Effects of Dietary Cation -Anion Difference on Performance, Acid-Base Status, and Nitrogen and Macromineral Metabolism of Lactating Dairy Cows
In the second experiment, 16 Holstein and 8 Jersey multiparous cows were used immediately after calving to compare two DCAD4 (22 and 47 meq/100 g of DM) in a completely randomized design. An additional 2.3 kg of alfalfa hay was fed during the first 5 days postpartum, and then milk, blood, and urine samples were collected weekly for 6 weeks. Repeated-measures, with an extra between-cow effect, mixed model analysis indicated that DCAD 4 did not affect DM intake, milk production, milk composition, and jugular venous pH and HCO3- concentration. Elevated concentration of plasma branched chain AA and ratio of essential AA to total AA in cows with DCAD4 of 47 versus 22 meq/100 g of DM indicated N metabolism in the rumen was affected, probably a result of more microbial protein flowing to the small intestine. Higher net acid excretion in cows with DCAD4 of 22 versus 47 meq/100 g of DM suggested that net acid excretion was a much more sensitive indicator of acid load than blood acid-base parameters in cows postpartum.
Agriculture, Animal Culture and Nutrition
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign