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Effect of the addition of malate on in vitro rumen fermentation of cereal grains
- Carro, M.D., Ranilla, M.J.
- British journal of nutrition 2003 v.89 no.2 pp. 181-188
- Merino, absorbance, acetates, alfalfa hay, barley, bottling, butyrates, corn, feed additives, fermentation, malates, methane, methane production, microorganisms, mixed culture, pH, propionic acid, rumen, rumen fermentation, sheep, volatile fatty acids, wheat, Spain
- Batch cultures of mixed rumen micro-organisms were used to study the effects of different concentrations of malate (Rumalato; Norel & Nature S.A., Barcelona, Spain; composed of disodium malate–calcium malate (0·16:0·84, w/w)) on the fermentation of four cereal grains (maize, barley, wheat and sorghum). Rumen contents were collected from four Merino sheep fed lucerne hay ad libitum and supplemented with 300 g concentrate/d. Rumalato was added to the incubation bottles to achieve final concentrations of 0, 4, 7 and 10 mm-malate. Gas production was measured at regular intervals up to 120 h. Malate increased (P<0·01) the average fermentation rate of all substrates, and the lag time decreased (P<0·05) linearly with increasing concentrations of malate for all substrates, with the exception of sorghum. In 17 h incubations, the final pH and total volatile fatty acid production increased (P<0·001) linearly for all substrates as malate concentration increased from 0 to 10 mm. Propionate and butyrate production increased (P<0·05), while the value of the acetate : propionate ratio and l-lactate concentrations decreased (P<0·05) linearly with increasing doses of malate. Malate treatment increased (P<0·05) the CO2 production and decreased the production of CH4, although this effect was not significant (P>0·05) for maize. Malate at 4 and 7 mm increased (P<0·05) optical density of the cultures measured at 600 nm for maize, with no differences for the other substrates. The results indicate that malate may be used as a feed additive for ruminant animals fed high proportions of cereal grains, because it increased pH and propionate production and decreased CH4 production and l-lactate concentrations; however, in general, no beneficial effects of 10 compared with 7 mm-malate were observed.