Yield, composition and nutritive value of leaf protein concentrates from mixed forages of cereals and legumes

Abstract

Leaf protein concentrates (LPC) were produced from high- and low-legume (high-cereal) mixtures of forage. The forages were obtained by sowing seed mixtures containing either 60% legume and 40% cereal or 60% cereal and 40% legume (air dry matter). The legumes used were vetch and pea, and the cereals were wheat, triticale and barley. Average green- and dry-matter yield was highest for high-legume mixtures containing vetch. Barley-containing mixtures gave higher yields than those containing wheat or triticale. The LPC were analysed for their gross composition and amino-acid content. Biological value and true digestibility of LPC protein were estimated in rats using the Thomas-Mitchell balance method. Protein content of LPC was low (32.3–46.7% dry matter basis). All concentrates were poor in sulphur amino acids and their content of basic amino acids was unexpectedly low. Protein extracted from low-legume forages was higher in biological value than that from high-legume forages, while true digestibility did not differ significantly. It can be concluded that increasing the proportion of legume in mixed (legume-cereal) forages increases the yield of green and dry matter per unit area, but significantly decreases nutritive value of extracted protein.