmonella enterica subsp. enterica serovar Enteritidis. We then analyzed the microbial community structure and metabolic profiles of cecal contents using microbial 16S amplicon sequencing and liquid chromatography-mass spectrometry (LC-MS) untargeted metabolomics, respectively. We also screened the marker metabolites using a multi-omics technique and assessed the effect of these markers on intestinal colonization by S. Enteritidis. Florfenicol administration significantly increased the loads of S. Enteritidis in cecal contents, spleen, and liver and prolonged the residence of S. Enteritidis. Moreover, florfenicol significantly affected cecal colony structures, with reduced abundances of Lactobacillus and Bacteroidetes and increased levels of Clostridia, Clostridium, and Dorea. The metabolome was greatly influenced by florfenicol administration, and perturbation in metabolic pathways related to linoleic acid metabolism (linoleic acid, conjugated linoleic acid [CLA], 12,13-EpOME, and 12,13-diHOME) was most prominently detected. We screened CLA and 12,13-diHOME as marker metabolites, which were highly associated with Lactobacillus, Clostridium, and Dorea. Supplementation with CLA maintained intestinal integrity, reduced intestinal inflammation, and accelerated Salmonella clearance from the gut and remission of enteropathy, whereas treatment with 12,13-diHOME promoted intestinal inflammation and disrupted intestinal barrier function to sustain Salmonella infection. Thus, these results highlight that florfenicol alters the intestinal microbiota and metabolism of neonatal chickens and promotes Salmonella infection mainly by affecting linoleic acid metabolism. IMPORTANCE Florfenicol is a broad-spectrum fluorine derivative of chloramphenicol frequently used in poultry to prevent/treat Salmonella. However, oral administration of florfenicol may lead to alterations in the microbiota and metabolome in the chicken intestine, thereby reducing colonization resistance to Salmonella infection, and the possible mechanisms linking antibiotics and Salmonella colonization in poultry have not yet been fully elucidated. In the current study, we show that increased colonization by S. Enteritidis in chickens administered florfenicol is associated with large shifts in the gut microbiota and metabolic profiles. The most influential linoleic acid metabolism is highly associated with the abundances of Lactobacillus, Clostridium, and Dorea in the intestine. The screened target metabolites in linoleic acid metabolism affect S. Enteritidis colonization, intestinal inflammation, and intestinal barrier function. Our findings provide a better understanding of the susceptibility of animal species to Salmonella after antibiotic intervention, which may help to elucidate infection mechanisms that are important for both animal and human health.

A Comparison of Production Performance, Egg Quality, and Cecal Microbiota in Laying Hens Receiving Graded Levels of Vitamin B12

The objective of the study was to investigate the effect of fortified diets with standard vs. high levels of vitamin B₁₂ on cecal microbiota composition, production performance, and eggshell quality of laying hens. Dietary treatments consisted of a basal diet with no supplementation of vitamin B₁₂ or supplemented with 25, 100, and 400 μg/kg vitamin B₁₂, respectively. A total of 432 laying hens were randomly assigned to four treatments with six replicates per treatment. No significant effect of dietary treatments on the production performance of hens was detected. The shell thickness of eggs from hens fed diet supplemented with 100 μg/kg of vitamin B₁₂ was higher (P < 0.01) than that of eggs from hens fed control diet or supplemented with 25 μg/kg vitamin B₁₂. The shell percentage of eggs from hens fed diet supplemented with 400 μg/kg of vitamin B₁₂ was higher (P < 0.01) than that of eggs from hens fed other treatment diets. Dietary vitamin B₁₂ did not modulate diversity of the cecal microbiota of the layers. At genus level, the cecal content from layers fed diet with supplemental level of 100 or 400 μg/kg of vitamin B₁₂ had higher (P < 0.01) abundance of Faecalibacterium and lower (P < 0.05) abundance of Acinetobacter compared with the cecal content from layers fed other two diets. The abundance of Lactobacillus in the cecal samples from layers fed 100 μg/kg of supplemental level of vitamin B₁₂ was higher (P < 0.05) than that from layers fed other three diets. The abundance of Butyricicoccus was higher (P < 0.05), while Bilophila was lower (P < 0.05) in the cecal content of layers fed 400 μg/kg of vitamin B₁₂ diet compared with those from layers fed other three diets. The results of PICRUSt analysis indicated that 10 predicted metabolic functions of the cecal microbial communities were positively correlated to dietary vitamin B₁₂ level. Overall, dietary supplementation of 100 or 400 μg/kg of vitamin B₁₂ had equivalent effects and caused the significant change in composition and metabolic functions of cecal microorganisms, which could positively impact eggshell quality, metabolism, and gut health of laying hens.

Effect of dietary serine supplementation on performance, egg quality, serum indices, and ileal mucosal immunity in laying hens fed a low crude protein diet

This study was designed to evaluate the effect of dietary Ser on performance, egg quality, serum indices, and ileal mucosal immunity in laying hens fed low crude protein (LCP), essential amino acids (EAA) balanced diets. A total of 480 Hy-Line Brown layers at 24 wk of age were randomly assigned into 5 dietary treatments with 8 replicates of 12 birds each. Treatments included a control diet (16.49% CP), and 4 LCP, EAA balanced diets (14.05% CP) supplemented with 0, 0.114%, 0.306%, 0.498% L-Ser, respectively. Dietary Ser supplementation linearly increased hen-day egg production (HDEP; P < 0.05) and decreased feed-to-egg ratio (P < 0.05) among LCP groups from wk 6 to 10, and the optimal HDEP of layers occurred at Ser level of 0.498%. At the end of wk 10, birds in the control had higher albumen height and thick white proportion than those fed the LCP diet without Ser addition (P < 0.05), and presented a lower yolk color score than all LCP groups (P < 0.05). Among LCP groups, serum total protein and globulin contents were significantly increased by dietary Ser addition at the levels of 0.306% and 0.498% (P < 0.05), and had a linear response to the supplemental Ser levels (P < 0.05). Furthermore, dietary 0.498% Ser supplementation significantly increased serum immunoglobulin G and immunoglobulin M contents (P < 0.05) and up-regulated the expression of mucin 2, secretory immunoglobulin A, and relevant glycosyltransferases of O-glycosylation in ileal mucosa (P < 0.05). The increased expression of proinflammatory cytokines IFN-γ and IL-1β induced by LCP diets (P < 0.05) was reversed following 0.498% Ser addition (P < 0.05). Collectively, dietary CP reduction by 2.44% could maintain the productive performance of layers when it was fortified with certain EAA, though poor albumen quality, and ileal inflammation were occurred. The addition of Ser to LCP diets improved performance probably through enhancing humoral and ileal mucosal immunity and attenuating the ileal inflammation of layers.

