Monday, 12 March 2018
How much copper is enough for deer?
With autumn fertiliser applications pending, it’s time to consider the copper (Cu) status of deer, the makeup of their diet, as well as what supplementary programme/s will be required.
Adequate availability of Cu in deer is particularly important for preventing Enzootic ataxia (swayback), which can happen from nine months onwards. Deficient young stock can also become more prone to sudden bone fractures and joint disease (osteochondrosis), which is seen as progressively worsening lameness.
Liver and herbage testing are the key measurements to determine your supplementary programme as it is fairly unusual for New Zealand soils to have a Cu deficiency. Deficiencies are usually induced in the animal where dietary factors such as molybdenum (Mo) in the presence of sulphur reduces the absorption of Cu from the gut. Elevated iron (Fe) levels in pasture can also do the same.
Farmers often ask if adding copper sulphate (CuSO4) to their fertiliser will be enough for stock and whether they can stop other supplementation, such as bullets or injections.
Unfortunately, there is no one simple answer to that. Addition of Cu to fertiliser can certainly be a successful strategy for boosting and maintaining levels in deer, but relies on the following:
- Peak copper requirements are in winter/spring, so it must be applied in the autumn fertiliser at minimum 10-12kg CuSO4/ha (not 5‐6kg/ha as with sheep/cattle).
- Deer must graze these pastures exclusively for 6‐8 weeks after application.
- Mo levels in mixed herbage should be less than 1mg/kg DM.
- Cu application needs to be repeated annually, but it always pays to check pasture and animal levels first.
Our Precision Blending Plant, in Christchurch, can now provide a new Copper polymer coated superphosphate product (Surflex range) that ensures every granule of fertiliser has copper attached to it. Trial work has shown that this technology significantly increases the plant Cu uptake compared to traditional Cu crystals mixed in with superphosphate.
Conducting pasture and/or liver testing in autumn is a good way to gain an understanding of what the most effective and economic treatment plan will be.
The liver is the storage vessel for Cu, so taking liver biopsies or testing livers from culled/slaughtered animals is a very good way to assess the Cu status in the mob. Up to five liver samples should be taken to give a representative sample.
When plant testing for animal health use mixed herbage to reflect the diet. It is important to request Mo and Fe levels also because they have an effect on the absorption and storage of copper.
Contact the Customer Centre or your local Agri Manager, to discuss your copper options.