Tree hay (sometimes also referred to as leaf fodder, leaf hay or tree fodder) is a source of animal fodder produced by harvesting the leaves and twigs of a variety of perennials, and in particular trees. It specifically refers to the practice of feeding the material to livestock directly after collection or more commonly after storing and sometimes drying the tree hay for a certain period of time. It hence does not include the browsing of trees and fodder hedges by livestock directly. It is a traditional practice that was once widespread, but has been largely forgotten as grass hay became the dominant practice in modern agriculture. However, recently the interest in this ancient practice, and tree fodder more generally, have started to revive. It relates to agroforestry and sustainable farming in general through shared goals of solving climate and biodiversity challenges. In part because trees and hedges are increasingly recognised as valuable elements beneficial for biodiversity and landscape. Additionally, a growing body of scientific research indicates that tree leaves can potentially serve as an additional source of relevant nutrients for livestock.
History Producing tree hay was once a common and widespread practice across Europe. Trees were often an essential source of seasonal livestock fodder for many agrarian communities. For some it was structurally part of the fodder stock in winter. In other regions trees were more of a backup source in case of failing grass hay production, for example due to extreme summer weather. Either way, trees were essential for the resilience of traditional agrarian communities.. Tree hay was most commonly harvested in the summer, possibly dried and stored until the hay was fed to the livestock in the winter. Cutting and drying methods varied per region, but a common practice was the bundling of 60 to 200 cm long twigs held together with twisted twigs of willow or hazel. The tree species that were harvested depended on the local conditions and culture as well as the type of livestock that was held and their preferences for certain species. In Europe's moderate climate zones Elm and ash seem to have been popular as fodder sources. But in harsh winters or after bad growing seasons even species like ivy and holly are known to have been cut as fodder.
Nutritional value Trees are part of the natural diet of sheep (20%), goats (60%), horses (15%) and cattle (10%). However, the nutritional value of trees can be very variable and is influenced by many different factors. Every species contains different nutrients in different amounts and the nutrients will also vary depending on soil type and season. Analysing tree fodder on site can be important to give insight to the nutritional value of a specific situation. However, the seasonal variations don't seem significant enough as to when the fodder should be fed. Generally, the in-vitro organic matter digestibility of tree leaves in comparison to grass is relatively low. But crude protein and mineral levels of some species are relatively high, which makes tree fodder a valuable complementary source of nutrients Dried tree leaves contain higher mineral levels compared to fresh leaves. Making tree hay a valuable source of minerals outside of the growing season. Tree fodder as a source of magnesium, selenium, zinc and copper in particular is interesting, as these minerals are significantly higher in some trees compared to grass.
Secondary compounds In addition to macro and micro nutrients, many tree fodder contain a number of secondary compounds that have medicinal properties. The most common secondary compounds are tannins. Tannins have a positive effect on the digestion of protein in ruminants and have shown to reduce intestinal parasites.
Comparison to alfalfa
White mulberry Alfalfa is considered one of the most nutrient-dense fodders for livestock. But when compared to for example white mulberry (Morus alba) leaves, we see that the mulberry is superior to alfalfa in most nutritional values. Mulberry contains on average less protein than alfalfa, but the difference is less than 1% (fresh and dried). Mulberry still contains 19% protein on average, ranging from 11% to 25% [1]. Moreover, mulberry contains less crude fiber making it more palatable and animals can ingest more of it before they are full. Mulberry contains less amino acids, but in better ratios, improving the overall digestibility. Mulberry also has better absorption of nutrition for animals. Because of this, animals may need to eat less, which can reduce the farmers' costs. Mulberry contains more secondary compounds, tannins in particular. When mulberry leaves are dried the tannin levels increase significantly. Alfalfa contains mostly saponins and flavonoids and does not contain any tannins. Mulberry leaves are rich in flavonoids. This increases biodiversity of the gut bacteria, causing more efficient digestion of nutrients and fiber and reduces methane emissions. The flavonoids in mulberry are also antioxidant, antimicrobial and anti-inflammatory.
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