Could Trees Supplement Forage?
Lindsay Whistance, livestock researcher at the Organic Research Centre, asks whether you could look to trees to supplement your forage needs in winter.
Climate changes can cause shortages of grazing
Changes in our climate are giving us more seasonal heatwaves that can causing serious shortages in available grazing. this can mean that next winter’s forage rations get eaten earlier than anticipated.
Trees as forage
A traditional feed source that can offer some help is for livestock to browse from trees and hedgerows. Tree fodder (harvested during the summer months and preserved as hay or silage) can certainly help supplement winter feed though planning ahead is important as it requires adequate storage facilities and knowledge of correct moisture content levels and mould development in both hay and silage.
What trees can be eaten?
Traditional fodder trees in UK include ash, elm and holly, though other species that are readily browsed include willow, poplar, rowan, hazel, oak and hawthorn, as well as fruit trees. Birch, beech and alder are edible but less palatable and there are, of course, poisonous trees such as yew and box that hungry animals may be tempted to try. All domestic animals willingly browse to some degree and trees constitute 12%, 21% and 60% of the annual diet of cattle, sheep and goats respectively. However, their daily intake of browse can rise to 55%, 76% and 93% when grass is scarce or with palatable early-season growth.
What are the nutritional qualities of trees?
In nutritional terms, browse (or tree fodder) can compare very well with grasses grown in the same environment and there is an online data base where the nutritional content of different species is recorded and updated as more is learned. Tree roots access minerals that are out of reach of grasses and these minerals are stored in the leaves, making them an excellent source. There is some evidence that selenium (e.g., willow) and copper (e.g., hazel) may help with resistance to bTB. Additionally, as with forbs, trees contain higher levels of condensed tannins (CTs) when compared to grasses. CTs are part of a plant’s defences and, in ruminants, they inhibit protein uptake in the rumen. However, the CTs are then broken down in the abomasum, delivering a high-quality protein to the small intestine. On top of this, CTs offer an effective gastrointestinal parasite control, to which worms cannot develop any resistance, further improving the utilisation of any feedstuff.
The practicalities of browse feeding
When feeding browse, tree and hedgerow management regulations should, of course, be observed but if available trees have branches below browse height, stock can browse directly. Alternatively, if any trees are being coppiced, pollarded or being harvested for fuel, etc, then stock can feed on the leaves and twigs before the wood is removed. Similarly, any hedges that are being cut can offer a valuable feed source if stock are given access to the fresh cuttings. Alternatively, animals could be allowed to browse direct from the hedgerows though this may require managing to avoid over-browsing. If hedges are thick with, particularly, blackthorn this may result in puncture wounds leading to infections.
In recognition of the value of trees to both arable and livestock farming systems, an EU-funded project Afinet has been set up with Agroforestry Innovation Networks that are designed to support innovation by promoting knowledge exchange between farmers, foresters, researchers and advisors. In the UK, the Afinet project is led by the Organic Research Centre (Jo Smith) and Abacus Agriculture and is further supported by the Farm Woodland Forum. If you are interested, have a look: Agroforestry Innovation Networks (AFINET)