Effects of proanthocyanidins, dehulling and removal of pericarp on digestion of barley grain by ruminal micro-organisms
✍ Scribed by Wang, Yuxi; McAllister, Tim A; Xu, Zhong J; Gruber, Margaret Y; Skadhauge, Birgitte; Jende-Strid, Barbro; Cheng, Kuo-Joan
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 341 KB
- Volume
- 79
- Category
- Article
- ISSN
- 0022-5142
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✦ Synopsis
The effects of proanthocyanidins (PA), dehulling, and removal of the pericarp on the rate and extent of barley digestion by ruminal micro-organisms were studied using a control barley (cv Harrington) and three PA-free barley lines (Caminant, Ca504316 and Ca802711). Each barley was studied in ®ve preparations: whole grain (W); dehulled kernels (DH); kernels with pericarp removed (DP); dry-rolled grain (DR), and the pericarp-testa fraction (PT) produced during preparation of DP. Vanillin-HCl staining and chemical analysis con®rmed that PA were present only in the Harrington barley, and localised in the pericarp-testa layer. Whole kernels, DH and DP were incubated with diluted ruminal ¯uid in vitro, and all ®ve preparations were incubated in situ (nylon bag technique).
Harrington DR and all four PT fractions were also incubated in vitro in the presence (0.074% w/v) and absence of polyethylene glycol (PEG), which speci®cally binds PA. The four barleys did not differ in in vitro dry matter disappearance (DMD) or gas production from W, DH or DP preparations, nor in in situ DMD rates from W, DH or DP (P b 0.05). In vitro DMD and gas production among PT fractions from the four barleys were also similar (P b 0.05), as were in vitro DMD from PEG-present and PEGabsent DR Harrington. With Harrington PT, in vitro ammonia concentrations were higher (P 0.05) with PEG than without. For each barley line, in vitro DMD rates were highest (P 0.01) with DP, followed by DH, and then by W (P 0.01). In in situ incubations also, DMD rates and effective degradabilities of DR samples exceeded (P 0.05) those of DH samples. It was concluded that the presence of proanthocyanidins did not affect ruminal digestion of barley grain, and that abrasive milling to breach the hull and pericarp may be a promising method by which to regulate the rate of barley digestion in the rumen.