Plant organic acids in fresh and ensiled forage plants

Timothy, red clover and white clover from two cuts and two stages of maturity and whole crops (WC) of barley, wheat and maize from three stages of maturity were analysed for individual plant organic acids (OAs) before and after ensiling in mini-silos. Total OA levels, as previously reported, were generally lower in WC (14-70g/kg dry matter) in comparison with leys (51-98g/kg dry matter). Succinic, shikimic and fumaric acid levels were very low in all samples, while quinic, malonic, malic and citric acid constituted >90% of total OAs in all samples except maize. Maize had lower total OA levels than any other species but was the only one containing detectable levels of oxalic and aconitic acid. The sum of oxalic and aconitic acid decreased, however, from 89% to 35% of total OAs from early to late maturity, while there was a parallel increase in citric acid with increasing harvest date. Total OA level was unaffected in the ley crops by maturity, cut and species (p>.1), but among WC, wheat was higher than maize (p<.05) and also higher at early, than late maturity (p<.01). Silage total OA levels were lower than in parent crops (p<.001). Individual OA levels decreased by 38%-56% from ensiling, except for oxalic acid, which was unaffected, and succinic acid, which increased >7-fold. Excluding succinic acid, which is also a fermentation product, average loss during ensiling was 44%.