Assessing the Value of Trace Mineral Supplementation.

The need to supplement livestock with trace minerals is essential in many parts of New Zealand. To this end, farmers spend many millions of dollars each year on various forms of supplementation. But I suspect there is often a question mark about the benefits obtained from this expenditure. Do you really need to spend as much as you do on trace minerals? Do they really improve health and production significantly? It can be hard to know.

Today, trace minerals come in a bewildering array of formulation, chemical forms, and administration options: not to mention price ranges. You may know you need to supplement with say, selenium, copper and cobalt, but what form and administration option is best for you to use?

You may approach each element separately, deciding to inject the cows with copper twice yearly, drench with selenium fortnightly, and topdress with cobalt annually. Alternatively, you may opt to cover all bases and drench daily or weekly with a product that includes every trace element known to man, with various macronutrients and vitamins added. Whatever you do, the cost per cow/day can vary widely, depending on what you use and your dosing regime. It would be nice to be assured that your money is well spent.

But perceptions as to the benefit or return on investment from any supplementation programme is usually subjective, made by comparison with production levels or management problems experienced in previous years. Testimonials abound that “production was up”, “conception rates were better”, or “calving problems minimised”, after just one years use of product “X”, but they are usually not supported by any controlled trial data.

This is not surprising, because under our predominantly pasture grazing system (compared say, to a feed-lot system) it is difficult to conduct a comparison trial on any individual farm to compare responses to different supplementation regimes in the same year The cost and complexity of conducting such trials scientifically is such that few manufacturers of trace element products perform them in New Zealand, although some do occur.

So if you change your supplementation programme, such as adding zinc or iodine to the regime, unless a dramatic effect is observed, you can well wonder whether it is really worth it. Most supplementation decisions are made after measuring pasture, blood, or liver levels and determining whether they are “adequate”, “marginal” or “deficient”. This is sensible and avoids unnecessary oversupplementation. However, a consideration of the results of any trial work that has been conducted on other farms can be added to your evaluation as to whether supplementing with something may be worthwhile.

For instance, a recent trial at Massey University supplementing one half of a dairy herd with a proprietary organic zinc complex, showed that the treated half experienced better milk production and lower SCC’s than the untreated half. This result was similar to trials conducted by universities in other parts of the world where initial zinc levels in the cows were not deficient. You might then compare your own herd’s characteristics, such as, feed intake, management style, initial SCC’s, etc, with those of the trial herds, to consider whether you might expect a similar response if you also supplemented with the product.

If you feel that university herds are too uncharacteristic of your own herd for a valid comparison to be made, the results from well conducted trials run with commercial herds may be more appropriate. Unfortunately, few of these have been conducted in NZ, but two recent trials have looked at supplementation with a combination of organic copper, zinc, cobalt and manganese. On one farm the results were unspectacular, but on the other, the return on investment from use of the product, measured as increased milk production and saving on use of CIDR’s due to better fertility, was about 4:1, or a net return of over $20,000.

Only by conducting a well controlled trial on your own farm will you ever really know what return on investment you get from whatever trace supplementation options you use. But by monitoring blood or liver levels to estimate necessary requirements, and evaluating whatever trial results there are to see if they may apply to your own circumstances, you can make more rational decisions on trace element expenditure.