Evaluation of yield formation and nutritive value of forage legumes and herbs with potential for diverse grasslands due to their concentration in plant specialized metabolites

Abstract

The use of forage legumes and herbs in temporary grassland swards is a promising strategy to enhance productivity, protein supply, herbage quality and species diversity in forage-based low input dairy production. Species containing plant specialized metabolites (PSM; e.g. tannins or polyphenol oxidase) are associated with positive effects on ruminants’ health, performance and nitrogen use efficiency. However, plant growth characteristics and the occurrence of PSMs with potential for improved nutritive value vary greatly depending on species and environment and to date, few species have been exploited agronomically. Thus, the current study aims to screen a range of forage species that are abundant in low input and semi-natural grasslands, in terms of productivity and forage quality for dairy cows under limited nitrogen availability in a ley system. Pure stands of eight legumes, six herbs and perennial ryegrass as reference, were established in a field experiment and sampled over two years (2010 and 2013) in their first full production year. Freeze-dried plant material was analysed for crude protein (CP), enzyme soluble organic matter (ESOM), fibre parameters (ADF, NDF), total phenolics (TP) and condensed tannins (CT). The species variation was significant for each parameter (P < 0.001). In comparison to high yielding legumes, herbage production of investigated alternative species was generally low, but for Cichorium intybus and Plantago lanceolata comparable or even higher than for Lolium perenne. Differences existed in yield development throughout the year, thus exhibiting temporal asynchrony for improved performance if grown in mixtures. Apart from Onobrychis viciifolia, the CP concentration in legume species was highest while ESOM was outstandingly high in herbs (except Plantago lanceolata). TP concentration was generally higher in herbs but in Onobrychis viciifolia and Lotus corniculatus the concentration of condensed tannins exceeded 10 g kg−1 DM. The results indicate that alternative forage species exist with high forage quality and potentially promising PSM concentrations, thus making them interesting additions for temperate grasslands.