Watch Copper Levels Following A Fe Period And Zinc Dosing

Climatically, its been an unusual summer. In my part of New Zealand, (just north of Auckland) grass growth has outstripped my herd’s ability to eat it, despite making hay where possible. (Bad stock and pasture management on my part I agree, but hey, I’m only human!). Problem now is , there’s too much rank grass and I’m worried about facial eczema.

I had a bad experience with facial eczema three years ago and some of the herd are still recovering from that. I used zinc oxide and grazing management to try and limit the damage of sporodesmin intake to my stock, but the strategy was inadequately applied. I lost two cows and the symptoms of liver damage were evident in other stock. I don’t intend to make the same mistake this year if spore counts get dangerous.

It is however, the longer term consequences of this episode that have interested me. Specifically, the reproductive performance of my herd. Compared to previously, conception rates and calf viability have been significantly lower for the past three years. No doubt the liver damage has played a part, but I looked little further to the mineral status of the cows.

Significantly, I found that liver copper levels were low. I am conscious that I farm in an area that is marginally copper deficient, and despite having the poor facilities that often go with small block beef farming, try to supplement the stock with copper as practically as possible. Over the years, I’ve generally been happy with their copper intake and status.

But in the face of a facial eczema threat and use of high level zinc dosing, liver copper levels can be severely depleted. Zinc is a well known antagonist to copper uptake from the gut and, at high intake levels, also seems to contribute to a loss of stored copper in the liver. So its not surprising that after several weeks of high zinc dosing, liver copper levels will be lowered unless steps are taken to counter this.

Giving a source of copper that is not severely antagonised by zinc is one option, such as providing copper amino acid complexes while zinc dosing. Giving a large booster dose of copper by injection or needles after high zinc dosing has stopped, is another. But whatever you do, it pays to ensure the copper depletion caused by zinc dosing is rectified as cattle enter the winter period and lead up to calving.

The reason is that low copper reserves during winter will result in calves born with low copper status and , unless corrected, cows with low copper as they start milking and prepare for mating. The consequence of this can be calves with lowered viability and immune system response capability and cows that may be harder to get back in calf.

Of course, copper isn’t the only trace element that influences calf welfare and reproductive performance, but it’s an important one to consider. Ideally, attention to copper and other mineral supplementation should gather in importance three to six weeks before calving if good calves, good milk production, and efficient reproductive performance are expected. It takes some time for cattle to achieve the optimal mineral status that helps them to counter the stresses associated with calving, milking, and mating, and starting regular mineral supplementation only at or after calving, is leaving things a bit late.

I now start feeding minerals with hay or silage at least a month before calving to counter the depletion that will have occurred as minerals are transferred to the growing calf, and pasture mineral availability becomes reduced during winter.

I should have done this three or more years ago, but calving and reproduction seemed all right and I guess I was complacent. It took a facial eczema scare to show me that it didn’t take much to upset the mineral balance and suffer poor calving results. Having recently pregnancy tested, it looks like conception rates are back to usual this year, but if I feel it necessary to use zinc to protect against facial eczema, I’ll make sure copper intake is properly attended to as well this time.