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Perennial grasses can provide very high biomass yields and a better environmental profile compared to most annual cereal crops. The grass biomass can be processed into a protein-rich fraction for monogastric feed and a fibrous pulp fraction for ruminant feed or energy production. We studied the effect of fertilization of tall fescue grown on two sandy sites in Denmark. Dry matter (DM) and crude protein (CP) yield of first cut was measured at four nitrogen (N) fertilization levels (0, 70, 140 or 210 kg N ha−1). Samples were processed in a screw press, achieving a pulp fraction and a juice fraction from which proteins were precipitated into a protein concentrate fraction. CP allocation between the fractions of protein concentrate and pulp was analysed as well as the amino acid (AA) profile. CP in the brown juice fraction was not analysed. CP concentration and CP yield of unprocessed tall fescue increased linearly with N fertilization, attaining concentrations up to 126 g kg−1 DM and yields up to 0.76-0.86 Mg ha−1. N fertilization did not affect CP allocation between concentrate and pulp in a consistent way. As a mean of all treatments and both sites, 17% of CP was recovered in the concentrate and 74% remained in the pulp. CP concentration increased linearly with fertilization in both concentrate and pulp with coefficients of 0.50 and 0.21 g kg−1 DM kg−1 N ha−1, i.e. with a higher increase in the concentrate fraction. The AA profile only differed slightly between the two fractions and between the fertilization levels, however, the total sulphur to N ratio in both fractions decreased with increased fertilization, and a similar trend was observed for the relative content of the sulphur-containing amino acids. The AA profile deviated considerably from soybean meal, particularly with higher leucine and lower glutamic acid content. In conclusion, fertilization can greatly increase CP concentration and CP y

Background: The amino acid profile of plants is an important parameter in assessments of their growth potential, resource-use efficiency and/or quality as food and feed. Screening studies may involve large number of samples but the classical amino acid analysis is limited by the fact that it is very time consuming with typical chromatographic run times of 70 min or more. Results: We have here developed a high-throughput method for analysis of amino acid profiles in plant materials. The method combines classical protein hydrolysis and derivatization with fast separation by UHPLC and detection by a single quadrupole (QDa) mass spectrometer. The chromatographic run time is reduced to 10 min and the precision, accuracy and sensitivity of the method are in line with other recent methods utilizing advanced and more expensive mass spectrometers. The sensitivity of the method is at least a factor 10 better than that of methods relying on detection by fluorescence or UV. It is possible to downscale sample size to 20 mg without compromising reproducibility, which makes the method ideal for analysis of very small sample amounts. Conclusion: The developed method allows high-throughput analysis of amino acid profiles in plant materials. The analysis is robust and accurate as well as compatible with both free amino acids and protein hydrolysates. The QDa detector offers high sensitivity and accuracy, while at the same time being relatively simple to operate and cheap to purchase, thus significantly reducing the overall analytical costs compared to methods based on more advanced mass spectrometers.