The role of feed enzymes in maintaining poultry intestinal health.

Gut health or intestinal health is frequently discussed without any clear definition as to its meaning. It is suggested that this should be defined as intestinal integrity and functionality as both are a pre-requisite for the health of the intestine itself and the host. The health of the intestine is dependent upon a successful evolution of the absorptive capacity of the intestine, which in turn is influenced by the co-evolution of the intestinal immune systems and the microbiota. Nutrient supply plays a significant role in this process and from the perspective of the microbiota this changes with age as the intestines and upper gastrointestinal tract (GIT) microbiota become more effective in nutrient removal. Feed enzymes play a significant role in this process. Phytases can improve digestion of minerals, amino acids and energy and as a result reduce the availability of nutrients in the lower intestines for the microbiota. Protease can have a similar effect with amino acid supply. Non-starch polysaccharidases (NSPases) have a unique role in that they not only improve diet digestibility from the hosts perspective, thus limiting nutrient supply to the microbiota, but they also release soluble fragments of fibre from the insoluble matrix and/or depolymerize high molecular weight viscous fibre fractions in to smaller, more fermentable carbohydrate fractions. This results in a more favourable balance between fermentable carbohydrate to protein supply, a ratio which is deemed critical to maintaining good intestinal health. The dynamic nature of this complex evolution needs greater consideration if antibiotic free production is to succeed. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

SnoopLigase Catalyzes Peptide-Peptide Locking and Enables Solid-Phase Conjugate Isolation.

Simple, efficient reactions for connecting biological building-blocks open up many new possibilities. Here we have designed SnoopLigase, a protein that catalyzes site-specific transamidation, forming an isopeptide bond with more than 95% efficiency between two peptide tags, SnoopTagJr and DogTag. We initially developed these components by three-part splitting of the Streptococcus pneumoniae adhesin RrgA. The units were then engineered, guided by structure, bioinformatic analysis of sequence homology, and computational prediction of stability. After engineering, SnoopLigase demonstrated high-yield coupling under a wide range of buffers and temperatures. SnoopTagJr and DogTag were functional at the N- or C-terminus, while DogTag was also functional at internal sites in proteins. Having directed reaction of SnoopTagJr and DogTag, SnoopLigase remained stably bound to the ligated product, thus reconstituting the parent domain. Separating products from unreacted starting material and catalyst is often as challenging as reactions themselves. However, solid-phase immobilization of SnoopLigase enabled the ligated SnoopTagJr-DogTag product to be eluted with high purity, free from SnoopLigase or unligated substrates. The solid-phase catalyst could then be reused multiple times. In search of a generic route to improve the resilience of enzymes, we fused SnoopTagJr to the N-terminus and DogTag to the C-terminus of model enzymes, allowing cyclization via SnoopLigase. While wild-type phytase and ß-lactamase irreversibly aggregated upon heating, cyclization using SnoopLigase conferred exceptional thermoresilience, with both enzymes retaining solubility and activity following heat treatment up to 100 °C. SnoopLigase should create new opportunities for conjugation and nanoassembly, while illustrating how to harness product inhibition and extend catalyst utility.

The evolution and application of enzymes in the animal feed industry: the role of data interpretation.

1. Enzymes have been used commercially for nearly 40 years and save significant costs through sparing of expensive nutrients but the mechanism by which this is achieved is still debated. 2. The research focused on non-starch polysaccharidase (NSPase) enzymes is used as an example of where greater progress could have been made if the details of the work had been described more fully and the analysis of the data generated had been broader in scope and more critical. 3. Lack of standardisation of the details presented in the materials and methods has been identified as a significant barrier to meaningful retrospective analysis and thus limits advances in the understanding of the mode of action of these enzymes. 4. The identity of the enzyme employed and its activity is often lacking, and more importantly the purity is rarely disclosed. Contaminant activities which are neither listed nor assayed could play a significant role in the responses observed. 5. The dose optimum of most enzymes is often considerably higher than that employed in most studies. Thus studies claiming synergy between two 'activities' should ensure that the response is not related to each enzyme simply augmenting the dose of just one activity in the finished feed. This is a common problem, and coupled with the lack of factorial experiments to justify the presence of each enzyme in a multi-enzyme product, it is not surprising that there is still debate as to whether single or multi-enzymes are best suited poultry rations. 6. The three proposed mechanisms for NSPases (viscosity, cell wall and prebiotic) are discussed, and along with their strengths and weaknesses it is suggested that a re-evaluation of each is needed. Viscosity may have to be re-evaluated as being a function not only of the cereal being fed, but of the age of the animal as well. The cell wall theory as described is poorly modelled in vitro and hence the validity of these data is questioned. The prebiotic theory may need significant modification as it appears that the quantities of oligomers produced are insufficient to generate the additional volatile fatty acids (VFA)'s reported. It is likely that all three mechanisms play a role in the responses observed, but the prebiotic mechanism probably plays by far the most important part in low viscosity diets. 7. Future research would be improved if it considered all potential mechanisms when designing a trial. Significant failings are apparent as a result of adherence to tenets in explanation of the results. Most importantly, it should be emphasised that a hypothesis is there to be tested, not defended.

