Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/25/2010
Publication Date: N/A
Technical Abstract: The study objective was to evaluate the effects of physically effective fiber source (peNDF) and starch sources with different rates of fermentation (ST). Thirty-two lactating Holstein cows (8 cannulated) were used in an incomplete Latin square design with 3 21-d periods. Dietary treatments were inclusion of chopped wheat straw (WS) or ensiled corn stover (ES) to provide 10% of diet DM as NDF, and inclusion of dry ground corn (DC) or high moisture shelled corn (HC) as the starch sources. Diets were formulated to contained similar concentrations of starch, N, and NDF. DMI was not affected by treatment. Time per day spent ruminating did not differ by diet, but time spent eating tended to be greater for cows with DC than for HC. At 2-h post-feeding, ruminal digesta DM% was greater with WS than ES. Rumen digesta DM kg did not differ by treatment. Ruminal digesta liquid kg tended to be greater with DC than HC on ES diets, but HC was greater than DC on WS diets. Ruminal pH was lower with WS than ES. In contrast, fecal pH was lower with ES than with WS. Neither pH was affected by ST. Lower ruminal pH and higher fecal pH with WS suggests that WS retained more feed to be digested in the rumen, whereas the reverse response with ES suggests that this peNDF source allowed more fermentable carbohydrate to pass from the rumen to ferment in the hindgut. Forage peNDF source may affect passage.