title: Influence of disodium malate on microbial growth and fermentation in rumen-simulation technique fermenters receiving medium- and high-concentrate diets.
abstract: Two incubation trials were carried out with the rumen-simulation technique (RUSITEC). In each trial, four vessels received a diet of grass hay and concentrate (600 and 400 g/kg DM, respectively; diet F), and the other four were fed a diet composed of concentrate and barley straw (900 and 100 g/kg DM, respectively; Diet C). Vessels were given 20 g of the corresponding diet daily, and half of them were supplemented with disodium malate to achieve a final concentration of 6.55 mM. There were no effects (P>0.05) of malate either on pH or on the daily production of NH3-N, but malate treatment increased (P<0.05) DM, neutral detergent and acid detergent fibre disappearance after 48 h incubation. The daily production of propionate and butyrate increased (P<0.001), and the ratio CH4:volatile fatty acids decreased (P<0.001) by supplementing both diets with malate. Whereas adding malate to the F diet produced an increase in acetate production (P=0.011) and the growth of solid-associated micro-organisms (P=0.037), no effects (P>0.05) were observed for diet C. For both diets, there were no differences (P>0.05) between treatments in the daily flow of liquid-associated micro-organisms measured using (15)N as a microbial marker. These results indicate that malate stimulated the in vitro fermentation of both diets by increasing the apparent disappearance of the diet and decreasing the ratio of CH4:volatile fatty acids, but a greater response was observed with diet F. If these results are confirmed in vivo, malate could be used as a feed additive for ruminants fed diets containing medium proportions of forage (i.e. dairy animals) and not only in animals fed high-concentrate diets, as has so far been proposed.
authors.affiliation: Departamento de Producción Animal I, Universidad de León, 24071 León, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Gómez
authors.forename: M L
authors.initials: ML
authors.lastname: Tejido
authors.forename: M D
authors.initials: MD
authors.lastname: Carro
mesh_terms: D000085:Acetates / Q000378:metabolism; D000821:Animal Feed; D000818:Animals; D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000096:biosynthesis; D002087:Butyrates / Q000378:metabolism; D002417:Cattle; D019587:Dietary Supplements; D005232:Fatty Acids, Volatile / Q000096:biosynthesis; D005285:Fermentation; D008293:Malates / Q000494:pharmacology*; D011422:Propionates / Q000378:metabolism; D012417:Rumen / Q000378:metabolism* / Q000382:microbiology; D012820:Silage
chemical_list: D000085:Acetates; D001426:Bacterial Proteins; D002087:Butyrates; D005232:Fatty Acids, Volatile; D008293:Malates; D011422:Propionates; C030298:malic acid