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Journal of Dairy Science Vol. 50 No. 2 214-220
© 1967 by American Dairy Science Association ®
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Measurement of Certain Metabolic Organic Acids in Forage, Silage, and Ruminal Fluid by Gas-Liquid Chromatography1

T. S. Rumsey, C. H. Noller, C. L. Rhykerd and J. C. Burns

Departments of Animal Sciences and Agronomy, Purdue University, Lafayette, Indiana

ABSTRACT

Gas-liquid chromatography was found applicable for measuring lactic, oxalic, malonic, fumaric, succinic, malic, alphaketoglutaric, and citric acids in forage, silage, and ruminal fluid. Aqueous extracts of ground and dried forage, extracted at 55 C, were lyophilized and the organic acids contained in the residue esterified with methanol and hydrochloric acid. Esters of the acids were then chromatographed. Aqueous extracts of silage and protein-free filtrates of ruminal fluid, prepared by acetone-ethanol precipitation, were analyzed.

Recoveries of all acids by adding known amounts of organic acids were near 100%. Two groups of forage samples, containing both freeze- and oven-dried samples, contained similar amounts of organic acids and the differences due to method of drying were analogous for both groups. Lactic acid measured in silage samples was comparable to that measured in the same samples by the FeCl3 and p-hydroxydiphenyl methods. Interfering peaks were encountered when some ruminal fluid samples were chromatographed. This interference may have been due to incomplete protein precipitation and was greatest with samples from an animal receiving high-grain ration,in contrast to samples from animals receiving a corn silage ration.

FOOTNOTES

1 This research was financed in part from a trust agreement between Purdue University and Normandy Farm, New Augusta, Indiana, Mr. and Mrs. Herman C. Krannert, owners, and is published with the approval of the Director of the Indiana Agricultural Experiment Station as Journal Series Paper no. 2859.

2 Present address: USDA, ARS, Animal Husbandry Research Division, Agricultural Research Center, Beltsville, Maryland.






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