Ovodefensins, an Oviduct-Specific Antimicrobial Gene Family, Have Evolved in Birds and Reptiles to Protect the Egg by Both Sequence and Intra-Six-Cysteine Sequence Motif Spacing.

Ovodefensins are a novel beta defensin-related family of antimicrobial peptides containing conserved glycine and six cysteine residues. Originally thought to be restricted to the albumen-producing region of the avian oviduct, expression was found in chicken, turkey, duck, and zebra finch in large quantities in many parts of the oviduct, but this varied between species and between gene forms in the same species. Using new search strategies, the ovodefensin family now has 35 members, including reptiles, but no representatives outside birds and reptiles have been found. Analysis of their evolution shows that ovodefensins divide into six groups based on the intra-cysteine amino acid spacing, representing a unique mechanism alongside traditional evolution of sequence. The groups have been used to base a nomenclature for the family. Antimicrobial activity for three ovodefensins from chicken and duck was confirmed against Escherichia coli and a pathogenic E. coli strain as well as a Gram-positive organism, Staphylococcus aureus, for the first time. However, activity varied greatly between peptides, with Gallus gallus OvoDA1 being the most potent, suggesting a link with the different structures. Expression of Gallus gallus OvoDA1 (gallin) in the oviduct was increased by estrogen and progesterone and in the reproductive state. Overall, the results support the hypothesis that ovodefensins evolved to protect the egg, but they are not necessarily restricted to the egg white. Therefore, divergent motif structure and sequence present an interesting area of research for antimicrobial peptide design and understanding protection of the cleidoic egg.

Basis for the diversity and extent in loss of digestible nutrients created by dietary phytin: Emphasis on fowl and swine.

Phytin is the Ca2+-Mg2+-K+ salt of phytic acid that is created and deposited in the aleurone layer and/or germ of grains and legumes. Its high presence in feedstuffs for fowl and swine diets results in it being a universal and significant impediment to optimum performance. Phytin impairs gastrointestinal recovery of a wide array of nutrients, the effect varying with the nutrient concerned. On exposure to low pH during gastric digestion, phytin dissociates into phytic acid and solubilized Ca2+. Even at low gastric pH, phytic acid is negatively charged which forms the basis of its anti-nutritive behavior. Pepsinogen has extensive basic amino acids on its activation peptide that are presented as cations at low pH which are targeted by pepsin for activation. Partially crystalized Ca2+ near the enzyme's active site further stabilizes its newly formed structure. Thus, phytic acid appears to interfere with gastric digestion by several mechanisms; interfering with pepsinogen activation by binding to the polypeptide's basic amino acids; coordinating free Ca2+, destabilizing pepsin; binding some dietary proteins directly, further compromising gastric proteolysis. Upon digesta attaining neutrality in the duodenum, Ca2+ and other cations re-bind with accessible anions, phytic acid being a significant contender. Phytate not only binds free cations but can also strip them from enzymes (e.g. Ca2+, Zn2+) which reduces their structural resistance to autolysis and ability as co-factors (e.g. Zn2+) to increase enzyme activity. Goblet cells initially employ Ca2+ as an electronic shield between mucin layers enabling granule formation and cell storage. After mucin granule release, Ca2+ is progressively displaced by Na+ to free the viscous mucins enabling its translocation. Mucin entangles with the glycocalyx of adjacent enterocytes thereby constructing the unstirred water layer (USWL). Excessive removal of Ca2+ from mucin by phytic acid increases its fluidity facilitating its loss from the USWL with its associated Na+. This partly explains increased mucin and Na+ losses noted with high phytate diets. This review suggests that phytic acid binding of Ca2+ and less so Zn2+ is the basis for the diversity in nutrient losses encountered and that such losses are in proportion to dietary phytate content.

Dietary fibre effects and the interplay with exogenous carbohydrases in poultry nutrition.

A comprehensive understanding of the role of dietary fibre in non-ruminant animal production is elusive. Equivocal and conflated definitions of fibre coupled with significant analytical complexity, interact with poorly defined host and microbiome relationships. Dietary fibre is known to influence gut development, feed intake and passage rate, nutrient absorption, microbiome taxonomy and function, gut pH, endogenous nutrient loss, environmental sustainability, animal welfare and more. Whilst significant gaps persist in our understanding of fibre in non-ruminant animal production, there is substantial interest in optimizing the fibre fraction of feed to induce high value phenotypes such as improved welfare, live performance and to reduce the environmental footprint of animal production systems. In order to achieve these aspirational goals, it is important to tackle dietary fibre with the same level of scrutiny as is currently done for other critical nutrient classes such as protein, minerals and vitamins. The chemical, mechanical and nutritional role of fibre must be explored at the level of monomeric sugars, oligosaccharides and polysaccharides of varying molecular weight and decoration, and this must be in parallel to standardisation of analytical tools and definitions for speciation. To further complicate subject, exogenous carbohydrases recognise dietary fibre as a focal substrate and have varying capacity to generate lower molecular weight carbohydrates that interact differentially with the host and the enteric microbiome. This short review article will explore the interactive space between dietary fibre and exogenous carbohydrases and will include their nutritional and health effects with emphasis on functional development of the gut, microbiome modulation and host metabolism.

