ARS | Publication request: EFFECTS OF VARYING DIETARY PROTEIN AND FIBER LEVELS ON THE PRODUCTION OF LACTATING DAIRY COWS

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: July 26, 2001
Publication Date: N/A

Technical Abstract: Eighteen primiparous and 45 multiparous Holstein cows were blocked by parity and DIM and randomly assigned to 7 squares in an incomplete Latin square trial with 4, 4-wk periods. Nine TMR, 3 levels of NDF each at 3 levels of CP, were formulated from alfalfa and corn silages, high moisture corn, solvent soybean meal, plus minerals and vitamins. Levels averaged (DM basis) 36, 32 and 28% NDF and 15.1, 16.7 and 18.4% CP. Milk yield and DMI were measured daily in the last 2 wk of each period; yield of milk components was determined one day in each of the last 2 wk of each period. Fecal and urine grab samples were collected in the last wk of each period to estimate N excretion. The statistical model included square, cow(square), period(square), CP and NDF level, and 2-way interactions; the error term was cow(square). No 2-way interactions or quadratic effects were significant (P $? 0.21). There were linear increases in DMI, MUN and urinary N excretion, and linear decreases in milk N/NI and fecal N excretion, with increasing dietary CP. There were linear increase in BW gain, yeild of milk and milk components and milk/DMI, and linear decreases in MUN, milk N/NI and urinary N excretion, with decreasing dietary NDF. Reducing dietary CP from 15.1 to 18.4 % had little effect on yeild but reduced N utilization.