In situ disappearance of malate from alfalfa and bermudagrass hay

The objectives of this study were to determine the rate of malate and dry m atter disappearance from different forages in the rumen. Four nonlactating, ruminally cannulated Holstein cows were fed a hay-based diet. Samples of e arly and late harvested alfalfa, Coastal bermudagrass, and Tifton 85 bermud agrass bays were ground, placed in nylon in situ bags, and ruminally incuba ted for 0, 0.5, 1, 2, 4, 8, 12, 24, and 48 h. After incubation, samples wer e rinsed, freeze-dried, extracted, and analyzed for malate content by HPLC with an organic acid column. When forages were incubated in the rumen, mala te concentrations were less than 0.55 mg/g of dry matter at 0.5 h and remai ned low for the 48-h incubation period. These results suggest that malate w as solublized and utilized within 30 min after reaching the rumen. Dry matt er digestibility of both forages increased with time and was different acro ss forages. Both alfalfa samples were digested to a greater extent between 0.5 and 24 h than either type of bermudagrass, but after 48 h the early mat urity Tifton 85 digestibility was similar to alfalfa. Even though it is mor e common to feed unground forages to ruminants, these in situ results sugge st that once malate is available in the rumen it will disappear quickly.