Unveiling the influence of adaptation time on xylanase and arabinoxylan-oligosaccharide efficacy: a study on nutrient digestibility, viscosity, and scanning electron microscopy in the small and large intestine of growing pigs fed insoluble fiber.

The experiment objective was to evaluate the impact of xylanase over time on viscosity and digestibility in growing pigs fed corn-based fiber. Twenty gilts with an initial body weight of 30.6 ±â€…0.2 kg (n = 5 per dietary treatment) were fitted with t-cannulae in the medial jejunum and terminal ileum, housed individually, and randomly assigned to one of four dietary treatments: low-fiber control (LF) with 10.4% total dietary fiber (TDF), 30% corn bran high-fiber control (HF; 26.4% TDF), HF + 100 mg xylanase/kg (XY; Econase XT 25P; AB Vista, Marlborough, UK), and HF + 50 mg arabinoxylan-oligosaccharide/kg (AX). Gilts were limit fed for three 17 d periods (P1, P2, P3); each included 5 d adaptation, 2 d fecal collection, 3 d ileal collection, 3 d jejunal collection, and 4 d related rate of passage study. Data were analyzed as repeated measures using a linear mixed model with surgery date as a random effect, and dietary treatment, period, and their interaction as fixed effects. Jejunal and ileal digesta viscosity did not differ among dietary treatments or periods (P > 0.10). There was a dietary treatment × period interaction for the apparent jejunal digestibility (AJD) of dry matter (DM), gross energy (GE), insoluble dietary fiber (IDF), neutral detergent fiber (NDF), total arabinoxylan (T-AX), total non-starch polysaccharide (T-NSP), and TDF (P≤ 0.05). In P1, LF had the greatest AJD of DM (15.5%), and relative to HF and AX, XY decreased it (9.3%, 10.1 %, and 6.3%, respectively). In P2, the AJD of DM in XY was greater than HF (11.7% vs. 9.1%) but did not differ from AX (10.5%). Relative to HF, in P3, XY increased AJD of DM (11.7 vs 15.3%), and AX decreased it (7.2%). For the AJD of NDF, AX performed intermediately in P1; in P2, relative to HF, XY, and AX increased the AJD of NDF (8.4%, 13.1%, and 11.7%, respectively), and in P3, XY, and LF did not differ (13.6 vs. 14.4%). A similar response was observed for the AJD of IDF and TDF, except for XY having the greatest AJD of IDF, T-AX, T-NSP, and TDF in P3 (P < 0.05). Compared to LF, irrespective of period, HF decreased the apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of IDF, TDF, and NDF (P < 0.05). Relative to HF, XY partially mitigated this effect, improving the AID and ATTD of TDF, IDF, and NDF (P < 0.05). Increased corn-based fiber decreased nutrient digestibility, but XY partially mitigated that effect in the small intestine through enhanced fiber digestibility when given sufficient adaptation time.

This study investigated the effects of xylanase and arabinoxylan-oligosaccharide supplementation on viscosity, nutrient and energy digestibility in growing pigs fed a high-fiber diet mainly composed of corn over three time periods. Twenty pigs were surgically fitted with cannula in their jejunum and ileum for sample collection. The pigs were randomly assigned to one of four dietary treatment groups: low-fiber control, high-fiber control, xylanase supplementation, and arabinoxylan-oligosaccharide supplementation. The results showed no significant differences in digesta viscosity among dietary treatments. However, there was an interaction between dietary treatment and time for the digestibility of dry matter, gross energy, and dietary fibers. Initially, xylanase did not impact digestibility, but it improved over time. Conversely, arabinoxylan-oligosaccharide initially improved digestibility but declined by the third period. Findings suggest that the efficacy of xylanase in enhancing nutrient and energy digestibility in pigs fed high-fiber diets may depend on the length of the adaptation period. Xylanase supplementation also demonstrated the potential to counteract the negative effects of high-fiber diets. Further research is needed to optimize the application of xylanase in swine production and determine the optimal conditions for its effectiveness.

Interactive effects of a stimbiotic supplementation and wheat bran inclusion in corn- or wheat-based diets on growth performance, ileal digestibility, and expression of nutrient transporters of broilers chickens.