Effects of IQW and IRW on Inflammation and Gut Microbiota in ETEC-Induced Diarrhea

Methods

The mice were randomly distributed into four groups: (a) control (CTRL) group, (b) ETEC group, (c) IQW-ETEC group, and (d) IRW-ETEC group. Villus length and crypt depth were measured after hematoxylin and eosin staining. The inflammatory reaction was analyzed via inflammatory cytokines (i.e., TNF-α, IL-1β, IL-6, and IL-10) using the enzyme-linked immunosorbent assay (ELISA). The microbiota in the colon was sequenced using 16S ribosomal RNA.

Results

The villus length decreased, the crypt depth decreased, and the expression of inflammatory cytokines (i.e., TNF-α, IL-1β, IL-6, and IL-10) increased due to ETEC. In the IRW-ETEC and IQW-ETEC groups, the Shannon index decreased (P < 0.05). IQW and IRW increased the abundance of Firmicutes, Proteobacteria, Clostridiales, Lachnospiraceae, and Alloprevotella; contrastingly, it decreased the abundance of Epsilonproteobacteria, Erysipelotrichales, Prevotellaceae, and Flavobacteriaceae compared to the ETEC group (P <0.05).

Conclusion

This study ascertained that the addition of IQW and IRW could alleviate jejunal inflammation and increase microbiota community diversity.

Black Soldier Fly (Hermetia illucens) Larvae Meal Modulates Intestinal Morphology and Microbiota in Xuefeng Black-Bone Chickens

The addition of Hermetia illucens larvae meal (HILM) to the feed could contribute to particular antimicrobial and intestinal health in animal husbandry. This study was conducted to investigate the effects of HILM on intestinal morphology and microbial diversity in different intestinal segments of Xuefeng black-bone chickens. All of 432 birds (45 weeks old) were randomly assigned to four equal groups with six replicates and 18 hens in each replicate: (A) basal diet, (B) basal diet with 1% HILM, (C) basal diet with 3% HILM, and (D) basal diet with 5% HILM. The results showed that, compared with the basal diet group, the HILM supplement significantly increased the abundance-based coverage estimator (ACE) and Chao index in cecum (p < 0.05). Diet with 1% HILM significantly increased the villus height (VH) of the duodenum (p < 0.05) and cecum microbial diversity as represented by the Simpson index (p < 0.05). In particular, 1% HILM displayed a markedly increase in the genus unclassified Bacteroidales (cecum, p < 0.05). A basal diet with 3% HILM markedly increased the beneficial genus Romboutsia (jejunum, p < 0.05). Also, principal component analysis (PCA) cluster analysis showed that 3% of HILM was more individual than other groups (p < 0.05). However, 5% HILM decreased the VH and the ratio of villus height to crypt depth (VH/CD) of the jejunum and increased beneficial bacteria such as Staphylococcus (p < 0.05), which was regarded as pathogenetic genera. In conclusion, we found that HILM improved intestinal morphology and increased microbiological diversity and species abundance. Together, dietary supplementation of 1 or 3% HILM might benefit the intestinal morphology and intestinal microbiota of Xuefeng black-bone chicken. However, the addition of 5% HILM could decrease VH and the ratio of VH/CD of the jejunum and increased pathogenetic genera. HILM was an excellent protein substitute for Xuefeng black-bone chickens, which could meet the nutritional requirements under the condition of less feed. These results provide information for HILM meal as an alternative source of soybean meal in Xuefeng black-bone chickens’ feed.

Dietary Valine Ameliorated Gut Health and Accelerated the Development of Nonalcoholic Fatty Liver Disease of Laying Hens

Valine is an important essential amino acid of laying hens. Dietary supplemented with BCAAs ameliorated gut microbiota, whereas elevated blood levels of BCAAs are positively associated with obesity, insulin resistance, and diabetes in both humans and rodents. General controlled nonrepressed (GCN2) kinase plays a crucial role in regulating intestinal inflammation and hepatic fatty acid homeostasis during amino acids deficiency, while GCN2 deficient results in enhanced intestinal inflammation and developed hepatic steatosis. However, how long-term dietary valine impacts gut health and the development of nonalcoholic fatty liver disease (NAFLD) remains unknown. Hence, in the present study, we elucidated the effects of dietary valine on intestinal barrier function, microbial homeostasis, and the development of NAFLD. A total of 960 healthy 33-weeks-old laying hens were randomly divided into five experimental groups and fed with valine at the following different levels in a feeding trial that lasted 8 weeks: 0.59, 0.64, 0.69, 0.74, and 0.79%, respectively. After 8 weeks of treatment, related tissues and cecal contents were obtained for further analysis. The results showed that diet supplemented with valine ameliorated gut health by improving intestinal villus morphology, enhancing intestinal barrier, decreasing cecum pathogenic bacteria abundances such as Fusobacteriota and Deferribacterota, and inhibiting inflammatory response mediated by GCN2. However, long-term intake of high levels of dietary valine (0.74 and 0.79%) accelerated the development of NAFLD of laying hens by promoting lipogenesis and inhibiting fatty acid oxidation mediated by GCN2-eIF2α-ATF4. Furthermore, NAFLD induced by high levels of dietary valine (0.74 and 0.79%) resulted in strengthening oxidative stress, ER stress, and inflammatory response. Our results revealed that high levels of valine are a key regulator of gut health and the adverse metabolic response to NAFLD and suggested reducing dietary valine as a new approach to preventing NAFLD of laying hens.

