Arabinoxylan digestion and endoxylanase functionality in ageing broilers fed wheat-based diets

Wheat (Triticum aestivum L.) is a major energy component in European broiler feeds. However, the dietary fibre fraction of wheat largely consists of non-starch carbohydrates (NSC), mainly arabinoxylans (AX) which are known to evoke antinutritional effects in the gastrointestinal tract (GIT) of broilers. To overcome these antinutritive effects, endo-β-1,4-xylanases are frequently added to broiler diets. Since 1990 three mechanisms of action of feed endoxylanases are put forward. They include the removal of the physical barrier, and hence the nutrient encapsulating effect, composed of wheat cell walls and the reduction in intestinal viscosity. The third mechanism of action is of more recent date and attributes the beneficial effects upon endoxylanase addition to the formation of prebiotic arabinoxylan-oligosaccharides (AXOS). These would reduce the risk of pathogen infection and positively affect the microbial composition and gastrointestinal health. In spite of the knowledge gained on these mechanisms, part of the large inconsistency in response to endoxylanases as a function of farm, flock and time remains unexplained. This implies that there is still a lack of understanding of how these enzymes exactly work in vivo in the GIT of broilers. Moreover, insight into the predominant mode of action of feed endoxylanases is often obscured by the wide variety in broiler-, diet- and enzyme-related factors that highly influence the efficacy of these enzymes. As a consequence, only little progress in the optimisation of these feed enzymes and their application has been made during the last decade. Against this background, this doctoral dissertation aimed to contribute to a better understanding of AX digestion in broilers and the functionality of dietary endoxylanases and AX included in wheat-based broiler feeds. To this end, an in-depth evaluation of AX hydrolysis and fermentation in the GIT of broilers as a function of age was performed. The impact of dietary AX type and endoxylanase type and dose on this AX digestion and endoxylanase efficacy was also investigated more in detail. Broiler age and the age-related development of the microbial community revealed to be very important factors in determining AX digestion, and hence endoxylanase functionality in the hindgut of broilers. The incapability of the first colonising microbiota to digest the dietary AX was noticed at young broiler ages by the very low AX digestibility values, but an evolution towards a microbial community capable to digest wheat AX well at slaughter age was observed by the significant increase in AX digestibility values at this age. As the prebiotic mechanism is nowadays sometimes pointed out as a main working mechanism of endoxylanases, the contribution of AXOS as AX hydrolysis products to the age-related AX digestion in the hindgut of broilers was examined in more detail. Therefore, beyond the well-documented health and prebiotic effects, the additive effect of AXOS addition at a level of 0.50% to wheat-based diets containing no endoxylanases was investigated further. Our results indicate that the provision of AXOS in broiler diets has the potential to kick-start the AX digestion capacity of the young broiler microbiota, thereby resulting in steady digestion of the dietary fibre fraction of the feed from young broiler ages onwards. Plausible mechanisms explaining this kick-starter effect are not fully elucidated but are most likely the result of enhanced colonisation by microbial species harbouring a greater armoury of AX-degrading enzymes and/or a stimulus of gastrointestinal hormone responses which could beneficially affect the physiology of the GIT. As AXOS is a rather expensive dietary fibre source to add on top of a wheat-based diet, the potential of a readily available by-product of the milling industry, i.e. wheat bran with reduced particle size (RPS-WB) on AX digestion was investigated further in a second broiler trial. In this trial, we set out to examine if this RPS-WB source was able to induce a similar kick-starter effect at young broiler ages. In addition, the potentiating of this kick-starter effect upon addition of endoxylanases in combination with 1.0% RPS-WB was investigated more in detail. Results indicated that RPS-WB could alter the microbial community by introducing a greater abundancy of butyrate-producing microbiota, as observed by increasing levels of butyric acid in the caeca of broilers towards slaughter age. Despite this beneficial effect, no improved digestion of dietary AX was observed with 1.0% RPS-WB addition compared to the control. On the contrary, endoxylanase addition resulted in a marked increase in AX digestion, especially at young broiler ages. No synergistic effects on AX digestion were observed when both an endoxylanase and RPS-WB were added to the broiler's feed. It was however assumed that in larger-scale trials a combination of these supplements in wheat-based broiler diets can result in both an improved health and nutritional response. The chemical and physical appearance of AX in the diet hence largely dictate microbial responses and endoxylanase efficacy. To back these results, further research should aim to characterise microbial populations conferring to the kick-starter effect. In a final broiler trial, the influence of two types and three dosages of commercial endoxylanase preparations on AX digestion profiles as a function of broiler age were examined. Introducing an endoxylanase in the broiler's feed generally improved the feed conversion ratio (FCR) compared to the control as long as the dose applied was sufficiently high. Adding two different types of endoxylanase preparations resulted in the formation along the hindgut of a heterogeneous pool of AX products with distinct structural and physicochemical properties. An endoxylanase produced from B. subtilis was able to stimulate precaecal digestion of dietary AX by creating a large pool of solubles, without negatively affecting intestinal viscosity. An endoxylanase produced from N. flexuosa mainly triggered caecal AX fermentation by delivering easily fermentable AX substrates having a low degree of polymerisation and a low arabinose to xylose ratio. Endoxylanases should modify the dietary AX in such a way that both antinutritional effects displayed by these AX are reduced and the AX degrading capacity of the young microbiome is stimulated. This strategy will most likely generate the largest benefits regarding broiler health and performance. This doctoral dissertation led to new insights in and strategies based on feed endoxylanase functionality, enabling them to stimulate the AX degrading capacity of the young microbiome and increase the overall dietary fibre digestibility. Broiler age and the form under which AX is present in the dietary matrix were shown to be two very important factors determining AX digestion and endoxylanase efficacy. These factors should hence be taken into account when formulating broiler feeds to allow a further optimisation of the functional and nutritional value of dietary fibre in animal feed. Advancements in analytical tools that would allow continuous tracking of how the dietary fibre fraction is digested and which microbial metabolites are produced upon this fibre digestion in vivo, can aid to further unravel the full complexity of the mechanisms of action of feed enzymes in general and endoxylanases in particular in the near future.status: publishe

