Increasingly intense summer droughts have led to a sharp decline in the yields and nutritional value of grassland forages. Producing sufficient supplies of quality forage has therefore become a genuine challenge for farmers. It is in this context that agroforestry could serve as an additional source of forage for ruminants, particularly during periods of summer drought.
Agroforestry for forage production refers to the use of fodder trees as a forage resource for livestock. The animals consume the leaves and young twigs, either directly from the tree or from previously pruned branches. Although fodder trees have been identified as an alternative source of forage since the very beginnings of agriculture, no data on the yield and nutritional value of tree leaves in Switzerland have been published to date. It was therefore essential to evaluate the forage potential of trees within the Swiss pedoclimatic context in order to provide support to livestock farmers in the management of trees and hedges grown for forage.
A study of seven common tree species in Switzerland was conducted on six farms participating in the Federal Office of Agriculture-funded Agro4estrie resource project (2022-2026). The forage potential of the seven tree species was evaluated in terms of leaf yield and nutritional value.
Fodder trees provide a useful forage supplement
The results show that branch diameter is a good indicator of branch forage availability for livestock feed planning. Branches with a diameter of 5 cm can produce between 250 and 600 g dry matter (DM) according to the tree species. Thus, six to seven 5-cm-diametre branches of common ash or white willow could provide 20% of the daily dry-matter ration of a dairy cow in the form of tree leaves, without counting the consumption of that year's young twigs.
The nutritional value of fodder-tree leaves is better than or equivalent to that of grass-based forage
The leaves of white willow, goat willow, common ash and sycamore are characterised by a high nitrogen and low fibre content and provide a better-quality forage than grass-based forage in summer. By and large, the trees' young twigs have very high levels of fibre, and hence low levels of digestibility; however, they also contain high levels of copper, calcium and zinc, which could help prevent mineral deficiencies in the animals.
Conclusions
- Fodder trees supply additional forage of high nutritional value in summer.
- Branch diameter is a good indicator of forage availability for planning feeding with pruned tree branches: branches with a diameter of 5 cm can produce between 250 and 600g DM according to the tree species.
- White willow, goat willow, common ash and sycamore are the species with the highest yields of leaves per branch and a high nitrogen content.
- Twigs can be an important source of zinc, copper and calcium, although their nutritional value is fairly poor.
Authors: Sébastien Dubois, Massimiliano Probo, Pierre Mariotte (all Agroscope), Sébastien Galland, Alice Dind, Nathaniel Schmid, Geoffrey Mesbahi (all FiBL Switzerland)
This article and the corresponding scientific article were published on 10 April 2024 on agrarforschungschweiz.ch.
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Links
- agrarforschungschweiz.ch: Article "Fodder trees: a supplementary forage resource for livestock"
- agrarforschungschweiz.ch: Scientific article "Rendement et valeur nutritive de sept espèces d'arbres fourragers" (in French)