It has been a relatively busy spring for our Disease Investigation Unit at the Western College of Veterinary Medicine in Saskatoon.
The cases we’ve seen include scenarios of lead toxicity, abortions and several cases of unusual disease syndromes in young calves including neurological disease and blindness.
After years of being involved in various disease outbreaks in cow-calf herds, I estimate about 80 percent of them have nutritional deficiencies or toxicities as part of the root cause of the disease outbreak.
This spring was no different. As a result, we often take blood samples from cows and calves to assess their trace mineral levels.
Several of the herds we’ve looked at have had very low copper levels in their blood. Copper deficiency is the most common trace mineral deficiency in Western Canada for a number of reasons.
First of all many of our soils and plants are naturally low in copper in some regions of Western Canada.
Secondly, there are many regions in Western Canada where other minerals can potentially tie up copper, making it less available for the animal to absorb and resulting in a secondary deficiency. High sulfate levels in water are common in areas affected by drought and dry conditions and even in some deep wells within various regions of the Prairies.
As well, high levels of molybdenum in forages can be an issue in some situations, which can also tie up copper and create secondary deficiencies.
Having low levels of copper in cows at this time of year is particularly dangerous. Copper deficiency in cattle has been associated with a range of problems including poor growth, diarrhea, loss in milk production, changes in hair colour, anemia (drop in red blood cells) and even nervous disease symptoms such as falling down and stumbling in young calves.
However, in my experience, identifying these severe and obvious clinical symptoms of copper deficiency is relatively rare in Western Canada. Instead, we often see more subtle signs of subclinical copper deficiency.
Copper plays a role in the immune response, and cattle that are copper deficient may be more prone to infectious diseases and may not appropriately respond to vaccinations.
Perhaps most importantly, copper deficiency has also been linked to reproductive failure and poor conception rates, which can cause significant losses in subsequent calf production and ultimately the rancher’s pocket book.
Cows that are copper deficient just before breeding season may not cycle and conceive and it is very difficult to improve trace mineral levels in the short time between calving and breeding.
We must ensure the cows have reasonable copper levels in their systems before calving time so that they don’t enter the breeding season with deficient levels. This requires a properly balanced, palatable mineral mix being fed to cows in the months leading up to calving and the breeding season.
The diet of cattle should contain about 10 parts per million of copper to supply. These levels may need to be even higher in areas where the forages are high in molybdenum or there are higher levels of sulfates in water.
The copper:molybdenum ratio in the ration is an important indicator of one of the causes of secondary deficiency and it should usually be a ratio of 5:1 or higher in the ration. Anything less than 3:1 for the ration’s copper:molybdenum ratio or if molybdenum exceeds 100 parts per million in the diet means secondary deficiencies are very likely.
Feed testing of winter feeds is important, but it is difficult to evaluate all factors that affect copper levels. Therefore, it might be more efficient to take some samples from your herd to determine their copper levels.
The easiest way is to take blood samples for a few cows in the herd to assess their serum copper levels. This is relatively quick and inexpensive and will accurately identify serious deficiencies. Sampling 10 percent of the herd should be adequate and could be done at a time when cattle are routinely being handled just before calving for scours vaccines or some other management procedure.
First- and second-calf heifers are most likely to show signs of deficiencies because they are still growing and they might be a group to target your sampling efforts on in order to identify any potential problems.
Copper is stored primarily in the liver and as a result, the blood copper may not drop to deficient levels until liver copper reaches very low levels. If blood copper levels are low, then the animal is truly deficient.
Another way to assess trace mineral status involves veterinarians performing a liver biopsy and taking a small liver sample. Because most of the copper is stored in the liver, this is probably a bit more accurate than blood copper, but is obviously more difficult and somewhat invasive.
An alternative is to obtain fresh liver samples from any animals that die in the herd or that go to local slaughter and send those samples to the lab for trace mineral levels.
The time period leading up to calving and the subsequent breeding season is the most critical in terms of effects on productivity and should be prioritized in terms of supplementation.
Some research has shown that force feeding mineral is more effective than free-choice, but that is not always possible in today’s production systems.
While we don’t have many injectable options available in Canada, there are some trace mineral boluses that might be useful in some situations.
You may want to consider chelated mineral sources or higher levels of copper if secondary deficiencies are possible.
While copper deficiency is a real and common problem, copper toxicity is also possible and can be fatal. Work with your nutritionist, veterinarian or livestock agrologist to design a mineral program that provides adequate levels of copper to your cattle.
John Campbell is a professor in the department of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.