Another Theory for the Action of Ruminal Buffer Salts: Decreased Starch Fermentation and Propionate Production

¹ Agricultural Research Service, USDA, and Section of Microbiology
² Department of Animal Science, Cornell University, Ithaca, NY 14853

Sodium carbonates have been fed to ruminants for more than 20 yr and, in many cases, have alleviated milk fat depression. These effects usually have been ascribed to increased ruminal buffering capacity, but this mode of action has several problems. For the buffering capacity to increase, the concentrations of ruminal bicarbonate, dissolved CO₂, and Na have to increase. Ruminal fluid already is saturated with CO₂, and the cation concentration of ruminal fluid is regulated closely to prevent hemoconcentration or hemodilution. Based on these latter observations, a significant increase in ruminal buffering capacity is unlikely. The action of bicarbonates is explained more easily by increased water intake, increased ruminal fluid dilution rate, increased flow of undegraded starch from the rumen, and decreased ruminal propionate production.

Key Words: rumen • buffers • propionate • milk fat

Submitted on August 26, 1992
Accepted on October 22, 1992

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