title: Dietary alteration of particle breakdown and passage from the rumen in lactating dairy cattle.
abstract: To evaluate the effect of dietary alteration on the rates of ruminal small particle passage or large particle breakdown, six ruminally cannulated Holstein cows 90 d postpartum were used in a 3 X 3 Latin square design. Experimental diets were 1) control: 60% concentrate, 40% corn silage; 2) bicarbonate: 60% concentrate (containing 2% sodium bicarbonate), 40% corn silage; and 3) hay: 60% concentrate, 30% corn silage, and 10% long alfalfa hay on a DM basis. Dry matter intake (kg/d), milk production (kg/d), percentage milk fat, rumination (min/d), ruminal fluid outflow (L/d), small particle (150 to 850 micron) passage rate (%h), and large particle (greater than 4.25 mm) breakdown rate for diets control, bicarbonate, and hay were 20.2, 20.9, 22.4; 26.6, 27.7, 26.8; 3.5, 3.6, 3.2; 405, 350, 370; 167, 184, 185; 6.5, 7.6, 7.4; and 7.2, 6.8, 7.4, respectively. Rumen DM content and digesta particle size were reduced at the end of a 24-h feeding period. Data suggested that small particle passage may be more closely related to ruminal fluid outflow and DM intake than large particle breakdown rate.
authors: Department of Animal Sciences, University of Illinois, Urbana 61801.
authors: S T
authors: ST
authors: Woodford
authors: M R
authors: MR
authors: Murphy
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004063:Digestion; D005260:Female; D005772:Gastrointestinal Transit; D007774:Lactation / Q000502:physiology*; D010316:Particle Size; D011247:Pregnancy; D012417:Rumen / Q000502:physiology*