Effect of Forage Physical Form on Chewing Activity, Dry Matter Intake, and Rumen Function of Dairy Cows

111 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.Forage particle size (FPS) has been extensively investigated as a modifier of dry matter intake (DMI), chewing activity, and digesta passage in sheep and steers fed all forage diets, but has not been examined using dairy cows in early lactation. The purpose of this study was to determine effect of reducing FPS on production, chewing, and digesta kinetic parameters in early lactation dairy cattle and the influence small particle (SP) passage rate and large particle (LP) breakdown rate have on DMI.In Trial 1, 42 Holstein cows (9 ruminally cannulated) were assigned 14 d postpartum to one of three experimental diets with concentrate: alfalfa haylage: alfalfa pellets ratio of: (A) 60:40:0; (B) 60:28:12; and (C) 60:12:28 on a dry matter basis. The trial ran through the 12th week postpartum and measurements of chewing activity and rumen parameters were made during the 4th, 8th, and 12th week postpartum. Dry matter intake (kg/d), milk production (kg/d), and butterfat percentage for diets A, B, and C were: 23.1, 23.0, 18.8, 33.7, 35.5, 31.8; and 3.1, 2.9, 2.6, respectively. Rumen parameters and chewing activities were linearly related to haylage level in the diet. Ruminal fluid dilution rat (%/h), volume (L), and outflow (L/d), rumination (min/d), total chewing (min/d), total chewing (min/kg DMI), ruminal acetate (molar %) and neutral detergent fiber digestibility (%) were: 16.6, 13.8, 10.0, 62, 58, 54; 243, 193, 137; 437, 367, 204; 649, 566, 376; 28.2, 24.1, 20.0; 58.6, 56.3, 53.8; and 32, 37, 23, respectively. These results suggest that the minimum amount of effective fiber needed to to optimize production and intake of early lactation cows can be met with at least 28% of the dry matter as haylage.In Trial 2, six ruminally cannulated Holstein cows, 90 days postpartum, were used in a replication 3 x 3 Latin square design with 21 d periods. Experimental diets were (C) 60% concentrate, 40% corn silage; BC) 60% concentrate, (containing 2% sodium bicarbonate), 40% corn silage; and HY) 60% concentrate, 30% corn silage, 10% long alfalfa hay on a DM basis. Dry matter intake (kg/d), milk production (kg/d), percentage butterfat, rumination (min/d), ruminal fluid outflow (L/d), SP (150-850 (mu)m) passage rate, and LP (greater than 4.25 mm) breakdown rate for diets C, BC, and HY 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 dry matter and digesta particle size were reduced at the end of a 24 h feeding period. Data suggested that DMI is more closely related to SP passage and ruminal fluid outflow then LP breakdown.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD