Temporal variations in leaf traits, chemical composition and in vitro true digestibility of four temperate fodder tree species

Context Many tree and shrub species are underestimated fodder resources due to insufficient knowledge about their potential feeding value, especially for goats. Aims The present work aimed at assessing productive and nutritional attributes of the foliage of the following four temperate tree species widespread in Europe: Acer pseudoplatanus, Fraxinus excelsior, Salix caprea and Sorbus aucuparia. Methods Leaf length and biomass, proximate composition, fatty acid profile, phenolic composition and in vitro true dry matter digestibility were determined along the vegetative season. Key results The leaf length of the four species was significantly related to leaf biomass and can be considered as a proficient proxy for estimating leaf biomass. The differences found among the species were remarkable, although weakly related to temporal changes, especially when considering fatty acid and phenolic compositions. Fraxinus excelsior sprouts were the most productive, with a mean biomass of 13.2 g dry matter (DM) per sprout at the end of the growing season. Its foliage showed also the lowest phenolic concentrations (average total extractable phenols of 11.25 g/kg DM), resulting in the highest digestibility values (average in vitro true dry matter digestibility of 56.5 g/kg DM). Digestibility of S. aucuparia was similar, but its lower polyunsaturated fatty acid concentration (average value of 62.13 g/kg DM) could reduce the interest for this species as a feeding resource for goat dairy products with healthy properties. The lower digestibility found for A. pseudoplatanus and S. caprea (average values of 43.3 and 46.2 g/kg DM, respectively) may be related to their higher phenolic concentrations (average total extractable phenols of 45.9 and 47.3 g/kg DM, respectively). Conclusions The four species could represent an appealing feedstuff for goat nutrition, due to the valuable and complementary nutritional characteristics of their foliage. Implications The use of the studied species as fodder resource may be particularly relevant during drought periods and in the late summer when herbage quality decreases, especially in terms of crude protein and fatty acid profile.