Physiological Functions of Threonine in Animals: Beyond Nutrition Metabolism

Threonine (Thr), an essential amino acid for animals and the limiting amino acid in swine and poultry diets, which plays a vital role in the modulation of nutritional metabolism, macromolecular biosynthesis, and gut homeostasis. Current evidence supports that the supplementation of Thr leads to benefits in terms of energy metabolism. Threonine is not only an important component of gastrointestinal mucin, but also acts as a nutritional modulator that influences the intestinal immune system via complex signaling networks, particularly mitogen-activated protein kinase (MAPK) and the target of the rapamycin (TOR) signal pathway. Threonine is also recognized as an indispensable nutrient for cell growth and proliferation. Hence, optimization of Thr requirement may exert a favorable impact on the factors linked to health and diseases in animals. This review focuses on the latest reports of Thr in metabolic pathways and nutritional regulation, as well as the relationship between Thr and relevant physiological functions.

Effect of increasing levels of Threonine relative to Lysine on the performance and meat quality of finishing pigs

Objective

The present study aimed to evaluate the effects of varying standardized ileal digestible lysine:threonine (SID Lys:Thr) ratio in the diet on the performance and meat quality of finishing pigs.

Methods

In total 192 crossbred pigs ([Landrace×Yorkshire]×Duroc, 17 weeks old), with an initial body weight (BW) of 70.6±3.9 kg were used in an 8-wk trial. Pigs were randomly allotted to one of six dietary treatments based on their initial BW and sex (8 replications; 4 pigs per pen, 2 barrows and 2 gilts). The pigs in the 6 treatments were fed diets having different SID Lys:Thr ratios such as 1:0.65, 1:0.66, 1:0.67, 1:0.68, 1:0.69, and 1:0.70.

Results

A linear increment (p<0.05) in average daily gain (ADG) and trends in reduction in feed conversion ratio (FCR) were observed during day 29 to 56 of the experiment and the apparent total tract digestibility (ATTD) of dry matter tended to increase linearly (p = 0.094) at the end of the experiment (day 56) with the increase in the dietary SID Lys:Thr ratios. The backfat thickness and lean percentage increased (linear effect, p<0.05) on day 28. In addition, at day 56, a linear (p<0.05) increment in lean percentage was observed. Significant quadratic responses (p = 0.02) for pH and drip loss at day 7 (p = 0.02), a linear increase (p<0.05) in cooking loss and drip loss at day 7, and a trend in quadratic response (p = 0.07) in the lightness of meat color (L*) were observed, whereas other meat quality indices were unaffected by varying the SID Lys:Thr ratios.

Conclusion

The SID Lys:Thr ratio for maximum ADG, minimum FCR and enhanced digestibility was found to be 0.70. However, for carcass trait and meat quality, the SID Lys:Thr ratio of 0.65 was enough.

Response of laying hens to l-arginine, l-citrulline and guanidinoacetic acid supplementation in reduced protein diet

A study was conducted with Hy-Line Brown laying hens to examine the effects of reduced protein diet, deficiency of arginine (Arg), and addition of crystalline Arg, citrulline (Cit) and guanidinoacetic acid (GAA) as substitutes for Arg. Hen performance, egg quality, serum uric acid, liver and reproductive organ weights, and energy and protein digestibility were measured using a completely randomized design with 5 treatments. Treatments were a standard diet (17% protein diet; SP), a reduced diet (13% protein diet deficient in Arg; RP) and RP with added Arg (0.35%, RP-Arg), GAA (0.46% equivalent to 0.35% Arg, RP-GAA) or Cit (0.35%, RP-Cit) to the level of SP. It was hypothesized that performance would decrease with Arg deficient RP diet and the addition of GAA or Cit in RP would allow birds to perform similar or greater than Arg-added RP treatment. The experiment was conducted from 20 to 39 wk of age but the treatment effect was seen only after 29 wk of age. The birds offered RP had reduced egg and albumin weights (P < 0.01), lower yolk color score (P < 0.01), lower protein intake and excretion (P < 0.01) than those offered SP. When Arg or Cit were added to RP to make them equivalent to SP, feed intake (FI) and egg production were not different than those of RP (P > 0.05). The birds offered RP-GAA decreased FI and egg production (P < 0.01) compared to those offered RP. The addition of Arg, Cit or GAA to the RP had no effect on egg quality parameters, protein and energy digestibilities (P > 0.05). However, birds offered the RP-Cit diet tended to have higher Haugh unit (P = 0.095) and lower shell breaking strength (P = 0.088) compared to all other treatments while those offered RP-GAA had higher energy digestibility (P < 0.05) than all other groups but RP. The limited performance response of hens fed RP with added Arg, GAA, or Cit may be due to deficiency of some other nutrients in RP such as phenylalanine, potassium or non-essential amino acids and other components of soybean meal in the diet.

