Dry matter yield, chemical composition and estimated extractable protein of legume and grass species during the spring growth

Knowledge of the variation of extractable protein amount in legumes and grasses as affected by harvest time is important for identifying optimal combinations to enable a high protein production in a biorefinery. The extractability of protein was estimated using the Cornell Net Carbohydrate and Protein System across six harvests during the spring growth.

The estimated extractable protein [g kg^-1 dry matter (DM)] defined as the easily available fractions B₁ +B₂ was significantly higher in white clover and lucerne at all harvests while, if the more cell wall attached fraction B₃ can be extracted, white clover had the highest extractable protein amongst all species. Total yield of B₁ +B₂ per ha was higher in white clover and red clover at the early growth while B₁ +B₂ +B₃ was by far the highest for red clover through all harvests.

White clover could be a good candidate for protein production purpose in a biorefinery due to its high extractable protein content per kg DM. In order to maximise the protein production capacity, harvest should take place during early growth due to a decline in protein extractability with maturity. The final economy of the concept will depend on the value of the fibre after extraction of the protein. © 2017 Society of Chemical Industry.