Non‐volatile organic acids of grasses

Abstract

Non-volatile organic acids have been determined in S24 ryegrass and S37 cocksfoot harvested on three cutting dates over the period of ear emergence and in eight grasses harvested on two cutting dates. In both S24 ryegrass and S37 cocksfoot the concentrations of shikimic, quinic and total acids decreased with increased age of the plant. Correlation coefficients are given between the concentrations of acids in eight grasses and the 'preference ranking' of the grasses estimated in an investigation into the grazing preferences of sheep and cattle, and a regression is given for relating 'preference ranking' to the contents of citric and quinic acids. IntroductionMeasurements of the organic acids in herbage indicate that they form a n appreciable part of the dry matter; Fergusonl found that the total organic acids, calculated as malic acid, ranged from 4% to 7% on a dry matter basis; the method he used was t o determine the total acids extracted by ether. Organic acid contents of 5% to 6.3% were found in hays when an aqueous extract was used.2 Again with an aqueous extraction, Fauconneau & Jarrige3 obtained values of 3 . 5 O / , to 5% in herbage. More recently, methods that have been developed for separating the individual acids and measuring them use ion-exchange chromatography4, 5 or partition chromatography on silica ge1.6, Information about the changes in the non-volatile organic acid contents of herbage was required in connexion with work on herbage digestibility.8 Three cuts each of S24 ryegrass and S37 cocksfoot, harvested over the period of ear emergence, were examined. The concentrations of the non-volatile organic acids were also determined in eight different grasses on two occasions. These latter samples were taken from an 322Jones & Barnes: Non-Volatile Organic Acids of Grasses investigation into the grazing preferences of sheep and ~a t t l e ,~ the results from which had suggested that some constituent of the water-soluble fraction of herbage might have a better correlation with preference ranking than any of the other chemical components which had been measured.Ion-exchange chromatography was used for the measurement of the non-volatile organic acids reported in this paper. Because this technique for the determination of these acids was lengthy, it was decided that this approach would not be continued in further investigations on the digestibility and 'palatability' of forage grasses. However it was thought desirable to place on record the results obtained in this preliminary study. Experimental SamplingHerbage samples were harvested, dried rapidly at 100" in a forced-air oven, ground to pass a 0.8 mm sieve and stored in wax cartons. ExtractionFour methods of extracting the acids were investigated: (a) Ether e~t r a c t i o n ;~ (b) Hot-water e~t r a c t i o n ;~ (c) Acetone extraction followed by extraction with 0.01 N-HC~;~O (d) extraction with 80-85% ethanol under reduced pre~sure.~ Extraction from herbage with 80-85% ethanol gave lower values of citric and malic acids compared with the other three me...

End product yields from the extraruminal fermentation of various polysaccharide, protein and nucleic acid components of biofuels feedstocks

“…Sucrose, available as major components of potential biomass crops such as sugar cane and sugar beets, was also readily fermented. Organic acids, also common forage constituents (Jones and Barnes, 1967;Muck et al, 1991), were not examined in this study, but their fermentation has been studied in detail (Russell and Van Soest, 1984).…”

In vitro fermentation patterns and methane production as influenced by cultivar and season of harvest of Lolium perenne L.

“…Differences in the amount and profile of organic acids within the herbage could also be exploited since the organic acid, malate, has been demonstrated to reduce CH 4 emissions in vitro (Martin and Streeter, 1995; Carro et al. , 1999) and to differ in perennial ryegrass ( Lolium perenne L.) cultivars (Jones and Barnes, 1967) and with maturity (Muck et al. , 1991; Martin et al.…”

Fresh and ensiled forage plants—total composition, silage losses and the prediction of silage composition from the crop

“…A summary was presented by Dijkshoorn () showing total levels in the range of 13–72 in temperate grasses and 30–100 g/kg DM in legumes. Analyses by Jones and Barnes () showed similar levels of 13–45 g/kg DM in some temperate grasses. Organic acid levels in plants are dictated by the excess of metal cations over inorganic anions and ash alkalinity can be used as an estimate of OA levels in plants (Dijkshoorn, ).…”