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Plasma Clearance of L-and D-Lactate in Steers Fed Alfalfa Hay or High Concentrate Diets¹

US Department of Agriculture^,3, Clay Center, NE 68933

Abstract

Experiments were conducted with 40 steers to evaluate the effects of diet (alfalfa hay vs high concentrate) on the rates of elimination of D- and L-lactate from plasma. Plasma L- and D-lactate clearance rates were determined before (Period I) and 114 d after (Period II) an abrupt switch from the alfalfa hay to the high concentrate diet. One group of steers received the hay diet throughout the experiment. Diet or period did not alter the rate of disappearance of L-lactate from plasma; the half-life was 13.5 to 15.5 min. D-lactate disappearance from plasma followed an exponential decay curve with at least two components; however, diet or period did not alter the calculated rates of disappearance. The half-life of the first component was 9 to 28 min and the second component was 207 min. Characteristics describing D- or L-lactate metabolism were not highly correlated with lactate utilization for fatty acid synthesis. These data demonstrate that, in steers adapted to a high concentrate diet consuming 18.2 Mcal Me • head^-1 • d^-1, clearance of D(-)- or L(+)-lactate is not different from that in steers fed alfalfa hay consuming 23.1 Mcal ME • head^-1 • d^-1.

¹ The cooperation of the Nebraska Agr. Exp. Sta., Univ. of Nebraska, Lincoln, is acknowledged. The author acknowledges the technical assistance of Ms. Julie Jacobson in directing laboratory operations and the secretarial assistance of Ms. Linda Parnell. The suggestions of Dr. G. Huntington in the design and during the execution of these experiments are appreciated.

² Research Chemist, Roman L. Hruska U.S. Meat Animal Research Center, Agr. Res. Service.

³ Mention of trade name, proprietary product or specific equipment does not constitute a guarantee or warranty by USDA and does not imply its approval to the exclusion of other products that may be suitable.