In vitro evaluation of the fermentation characteristics of the carbohydrate fractions of hulless barley and other cereals in the gastrointestinal tract of pigs

An in vitro model was used to study the fermentation characteristics of carbohydrate fractions of hulless barley (hB), in comparison to hulled barley (HB), hulled oat and oat groats (OG) in the pig intestine. For this purpose, 6 hulless barley cultivars (hB), varying in -glucan content (36–99 g/kg DM), were compared to 3 HB cultivars, 2 oat groat samples (OG), 3 oat varieties and a reference sample of wheat. The residue of a pepsin–pancreatin hydrolysis was incubated in a buffered mineral solution inoculated with pig faeces. Gas production, proportional to the amount of fermented carbohydrates, was measured for 48 h and kinetics modelled. The fermented solution was subsequently analyzed for microbial production of short-chain fatty acids (SCFA) and ammonia. In vitro dry matter degradability varied according to ingredient (P<0.001). Higher values were observed for OG, ranging from 0.88 to 0.99 as compared to oat, hB and HB, for which degradability ranged from 0.63 to 0.73, 0.68 to 0.80 and 0.69 to 0.71, respectively. A “cereal type” effect (P<0.05) was observed on fermentation kinetics parameters. Total gas production was higher (P<0.05) with hB (224 ml/g DM incubated) than with HB and oat (188 and 55 ml/g DM incubated, respectively). No difference was observed between hB cultivars (P>0.05) for total gas production but differences (P<0.001) were found for lag time and the fractional rate of degradation. Hulless barley cultivar CDC Fibar (waxy starch) and CDC McGwire (normal starch) started to ferment sooner (lag time of 0.7 and 0.9 h, respectively) than SH99250 (high amylose starch; 1.7 h). The fractional rate of degradation was similar in both hB and OG (0.15/h on average), which was higher than that of HB (0.12/h). The production of SCFA was also higher (P<0.05) with hB (6.1 mmol/g DM incubated, on average) than with HB and oat (4.9 and 2.9 mmol/g DM incubated, respectively). Similar trends were found for SCFA production expressed per g fermented carbohydrates, with higher butyrate and lower acetate ratio. In contrast, oat fermentation generated higher (P<0.05) ammonia concentration (1.4 mmol/g DM incubated, on average) than hB (1.0 mmol/g DM incubated). In summary, hulless barleys, irrespective of cultivar type had higher in vitro fermentability and produced more SCFA Abbreviations: AA, acetic acid; ADF, acid detergent fibre; AOAC, Association of Official Analytical Chemists; BA, butyric acid; BCFA, branched-chain fatty acids; G, -glucan; CDC, Crop Development Centre; CHO, Carbohydrate; CP, crude protein; DF, dietary fibre; DM, dry matter; GC, gas chromatography; hB, hulless barley; HB, hulled barley; iNSP, insoluble non-starch polysaccharides; IVDMD, In vitro dry matter degradability; NDF, neutral detergent fibre; NSP, non-starch polysaccharides; OG, oat groat; PA, propionic acid; SCFA, short-chain fatty acids; sNSP, soluble non-starch polysaccharides. ∗ Corresponding author at: Prairie Swine Centre Inc. P.O. Box 21057, 2105 8th St. E. , Saskatoon, SK, Canada S7H 5N9. Tel. : +1 306 667 7445; fax: +1 306 955 2510. E-mail address: pascal.leterme@usask.ca (P. Leterme). 0377-8401/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci. 2010.10. 006 186 R. Jha et al. / Animal Feed Science and Technology 163 (2011) 185–193 and less ammonia than hulled barley and oat. Thus, hulless barleys have a better potential to be used in pig nutrition to manipulate the fermentation activity in the intestine of pigs. © 2010 Elsevier B.V. All rights reserved.