Alterations and Correlations of the Gut Microbiome, Performance, Egg Quality, and Serum Biochemical Indexes in Laying Hens with Low-Protein Amino Acid-Deficient Diets

The present study was carried out to investigate the effects of methionine (Met), lysine (Lys), isoleucine (Ile), and threonine (Thr) deficiency in a low-protein diet on laying performance, egg quality, serum biochemical indices, and the gut microbiota in laying hens. A total of 300 Peking Pink laying hens, at 38 weeks of age, were randomly allocated to five dietary treatments, each of which included six replicates of ten hens. Hens were fed an amino acid-balanced diet (Met: 0.46%; Lys: 0.76%; Ile: 0.72%; Thr: 0.56%; positive control, PC), Met deficiency diet (Met-, 0.25%), Lys deficiency diet (Lys-, 0.56%), Ile deficiency diet (Ile-, 0.54%), and Thr deficiency diet (Thr-, 0.46%) for 12 weeks. Hens were housed in pairs in 45 × 45 × 45 cm wire cages with three ladders and three birds per cage. Feed and water were provided ad libitum during the entire experimental period. All data were analyzed using one-way ANOVA with Turkey's multiple range test. Here, compared to the PC group, final body weight (FBW), average daily gain (ADG), egg production (EP), egg weight (EW), average daily egg mass (EM), average daily feed intake (ADFI), and yield of abdominal fat (AFY) in the Met-group were lower, while EW and EM were higher in the Lys-group. The feed egg ratio (FER) was increased in the Met- and Lys-groups, and EW and AFY were decreased in the Ile-group compared to the controls. Meanwhile, ADG, EP, EM, and ADFI were lower in the Thr group than the PC group. The level of triglycerides (TGs) in the four groups was lower and the concentrations of uric acid (UA) in the Met-group were higher than those in the PC group. The shell color in the Thr group was lower than the PC group. Of note, amino acid deficiency altered the gut microbial structure (e.g., increasing the level of Parabacteroides and decreasing the abundance of Lactobacillus) in hens. The correlation analysis showed that amino acid deficiency-induced gut microbiota alteration is closely associated with the change in key parameters: FER, UA, AFY, EW, EM, TG, FBW, EP, and ADFI. Collectively, our results highlight the role of adequate amino acid ratio supplementation in the low-crude-protein diet structure for laying hens.

Zinc hydroxychloride supplementation improves tibia bone development and intestinal health of broiler chickens

This study was conducted to investigate the effects of zinc (Zn), as a combination of oxide (ZnO) and sulfate (ZnSO₄), compared with incremental levels of zinc hydroxychloride (ZH) on tibia traits, intestinal integrity, expression of selected jejunal genes, cecal short chain fatty acids and microbial composition in broilers. Day-old male Ross 308 chicks (n = 784) were randomly allocated to seven dietary treatments, each replicated seven times with 16 chicks per replication. The dietary treatments included a negative control diet (NC) with no supplemental Zn, a positive control (PC) with 100 mg/kg supplemental Zn from an ionic bound source combination (50 mg/kg ZnO + 50 mg/kg ZnSO₄), and the NC diet supplemented with one of 20, 40, 60, 80, or 100 mg/kg Zn as ZH. The diets were fed over starter (1–14 d) and grower (14–35 d) phases, with tissue and digesta samples collected from 3 birds per replicate on days 14 and 35. The results showed that dietary Zn level had a significant effect on tibia breaking strength on d 35 (P < 0.05), and tibia Zn concentration both on d 14 and d 35 (P < 0.01). Dietary Zn levels linearly (P < 0.01) increased cecal lactic acid production, increased Lactobacillus, and decreased Bacillus and total bacteria counts (P < 0.05). Inclusion of 80 and 100 mg/kg Zn as ZH tended to upregulate the expression of claudin-1 (P = 0.088) and tight junction protein-1 (P = 0.086). The results obtained in this study suggest that a non-Zn supplemented diet can negatively influence tibia development and gut microbiota composition in broiler chickens. Higher supplemental Zn in the diet alters cecal microbiota population in favor of Lactobacillus and can decrease the total bacterial load. Supplemental Zn level in the feed have the potential to manipulate the jejunal gut integrity at a molecular level.

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.

Microbial Diversity and Community Variation in the Intestines of Layer Chickens

The intestinal microbiota is increasingly recognized as an important component of host health, metabolism and immunity. Early gut colonizers are pivotal in the establishment of microbial community structures affecting the health and growth performance of chickens. White Lohmann layer is a common commercial breed. Therefore, this breed was selected to study the pattern of changes of microbiota with age. In this study, the duodenum, caecum and colorectum contents of white Lohmann layer chickens from same environment control farm were collected and analyzed using 16S rRNA sequencing to explore the spatial and temporal variations in intestinal microbiota. The results showed that the diversity of the microbial community structure in the duodenum, caecum and colorectum increased with age and tended to be stable when the layer chickens reached 50 days of age and the distinct succession patterns of the intestinal microbiota between the duodenum and large intestine (caecum and colorectum). On day 0, the diversity of microbes in the duodenum was higher than that in the caecum and colorectum, but the compositions of intestinal microbes were relatively similar, with facultative anaerobic Proteobacteria as the main microbes. However, the relative abundance of facultative anaerobic bacteria (Escherichia) gradually decreased and was replaced by anaerobic bacteria (Bacteroides and Ruminococcaceae). By day 50, the structure of intestinal microbes had gradually become stable, and Lactobacillus was the dominant bacteria in the duodenum (41.1%). The compositions of dominant microbes in the caecum and colorectum were more complex, but there were certain similarities. Bacteroides, Odoribacter and Clostridiales vadin BB60 group were dominant. The results of this study provide evidence that time and spatial factors are important factors affecting the intestinal microbiota composition. This study provides new knowledge of the intestinal microbiota colonization pattern of layer chickens in early life to improve the intestinal health of layer chickens.

