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How much copper are you putting down?

Gary Wegner Published on 29 October 2010

“The use of copper sulfate footbaths is no big deal. Don’t worry about it!” Is this what you and your neighbors are saying? Let’s evaluate that position and see if it holds water.

First, we need to understand that copper is an essential nutrient. Copper is an essential element for all living organisms so animals, plants and all life forms, including microbes, need a constant “small supply.” We also might like to know that copper deficiency in the soil is a common problem.

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If the cow needs copper and the soil needs copper, why could there be a problem? The problem arises when copper is in excess and the balance of nutrients is disrupted.

Too much copper can create toxicity. That is why copper sulfate is such a good bactericide and is used as a footbath to kill unwanted organisms. Yet it can also harm the dairy – from the soil to the cows.

Copper sulfate drained from footbaths can kill the beneficial bacteria in a dairy’s manure lagoon.

If applied to the field, the copper will accumulate in the soil. Most agricultural labs typically advise two parts per million (ppm) in the soil as an adequate level of copper. Be sure to analyze for copper and zinc. The zinc level should be double the copper level.

How much is too much? Let’s look at a simple example that you can apply to your dairy. Let’s say your dairy milks 2,000 cows and uses 2 tons of copper sulfate per month. Two times 12 months is 24 tons of copper sulfate per year.

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Copper sulfate is 25 percent copper; the rest is sulfur and oxygen. Divide that 48,000 pounds by four to give 12,000 pounds of pure copper. Then divide that by the number of acres of cropland where manure is applied. If the number of acres is 500, the result is 24 pounds of copper per acre per year.

One 200-bushel corn crop removes 0.15 pound of copper; or 24 pounds of copper is enough copper to produce a 200-bushel corn crop for 160 consecutive years.

Copper sulfate in footbaths is not the only source of copper on a dairy. A well-balanced ration will contain copper, as it is an essential nutrient. The manure from that balanced ration will provide the soil with adequate copper. That means that virtually all copper from copper sulfate is “excess copper” for the dairy farm soils.

The crops can also take up the excess copper from the soil and if not monitored in the ration, can lead to copper toxicity in the cows. The first clinical evidence of this is lameness. Toxicity makes cows lethargic, lose body condition, produce less milk and eventually die.

Rodney P. Kromann, animal nutritionist and biochemist in Grove City, Minnesota, shared with me a few years ago that there are many cows that are being poisoned by excessive dietary copper. A recent survey indicated that the liver copper concentrations in more than 50 percent of Holstein cows in Minnesota were in excess of the established normal ranges of liver copper concentration (75 to 300 ppm dry basis or 25 to 100 ppm, wet basis).

The high liver copper level is directly related to the excessive amount of copper ingested by the animal. Dietary nutrients in excess of requirements are more detrimental to the metabolism of the animal than slight deficiencies, he said.

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In some herds with chronic copper toxicity, he witnessed cows with varying signs. The most prominent sign was that the cows were in very poor condition and did not gain body condition toward the end of lactation. Dry matter intake had decreased, and the cows sorted their ration. Salt consumption was excessive.

The cows had sunken and opaque-looking eyes. Hair coat colors were dull. Most cows had sore feet and had difficulty walking. Health problems were abundant because the immune system was impaired and displaced abomasums were excessive. Some cows had lesions and abscesses in the hock area.

In extreme cases, the cows were moaning and walked with humped backs. Reproduction was extremely poor, leading to extended days in milk. Calves were unthrifty, and in one case the calves died within 12 hours of birth.

Chronic copper poisoning is the result of an excess amount of copper ingested in relation to the recommended levels over a period of time. The period of time can be weeks, months or years, Kromann said.

Not only are cows lost to mortality, but also the effects on the remaining cattle are long-lasting. In Kromann’s experience, herd production efficiency was damaged and the cows never regained the losses incurred. One dairy producer told him that the recovery of his herd took eight years.

Where do we go from here?

Most dairy farms find it very difficult to eliminate the use of copper sulfate because of hoof health problems. Answers lie in flush water and manure lagoon management. Spirochetes, a known causative agent related to hairy hoof warts, are propagated in typical stagnant lagoon water. The flush water can hang on hooves and create the perfect incubator for hairy hoof wart organisms.

Finding ways to clean flush water or alleyways is one alternative. When cows’ hooves are clean, the need for copper sulfate can be eliminated. There are also alternative products that can be used as a direct spray to the hoof once or twice a week in lockup. Clean hooves eliminate the major cause of the problem.

The overuse of copper can cause damage on a farm. By looking into alternative processes and monitoring the amount of copper in the soil and ration, overuse of copper is a challenge that can be overcome. PD

Gary Wegner is a nutrionist with CIRCUL8Systems. Email Gary Wegner.

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