Isolated non-starch polysaccharides (NSP), especially isolated β-glucan, are reported to have prebiotic effects in pigs. However, little information is available on their possible functional properties when they are still present in the fibrous matrix of whole cereals. Hulless barleys (hB) are rich but variable sources of β-glucan. In order to evaluate their potential as functional feeds, an in vitro experiment was carried out to study the fermentation characteristics of 6 hB varieties and breeding lines varying in their β-glucan content (36–99 g/kg DM) in comparison to three hulled barleys (HB), two oat groats, three oats and one wheat, taken as reference. After pepsin–pancreatin hydrolysis, the ingredients were incubated in a buffered mineral solution and pig faeces (inoculum). The accumulated gas production, proportional to the amount of fibre fermented, was measured for 48 h and modelled. Short-chain fatty acid (SCFA) and ammonia concentrations were measured in the fermented solutions. A cereal type effect was observed on the fermentation kinetics parameters. Rates of degradation and total gas productions were higher with hB than with oat. Differences were also found between hB for total gas production, lag time and rate of degradation. The production of SCFA was also higher with hB (6.1 mMol/g DM incubated) than with hulled barley and oat (4.9 and 2.9 mMol/g DM incubated respectively). In contrast, oat generated higher ammonia production (1.4 mMol/g DM incubated, on average) than both hB and HB (1.0 mMol/g). In conclusion, hB are better fermented, produce more beneficial (SCFA) and less harmful (ammonia) metabolites and have a better potential than other cereal species to modulate gut microbiota and improve gut health.

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