Copper deficiency in cattle has been associated with a range of problems.
They include poor growth, loss in milk production, changes in hair colour, anemia and nervous disease symptoms such as falling down and stumbling.
Copper has also been suggested to play a role in the immune response, and cattle that are copper deficient may be more prone to infectious diseases.
As well, copper deficiency has been linked to reproductive failure, although this association has been controversial.
Copper deficiency can occur in two ways:
- Primary copper deficiency can occur when cattle are fed a diet deficient in copper, which may occur in particular geographic areas that have soil that is deficient in copper.
- Secondary copper deficiencies occur when cattle are fed diets that are high in molybdenum or sulfate. Molybdenum and sulfates are antagonistic to copper. They form complexes with copper that make it unavailable to the animal.
Low forage copper, high levels of molybdenum in forage and sulfates in water are not uncommon on the northern Great Plains, and a recent research project by Dr. Leanne VandeWeyer and Dr. Cheryl Waldner of the Western College of Veterinary Medicine provided more insight into the extent of the problem in Western Canada.
Blood samples were collected from slightly more than 780 beef cows from 66 cow-calf herds as part of a larger study on beef herd productivity.
The blood samples were collected from all of the available cows diagnosed as non-pregnant, as well as from some randomly selected pregnant cows on each farm.
VandeWeyer’s study found that 16 percent of the cows were deficient in blood copper levels, although other studies in North America have shown significantly higher percentages.
However, these samples were collected in the fall when copper levels are traditionally higher than if measured in the spring. This may have accounted for the lower prevalence of deficiencies.
Liver copper provides the best indication of true copper reserves, but liver biopsies are not routinely done.
Blood copper levels may not give a true indication of the copper reserves available in the animal because animals will deplete their liver copper levels to keep their blood copper levels at a normal level.
However, we know that the animal is truly deficient in copper and that liver copper levels have been depleted if blood levels of copper are low.
VandeWeyer’s study showed that herds in the northern continental divide ecoregion had significantly lower copper levels than other areas of the study. It is the mountainous region spanning the southern Alberta-British Columbia border.
Gray soil in this region has previously been associated with low soil copper levels.
Molybdenum levels were also high in areas with grey soil and in areas with higher amounts of precipitation.
Secondary copper deficiency is known to occur when molybdenum exceeds 100 parts per million in the diet of cattle or when the ratio of copper to molybdenum drops below 3:1.
VandeWeyer’s study did not show a relationship between low blood copper measured in the fall and the cows’ reproductive status. Cows with low blood copper were not at a higher risk of being open.
However, in a previous study, VandeWeyer demonstrated a relationship between low copper levels in the pre-breeding period and lower fertility rates.
It appears that the best time to test for blood copper levels in cows is in the spring during the pre-breeding period.
This may give a better indication of the risk of primary or secondary copper deficiency and allows producers to consider appropriate supplements.
Copper deficiency symptoms can appear similar to other conditions.
For example, poor growth because of internal parasites or malnutrition caused by energy protein deficiencies may look similar to copper deficiency.
As a result, it is important to assess the overall nutritional program and parasite control program when investigating these problems.
It is also important to consult with a nutritionist and a veterinarian about appropriate mineral supplementation.
Copper deficiency is one of the most common mineral deficiencies in Western Canada, and producers should test their feed and forage for minerals and consider sampling cows during the pre-breeding period to assess mineral status.
John Campbell is head of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.