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Buffering Ability of several Compounds In Vitro and the Effect of a Selected Buffer Combination on Ruminal Acid Production In Vivo¹ ,^,2

Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506

ABSTRACT

The buffering ability of several compounds was tested in vitro with rumen fluid from cattle fed roughage-concentrate or all-concentrate rations. The in vitro system developed to test the buffers involved incubating 100 ml rumen fluid (after flushing with carbon dioxide) with 1% buffer and 5% ground extrusion-cooked corn 6 h at 39 C. This then was titrated with acid or base for buffering capacity. A computer selected combinations of buffers on their performance singly. With rare exception, hydroxides and oxides were poor buffers alone or in combination because their response often was erratic and usually caused excessive pH changes immediately after addition to rumen fluid. In proper combination, carbonates and bicarbonates were the most promising anions. Occasional benefits were derived from phosphates. Some buffer salts, rated fair or poor alone, balanced out each other's defects and combined into a good buffer.

Several buffer combinations were selected by computer for both all-concentrate and concentrate-roughage rations. One such combination for the concentrate ration consisted of bentonite, monobasic potassium phosphate, magnesium carbonate, magnesium oxide, and sodium carbonate combined in a 5:22:22:35:16 ratio. This combination without bentonite was fed as a supplement (.227 kg/ head per day) to dairy steers consuming an all-concentrate ration. Animals fed the buffer had a slightly higher rumen fluid pH, higher rumen acetate, lower propionate, and higher lactate concentration than did the controls.

¹ Contribution no. 958-j, Department of Dairy and Poultry Science, and no. 290-j, Department of Statistics, Kansas Agricultural Experiment Station, Manhattan 66506.

² This research was supported in part by a grant from Church and Dwight Co., Inc., New York, NY 10001.

³ This material is part of a thesis submitted by the senior author in partial fulfillment of the requirements for the M.S. degree in Animal Nutrition at Kansas State University.