A 42-day experiment was conducted to investigate the interactive effects of a stimbiotic (STB) and wheat bran (WB) in broiler chickens receiving diets (DT) based on corn or wheat. A total of 960 Cobb 500 male broiler chicks at zero-day old were allocated to 64 pens with 8 treatments, 8 replicates per treatment, and 15 birds per replicate. The treatments were arranged in a randomized complete block design with 2 × 2 × 2 factorial, with the factors as diet (corn-soybean meal or wheat-soybean meal), STB (with or without), and WB (0 or 50 g/kg). Body weight gain (BWG), feed intake (FI), and mortality-corrected FCR data were collected for the starter (d 0-10), grower (d 10-28), and finisher (d 28-42) phases. Ileal digesta and jejunal tissue were collected on d 18 and 42. Data were analyzed as a 2 × 2 × 2 factorial using a mixed model of JMP. There was no significant 3-way interaction for growth performance and expression of nutrient transporters. There was a significant SB × WB for FCR (P < 0.05) in the grower phase. Stimbiotic supplementation and WB inclusion individually improved (P < 0.05) FCR regardless of cereal type, but this effect was not observed when the two were combined. In the overall phase (d 0-42), birds receiving corn-based diets had higher (P < 0.05) FI and BWG than those receiving wheat-based diets. There was a significant 3-way interaction for ileal digestible energy (IDE) (P < 0.05) and N digestibility (ND) on d 18 and 42 (P < 0.05). There was no effect of STB or WB in corn-based diets, whereas WB inclusion decreased IDE in wheat-based diets, but STB supplementation increased IDE with or without WB. In corn-based diets, WB inclusion increased ND, whereas ND was decreased in wheat-based diets. Supplementation with STB had no effect on ND, but STB increased ND in wheat-based diets with and without WB. Ileal DE was greater (P < 0.05) for wheat- than corn-based diets on d 42. Wheat bran inclusion increased ND in corn-based diets whereas, with STB supplementation, there was no difference in ND with or without WB. There was no difference in ND with or without STB or WB in wheat-based diets. There was a significant STB × DT on the expression of GLUT-1 (P < 0.05). In corn-based diets, STB produced an upward expression of GLUT-1, whereas in wheat-based diets, STB supplementation had no effect. On d 42, stimbiotic supplementation produced upward (P < 0.05) expression of SGLT-1. In conclusion, STB supplementation in wheat- or corn-based diets and with WB inclusion improved energy digestibility. On the other hand, WB inclusion in wheat-based diets decreased nutrient digestibility especially on d 18, thus making room for a positive response to STB supplementation in wheat-based diets compared to the marginal response to STB supplementation observed in corn-based diets.

Dietary xylo-oligosaccharides and arabinoxylans improved growth efficiency by reducing gut epithelial cell turnover in broiler chickens.

BACKGROUND: One of the main roles of the intestinal mucosa is to protect against environmental hazards. Supplementation of xylo-oligosaccharides (XOS) is known to selectively stimulate the growth of beneficial intestinal bacteria and improve gut health and function in chickens. XOS may have an impact on the integrity of the intestinal epithelia where cell turnover is critical to maintain the compatibility between the digestive and barrier functions. The aim of the study was to evaluate the effect of XOS and an arabinoxylan-rich fraction (AXRF) supplementation on gut function and epithelial integrity in broiler chickens. METHODS: A total of 128 broiler chickens (Ross 308) were assigned into one of two different dietary treatments for a period of 42 d: 1) control diet consisting of a corn/soybean meal-based diet; or 2) a control diet supplemented with 0.5% XOS and 1% AXRF. Each treatment was randomly distributed across 8 pens (n = 8) with 8 chickens each. Feed intake and body weight were recorded weekly. On d 42, one male chicken per pen was selected based on average weight and euthanized, jejunum samples were collected for proteomics analysis. RESULTS: Dietary XOS/AXRF supplementation improved feed efficiency (P < 0.05) from d 1 to 42 compared to the control group. Proteomic analysis was used to understand the mechanism of improved efficiency uncovering 346 differentially abundant proteins (DAP) (Padj < 0.00001) in supplemented chickens compared to the non-supplemented group. In the jejunum, the DAP translated into decreased ATP production indicating lower energy expenditure by the tissue (e.g., inhibition of glycolysis and tricarboxylic acid cycle pathways). In addition, DAP were associated with decreased epithelial cell differentiation, and migration by reducing the actin polymerization pathway. Putting the two main pathways together, XOS/AXRF supplementation may decrease around 19% the energy required for the maintenance of the gastrointestinal tract. CONCLUSIONS: Dietary XOS/AXRF supplementation improved growth efficiency by reducing epithelial cell migration and differentiation (hence, turnover), actin polymerization, and consequently energy requirement for maintenance of the jejunum of broiler chickens.

Using in feed xylanase or stimbiotic to reduce the variability in corn nutritive value for broiler chickens.

This study investigated the effects of xylanase and stimbiotic (fiber fermentation enhancer) on the response of broiler chickens fed different corn varieties and determine correlations between variables of interest. Four corn genetic varieties were selected based on their range in nutrient composition. Diets containing 600 g/kg of each corn were supplemented with 0 or 100 g/ton of xylanase or stimbiotic. A total of 1,152 one-day-old male broiler chicks (Ross 308) were divided into 12 treatments, each with 8 pens and 12 birds per pen, for a 21-day study. On d 21, performance parameters were measured, and the ileal energy and organic matter (OM) digestibility and cecal xylanase activity determined. Stimbiotic supplementation improved mFCR compared with all other treatments. There was a treatment by corn variety interaction for body weight (BW), BW gain and coefficient of variation (CV) of BW (P ≤ 0.05). Birds fed corn Variety 1 (highest neutral dietary fiber, protein and soluble arabinoxylan content) supplemented with stimbiotic had the highest BW, while Variety 2 control diet had the lowest. The BW CV in corn Variety 2 was the highest, which improved with stimbiotic supplementation. The BW CV in corn Variety 1 responded better to stimbiotic than xylanase. There were no treatment differences on BW CV in corn Varieties 3 and 4. The lowest OM digestibility was observed in birds fed corn Variety 1 with xylanase, and the highest value was associated with corn Variety 3 with xylanase (highest total arabinoxylan). Xylanase and stimbiotic supplementation increased the endogenous xylanase activity regardless of the corn variety (P ≤ 0.05). Positive correlations between corn fiber contents and phytic acid and the arabinose:xylose ratio were seen, while nonstarch polysaccharide content was negatively correlated with apparent metabolizable energy. In conclusion, corn variety influenced nutrient digestibility and broiler chicken growth. The response to supplementation with xylanase or stimbiotic varied based on the nutritional profile of corn with regards to improvements in digestibility and performance in broiler chickens.

