Effect of Dietary Lactic Acid Content and Energy Level on Rumen Lactate Metabolism in Sheep

Publisher Website
Google Scholar
Abstract
Adult fistulated wethers were limit fed hay (H) (five sheep) or hay plus 5% w/w DL-lactic acid (HL) (six sheep)-for 20 days (phase I). All sheep then received ad libitum 50, 70 and 90% concentrate diets for 5, 5 and 10 days, respectively (phase II). Rumen fluid samples were taken the first day and every 5 days thereafter. These samples were inocula sources for in vitro lactate disappearance (IVLD) studies. L(+) or D(−) lactate was added to inocula, giving initial concentrations of 200 ug lactage per ml and incubated in vitro for 10, 20 and 30 minutes. During phase II, additional rumen fluid samples were taken 2 hr postfeeding each sample day. There was no difference in ad libitum intake between treatment means during phase II. No gross symptoms of acidosis were observed in any sheep. H and HL means (µg/ml), respectively, were 50, 46 for total lactate 22 hr postfeeding; 130, 75 for 2 hr total lactate; 38,16 for 2-hr L (+) lactate and 92, 59 for 2-hr D(−) lactate. HL values for all 2-hr lactate criteria were lower (P<.05) than corresponding H values. Dring phase II, isomer proportions of 2-hr rumen lactate shifted from predominantly L(+) to almost all D(−) lactate by the end of the experiment, with the greatest shift seen 5 days after sheep received the 90% concentrate diet. IVLD rates (ug min-1 ml-1) gradually increased for HL sheep during phase I and were higher (P<.01) than those observed in H sheep by the end of phase I (.368 for H, 1.375 for HL). During phase II, IVLD was similar for both treatments, indicating that the advantage of HL sheep was not sustained. Maximum IVLD observed was approximately 9.4. L(+) and D(−) isomers disappeared at similar in vitro rates throughout the experiment. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.