News & Advice

The complications of copper (and other trace elements)

Apr 16, 2021 | Dairy, Minerals

Julia Baynes, Anexa Vets Morrinsville

A Morrinsville farmer’s story

Last season, one of our Morrinsville farmers found themselves in a complicated position with copper in Autumn with:

  • a deficiency in their R1 and R2 heifers (both on and off farm)
  • toxic liver levels in their milking herd

The farm

This is a high performing system 5 dairy farm milking over 700 cows, with 170 R2 heifers and 170 R1 yearlings. The youngstock are historically grown well, with smaller, lighter animals remaining on the home farm, and heavier animals being sent to grazing locally.

The R1s

The calves looked fine at weaning, and were weaned by eye at around 100kg. However, at the end of January, there was an obvious tail end of ill-thrifty animals with some scouring. Feed was adequate and worming was up to date with a good quality double-active oral drench. The farmer thought selenium prills may have gone on in the Autumn fertilizer, but wasn’t 100% sure. There hadn’t been any other mineral supplementation.

Blood samples were collected from 10 random but healthy R1s to measure copper, selenium and B12 levels. While the copper levels were adequate, these animals were severely selenium and B12 deficient. This could be the cause of the ill-thrift and scouring. In this case, a long-acting Selenium injection with monthly B12 injections were given, and the yearlings improved.

Rather than re-testing trace element levels in autumn, we opted to give the yearlings an All-Trace®bolus. These long-acting ruminal boluses give 8 months trace element supplementation of copper, selenium, cobalt, amongst other important microminerals. This ensured they had adequate minerals through their first mating period.

The R2s

The R2s were split into two mobs:

  • the heavier animals had been sent to a local grazier (with an unknown mineral status)
  • the lighter animals remained at home and grazed the same run-off area as the R1s. These animals were in beautiful condition – well-grown, with shiny coats and no obvious health issues.

The mob had a good empty rate although there were more later calving heifers than ideal. Therefore, in January blood samples were collected from 10 random but healthy R2s to measure copper, selenium and B12 levels.
The results were concerning: the blood coppers were very low – indicating that these animals had almost exhausted all of their copper reserves, the selenium levels were low, and the B12 levels were marginal. These low trace element levels were likely reducing growth, fertility and general health.

There were several supplementation options available – but we had to make sure the solution was practical. These heifers were due to be given zinc boluses so we had to be careful about any potential product interactions. In addition, these heifers would be returning to the herd in May, where they would receive the trace mineral mix, so we had to avoid long-acting options that could lead to toxicity.

The R2 heifers received a 30g copper bolus which provided 3 to 4 months of supplementation.

These boluses are safe to be given alongside zinc boluses because they sit in the cow’s abomasum (acid stomach), not in the rumen.

They also received monthly selenium and B12 injections until they returned home in May. This allowed us to keep their trace element supplementation adequate until all of the R2 heifers were back on the dairy platform, it was important that we did follow-up testing in May, to determine any additional supplementation they may require over winter.

In May, once the heifers were settled back at home, we collected liver biopsies and blood samples to re-check copper, selenium and B12. Late pregnancy is when cows have their biggest copper demand, and it is least available from the pasture. They are relying on liver stores (as well as any on-farm supplementation) to get them through calving, and mating. Therefore, this is a crucial time for testing.
The liver biopsies showed that while the heifers were no longer copper deficient, they didn’t have adequate copper reserves to get them through the winter without further copper supplementation. Their selenium and B12 levels were adequate and no additional supplementation was required.

The trace mineral mix that was mixed in with the feed would provide adequate extra copper supplementation to the heifers.

The cows

Unfortunately, there was an additional challenge. The annual routine herd trace element testing that was done on this farm, identified 3 out of 10 cows sampled, with toxic liver copper levels. Copper toxicity is a very real and potentially serious problem in cows, and in a worst case scenario, can cause sudden death. We had to remove the copper from the trace mineral mix to prevent this problem from getting worse.

In short:

  • The R2 heifers would become copper deficient over winter without active copper supplementation
  • The cows had toxic copper levels in their liver and were being supplemented with an in-feed mineral mix including copper
    It wouldn’t be possible to run the heifers in a completely separate mob for the cows, so we had to come up with a workable solution.


The plan:

  • Remove copper from the trace element mix immediately – continue supplementing all animals with no copper mix to ensure selenium and cobalt was available to them through winter/spring
  • Treat the R2 heifers with another 30g copper bolus that would supplement them until mating
  • Re-test copper and selenium levels in a random sample cows and heifers pre-mating to determine when copper should be re-introduced into the trace mineral mix.

This story isn’t uncommon on dairy farms around our district. Trace elements – especially copper – can be complicated. When mobs of animals are being grazed on different parts of the farm, or off farm, their mineral status can be dramatically different. Copper levels can vary significantly year to year, regardless of the mineral mix and feeding regimes staying the same. This is why we encourage trace element testing in the autumn and spring, with liver biopsies and blood samples being collected from each mob/age group. It is critical to assess whether the current mineral plan is working, and ensure we can take quick action to correct any deficiencies we find. Copper and selenium are critical trace elements for cows that influence general health, growth, reproduction, milk yield. Therefore, it is vital that we help you to have robust supplementation and monitoring plans in place.

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