Endogenous mucin conveyed to the mucosa with microbes can assure lumen fermentation and large intestinal security-swine versus fowl.

Endogenous protein leaving the ileum largely consists of accrued mucins from the upper gastrointestinal tract (GIT) that had resisted digestion. The amounts released rely on their mucosal generation during enteral feeding which vary with age as well as diet. These digestion resistant proteins of endogenous origin continue to be unavailable in the large intestine, whereas those of dietary origin provide amino acids that largely support the existing microbial population while denying limited amounts for absorption. Other mucins pre-exist within the large intestine as two layers at the lumen surface. A loose layer harboring a diverse microbial population is superimposed on the unstirred water layer (USWL) which simultaneously acts as an obstacle to microbes at the loose layer while performing as a molecular sieve for nutrients. The USWL is formed through interplay between enterocyte and goblet cells; however, the basis for presence of the loose layer is elusive. Large intestinal fermentation predominates within the colon of swine, whereas fowl employ their ceca. Motility within the colon of swine segregates fine materials into haustrae out-pocketings that parallel their placement within the ceca of fowl. Viscous mucins from small intestinal endogenous losses may envelop microbes within the large intestinal lumen to present successive adherents on the USWL that assemble its loose layer. The loose layer continually functions as a microbial reservoir in support of lumen fermentation. Microbial catabolism of mucin within the loose layer is known to be slow, but its proximity to the enterocyte is of advantage to enterocyte absorption with by-product amino acids fostering the USWL.

Reduced-particle size wheat bran and endoxylanase supplementation in broiler feed affect arabinoxylan hydrolysis and fermentation with broiler age differently.

Since the caecal microbiota of young broilers are not yet able to ferment the dietary fibre (DF) fraction of the feed to a large extent, increasing the accessibility of DF substrates along the gastrointestinal tract is crucial to benefit from the health stimulating metabolic end-products (e.g. butyric acid) generated upon microbial DF fermentation. Therefore, the present study aimed to evaluate the potential of reduced-particle size wheat bran (RPS-WB) and endoxylanases as feed additives to stimulate arabinoxylan (AX) hydrolysis and fermentation along the hindgut of young broilers. To this end, RPS-WB and endoxylanase supplementation were evaluated in a 2 × 2 factorial design using a total of 256 male 1-d-old chicks (Ross 308). Broilers were assigned to 4 dietary treatments: a basal wheat-based diet with (1) no feed additives (control, CTRL), (2) an endoxylanase (XYL; Econase XT 25 at 0.10 g/kg diet), (3) 1% wheat bran with an average reduced particle size of 297 µm (RPS-WB) and (4) an endoxylanase and 1% RPS-WB (RPS-WB + XYL). Each dietary treatment was replicated 8 times and on d 10 and 28, respectively, 24 and 16 broilers per treatment group were euthanised to analyse AX degradation, short-chain fatty acid production and digesta viscosity in the ileum and caecum. Broilers receiving XYL in their diet showed increased AX solubilisation and fermentation at both d 10 and 28 compared to the CTRL group (P < 0.05). Adding RPS-WB to the diet stimulated wheat AX utilisation by the primary AX degraders in the caecum at 10 d of age compared to the CTRL group, as observed by the high AX digestibility coefficient for the RPS-WB supplemented group at this young age (P < 0.05). At 28 d, RPS-WB supplementation lowered body-weight gains but increased butyric acid concentrations compared to the XYL and CTRL group (P < 0.05). Although no synergistic effect for RPS-WB + XYL broilers was observed for AX hydrolysis and fermentation, these findings suggest that both additives can raise a dual benefit to the broiler as a butyrogenic effect and improved AX fermentation along the ileum and caecum were observed throughout the broiler's life.

Calcium Nutrition of Broilers: Current Perspectives and Challenges.

Calcium (Ca) plays an essential role in poultry nutrition as 99% of Ca is located in birds' skeletal system. However, oversupply of Ca rather than deficiency of Ca is the current concern in commercial broiler diets. Calcium is an inexpensive dietary nutrient due to the cheap and abundant availability of limestone, the major Ca source; therefore, little attention was given to the oversupply of Ca in the past. The recent shift in the use of digestible P in broiler feed formulations has necessitated a closer look at digestible Ca, as Ca and P are interrelated in their absorption and postabsorptive utilisation. In this context, data on ileal digestibility of Ca and P in ingredients has been determined. Preliminary data on the digestible Ca and digestible P requirements for the different growth stages of broilers have also recently become available. The present review focusses on these recent advances in Ca nutrition. In addition, aspects of homeostatic control mechanisms, different Ca sources and factors influencing Ca digestibility in poultry are covered.

Accentuating the positive and eliminating the negative: Efficacy of TiO2 as digestibility index marker for poultry nutrition studies.

Inert digestibility index markers such as titanium dioxide are universally accepted to provide simple measurement of digestive tract retention and relative digestibility in poultry feeding trials. Their use underpins industry practice: specifically dosing regimens for adjunct enzymes added to animal feed. Among these, phytases, enzymes that degrade dietary phytate, inositol hexakisphosphate, represent a billion-dollar sector in an industry that raises ca. 70 billion chickens/annum. Unbeknown to the feed enzyme sector, is the growth in cell biology of use of titanium dioxide for enrichment of inositol phosphates from extracts of cells and tissues. The adoption of titanium dioxide in cell biology arises from its affinity under acid conditions for phosphates, suggesting that in feeding trial contexts that target phytate degradation this marker may not be as inert as assumed. We show that feed grade titanium dioxide enriches a mixed population of higher and lower inositol phosphates from acid solutions. Additionally, we compared the extractable inositol phosphates in gizzard and ileal digesta of 21day old male Ross 308 broilers fed three phytase doses (0, 500 and 6000 FTU/kg feed) and one inositol dose (2g/kg feed). This experiment was performed with or without titanium dioxide added as a digestibility index marker at a level of 0.5%, with all diets fed for 21 days. Analysis yielded no significant difference in effect of phytase inclusion in the presence or absence of titanium dioxide. Thus, despite the utility of titanium dioxide for recovery of inositol phosphates from biological samples, it seems that its use as an inert marker in digestibility trials is justified-as its inclusion in mash diets does not interfere with the recovery of inositol phosphates from digesta samples.

Stimbiotic supplementation and xylose-rich carbohydrates modulate broiler's capacity to ferment fibre.

Stimbiotics are a new category of feed additives that can increase fibre fermentability by stimulating fibre-degrading microbiota in the gut. The aim of this study was to test, ex vivo, if the microbiota of broilers fed a stimbiotic are better able to ferment different xylose-rich substrates in an ileal and a caecal environment. The ileal and caecal contents from broiler chickens fed a stimbiotic or from a control group were used as an inoculum in the ex vivo fermentation experiment. Different xylose-rich substrates including monomeric xylose (XYL), XOS with DP 2 to 6 (XOS), short DP XOS of 2 to 3 (sDP-XOS), long DP XOS of 4 to 6 (lDP-XOS) and de-starched wheat bran (WB), were added to each ileal and caecal inoculum in fermentation vessels. Total gas, short-chain fatty acids (SCFA) production, bacterial quantification, and carbohydrate utilisation were monitored for 9 h post-inoculation. No significant interactions were observed in any of the parameters measured in either the ileal or caecal contents (p > 0.05). Stimbiotic ileal inocula resulted in higher total gas (p < 0.001) and volatile fatty acid (VFA) (p < 0.001) production, increased numbers of Lactobacillus spp. (p < 0.001), and decreased numbers of Enterococcus spp. (p < 0.01) after 9 h regardless of the xylose-rich substrate added. Stimbiotic caecal inocula resulted in a higher ratio of VFA to branched-chain fatty acids (BCFAs) by up to +9% (p < 0.05). Ileal microbiota were found to preferentially metabolise WB, while caecal microbiota favoured XOS substrates, particularly lDP-XOS. These results indicate that stimbiotics can promote the abundance of lactic acid bacteria involved in the establishment of fibre-degrading bacteria and VFA content in the gut, which could have beneficial effects on broiler performance. Further, ileal and caecal microbiota differ in their utilisation of different substrates which may impact the effectiveness of different stimbiotic products.

Diet medication and beta-glucanase affect ileal digesta soluble beta-glucan molecular weight, carbohydrate fermentation, and performance of coccidiosis vaccinated broiler chickens given wheat-based diets.

Exogenous enzymes as alternatives to feed antibiotics in poultry has become an emerging research area with the emergence of antibiotic resistance. The objective was to evaluate the effects of diet medication (antibiotics) and ß-glucanase (BGase) on digesta soluble ß-glucan depolymerization, carbohydrate fermentation, and performance of coccidiosis-vaccinated broiler chickens fed wheat-based diets. A total of 1,782 broilers were raised on litter floor pens, and each treatment was assigned to 1 pen in each of the 9 rooms. The 3 dietary treatments were based on wheat as the sole grain (control, control + medication and control + 0.1% BGase), and the birds were fed the respective treatments ad libitum from 0 to 33 d. Treatments were arranged in a randomized complete block design and analyzed as a one-way ANOVA. Beta-glucanase reduced the peak molecular weight, weight average molecular weight (Mw) and maximum molecular weight for the smallest 10% ß-glucan molecules (MW-10%) in ileal digesta at d 11 and 33, whereas diet medication reduced Mw and MW-10% at d 33 compared to the control (P < 0.01). Beta-glucanase and medication reduced the ileal viscosity at d 11 compared to the control (P = 0.010). Ileal propionic acid concentration at d 11 and caecal total SCFA, acetic, and butyric acid concentrations at d 33 were lower in the BGase-supplemented diet than in the control (P < 0.05). The BGase-added diet had higher duodenal pH compared to the control at d 33 (P = 0.026). The effect of medication on carbohydrate fermentation was minimal. Diet medication increased weight gain after d 11, whereas BGase increased the gain for the total trial period compared to the control (P < 0.001). Feed intake was not affected by the dietary treatment. Medication and BGase improved feed efficiency after d 11 compared to the control (P < 0.001). The response to diet medication was larger than BGase, considering weight gain and feed efficiency after d 11 (P < 0.001). In conclusion, diet medication and BGase depolymerized high molecular weight ileal soluble ß-glucan and increased overall bird performance. Dietary BGase may benefit bird health in broilers fed wheat-based diets without medication.

Improving sorghum digestion in broilers by targeting fermentation of xylan.

This study was to examine if it is possible to accelerate sorghum digestion in broiler chickens by targeting fermentation of the xylan. Cobb 500 broilers (n = 960, 80 birds per treatment) were fed 12 sorghum-soybean meal-based dietary treatments fed as 3 phases (starter d 0 to 12, grower d 13 to 23, finisher d 24 to 35), with 8 replicate pens of 10 birds per treatment. For half of the treatments (n = 6), 10% of the sorghum in the diet was directly replaced with 10% wheat bran, as a source of fermentable fibre. The diets were supplemented with either 0, 50 or 2,000 mg/kg xylo-oligosaccharides (XOS), with or without xylanase application. Body weight gain (BWG), feed intake (FI) and feed conversion corrected for mortality (cFCR) was determined at d 0 to 35, and male and female body weight were measured on d 35. On d 35, ileum and caeca samples were collected from 2 birds per pen, for determination of caecal cellulase and xylanase activity, microbiota composition and short chain fatty acid (SCFA) concentration, and ileal XOS concentration. Supplementation with 2,000 mg/kg XOS caused increased BWG at d 0 to 35 (P = 0.007) and enhanced caecal propionic, valeric and succinic acid concentration (P < 0.05). Wheat bran increased FI (P = 0.018) and BWG (P = 0.016), as well as caecal Bifidobacteria concentration (P < 0.001). Ileal XOS concentration was greatest when feeding combined wheat bran, 2,000 mg/kg XOS, and xylanase, resulting in increased caecal total SCFA, acetic acid and butyric acid concentration, and xylanase and cellulase activity (P < 0.05). Results from this study present that feed efficiency in birds fed sorghum-based diets is improved as a consequence of supplementing with fermentable fibre, xylanase and XOS.

Large intestinal dynamics differ between fowl and swine: Anatomical modifications, microbial collaboration, and digestive advantages from fibrolytic enzymes.

The large intestinal systems of fowl and swine recover nutrients from ileal indigesta by a strategically different manner. Indigesta with fowl enter a short colon where retro-peristalsis using urine from the urodeum carries small particulates and solutes into both ceca while coarse materials collect in the cloaca. Fowl repetitively add fine and soluble materials into both ceca to continue fermentation until complexity of the remainder exceeds microbial action, then contents apart from faeces are entirely evacuated. Indigesta with swine initially enter a short cecum followed by a lengthy progression through to the rectal ampulla. Wall out-pocketings of circular muscle or haustrae occur throughout the length of the pig's cecum and helicoidal colon. Each pocket carries contents acquired earlier in the cecum. Motility collects fines and solutes into haustrae during their progression through the colon whereas coarse particulates assemble in the core. Haustrae contents continually ferment during movement to the distal colon with resulting volatile fatty acids (VFA) and electrolytes being absorbed. Mucin loosely covers the lumen surface in caeca as well as helicoidal colon that may capture microbes from active intestinal contents as well as release others to sustain fermentation. The microbial community continually modifies to accommodate fibre complexity as encountered. Resistant starches (RS) and simple oligosaccharides rapidly ferment to yield VFA while encouraging butyric acid in the cecum and anterior colon, whereas non-starch polysaccharides (NSP) complexity requires extended durations through the remaining colon that enhance acetic acid. Residual fibre eventually results in undue complexity for fermentation and consolidates at termination of the colon. These compact pellets are placed on core contents to form faeces having a nodular surface. Acetic, propionic, and butyric acids represent the bulk of VFA and are derived from non-digestible carbohydrates. Fibrolytic enzymes, when supplemented to feed, may increase the proportion of oligosaccharides and simpler NSP to further the rate as well as extent of fermentation. Active absorption of VFA by mucosal enterocytes employs its ionized form together with Na+, whereas direct membrane passage occurs when non-dissociated. Most absorbed VFA favour use by the host with a portion of butyric acid together with by-products from protein digestion being retained to reform mucin and sustain mucosal integrity.

Effects of supplemental myo-inositol on growth performance and apparent total tract digestibility of weanling piglets fed reduced protein high-phytate diets and intestinal epithelial cell proliferation and function.

