Effect of fiber source and ruminal starch degradability on site and extent of digestion in dairy cows

Four duodenally cannulated Holstein cows (166 DIM) were used in a 4 X 4 Latin square with a 2 X 2 factorial arrangement of treatments to study effects of forage fiber source and ruminal starch degradability on digestion events. Forage NDF (21% of dietary DM) was from either alfalfa hay or a 1:2 (sub...

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Bibliographic Details
Published in:Journal of dairy science 1993-08, Vol.76 (8), p.2244-2253
Main Authors: Poore, M.H, Moore, J.A, Eck, T.P, Swingle, R.S, Theurer, C.B
Format: Article
Language:English
Subjects:
alfalfa
alfalfa hay
Biological and medical sciences
cattle feeding
dairy cows
digestibility
dry matter
dry-rolled sorghum grain
duodenum
feed intake
fiber content
flow
forage
Fundamental and applied biological sciences. Psychology
General aspects
hay
milk composition
milk yield
nutrient content
rumen fermentation
Sorghum (Poaceae)
starch digestion
steam-flaked sorghum grain
Vertebrates: digestive system
wheat straw
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Summary:Four duodenally cannulated Holstein cows (166 DIM) were used in a 4 X 4 Latin square with a 2 X 2 factorial arrangement of treatments to study effects of forage fiber source and ruminal starch degradability on digestion events. Forage NDF (21% of dietary DM) was from either alfalfa hay or a 1:2 (substituted on an NDF basis) ratio of alfalfa hay to wheat straw. Low and high ruminal starch degradabilities were achieved by use of either dry-rolled or steam-flaked sorghum grain, respectively. Dry matter intake did not differ among treatments (21 kg/d). Ruminal and total tract digestibilities of dietary OM, N, AWF, and ADF and flow of N fractions to the duodenum were not affected by fiber source. Diets with steam-flaked grain had higher ruminal (74 vs. 48%) and total tract (98 vs. 83%) starch digestibilities than did those diets with dry-rolled grain. Digestibilities of feed OM (63 vs. 51%) and CP (61 vs. 53%) and duodenal flows of nonammonia N (120 vs. 110% of intake) and bacterial N (.45 vs. .35 kg/d) also were higher, but microbial yield efficiency was not influenced by degradability of starch. Steam-flaked sorghum grain improved ruminal and total tract digestion of starch by lactating dairy cows and enhanced bacterial protein synthesis. Wheat straw NDF was substituted for two-thirds of the alfalfa hay NDF in diets for midlactation cows without adversely affecting digestion events or nutrient flow to the duodenum.
ISSN:0022-0302
1525-3198
DOI:10.3168/jds.S0022-0302(93)77561-X