The Nutritional and
Medicinal Value of Trees
in a Dairy System
Tim Saunders
Introduction
• The sustainability of a farm business is becoming increasingly
important, as customer expectations change and
environmental pressure grows.
• Sustainable dairy systems- carbon and nitrogen efficient while
remaining economically viable.
• Tree fodder integrated into the diet of dairy cows may help
achieve this at the same time as giving health benefits.
• Trees can help reduce the use of bought-in concentrates and
the wasteful output of nitrogen, whilst attempting to maintain
high milk yields.
Silvopastoral Systems
• Ancient systems
adapted to solve
modern problems
• Still used in NZ,
especially with
willows and poplars.
• Recent interest as a
supplement rather
than a bulk feed.
Nutrients from trees
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Crude protein/dry matter
Nitrogen efficiency
Minerals (trace elements)
Secondary metabolites
Digestibility
Protein content
• Many tree species have a relatively high crude
protein content in the foliage.
• Willow and willow silage (Smith et al., 2014)
• Digestibility?
Minerals
• Trace element deficiencies may reduce milk yield,
reproductive capacity and immune response.
• Selenium and copper may help with resistance to bTB.
• Trees such as willow store much higher quantities of trace
elements, including copper, zinc and selenium, in their foliage
than pasture species (Robinson et al., 2008) (Anderson et al.,
2012).
• Potential exists for supplementation through browsing rather
than bought in mineral concentrates.
Condensed tannins (CTs)
• Condensed tannins (CTs) are compounds often
found at higher concentrations in tree fodder
than in traditional forage.
• Traditionally these have been considered to be
anti-nutritional factors (anti-herbivory response
in some plant species).
• CTs have a pH dependant ability to bind and
proteins, making them insoluble. This activity can
alter the site of protein digestion in ruminants.
CTs: Nitrogen Efficiency
• RDP vs RUP
• Condensed tannins can act to increase the
ratio of RUP to RDP, improving nitrogen
efficiency.
• Lower risk of bloat.
CTs: Medicinal Benefits
• Condensed tannins reduce parasite load.
• Studies from NZ using sheep and goats show
up to 50% reductions in faecal egg count and a
reduced % of successfully hatching nematode
eggs.
• Potentially of use against brown stomach
worm (Ostertagia ostertagi ).
Other medicinal benefits
• Secondary metabolites such as salicylic acid may be behind
self-medication by cattle.
• McKinnon et al. (2000) showed that sheep choose willow and
poplar with high salicylic acid content, possibly due to the
beneficial anti-inflammatory effects.
Management
• Rotation effects the chemical trait of the fodder, as
well as climate, soils, etc.
• 4 yr SRC willow had higher biomass yield, higher
cellulose and lower lignin than a 2 year cycle (Guidi
et al., 2009).
• Willow silage- a useful winter supplement? Smith et
al. (2014).
Tree species choices
• Protein availability, type, digestibility, secondary metabolite
types and concentrations are all factors to consider.
• Willows and poplars have been used as fodder traditionally
in temperate climates . These groups of species may not be
optimal fodder material in all cases, although their high
productivity is important in ensuring a continuing supply of
browse.
• Species choice depends on management preferences.
Future work
• Dairy cow tree species preferences and browsing
behaviour studies- Tim Downes’ ‘Slang’ field
• 50 trees/ ha
• Species planted are small-leaved lime,
Hornbeam, Sycamore and Elm.
• Trees assessed for browse rates
after each rotation.
References
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Anderson, C. W., Robinson, B. H., West, D. M., Clucas, L., & Portmann, D. (2012).
Zinc-enriched and zinc-biofortified feed as a possible animal remedy in pastoral
agriculture: Animal health and environmental benefits. Journal of Geochemical
Exploration, 121, 30-35.
Guidi, W., Tozzini, C., & Bonari, E. (2009). Estimation of chemical traits in poplar
short-rotation coppice at stand level. Biomass and Bioenergy, 33(12), 1703-1709.
Min, D., Pomroy, W., Hart, S. and Sahlu, T. 2004. The effect of short-term
consumption of a forage containing condensed tannins on gastro-intestinal
nematode parasite infections in grazing wether goats. Small Ruminant Research,
51(3), 279-283.
Novobilský, A., Mueller-Harvey, I., & Thamsborg, S. M. (2011). Condensed tannins
act against cattle nematodes. Veterinary Parasitology, 182(2), 213-220.
Smith, J., Peirce, B. and Wolfe, M. 2012. A European perspective for developing
modern multifunctional agroforestry systems for sustainable intensification.
Renewable Agriculture and Food Systems, 27(4), 323-332.