Screw-pressed fractions from green forages as animal feed: Chemical composition and mass balances

Abstract

In colder humid areas, green forages are recognised as high protein yielding crops and have the potential to be a locally grown sustainable protein source. However, without processing, the protein cannot be properly utilised by monogastrics. By screw pressing, a pulp fraction suitable for ruminants and a protein concentrate suitable for monogastrics can be produced. The aim of this study was to analyse the chemical composition of the produced fractions and the mass balance distribution of protein and dry matter (DM) between the fractions. Mass balances are important in order to determine the potential of biorefining of forages as a tool for sustainable feed production.White clover, red clover, lucerne, and perennial ryegrass were separated into a green juice and a fibrous pulp in a screw-press, and a protein concentrate was precipitated from the green juice by heat or acidic precipitation.The pulp and green juice had an average crude protein (CP) concentration of 203 g/kg DM and 249 g/kg DM, respectively. The majority of the DM and the CP from the plant was retained in the fibrous pulp. Protein concentrates from the green juice and pulp contained higher concentrations of the essential amino acids for monogastrics and ruminants compared with unprocessed forage.The results demonstrate that fractions with high protein concentration and balanced amino acid composition can be produced, which combined with a high recovery highlight the potential of both fractions as a protein source for livestock.