Dietary Sodium Bicarbonate and Magnesium Oxide for Early Postpartum Lactating Dairy Cows: Effects of Production, Acid-Based Metabolism, and Digestion

Open Access
Publisher Website
Google Scholar
Abstract
In 2 experiments with cows in early lactation fed 40% corn silage and 60% concentrate diets (dry basis), the effects of 1.0% dietary sodium bicarbonate and 0.8% magnesium oxide in a 2 .times. 2 factorial arrangement on performance, acid-base metabolism, and digestion were examined. In experiment 1 and 20 Holstein and 4 Jersey cows, intake and milk production were not affected by treatment through 12 wk postpartum. In digestion trials at 3, 6, 9 and 12 wk postpartum, addition of magnesium oxide increased digestibility of dry matter 1.8% units. Starch digestion was decreased 1.8% units by sodium bicarbonate, whereas acid detergent fiber digestion increased 9-12% units with addition of either buffer. In experiment 2, with 4 fistulated Holstein cows in a Latin square design, intake per unit body weight was increased 0.18% units by dietary sodium bicarbonate while milk production was unaffected. Dry matter and acid detergent fiber digestion were increased slightly by sodium bicarbonate plus magnesium oxide addition; N balance increased 23 g/day in cows fed magnesium oxide alone. Because of the low fiber content of the ration, milk fat percent increased 0.5-0.9% by addition of either buffer in both experiments and resulted in corresponding increases in fat-corrected milk. Sodium bicarbonate and magnesium oxide prevented rapid declines in rumen pH associated with feeding in experiment 2, which related to changes in acid detergent fiber digestion. Blood acid-base metabolites were relatively unchanged by treatment in either experiment. Urinary bicarbonate and net acid excretion rates were changed on the average by +41 and +43 meq/h by sodium bicarbonate or magnesium oxide but could not be related to changes in intake and production.