Influence of Glycyrrhiza glabra Extract on Growth, Gene Expression of Gut Integrity, and Campylobacter jejuni Colonization in Broiler Chickens

Phytogenic feed additives have been gaining considerable interest due to their ability to improve gut health and thereby performance of broiler chickens. The impact of Glycyrrhiza glabra (licorice) extract (GE) on expression of genes coding for tight junction proteins and gut protection and Campylobacter jejuni colonization in broilers has not been discussed until now. Thus, the current study assessed the effective dose of GE for maximum growth in broiler chickens, clear-cut molecular mechanisms related to integrity and health of intestine, and controlling C. jejuni colonization. Over a 35-day feeding period, a total of 500 Ross broiler chicks were allocated to five groups; the first group was fed a control diet without GE and the second group to the fifth group were fed a control diet with GE (0.25, 0.5, 1, and 2 g/kg of diet); each group comprised 100 chicks with 10 replicates (10 birds/replicate). Birds fed GE had an improved body weight gain and feed conversion ratio. Furthermore, the highest body weight gain was observed in the group that received 1 g/kg of GE (P < 0.05). The expression of genes coding for tight junction proteins [occludin and junctional adhesion molecules (JAM)] was upregulated in all groups supplemented with GE. Moreover, birds fed 1 g/kg of GE exhibited the maximum gene expression of occludin and JAM [0.2 and 0.3 fold change, respectively (P < 0.05)]. In relation to enterocyte protective genes [glucagon-like peptide (GLP-2) and fatty acid-binding protein (FABP-6)], use of GE significantly upregulated expression of GLP-2 gene with 0.8 fold change in 2 g/kg of the GE supplemented group (P < 0.05) while the expression of FABP-6 gene was not affected by GE supplementation (P > 0.05). After challenge with C. jejuni, the expression of mucin (MUC-2) gene was upregulated and the inflammatory markers such as Toll-like receptors (TLR-4) and interleukin (IL-1β) were downregulated with increasing level of supplemented GE (P < 0.05). The mean log10 count of C. jejuni in cecal samples after 7 days post-infection by culture and real-time qPCR was decreased in groups fed GE in a dose-dependent manner (P < 0.05). In addition, the highest reduction of C. jejuni count in cecal samples by culture and real-time qPCR was observed in the group fed 2 g/kg of GE (2.58 and 2.28 log10 CFU/g, respectively). Results from this study suggested that G. glabra extract (1 g/kg) improved growth performance of broiler chickens, as well as influenced the maintenance of intestinal integrity and reduced C. jejuni shedding from infected birds.

Maternal dietary linoleic acid altered intestinal barrier function in domestic pigeons (Columba livia)

Linoleic acid (LA) is predominantly essential for poultry. Poultry lacking LA show retarded growth and reduced disease resistance. Intestinal barrier function plays an important role in pigeon squab growth, whereas research on the effects of LA on intestinal health in altrices is scant. Considering that squabs are fed by their parents, the study aimed to explore the effects of maternal dietary LA on intestinal morphology, tight junction proteins, immune cytokines and microbial flora in squabs. A completely randomised design with a control group, 1 % LA supplementation group, 2 % LA supplementation group and 4 % LA supplementation group was used. Six squabs from each treatment were randomly sampled at 21 d post-hatching. The results indicated that LA supplementation improved intestinal morphology, as reflected by increased villus height, villus area and the ratio of villi to crypts. Also, 1 % LA supplementation elevated the density of goblet cells in the intestine and strengthened tight junctions by up-regulating claudin-3 and occludin gene expression but down-regulating claudin-2 gene expression. Moreover, 1 % LA supplementation reduced the secretion of proinflammatory cytokines and partly increased anti-inflammatory cytokines. The intestinal microbial diversity in the 1 % LA supplementation group was higher than that in the other groups. As beneficial bacteria, Butyrivibrio was the biomarker of 1 % LA supplementation. However, excessive (4 %) LA supplementation led to adverse impacts on intestinal immunity and microbiota. In conclusion, maternal dietary LA might alter intestinal barrier function in pigeon squabs in a dose-dependent manner. Supplementation with 1 % LA was suggested in parental pigeons.

Effects of grazing mixed-grass pastures on growth performance, immune responses, and intestinal microbiota in free-range Beijing-you chickens

There is an increasing interest in free-range poultry with the increasing focus on food safety and animal welfare. This study was conducted to evaluate the effects of grazing mixed-grass pastures on growth performance, immune responses, and intestinal microbiota in free-range laying chickens. Ten-week-old female Beijing-you chickens were blocked by the BW and randomly assigned to 3 free-range systems in poplar plantations for 120 d: forage-removed paddocks with a high stocking density of 5 m²/hen (control [CK]); mixed-grass pastures with a low stocking density of 6 m²/hen ;or mixed-grass pastures with a high stocking density of 5 m²/hen. Intestinal microbial community analysis was performed by 16S rRNA gene sequencing using Illumina MiSeq. The results revealed that no differences (P > 0.05) were found between the 3 raising systems for the BW and ADG. Chickens grazing mixed-grass pastures exhibited decreased (P > 0.05) mortality and improved immune responses as evidenced by increased T-lymphocyte proliferation (P > 0.05) and immunoglobulin A (P > 0.05) and immunoglobulin M concentrations (P < 0.05) compared with those raised in forage-removed paddocks. Metagenomic analysis indicated that grazing mixed-grass pastures regulated the intestinal microbiota by increasing the prevalence of beneficial bacteria, such as Lactobacillus, Bacteroides, and Faecalibacterium, and reducing potentially pathogenic bacteria population, such as the Rikenellaceae_RC9_gut_group compared with the CK. Therefore, this study indicated that grazing mixed-grass pastures could positively influence intestinal microbiota that may contribute to the overall growth and immunity of free-range chickens and that a low stocking density of 6 m²/hen was optimal to Beijing-you chickens grazing mixed-grass pastures.

Effects of Housing Types on Cecal Microbiota of Two Different Strains of Laying Hens During the Late Production Phase

Due to animal welfare issues, European Union has banned the use of conventional cages (CC) and non-EU countries including the US are also under constant public pressure to restrict their use in egg production. Very limited information is available on the composition of the microbial community of hens raised in different housing environments. This study was conducted to determine the effects of CC and enriched colony cages (EC) on cecal microbiota of two commercial laying hen strains, Hy-Line W36 (W36) and Hy-Line Brown (HB) during the late production stage (53, 58, 67, and 72 weeks of age). Cecal microbiota was studied by analyzing 16S rRNA gene sequences with Quantitative Insights Into Microbial Ecology (QIIME) 2 ver. 2018.8. Differentially abundant taxa were identified by Linear discriminant analysis Effect Size (LEfSe) analysis (P < 0.05, LDA score > 2.0). At phylum level, Actinobacteria was significantly enriched in W36 at all time points while Synergistetes (53 weeks), Spirochaetes (58 weeks), and Synergistetes and Spirochaetes (67 weeks) were significantly higher in HB. At genus level, Bifidobacterium (at all time points) and butyric acid producing genera such as Butyricicoccus and Subdoligranulum (58 and 72 weeks) were significantly higher in W36 as compared to HB. Moreover, Proteobacteria (72 weeks) and its associated genus Campylobacter (67 and 72 weeks) were significantly enriched in EC as compared to CC. Alpha diversity was significantly higher in HB (at all time points) and in EC (67 weeks) as compared to W36 and CC, respectively. Similarly, there was a significant difference in community structure (beta diversity) between W36 and HB (all time points) as well as between EC and CC (67 weeks). The effect of housing and strains was not only seen at the bacterial composition and structure but also reflected at their functional level. Notably, KEGG metabolic pathways predicted to be involved in carbohydrates degradation and amino acids biosynthesis by PICRUSt analysis were significantly different between W36 and HB housed at CC and EC. In sum, cecal microbiota composition, diversities, and their functional pathways were affected by housing type which further varied between two commercial laying hen strains, HB and W36. This suggests that both housing and genetic strains of laying hens should be considered for selection of the alternative housing systems such as enriched colony cage.

The Gut Microbiota of Laying Hens and Its Manipulation with Prebiotics and Probiotics To Enhance Gut Health and Food Safety

The microbiota plays a vital role in maintaining gut health and influences the overall performance of chickens. Most gut microbiota-related studies have been performed in broilers, which have different microbial communities compared to those of layers. The normal gut microbiota of laying chickens is dominated by Proteobacteria, Firmicutes, Bacteroidetes, Fusobacteria, and Actinobacteria at the phylum level. The composition of the gut microbiota changes with chicken age, genotype, and production system. The metabolites of gut microbiota, such as short-chain fatty acids, indole, tryptamine, vitamins, and bacteriocins, are involved in host-microbiota cross talk, maintenance of barrier function, and immune homeostasis. Resident gut microbiota members also limit and control the colonization of foodborne pathogens. In-feed supplementations of prebiotics and probiotics strengthen the gut microbiota for improved host performance and colonization resistance to gut pathogens, such as Salmonella and Campylobacter The mechanisms of action of prebiotics and probiotics come through the production of organic acids, activation of the host immune system, and production of antimicrobial agents. Probiotic candidates, including Lactobacillus, Bifidobacterium, Bacillus, Saccharomyces, and Faecalibacterium isolates, have shown promising results toward enhancing food safety and gut health. Additionally, a range of complex carbohydrates, including mannose oligosaccharides, fructo-oligosaccharides, and galacto-oligosaccharides, and inulin are promising candidates for improving gut health. Here, we review the potential roles of prebiotics and probiotics in the reshaping of the gut microbiota of layer chickens to enhance gut health and food safety.

Diet complexity and l-threonine supplementation: effects on nutrient digestibility, nitrogen and energy balance, and body composition in nursery pigs

This study was conducted to investigate the effects of dietary complexity and l-Thr supplementation on energy and nutrient utilization in nursery pigs. Thirty-two nursery pigs (7.23 ± 0.48 kg) were randomly assigned to a 2 × 2 factorial treatment arrangement based on diet complexity (complex vs. simple) with different levels of l-Thr supplementation. The complex diet contained animal protein sources (e.g., fish meal and plasma) and a dairy product (e.g., dried whey) to mimic a conventional nursery diet. The simple diet was formulated with corn, wheat, and soybean meal. Both diets were supplemented with l-Thr to contain either 100% or 115% (SUP Thr) of the estimated standardized ileal digestible Thr requirement for 9 kg body weight pigs (NRC, 2012). The pigs were individually housed in metabolism crates and fed an experimental diet ad libitum for a 7-d adaptation period and 5 d of total but separate urine and fecal collection. On day 14, all pigs were euthanized to determine body composition. The diet complexity, l-Thr supplementation, and their interactions were considered main effects. Pigs fed the complex diet tended to exhibit greater (P < 0.10) apparent total tract digestibility (ATTD) of ash and urinary energy output than those fed the simple diet. The complex diet had greater (P < 0.05) digestible energy and net energy contents than the simple diet. Furthermore, the complex diet-fed pigs had lower (P < 0.05) plasma urea nitrogen concentration on day 14 than simple diet-fed pigs. The SUP Thr decreased (P < 0.05) ATTD of acid detergent fiber but trended (P < 0.10) toward a decrease in urinary nitrogen (N) output and an increase in N retention and body N mass. In conclusion, the simple diet for nursery pigs had lower digestible and net energy contents than a complex diet. The SUP Thr can improve N utilization and body protein deposition, irrespective of diet complexity.

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

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

Alterations in cecal microbiota and intestinal barrier function of laying hens fed on fluoride supplemented diets

The objective of this study was to investigate the effects of fluorine at levels of 31, 431, 1237 mg/kg feed on cecum microbe, short-chain fatty acids (SCFAs) and intestinal barrier function of laying hens. The results showed that the intestinal morphology and ultrastructure were damaged by dietary high F intake. The mRNA expression levels of zonula occludens-1, zonula occludens-2, claudin-1, and claudin-4 were decreased in jejunum and ileum. However, the concentrations of serum diamine oxidase, and D-lactic acid and intestinal contents of interleukin 1 beta, interleukin 6, and Tumor necrosis factor-alpha were increased. Consistent with this, dietary high F intake altered the cecum microbiota, with increasing the concentration of pathogens, such as Proteobacteria and Escherichia-Shigella, as well as, decreasing the contents of beneficial bacteria, such as Lactobacillus, and expectedly, reduced the SCFAs concentrations. In conclusion, the actual results confirmed that (1) high dietary F intake could damage the intestinal structure and function, with impaired intestinal barrier and intestinal inflammation, and (2) destroy the cecum microbial homeostasis, and decrease the concentrations of SCFAs, which aggravate the incidence of intestinal inflammation in laying hens.

Efficacy of ajwain (Trachyspermum ammi L.) seed at graded levels of dietary threonine on growth performance, serum metabolites, intestinal morphology and microbial population in broiler chickens

The present study investigated the influence of dietary threonine (Thr) levels and ajwain seed (AS) on the growth performance, immunity, blood metabolites, ileal microflora and jejunum morphology of broiler chickens. A total of 600-day-old male broiler chickens (Ross 308) were randomly allocated among five replicates of eight dietary treatments according to a 4 × 2 factorial arrangement of treatments, including four different levels of Thr (100, 105, 110 and 115% of requirements) and two inclusion rates of AS (0 or 10 g/kg of the diet). Body weight gain and FCR improved in broiler chickens fed 105% Thr supplement during the starter, finisher and whole periods of the experiment (p < .05). The broiler chickens fed AS supplemented diet had a greater weight gain (25-42 days) and better FCR (1-10 and 25-42 days) than those without AS (p < .05). A significant interaction was observed between Thr and AS supplementation for lymphocyte, heterophil/lymphocyte (H/L), bursa and spleen (p < .05). The liver enzyme activity of aspartate aminotransferase (AST) was higher in the chicks that received diet without AS supplement than those fed AS diet (p < .05). Inclusion of 105% dietary Thr and 10 g/kg AS increased the viable cell counts of Lactobacilli and decreased the population of the Escherichia coli in broilers (p < .05). In jejunum morphology, the broiler chickens fed 105% Thr diet had a greater villus length, width and crypt depth (p < .05). Also, the villus length was longer in broilers that received AS supplemented diet (p < .05). It is concluded that the dietary 105% of Thr and AS supplement individually improved growth performance, ileal microbial population and jejunum morphology of broiler chickens.

Dietary High Sodium Fluoride Impairs Digestion and Absorption Ability, Mucosal Immunity, and Alters Cecum Microbial Community of Laying Hens

(1) Background: This study was conducted to investigate the effects of dietary fluoride (F) on tissue retention, digestive enzymes activities, mucosal immunity, and cecum microbial community of laying hens. (2) Methods: Total of 288 37-week-old Hy-Line Gray laying hens with similar laying rate (85.16% ± 3.87%) were adapted to the basal diets for ten days, and then allocated into three groups at random (n = 9, 6, 6 replicates/group). The concentrations of F in the diets were 31.19 (the control group, CON), 431.38 (F400, low-F group) and 1237.16 mg/kg (F1200, high-F group), respectively. The trial lasted for 59 days. (3) Results: Results suggested that F residuals in duodenum responded to dietary F concentrations positively. The activities of amylase, maltase and lactase were decreased in high-F group, compared with those in the control group. The mRNA expression levels of jejunum and ileum secretory immunoglobulin A (sIgA) and Mucin 2, and sIgA concentrations were decreased inhigh-F group, than those in the control group. The observed operational taxonomic units (OTUs) of laying hens in high-F group were higher than the CON and low-F groups, and the bacterial structure was different from the other two groups. The Lactobacillus was higher in the control group, while Gammaproteobacteria, Escherichia-Shigella, Streptococcaceae, and Enterobacteriaceae were higher in the high-F group. (4) Conclusions: The actual results confirmed that dietary high F intake increased the F residuals in duodenum, and reduced the digestion and absorption of nutrients and immunity via decreasing the activities of digestive enzymes, impairing intestine mucosal immunity, and disturbing the cecum microbial homeostasis of laying hens.

Effects of dietary threonine supplementation on productivity and expression of genes related to protein deposition and amino acid transportation in breeder hens of yellow-feathered chicken and their offspring

This study investigated the effects of the dietary threonine (Thr) levels on the performance, offspring traits, embryo amino acid transportation, and protein deposition in breeder hens of yellow-feathered chickens. In total, 720 breeder hens of Lingnan yellow-feathered chickens were randomly assigned to 1 of 6 dietary treatments, with 6 replicates per treatment (20 birds per replicate). The breeder hens were fed either basal diet (Thr = 0.38%) or basal diet supplemented with 0.12, 0.24, 0.36, 0.48, or 0.60% Thr from 197 to 266 D. There was a positive response in terms of the laying rate after adding different levels of Thr to the diet, but no significant effects on the average daily gain, average daily egg weight, feed conversion ratio, average broken eggs, and unqualified egg rate (P > 0.05). However, the eggshell strength and eggshell percentage decreased in a linear manner as the dietary Thr concentration increased (P = 0.05). Dietary supplementation with Thr had significant effects on the expression of mucin 2 (MUC2) in the uterus and zonula occludens protein 1 (ZO-1) in the duodenum of breeders (P < 0.05). In chick embryos at embryonic age 18 D, significant upregulation of poultry target of rapamycin (pTOR) occurred in the liver and breast muscle, as well as threonine dehydrogenase (TDH) in the thigh, and aminopeptidase (ANPEP) (P < 0.05) in the duodenum and ileum due to dietary Thr supplementation, but there were no effects on MUC2 expression in the duodenum and ileum (P > 0.05). The livability of the progeny broilers tended to increase with the dietary Thr concentration (quadratic, P = 0.08). Thus, dietary supplementation with Thr had positive effects on the laying production by breeder hens and offspring performance, and it also regulated the expression levels of genes related to amino acid transportation and protein deposition. The optimal dietary Thr concentration that maximized the laying rate in yellow-feathered chicken breeders aged 197 to 266 D was 0.68% according to quadratic regression analysis.

