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Potassium Carbonate as a Potassium Source and Dietary Buffer for Lactating Holstein Cows During Hot Weather¹

Department of Animal Science, Texas A&M University

L. D. Rowe, Jr.

Veterinary Toxicology & Entomology Research Laboratory, Agricultural Research Service, US Department of Agriculture College Station 77841

ABSTRACT

Twenty-four lactating Holstein cows were offered diets containing .93, 1.29, and 1.53% potassium during hot weather. Cows fed 1.53% potassium consumed more dry matter than cows fed either .93 or 1.29% potassium. Milk production and composition were not different. Potassium intake and fractional excretion increased, and fecal output as a percentage of intake declined with diets containing 1.29 and 1.53% potassium. Magnesium fractional excretion was least and fecal output greatest in cows fed 1.29% potassium. Fecal sodium output and fecal output as a percentage of intake was reduced by 1.53% dietary potassium.

During comparison period 2, potassium carbonate at 0, .5, or 1.0% had no effect on feed consumption or milk yield, but buffered diets increased milk fat percentage and depressed milk protein percentage. No effects of buffers on ruminal pH, volatile fatty acids, or digestibility of dry matter or fiber were noted.

Cows responded favorably during hot weather to potassium supplementation at 1.53% of the diet, but with high dietary potassium, effects on other minerals must be considered. Chloride, although present above requirements in all diets, was greater in the highest potassium diet. Potassium carbonate was effective as a buffer, which raised a depressed milk fat percentage.

¹ Technical Article 21390 by the Texas Agricultural Experiment Station, College Station 77843.

² Department of Animal Science, Coastal Plain Experiment Station, University of Georgia, Tifton 31793.