Myo-inositol is a breakdown product of phytate produced in the gut through the action of phytase. Although the effect of phytase-released phosphorus (P) on growth performance of animals has been well characterized, there is still little understanding of the effect of myo-inositol. The first objective of this study was to determine the effects of added myo-inositol to a phytate-rich low-protein diet on growth performance and apparent total tract digestibility (ATTD) in growing piglets. The second objective was to determine whether myo-inositol could directly affect intestinal epithelial cell proliferation and function for which we used intestinal porcine epithelial cells (IPEC-J2). A total of 128 weanling piglets were allotted to four dietary treatments consisting of eight replicates per treatment and four piglets per replicate in a randomized complete block design for 4 wk. The four experimental diets comprised the positive control [PC; 20% crude protein (CP)], negative control (NC; 17% CP), negative control plus 2.0g/kg myo-inositol (NC+INO; 17% CP), and negative control plus 3000FTU/kg phytase (NC+PHY; 17% CP). Average daily feed intake (ADFI), average daily gain (ADG), and gain-feed ratio (G: F) were recorded. Phytase supplementation in the protein-deficient NC diet increased the G:F ratio (P < 0.05) without myo-inositol effects on growth performance. Phosphorus digestibility in the phytase-supplemented group increased compared to the PC, NC, and NC+INO groups, whereas plasma myo-inositol concentration was significantly higher (P < 0.05) in the NC+INO group. Due to the lack of myo-inositol effect on growth performance, an additional in vitro study was conducted to determine the direct effect of myo-inositol on the intestinal epithelium that might not be reflected in growth performance. Myo-inositol increased the mRNA abundance of selected nutrient transporters in a concentration-dependent manner (P < 0.05). Myo-inositol also enhanced barrier integrity in the IPEC-J2 monolayer by increasing the transepithelial electrical resistance (TEER) with reduced paracellular permeability of FITC-dextran (P < 0.05). In conclusion, despite the lack of myo-inositol effect on animal performance, the in vitro data indicate that myo-inositol may directly regulate gut barrier integrity. Addition of myo-inositol to pig diets at levels that enhance intestinal epithelial cell function may result in effects on growth performance and gut health of pigs.

After weaning, piglets undergo various kinds of stress that limit feed intake and nutrient digestibility. Much of the effects are strongest at the still-developing gastrointestinal tract where active feed digestion and nutrient uptake takes place. To sustain intestinal development and function during this stage of life, several nutrient additives are included in diets to promote intestinal function and nutrient uptake. The objective of this study was to assess the effects of phytase and myo-inositol on growth performance and apparent total tract digestibility (ATTD) in growing piglets and determine whether they had any effects on integrity in a cell culture model. In the animal study, phytase supplementation in the protein-reduced diets enhanced the rate of feed conversion, whereas the effect of myo-inositol on growth was not pronounced. Also, plasma concentration increased with myo-inositol addition. Under cell culture condition, myo-inositol enhanced the machinery for nutrients uptake and protein formation of the cells in a fashion that is dependent on its concentration. This study provides information on the potential role of myo-inositol on growth performance of growing piglets.

Effects of diet hulless barley and beta-glucanase levels on ileal digesta soluble beta-glucan molecular weight and carbohydrate fermentation in laying hens.

Exogenous ß-glucanase (BGase) improves nutrient digestibility and production performance in laying hens fed barley-based diets, but the effect of enzyme and the dosage on ß-glucan depolymerization and fermentation in the gastrointestinal tract is poorly understood. The objectives of the study were to determine the effects of hulless barley (HB) and BGase levels on digestive tract ß-glucan depolymerization and fermentation in laying hens. A total of 108 Lohman-LSL Lite hens were housed in cages and fed 2 levels of HB (CDC Fibar; 0 and 73%) by substituting wheat in the diet and graded levels of BGase (Econase GT 200 P from ABVista; 0, 0.01 and 0.1% - 0, 20,000, and 200,000 BU/kg) in a 2 × 3 factorial arrangement. Birds were fed experimental diets for 8 weeks, starting at 35 wk of age. Digestive tract samples were collected at the end of the experiment. Statistical significance was set at P ≤ 0.05. Beta-glucan peak molecular weight was lower with the 0.1 compared to both 0 and 0.01% BGase levels, whereas weight average molecular weight was lower with the 0.1 compared to 0% BGase for 73% HB. The maximum molecular weight for the smallest 10% ß-glucan molecules decreased with the increasing BGase. Overall, ß-glucan molecular weight in the ileum was higher when the birds were given 73 in comparison to 0% HB diets. Total and major short chain fatty acids (SCFA) in the ileum were lower with 0.1 and 0.01 (except propionic acid) compared to 0% BGase in the birds fed 73% HB, but not 0% HB. Interactions between the main effects were found for the cecal acetic and isobutyric acids. In conclusion, exogenous BGase depolymerized high molecular weight ß-glucan in HB and wheat. The effects of HB and BGase on carbohydrate fermentation were not apparent, although it appears ileal SCFA concentrations were lower with increasing levels of BGase.