We have had several new producers this winter trying to convince us it just isn’t true that sheep cannot be fed copper. Apparently they are doing it without any problems. Since we are coming into lambing season it is a good time to address these ideas.
It needs to be clear that sheep and goats and cattle absolutely do not have the same copper needs. Over the years I have personally known two sheep producers who faced copper toxicity in their flock and it was devastating both financially and emotionally. Both times it was due to feeding a product that was supposed to be for sheep but the feed mill had mixed it wrong. The sheep were fed the product for several months with no ill effects. Then there was a weather stress. Immediately the flocks started to experience death loss. The feed was tested and discontinued but the damage was done. There was little the university or veterinarians could do and it took several months and much financial/emotional hardship before this settled. Therefore our management recommendations reflect a healthy respect for this condition.
Generally, sheep require about five ppm (parts per million or mg/kg) of copper in their total diet. Sheep absorb copper from their diet in proportion to the amount of copper offered, not according to their dietary needs. Excess copper is stored in the liver. The storage level in the liver can take months or even years to reach a toxic level (more than 1,000 ppm DM). Toxicity can occur at levels above 25 ppm. However, dietary molybdenum levels also affect copper requirements and there are areas of Manitoba where high or low molybdenum levels can be an issue. If in doubt it is best to contact the local agricultural extension office or the provincial sheep specialist in your province for this information.
If molybdenum is high in feed, a special mineral mix can be ordered with a nutritionist’s prescription. Molybdenum forms an insoluble complex with copper to prevent copper absorption. If molybdenum levels are low (less than 1 ppm), sheep are more susceptible to copper toxicity. If molybdenum intakes exceed 10 ppm, copper deficiency may occur on diets that would normally be adequate. Sulphur further complicates the copper: molybdenum relationship by binding with the molybdenum.
Copper toxicity in sheep usually results from the accumulation of excess copper in the liver over a period of a few weeks to more than a year with no clinical signs. This usually occurs when sheep are fed a product that is made for cattle or specifically for goats. Cattle need about 10 times more copper than a sheep. When a sheep is under any kind of stress the liver will allow a sudden release of copper stores to a rapid breakdown of red blood cells. Affected sheep are lethargic and anemic. They may grind their teeth incessantly and experience extreme thirst. Membranes are very pale and may appear yellow, as jaundice sets in. Urine is a bloody colour. Death usually occurs one to two days after the onset of clinical symptoms. At post-mortem, tissues are pale to dark yellow and the kidneys are a very dark colour.
Other copper sources
Copper can be added in places other than feed or mineral mixes. In recent years, copper oxide wire particles (copper boluses) have been recommended as an anthelmintic (agent causing parasite death) for sheep and goats. Researchers are also re-evaluating copper sulphate drenches as a deworming agent. Copper has anthelmintic activity and has been historically used as a deworming agent in sheep; however, its use was discontinued because of toxicity issues. This is the situation with many “natural dewormers.” They can control parasites, but in effective doses they can increase the risk toxicity to the animal.
Copper deficiency in sheep can occur, although it rarely happens. It bears mentioning only because of the fact that soils in some areas are very high in molybdenum. Fresh grasses are poor sources of copper in comparison to hay. Acid soils increase copper and lower molybdenum in forages. Liming can increase molybdenum in the forage and alter the copper: molybdenum ratio. Where two or more of these three elements exist together on a farm, in quite ‘normal’ concentrations, they will act synergistically to bind out copper from a diet.
Effects of deficiency
Copper deficiency in ewes during mid-pregnancy may lead to swayback in lambs. This is due to a lack of copper during the formation of the neural tube. In young lambs, a copper deficiency may result in a poor fleece without its natural “crimp” which has been described as “steely wool.” Poor growth, anaemia, and increased susceptibility to bacterial infections can also be seen. Caution should be used in diagnosing a copper deficiency in sheep due to delicate balance of this mineral. Soil testing is highly recommended if a deficiency is suspected. The local agriculture office can help with this. There is also an online resource for water and soil testing in Canada at: www.certifiedorganic.bc.ca/rcbtoa/services/soil-testing-services.html.
A common inquiry is if people can house their goats and sheep together. We do not recommend it. Keeping our sheep housing separate for the winter months works the best for us. Over the years we have seen a lowering of fertility in our bucks if housed with our rams. We have seen does with kids that presented copper deficiency symptoms when housed with ewes. We do graze them on the same pastures but they are kept in separate night pens so they have access to their own mineral mixes.
Every season brings with it a new bunch of things to learn. Our wish is that people don’t have to learn things the way others have — the hard way. Minimizing the financial and emotional impact of mass death loss is a goal.