Article

Volatile fatty acids in laboratory and field silage

Division of Agricultural Biochemistry, Department of Biological Chemistry, University of Aberdeen
Journal of the Science of Food and Agriculture (Impact Factor: 1.88). 09/2006; 5(3):120 - 126. DOI: 10.1002/jsfa.2740050302

ABSTRACT The results of work conducted on the formation of volatile fatty acids in laboratory slurries of minced crop and water mixtures is presented. The absence of formic acid in such slurries has been noted. The occurrence of acids higher than C6, under varying conditions of temperature, aeration or anaerobiosis, has not been demonstrated. Straight-chain volatile acids from C1 to C8 have been shown to occur in field silage but only occasionally has the presence of branched-chain acids been noted. The principal volatile acid present is acetic acid.

0 Bookmarks
 · 
153 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: A method is described for the separation of butyric, propionic, acetic, formic, succinic and lactic acids from silage extracts by chromatography on columns of silica gel eluted with mixtures of benzene and n-butanol. Separated acids were estimated by titration with barium hydroxide solution. The method has been applied to silages made from pure species of herbages at different stages of growth and receiving different treatments before ensilage.Lactic acid concentrations up to 11.5% of the dry matter were recorded, giving rise to low pH values. Butyric acid concentrations of up to 5% raised the pH and under these conditions only small amounts of lactic acid were present; propionic acid concentrations rose to 1–2% in some cases and trace amounts of formic acid could be detected. Acetic acid was present in all silages at concentrations of up to 7% of the dry matter, and appeared to fall off as the nitrogen content of the crop decreased. As the herbage matured, the total acid concentration of the silage decreased.
    Journal of the Science of Food and Agriculture 05/2006; 15(4):208 - 213. · 1.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Results are presented for the composition and digestibilities of the constituents of a medium-protein grass-clover mixture and of molassed and unmolassed silages derived from it. Determinations of soluble sugar and fructosan values have carried out in addition to the usual estimations, and the possible effects of the reduction of soluble carbohydrate resulting from fermentation during ensilage, on the nutritional value of the silage product, have been discussed.The losses of fresh material, dry matter and nitrogen which have been observed were exceptionally low compared with the losses generally reported for this type of experiment, and, for both types of silage, weights of lactic and lower fatty acids have been found considerably in excess of the equivalent soluble carbohydrate losses.Little difference in quality and feeding value has been observed between molassed and ordinary silage at a crude protein level of 12–13% dry matter and both types of silage compared very favourably with the original grass.
    Journal of the Science of Food and Agriculture 05/2006; 7(3):189 - 196. · 1.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two hundred and ninety-four plastic bag silos were prepared to determine the effect of adding urea or soybean meal on the corn plant fermentation process. Urea was added at 0.5, 0.75, and 1.0% of fresh silage weight at ensiling. Equivalent amounts of nitrogen from soybean meal were added for a comparative treatment. The corn was harvested at three stages of maturity, 25.6, 30.4, and 52.0% dry matter. Only the lowest level of urea and soybean meal was added to the silage containing 52.0% dry matter. Triplicate silages were prepared and analyzed after 0, 0.5, 1, 3, 7, 21, and 42 days of storage.Over all treatments the average pH of urea-treated corn silage (4.85) was higher than that of soybean meal-treated corn silage (4.69). Differences between treatments after 42 days of fermentation were greater with either low or high dry matter silages than with medium dry matter. Total organic acid concentration declined from 11.94% of dry matter in low dry matter samples after 42 days of storage to 3.14% of dry matter in high dry matter samples averaged over all treatments. The concentration of these acids increased (P < .01) with storage time and was higher in the urea-treated samples. Contrary to what was observed with lactic acid, volatile fatty acids were higher with the lower nitrogen supplementation. Acetic acid comprised 90% of the total volatile fatty acids.
    Journal of Dairy Science. 01/1970; 53(9):1225-1232.