Xavière Rousseau

Global  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 charac- terize fibre beyond the traditional measurement of crude fibre in poultry, or Neutral Deter- gent Fibre (NDF) and Acid Detergent Fibre (ADF) in swine. Thanks to the NIR technology it is now feasible to quickly and robustly assess the charac- teristics 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 cri- terion to look at, due to their effect on viscosi- ty, 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 pub- lication), but to obtain this response it needs to be used correctly.

In broiler chickens, Nguyen et al. from Univer- sity of New England, Australia, investigated the effect of fibre on  gastro-intestinal tract develop- ment, 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 pro- portion 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 differ- ent 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 micro- biome and explain therefore why different results can be achieved depending on how studies are conducted. Nguyen et al. also showed that more solu- ble NSP in the diet means lower pH in the lower gut, reflecting more fermentation of carbohydrates into SCFA, giving less opportunity for pathogen- ic bacteria to establish as described previously by Apajalahti (2005). When calculating the total feed fibre composition from the diets reported by Nguy- en, 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 + Xy- lose  fraction while the other soluble components had limited or even negative effect in terms of fibre fermentability. These results reinforce that beyond the relevance to look at NSP solubility, it’s also im- portant 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 ver- sus 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 vari- ability in a grain crop. Regarding fibre, a large vari- ation was also observed for total and soluble NSPs including the arabinoxylan (AX) concentration. Al- though the AX concentration in maize is low com- pared 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-glu- canase, although reducing the viscosity and the molecular weight of β-glucan, did not affect the fer- mentation or the production of SCFA (Karunaratne et 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-glu- cans 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 prov- en 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 en- zymes 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  mi- crobiome modulation (Cordero et al., 2019; Par- ra Perez et al., 2021) through the stimulation of the fibrolytic bacteria that results in higher SCFA, low pH and increased  caecal bacterial enzyme ac- tivity (Marinho  et  al., 2007;  González-Ortiz et al., 2021). Altogether allowing a better gut resil- ience making animals better able to cope with en- teric 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 en- teric 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 condi- tions, but also reduced the number of antibiotic interventions by 45%. Stimulating a more fibro- lytic microbiome and lowering protein fermenta- tion resulted in higher performing animals.

In  conclusion, there is clear evidence that  pro- moting 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 charac- terisation 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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