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Alfalfa Morphological Stage and its Relation to in Situ Digestibility of Detergent Fiber Fractions of Stems
Author(s) -
Sanderson Matt A.,
Hornstein J. S.,
Wedin W. F.
Publication year - 1989
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1989.0011183x002900050045x
Subject(s) - hemicellulose , neutral detergent fiber , cellulose , zoology , digestion (alchemy) , rumen , biology , poaceae , botany , fiber , monogastric , agronomy , ruminant , dry matter , chemistry , food science , biochemistry , chromatography , pasture , fermentation , organic chemistry
A reliable index for quantifying maturity and predicting herbage quality of alfalfa ( Medicago sativa L.) grown in diverse environments would be useful. An index developed at Cornell University was used to compare the in situ rate and extent of digestibility of neutral‐detergent fiber (NDF), cellulose, and hemicellulose of spring‐ and summer‐grown alfalfa stems at similar morphological stages. Stems were harvested every 10 d during spring growth and summer regrowth of 1984 and 1985. Maturity at each harvest was classified on a scale of 0 to 9, and a mean stage number was calculated. Ground (2 mm) stems were ruminally incubated in dacron bags for 0 and 48 h in 1984 and 0, 3, 6, 9, 12, 24, 48, and 72 h in 1985. Residues were extracted sequentially with neutral and acid detergent to determine residual NDF, cellulose, and hemicellulose. Rate of digestion (1985 data only) was calculated via nonlinear regression. After 48 h in the rumen, NDF, cellulose, and hemicellulose of spring‐grown stems were digested to a greater extent than summer‐grown stems of comparable chronological age. Digestibility of NDF [ R 2 = 0.78, root error mean square (REMS) = 64 g kg −1 , cellulose ( R 2 = 0.78 REMS = 58 g kg −1 ), and hemicellulose ( R 2 = 0.83, REMS = 59 g kg −1 ) declined nonlinearly with increasing maturity stage. Digestion rate of NDF, cellulose, and hemicellulose was faster in vegetative stems (average = 0.164 h −1 ) compared with reproductive stems (average = 0.093 h −1 ). Hemicellulose was digested 80% faster than cellulose. Our data demonstrated a close association between in situ digestibility of detergent‐fiber fractions and the Cornell index and further supports its utility.