Agroscope, Institute for Plant Production Sciences IPS, 1260 Nyon, Switzerland

Nutritive value of grassland plants. Phenolic compounds

Ten main grassland species were cultivated in pure stand in 3 experiments located at different altitude. During two years their chemical composition was regularly assessed the end of the growing period. This paper presents the content and the biological activity of phenolic compounds in the different species and their evolution when the plants grow older. In grasses the content of esterified phenolic acids increases with the content of cell wall constituents and is much higher than in legumes and herbs. On the contrary grasses contain generally less soluble phenolic compounds than legumes and herbs. These compounds are closely correlated with the index of potential negative action (IANP). This index measures the inhibitory effect of secondary metabolites on the enzymatic hydrolysis of cell wall constituents. Ryegrasses (L. perenne and L. multiflorum), white clover and alfalfa present the lowest IANP. The highest values were observed in dandelion (Taraxacum officinale) and wild chervil (Anthriscus sylvestris). For both species a negative effect of the phenolic compounds on the digestibility of the organic matter cannot be excluded.

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