Effects of Dietary Threonine Levels on Intestinal Immunity and Antioxidant Capacity Based on Cecal Metabolites and Transcription Sequencing of Broiler

Simple Summary

Threonine (Thr), an indispensable amino acid for animals and the third limiting amino acid of broilers, plays a vital role in the synthesis of gut mucosal proteins, which also has better effects on growth performance, biochemical indexes, antioxidant function, and gut morphology, as well as acting as a nutrient immunomodulator that affects the intestinal barrier function of broilers. However, it is not clear how it works in depth. The objective of the current study was to investigate the mechanism of effects of different dietary threonine levels on the antioxidant and immune capacity of broilers. Our findings suggest that a Thr level of 125% NRC (Nutrient Requirements of Poultry, 1994) recommendations had better effects on antioxidant and immune capacity, including resisting viruses and decreasing the abnormal proliferation of cells. As well as this, it also had better effects on maintaining the homeostasis of the body.

Abstract

This study aimed to determine the effects of different dietary threonine levels on the antioxidant and immune capacity and the immunity of broilers. A total of 432 one-day-old Arbor Acres (AA) broilers were randomly assigned to 4 groups, each with 6 replicates of 18 broilers. The amount of dietary threonine in the four treatments reached 85%, 100%, 125%, and 150% of the NRC (Nutrient Requirements of Poultry, 1994) recommendation for broilers (marked as THR85, THR100, THR125, and THR150). After 42 days of feeding, the cecum contents and jejunum mucosa were collected for metabolic analysis and transcriptional sequencing. The results indicated that under the condition of regular and non-disease growth of broilers, compared with that of the THR85 and THR150 groups, the metabolic profile of the THR125 group was significantly higher than that of the standard requirement group. Compared with the THR100 group, the THR125 group improved antioxidant ability and immunity of broilers and enhanced the ability of resisting viruses. The antioxidant gene CAT was upregulated. PLCD1, which is involved in immune signal transduction and plays a role in cancer suppression, was also upregulated. Carcinogenic or indirect genes PKM2, ACY1, HK2, and TBXA2 were down-regulated. The genes GPT2, glude2, and G6PC, which played an important role in maintaining homeostasis, were up-regulated. Therefore, the present study suggests that 125% of the NRC recommendations for Thr level had better effects on antioxidant and immune capacity, as well as maintaining the homeostasis of the body.

A deficient or an excess of dietary threonine level affects intestinal mucosal integrity and barrier function in broiler chickens

The aim of this study was to investigate the effects of deficient or excess of dietary threonine (Thr) levels on intestinal integrity and barrier function of broilers. A total of 432 1-day-old commercial broilers (Arbor Acre) were assigned to four experiment groups consisting of six replicates of 18 birds. The treatments were designed as follows: 85%, 100%, 125% and 150% of NRC (Nutrient requirements of poultry (9th edn). Washington, DC: The National Academies Press, 1994) recommendations. The results indicated that expressions of jejunal and ileal secretory immunoglobulin A (sIgA) mRNA were increased linearly or quadratically by increasing Thr (p < .05), and the highest sIgA mRNA abundance was obtained in 125% Thr level. Likewise, the intestinal sIgA content showed similar increasing trend with the intestinal sIgA gene expression in this instance. The high level of Thr inclusion upregulated mucin 2 (MUC2) mRNA expression in the jejunum and ileum (p < .05). In addition, on day 21, the expression levels of jejunal zonula occludens-2 (ZO-2) and ileal zonula occludens-1 (ZO-1) decreased then increased with increasing Thr level (p < .05), whereas, the mRNA expressions of occludin in the jejunum and ileum had no significant difference amongst groups (p >.05). On day 42, Thr treatments did not affect the mRNA abundance of measured genes in the jejunum and ileum (p > .05). These findings suggested that Thr might be a nutrient immunomodulator that affects intestinal barrier function, moreover, 125% of the NRC (1994) recommendations Thr level was optimum.

Analysis of excreta bacterial community after forced molting in aged laying hens

Objective

As laying hens become aged, laying performance and egg quality are generally impaired. One of the practical methods to rejuvenate production and egg quality of aged laying hens with decreasing productivity is a forced molting. However, the changes in intestinal microbiota after forced molting of aged hens are not clearly known. The aim of the present study was to analyze the changes in excreta bacterial communities after forced molting of aged laying hens.

Methods

A total of one hundred 66-wk-old Hy-Line Brown laying hens were induced to molt by a 2-d water removal and an 11-d fasting until egg production completely ceased. The excreta samples of 16 hens with similar body weight were collected before and immediately after molting. Excreta bacterial communities were analyzed by high-throughput sequencing of bacterial 16S rRNA genes.

Results

Bacteroidetes, Firmicutes, and Proteobacteria were the three major bacterial phyla in pre-molting and immediate post-molting hens, accounting for more than 98.0%. Lactobacillus genus had relatively high abundance in both group, but decreased by molting (62.3% in pre-molting and 24.9% in post-molting hens). Moreover, pathogenic bacteria such as Enterococcus cecorum and Escherichia coli were more abundant in immediate post-molting hens than in pre-molting hens. Forced molting influenced the alpha diversity, with higher Chao1 (p = 0.012), phylogenetic diversity whole tree (p = 0.014), observed operational taxonomic unit indices (p = 0.006), and Simpson indices (p<0.001), which indicated that forced molting increased excreta bacterial richness of aged laying hens.

Conclusion

This study improves the current knowledge of bacterial community alterations in the excreta by forced molting in aged laying hens, which can provide increasing opportunity to develop novel dietary and management skills for improving the gastrointestinal health of aged laying hens after molting.