What is the effect of clinical or subclinical Copper deficiency in sheep?

Clinical copper deficiency is rare these days but historically was a large issue, causing swayback in lambs, bone fragility, and pigment changes and crimp loss in wool. Copper is essential to sheep and deficiency can be primary (reduced intake) or secondary – caused by other elements interfering with its uptake.

Why don’t we want to supplement unnecessarily?

Apart from the cost and labour, the injections can cause swellings/pain and Copper overdose is toxic to sheep.

How do we know if ewes are deficient in copper?

There are two ways we can test for Copper deficiency – by taking blood or a liver sample. Blood levels only drop to low levels when the liver levels are very low, so it is only useful at the lowest levels- when diagnosing clinical deficiency. The liver stores copper so taking a sample gives a much better understanding of the levels in the animal.

Practical ways of taking liver samples include sending a form with cull ewes to the works (just ask us for a filled out form), or taking a fresh sample from ewes killed for dog food. Liver biopsies in ewes can be done but are a bit more complicated than in cattle, requiring a sedation and a veterinarian experienced in the technique.

Many farmers supplement their ewes with Copper at scanning time but is it really needed?

A recent trial that Anexa Vets Raglan and Cognosco did with the support of the North Waikato Veterinary trust set out to see if supplementing Copper to ewes made any effect on the ewe weights, lamb weights, and lamb survival (lambing and weaning percentages).
At scanning time, 340 ewes were allocated to one of three groups. These ewes were either a control group and given no treatment, given a 1ml injection of copper or administered a 4g Copper bolus.
30 Liver biopsies were taken from each group to get a true representation of the copper levels in the ewes, and weights, body condition scores and dag scores were taken too. This was repeated at docking and the lambs were also counted and weighed at docking and weaning.

So, what did we find?

The Copper levels in the ewes (across all the groups) dropped from scanning to docking, though the drop was not as significant in the ewes that had been given Copper boluses or injections. 30% of the control ewes were deficient at docking, none at scanning.
There was no difference between the groups’ weights, body condition scores or dag scores at each of the times taken. The lamb weights, lambing and weaning percentages were all the same between groups. Therefore there was no production effect of giving copper to these not-deficient ewes at scanning time.

In conclusion, there was no production benefit to giving copper to these ewes at scanning, but it did have an effect in that it helped prevent deficiency at docking. This trial proved once again, the question “Do I need to give Copper to my ewes?” will need to be answered with another question – “Are they deficient?” Don’t waste your time and money supplementing ewes if they aren’t deficient, test first it’s not too late.