Effect of variety and environment on the contents of crude nutrients and amino acids in organically produced cereal and legume grains

Cereals and home-grown grain legumes are main feedstuffs for monogastric animals. Thus, knowledge on variations of their crude nutrient and amino acid composition is of great interest in animal nutrition. Genetic and environmental factors are known to be able to affect the nutrient composition of crops. Thus, the aim of the study was to analyse a selection of grains of organic cereal and grain legume species for their crude nutrient and amino acid contents and to determine the effect of variety and environmental conditions on the variations. Furthermore, the use of equations to predict amino acid contents from the crude protein content of cereals and grain legumes was tested. The contents of the crude nutrients and 18 amino acids of 835 samples of ten different cereal and grain legume species were analysed. Selected nutrients were subjected to correlation analyses. Furthermore, generalised linear models with multiple comparisons were conducted to assess the effect of species as well as of variety, harvest site and harvest year on the analysed ingredients. The contents of all crude nutrients and amino acids varied depending on the species and the considered nutrient. The lowest variation coefficients (1.3–2.6% in cereals and 3.1, 3.5 and 6.8% in field peas, field beans and blue lupins, respectively) were observed for the contents of nitrogen-free extracts. The crude protein contents varied widely, specifically in winter rye (coefficient of variation: CV = 17.4%). However, compared to table values, the cereals and grain legumes of the present study tended to contain low amounts of crude protein and high amounts of starch. Due to the wide variations, there is no distinct consistency between table values and the results of this study. High negative correlations between starch and crude protein contents were observed in eight species. Furthermore, the amino acid profile of cereals and grain legumes varied depending on the crude protein contents. Higher crude protein contents were often related to lower contents of several essential amino acids in favour of glutamine/glutamic acid, proline and phenylalanine in cereals as well as of arginine in grain legumes. Furthermore, variety, harvest site and harvest year affected the contents of the analysed ingredients depending on the species. However, the environmental factors had a greater influence than the variety. The observed variations must be regarded in diet formulation. Equations can be used to estimate the amino acid contents of cereals and grain legumes from their crude protein content. However, additional analysis results are needed to improve the predictability with equations.