title: In situ disappearance of malate from alfalfa and bermudagrass hay.
abstract: The objectives of this study were to determine the rate of malate and dry matter disappearance from different forages in the rumen. Four nonlactating, ruminally cannulated Holstein cows were fed a hay-based diet. Samples of early and late harvested alfalfa, Coastal bermudagrass, and Tifton 85 bermudagrass hays were ground, placed in nylon in situ bags, and ruminally incubated for 0, 0.5, 1, 2, 4, 8, 12, 24, and 48 h. After incubation, samples were rinsed, freeze-dried, extracted, and analyzed for malate content by HPLC with an organic acid column. When forages were incubated in the rumen, malate concentrations were less than 0.55 mg/g of dry matter at 0.5 h and remained low for the 48-h incubation period. These results suggest that malate was solublized and utilized within 30 min after reaching the rumen. Dry matter digestibility of both forages increased with time and was different across 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 maturity Tifton 85 digestibility was similar to alfalfa. Even though it is more common to feed unground forages to ruminants, these in situ results suggest that once malate is available in the rumen it will disappear quickly.
authors.affiliation: Department of Animal and Dairy Science, The University of Georgia, Athens 30602-2771, USA. scottm@arches.uga.edu
authors.forename: S A
authors.initials: SA
authors.lastname: Martin
authors.forename: J A
authors.initials: JA
authors.lastname: Bertrand
authors.forename: B
authors.initials: B
authors.lastname: Sauls
authors.forename: G M
authors.initials: GM
authors.lastname: Hill
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002417:Cattle / Q000378:metabolism* / Q000502:physiology; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D004043:Dietary Fiber / Q000378:metabolism; D005260:Female; D016014:Linear Models; D008293:Malates / Q000032:analysis / Q000378:metabolism*; D000455:Medicago sativa / Q000378:metabolism; D006109:Poaceae / Q000378:metabolism*; D012417:Rumen / Q000378:metabolism / Q000502:physiology
chemical_list: D004043:Dietary Fiber; D008293:Malates; C030298:malic acid