Nutrient composition, fermentation characteristics and mass balance of press juice and press cake obtained from biorefining of grass-clover and red clover silage

Abstract

Biorefining is seen as a potential method to produce protein-rich feed for monogastric farm animals from grassland, which does not compete with human nutrition. Therefore, a new biorefinery facility was constructed and tested in this experiment by using silages from grass clover mixture and red clover. After biorefining, press juice was stored for further use while press cake was re-ensiled. Samples from silage, press juice, fresh press cake and re-ensiled press cake were analysed for nutrient composition, fermentation parameters, amino acids (AA) and biogenic amines (BA) concentrations. Furthermore, digestibility of silage and re-ensiled press cake was tested in wethers. We found that press juice contained about 205 g crude protein (CP), more than 180 g crude ash and more than 130 g volatile organic compounds (VOC, all values per kg dry matter [DM]). Furthermore, press juice had an unfavourable AA ratio for use as a monogastric feed (methionine and cysteine were reduced). Forage type hardly affected nutritive value of press juice. Re-ensiling of press cake was successful as a sufficient decrease of pH and VOC concentration was observed. Press cake had 26–36 g/kg DM lower CP content and 0.77–1.12 MJ/kg DM lower metabolisable energy content than silage with greater differences in red clover than in grass clover mixture. Press juice can be used as feed in monogastric animals, but its use is limited due to its low CP content and unfavourable AA profile. Press cake could be an appropriate feed for ruminants, especially dry cows or heifers.