Influence of Buffer pH and Raw Corn Starch Addition on In Vitro Fiber Digestion Kinetics

The impact was studied of buffer pH (5.8, 6.2, and 6.8) on in vitro digestion kinetics of NDF from alfalfa hay, bromegrass hay, corn silage, and alfalfa and bromegrass hays with raw corn starch added to approximate a ration containing 30% NDF. Ash-free NDF was determined at 0, 6, 12, 18, 24, 30, 36,...

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Bibliographic Details
Published in:Journal of dairy science 1992-10, Vol.75 (10), p.2762-2768
Main Authors: Grant, R.H., Mertens, D.R.
Format: Article
Language:English
Subjects:
ALFALFA
ALMIDON
AMIDON
Animal Feed
Animals
artificial rumen
associative effects
Biological and medical sciences
Buffers
Cattle - physiology
Dietary Fiber - metabolism
DIGESTIBILIDAD
DIGESTIBILITE
Digestion - physiology
digestion rate
ENSILADO
ENSILAGE (PRODUIT)
EXPERIMENTACION IN VITRO
EXPERIMENTATION IN VITRO
extent of digestion
Feed and pet food industries
Female
FIBRA DE LA DIETA
FIBRE ALIMENTAIRE
FOIN
Food industries
Fundamental and applied biological sciences. Psychology
HENO
Hydrogen-Ion Concentration
Kinetics
LUZERNE
MAIS
MAIZ
Medicago sativa
POUVOIR TAMPON
RUMEN
SOLUCIONES REGULADORAS
Starch - pharmacology
Zea mays
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Summary:The impact was studied of buffer pH (5.8, 6.2, and 6.8) on in vitro digestion kinetics of NDF from alfalfa hay, bromegrass hay, corn silage, and alfalfa and bromegrass hays with raw corn starch added to approximate a ration containing 30% NDF. Ash-free NDF was determined at 0, 6, 12, 18, 24, 30, 36, 48, 72, and 96h of fermentation. Kinetic parameters were estimated by nonlinear regression using an iteratively reweighted least squares technique. Addition of raw corn starch decreased fiber digestion rate for alfalfa hay and lag for bromegrass hay. Both rate and lag of NDF digestion of all substrates were affected negatively below pH 6.2. Predicted ruminal NDF digestibilities (as percentage of that at pH 6.8 treatment) declined below pH 6.2 for all forages; addition of starch decreased predicted ruminal NDF digestibility by 23% for both alfalfa and bromegrass hays, even at pH 6.8. Results suggest that low pH decreases fiber digestion rate and increases lag and that starch accentuates this effect for some substrates.
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.S0022-0302(92)78039-4