Xavière RousseauGlobal Poultry Technical Manager – AB Vista
There is a high interest towards fibre understanding and how this can be optimally used in feed formulation for monogastric, to improve performance and guarantee a good gastrointestinal health. The past years a lot of work has been conducted by the AB Vista team, in cooperation with researchers from across the globe, in the area of fibre for monogastric nutrition.
Extensive work has been done to better characterize fibre beyond the traditional measurement of crude fibre in poultry, or Neutral Detergent Fibre (NDF) and Acid Detergent Fibre (ADF) in swine. Thanks to the NIR technology it is now feasible to quickly and robustly assess the characteristics of the total dietary fibre including lignin and total and soluble Non-Starch Polysaccharides (NSPs) based on constituent sugars (Gomes et al., 2020). Soluble NSPs seems to be a relevant criterion to look at, due to their effect on viscosity, transit rate, digestibility as well as in being the main substrate for hindgut fermentation resulting in Short Chain Fatty Acid (SCFA) production. Recent data suggests that more mature animals, with an established fibre fermenting microbiome, respond positively to higher level of soluble NSPs whilst younger animals, if the microbiome has not been stimulated to ferment fibre, would respond negatively in terms of performance (Gomes et al., under publication).
Soluble NSPs can be beneficial in terms of growth performance and gut functionality through the development of a fibrolytic environment and limiting the potential pathogenic bacteria growth (Nguyen et al., 2021; Rousseau et al., under publication), but to obtain this response it needs to be used correctly. In broiler chickens, Nguyen et al. from University of New England, Australia, investigated the effect of fibre on gastro-intestinal tract development, welfare and behaviour. They confirmed what Bedford et al., (1991) observed earlier as a linear increase of ileal viscosity with higher concentration of soluble NSPs. This effect is more pronounced in wheat than in corn-based diets, mainly because of the higher NSP content in wheat and greater proportion of higher molecular weight NSP in wheat compared to corn (Bedford et al., 1991; Kiarie et al., 2014) but could also be explained by the different soluble components proportion between both cereals. How the birds can deal with soluble NSP depends on several factors (environment, litter etc) as it will determine the establishment of the microbiome and explain therefore why different results can be achieved depending on how studies are conducted. Nguyen et al. also showed that more soluble NSP in the diet means lower pH in the lower gut, reflecting more fermentation of carbohydrates into SCFA, giving less opportunity for pathogenic bacteria to establish as described previously by Apajalahti (2005). When calculating the total feed fibre composition from the diets reported by Nguyen, using the values reported in the Fibre Guide (AB Vista), it was possible to isolate the effects of the different soluble NSPs and the main driver for SCFA production was the soluble Arabinose + Xylose fraction while the other soluble components had limited or even negative effect in terms of fibre ermentability. These results reinforce that beyond the relevance to look at NSP solubility, it’s also important to look at the different components within this fraction.
Researchers from the Universitat Autonoma de Barcelona used the AB Vista FQS NIR calibrations to explore the nutrient variability depending on the genetics of 8 maize hybrids as well as position of the grains in the cob (basal, well developed grains versus apical, less well-developed grains; Melo-Duran et al., 2021). Interestingly, in the majority of the criteria evaluated, there was an interaction between the genetic and the position of the grain (apical vs basal), often indicating poorer feeding value of the apical grains but for some of the hybrids there were minor differences between apical and basal grains, suggesting that those hybrids would give less variability in a grain crop. Regarding fibre, a large variation was also observed for total and soluble NSPs including the arabinoxylan (AX) concentration. Although the AX concentration in maize is low compared to other cereals this work showed that genetics can play an important role with a range from 2.2 g/kg to 5.3 g/kg AX. This explains why some corns could behave like wheats in terms of viscosity but also highlights why the effect of xylanase in corn-based diet can fluctuate.
Xylanase and even more a stimbiotic product through the arabino xylo-oligosaccharides (AXOS) and xylo-oligosaccharides (XOS) production would be beneficial in bringing soluble compounds able to modulate the microbiome in the caeca. Relevance of a β-glucanase in highly viscous diets (containing both β-glucan and AX) is being questioned. β-glucanase, although reducing the viscosity and the molecular weight of β-glucan, did not affect the fermentation or the production of SCFA (Karunaratneet al., under publication). Morgan et al. from the University of New England (under publication) has shown that, in broilers fed wheat-barley based diet, a stimbiotic decreased the concentration of β-glucans in the ileal digesta and reduced the viscosity to the same extent as a combination of a xylanase and a β-glucanase but only the stimbiotic was proven to increase SCFA concentration in the hindgut, showing increased carbohydrate fermentation. Even though the stimbiotic product does not contain a β-glucanase itself, it could potentially stimulated production of this and other fibre degrading enzymes by the microbiome (and hence reduced β-glucan concentration as well as viscosity) which is an efficient strategy to alleviate the negative effect of barley in broiler diets.
In fact, several studies reported the beneficial effect from stimbiotic supplementation on microbiome modulation (Cordero et al., 2019; Parra Perez et al., 2021) through the stimulation of the fibrolytic bacteria that results in higher SCFA, low pH and increased caecal bacterial enzyme activity (Marinho et al., 2007; González-Ortiz et al., 2021). Altogether allowing a better gut resilience making animals better able to cope with enteric challenges. In fact, recent studies in poultry (Rousseau et al., under publication) and in swine (Cho et al., 2020) have demonstrated that the stimbiotic may be of interest to mitigate the enteric challenges animals are facing in commercial production systems. In the study from Cho et al., (2020), the stimbiotic reduced the inflammatory response from pigs placed in poor sanitary conditions, but also reduced the number of antibiotic interventions by 45%. Stimulating a more fibrolytic microbiome and lowering protein fermentation resulted in higher performing animals.
In conclusion, there is clear evidence that promoting carbohydrate fermentation is something to consider and must be a goal to achieve for anyone who wants to extract the hidden value from hindgut fermentation with healthier animals. Better characterisation of the fibre content of feed ingredients and use of stimbiotic represents a relevant strategy to bring better gut resilience to the animals facing multifactorial sources of challenges in commercial production systems.
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About Dr Xavière Rousseau
Dr Xavière Rousseau is Global Poultry Technical Manager in AB Vista based in France. She joined the company 9 years ago after completing her PhD working on dietary phosphorus optimisation in poultry and pigs with INRAE (France) and Agriculture and Agri-Food Canada. During this time, she built her knowledge on animal physiology and on the interactions between calcium, phosphorus and animal physiology before joining AB Vista team where she has developed her expertise on enzymes and how-to bring enzymes value to reach the different production objectives. Her last area of interest is to look at the dietary fibre fraction and how to better characterize this substrate as looking at the tools to analyse in order to define different strategies to optimize their use that would make sense for monogastric nutritionists looking for better productivity.