Effects of Early supplementation  of xylanase-xylo-oligosaccharides
The postnatal period is crucial for early development. Given the high plasticity of the digestive tract, this timeframe presents a unique opportunity to orientate digestive phenotypes early. Xylo- oligosaccharides (XOSs) produced from the hydrolysis of non-starch polysaccharides by xylanase are known to act on the caecal microbiota composition of chicken. Based on a factorial design, we analysed the short- and long-term effects of early supplementation with a mixture of xylanase and XOS (Xyl.XOS) on growth performance, ileal sugar content, metabolome and caecal microbiota composition. A total of 240 chicks fed a basal diet rich in non-starch polysaccharides were divided into four groups: without additive (days 0–23), supplementation of Xyl.XOS during the starter period (days 0–9), grower diet (days 10–23) or the entire period (days 0–23). During the starting period, the early supplementation of Xyl.XOS exerted a positive effect on average daily gain and decreased the abundance of two Lachnospiraceae genera accompanied by a reduction in the concentration of two short chain fatty acids in the caeca content. The ileum content revealed a decrease in the concentration and proportion of soluble sugars, likely illustrating an improvement in absorption. In contrast, in the long term, early Xyl.XOS supplementation led to an increase in the abundance of two Lachnospiraceae genera, leading to increased butyrate and acetate production. With Eimeria tenella infection, late Xyl.XOS supplementation was beneficial for maintaining animal performance to the level of non- infected chickens. In conclusion, early Xyl.XOS supplementation showed both short-and long-term effects on animal growth. In the short term, it enhances the absorption of soluble sugars at the ileal level. In the long term, it alters the microbiota composition at the caecal level.