Fibres making up wheat cell walls in the context of broiler diets

status: Published onlin

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

Feed endoxylanase type and dose affect arabinoxylan hydrolysis and fermentation in ageing broilers

status: accepte

Arabinoxylan-oligosaccharides kick-start arabinoxylan digestion in the aging broiler

While arabinoxylans (AX), an important dietary fiber fraction of wheat-based broiler diets, are known for exerting antinutritional effects in the gastrointestinal (GI) tract of broilers, the prebiotic potential of arabinoxylan-oligosaccharides (AXOS) is also well-documented. However, inconsistent performance responses as well as the effectiveness of low amounts of AXOS used in diets of previously conducted experiments, put into question the classical prebiotic route being the sole mode of action of AXOS. The objective of this study was to investigate the effects of dietary AXOS addition on the rate of AX digestion in the GI tract of broilers as a function of broiler age in order to gain more insight in the mode of action of these oligosaccharides. A feeding trial was performed on 480 one-day-old chicks (Ross 308) receiving a wheat-based diet supplemented with or without 0.50% AXOS, containing no endoxylanases. Digesta samples from ileum and caeca and fecal samples were analyzed for AX content, AX digestibility, intestinal viscosity and microbial AX degrading enzyme activities at six different ages (d 5, 10, 15, 21, 28, 35). Chicks fed from hatching with 0.50% AXOS demonstrated a higher ileal viscosity (P < 0.05). Also higher levels of AX solubilization and fermentation compared to control birds at 10 d were observed. This was noted by the higher total tract AX digestibilities of water-extractable AX (WE-AX) and total AX (TOT-AX) at this age (P < 0.05). Although no significant difference in AX degrading enzyme activities was observed among the dietary treatments, AXOS supplementation in young broilers was shown to stimulate or “kick-start” dietary AX degradation, thereby speeding up the development of a fiber fermenting microbiome in the young broiler. This stimulation effect of AXOS could enable greater functional value to be extracted from dietary fiber in broiler feeds.status: publishe

Adaptation of the microbiome towards fibre digestion: Effects of age and dietary ingredients

status: Published onlin

Sugar Levels Determine Fermentation Dynamics during Yeast Pastry Making and Its Impact on Dough and Product Characteristics

Fermented pastry products are produced by fermenting and baking multi-layered dough. Increasing our knowledge of the impact of the fermentation process during pastry making could offer opportunities for improving the production process or end-product quality, whereas increasing our knowledge on the sugar release and consumption dynamics by yeast could help to design sugar reduction strategies. Therefore, this study investigates the impact of yeast fermentation and different sugar concentrations on pastry dough properties and product quality characteristics. First, yeasted pastry samples were made with 8% yeast and 14% sucrose on a wheat flour dry matter base and compared to non-yeasted samples. Analysis of saccharide concentrations revealed that sucrose was almost entirely degraded by invertase in yeasted samples after mixing. Fructans were also degraded extensively, but more slowly. At least 23.6 ± 2.6% of the released glucose was consumed during fermentation. CO2 production during fermentation contributed more to product height development than water and ethanol evaporation during baking. Yeast metabolites weakened the gluten network, causing a reduction in dough strength and extensibility. However, fermentation time had a more significant impact on dough rheology parameters than the presence of yeast. In balance, yeast fermentation did not significantly affect the calculated sweetness factor of the pastry product with 14% added sucrose. Increasing the sugar content (21%) led to higher osmotic stress, resulting in reduced sugar consumption, reduced CO2 and ethanol production and a lower product volume. A darker colour and a higher sweetness factor were obtained. Reducing the sugar content (7%) had the opposite effect. Eliminating sucrose from the recipe (0%) resulted in a shortened productive fermentation time due to sugar depletion. Dough rheology was affected to a limited extent by changes in sucrose addition, although no sucrose addition or a very high sucrose level (21%) reduced the maximum dough strength. Based on the insights obtained in this study, yeast-based strategies can be developed to improve the production and quality of fermented pastry

Toward Renewable-Based Prebiotics from Woody Biomass: Potential of Tailored Xylo-Oligosaccharides Obtained by Enzymatic Hydrolysis of Beechwood Xylan as a Prebiotic Feed Supplement for Young Broilers

Although antibiotic resistance emerges naturally, this process has been accelerated by the worldwide overuse and misuse of antibiotics. It is essential to find effective alternatives in the broiler industry to improve poultry health while maintaining production efficiency and product safety. In this study, we aimed to evaluate a potential alternative: wood-derived xylo-oligosaccharides (XOS). The objective of this research was to investigate the potential of XOS prepared using enzymatic hydrolysis of beechwood xylan as a prebiotic feed supplement for broilers. A pilot study was conducted to explore the optimal XOS fraction profile by in vitro fermentation. Subsequently, a semi-continuous enzyme membrane reactor was used, allowing for the production of tailored XOS in large quantities. Given the strong bidirectional relationship between intestinal health, nutrition, and intestinal microbiota composition in broilers, an in vivo experiment was performed to explore the potential of XOS as a prebiotic feed supplement by investigating growth performance, feed conversion ratio, caecal short and medium chain fatty acid (SCFA and MCFA) concentration, and microbiological composition of the caecal content. Results from the pilot study indicated that higher enzyme concentrations in the hydrolysis process yield a product that leads to a higher total SCFA and MCFA- and butyric acid production during in vitro fermentation by caecal bacteria. Supplementation of the tailored XOS to the broiler diet (day 1 (d1)-d8 0.13% wt/wt XOS, d9-d15 0.32% XOS) resulted in higher Bifidobacterium counts, beneficial to the health of birds, on d11 and d15

The effect of reduced balanced protein diet on the behavior of female broiler breeders in 2 two generations

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The effect of reduced balanced protein diet on the behavior of female broiler breeders in 2 generations

The behavior of 2 generations of broiler breeders undergoing a 25% reduced balanced protein (RP) dietary treatment was investigated in the current study. There were 2 treatments for the F0 generation: control (C) breeders fed with standard C diets and RP breeders fed with RP diets. The female progeny of each treatment was again subjected to 2 dietary treatments, resulting in 4 treatments for F1 generation: C/C, C/RP, RP/C, and RP/RP (breeder feed in F0/F1 generation). To maintain the target body weights throughout the trial, breeders on RP diet received on average 10% more feed than C diet breeders. The behavior of the breeders at 8h30 (30 min before feeding at 9h00), 12h00, and 15h30 in weeks 23 and 37 of the F0 generation and in week 6, 11, and 22 of the F1 generation was observed. Litter scratching, feather pecking, and object pecking were occasionally increased by RP diet feeding which indicated feeding frustration. Drinking behavior decreased dramatically by the RP dietary feeding and resulting in a better litter condition which could benefit dust bathing behavior. In addition, feeding the breeders RP diet in the F0 generation decreased litter scratching (week 6) and feather pecking (week 22, 15h30) but increased sitting (week 11, 15h30) and drinking (a tendency in week 6 and a significant effect in week 11) behavior of offspring breeders (F1 generation). In general, breeders fed with reduced balanced protein diets, to some extent, spent less time drinking and their offspring could have an adaptation to the maternal RP diet. The mechanism of this adaptation still needs to be further investigated. In general, positive effects were found by reducing protein level of breeder diets. However, negative side effects such as feeding frustration were also observed, which merit further study.status: publishe