Copper- Who Ya Gonna Call?

I don’t think any trace element creates more discussion or controversy than copper. What form to use, how much, when, how, and why, can lead to heated discussion whenever the topic arises, be it a group of farmers, nutritionists, veterinarians, or academics.

Over the past month I have seen so much written about copper in the farming press and professional literature, that I hesitate to add to the subject further. But at this time of year, how best to identify and maintain the copper status of dairy cows over winter and into calving is obviously an important issue. Judging by the calls and contacts I’ve received recently, there’s still confusion about how best to manage copper supplementation.

Personally, I believe virtually every farm’s requirements for copper is different. Therein lies a major cause of the confusion and controversy. What may be best for you may differ significantly from what is best for your neighbours. This is because the copper status of the soil, pasture, and livestock is affected by many variables, by past history of copper supplementation procedures, and by personal farm management policy and philosophy. So what is best for you to do, needs a bit of thinking about.

Unless you’ve struck on a copper supplementation regime with which you are completely happy, the first thing to do before winter is to determine the current copper status of your herd; what their liver copper reserves are. There’s only one accurate way to do this - by liver biopsy of a representative proportion of your herd. Usually, sampling about 10 cows is sufficient. Liver analysis on cull cows is the next best option, but the results may not be truly representative of your main herd. In my opinion, blood analysis is next to useless at indicating a cow or herd’s copper status.

Having got representative liver level results, you are now in a position to make some rational decisions. Firstly, do you need to copper supplement over the winter/spring period, or not? If the herd’s average liver reserves are high, you may opt to do nothing until after calving as their reserve tanks are reasonably full. But how full is full enough? This is the first controversy!

For my cattle, in my area (north of Auckland, moderate copper deficient area), if sampled in April/May, with calving due about end of August, I’m happy if liver levels average 1000µmol/kg. I’ll not supplement ‘til after calving Some accept higher or lower levels as satisfactory - it all depends on the area and many other factors. If you’re not sure what is a good reserve level for your cows, I recommend discussing this with others, including your vet. Local knowledge and personal preference strongly affect any decision to supplement for winter based on liver levels.

But if average liver levels are low, say below 150µmol/kg, then its probably wise to supplement. Next controversy! What with and by how much?

This relates to personal preference, convenience, cost, and intended maintenance supplementation regime planned for after calving. Your options are many. Long-lasting copper injections, copper needles, or copper bullets, copper licks, copper sulphate via water troughs, direct daily commercial copper supplementation via feed or water, or pasture top-dressing.

Consider some basic principles. Available copper from pasture declines during winter. A cow’s daily use and mobilisation of copper increases over winter as the growing calf increases demand. Cows vary in their daily requirements for copper depending on their individual metabolism and stresses experienced. To be useful to the cow, copper must be absorbed to reach the liver in a form that can be utilised. Copper uptake can be severely compromised by antagonists like molybdenum, iron, sulphates, zinc, and phytates.

Ideally, daily utilisable copper uptake should at least match daily metabolic needs. Ideally, we should supplement copper in a way that enables flexibility of dose to meet changing needs, in a form that allows a good predictability of uptake and utilisation.

Only daily supplementation with a predictably absorbed form of copper allows the flexibility to match dose to your herd’s changing needs. This is the major benefit of regular dietary supplementation. You can optimise copper intake to copper demands.

Long-acting copper oxide needles certainly maintain a daily copper intake, and are convenient once the hassle of dosing is over, but they lack flexibility of dose and certainty as to when their copper content is exhausted by any particular cow. Copper injections help fill the liver tank, but to what level and for how long, can be uncertain.

Copper sulphate supplementation by feed, water, or licks, suffers from unpredictable uptake and utilisation due to antagonists and poor absorption. Regular organic copper supplementation provides both flexibility of dose to meet individual farm circumstances and predictability of uptake.

Its very difficult to remain impartial when discussing copper supplementation. Usually, any supplementation is better than none in New Zealand, but optimising regular copper intake to meet the changing demands of cattle on a particular property makes more sense to me than just punting in a load of copper and hoping for the best. The most cost effective and production beneficial approach is to think out your herd’s particular strategic copper needs based on accurate diagnosis of reserves and needs, and to select the supplementation option that best suits your farm and farming practice. In my opinion, your local veterinarian or farm advisor is best able to help with this because each circumstance can be different.