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Addition of Buffers to High Quality Alfalfa Hay-Based Diets for Dairy Cows in Early Lactation¹

Department of Dairy and Animal Science, The Pennsylvania State University, and US Dairy Forage Research Center (PA Cluster) and US Regional Pasture Research Laboratory, University Park 16802

³ Request reprints.

ABSTRACT

Beginning 4 wk postpartum, 14 Holstein cows were paired according to expected calving date and lactation number and assigned randomly to one of two treatments in a single reversal experiment designed to study the effects of added buffers to high quality alfalfa hay-based diets. Cows were offered daily 14.5 kg of concentrate containing 0 or 2% sodium bicarbonate and .5% magnesium oxide (as fed), plus free choice high quality alfalfa hay in a ratio of forage:grain approaching 50:50 (dry matter). No differences were in milk production, milk fat percentage, fat-corrected milk, or dry matter intake. Dry matter intake of grain was decreased with addition of buffers. Kilograms fat-corrected milk per kilogram of dry matter intake were 1.41 and 1.45 for control and buffered diets. No differences were significant for rumen pH, ammonia concentration, molar proportions of acetate and propionate, or ratio of acetate: propionate. Concentrations of total volatile fatty acids were higher for cows fed the buffered diet. No differences were in blood acid-base status or in various serum metabolites. Urine pH was 8.11 and 8.20 for control and buffered diets. Fractional urinary excretion of magnesium and sodium was greater when cows consumed the buffered diet. Diet digestibilities and rate of passage were not affected by dietary buffers. Addition of sodium bicarbonate plus magnesium oxide did not improve performance of early lactation cows fed high quality alfalfa hay as the sole forage.

¹ Authorized for publication as Paper No. 6984 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

² Department of Animal Sciences, University of Maryland, College Park 20742.

⁴ US Dairy Forage Research Center (PA Cluster), US Regional Pasture Research Laboratory, University Park 16802.