By Karen Stewart, SRUC beef specialist

Macro minerals, trace elements and vitamins are essential to maintaining health, reproduction and growth in cattle. All have different functions within the body, whether it is catalysts for metabolic processes or involved in cell division for growth, they are a necessary part of the diet.

The largest variable we have in cattle rations, with the exception of intensive barley beef rations, is the forage the cattle are fed and the level of concentrate feeding.

The type and specification of mineral required will depend on a number of factors and these should be considered when purchasing a mineral:

1. The base forage the cattle are on (straw, wholecrop, grass silage, hay)

2. What other feeds are in the ration

3. Level of concentrate feeding

4. What stage in the production cycle the cattle are at (i.e. lactating cow, dry cow, pre-calving, growing, finishing)

For example, a suckler cow on a straw-based ration needs a much higher specification mineral than a suckler cow on a mainly grass silage ration, as mineral levels in straw are significantly lower compared to grass silage.

Grass silage rations can vary greatly in mineral status depending on the type of soil and sward. Soil status, especially pH can affect mineral uptake in the plant.

Test forage and soils for minerals every 2-3 years to identify problem fields/areas where there are specific deficiencies or problems such as high levels of antagonists like iron, sulphur and molybdenum, which can affect copper absorption in the gut.

Once you have your results, work with an experienced nutritionist to formulate rations and advise on the most appropriate mineral supplementation for the different classes of stock on your farm. Bespoke minerals are a possibility if a particular issue is found, however if there are no issues many standard products will do the job well.

Remember we are feeding a group of animals, not individuals, so there will always be some variation in intakes but this can be reduced by feeding down the trough or through a total mixed ration (TMR) as opposed to relying on free access powdered minerals, buckets or blocks.

When feeding minerals there are always uncertainties involved with requirements and absorption. For example calves are around 10 times more efficient at absorbing copper than adult cattle and so more at risk of toxicity if a high level of copper is fed. If there are high level of antagonists to copper in the ration feeding chelated/more available sources may be justified, rather than increasing the overall copper content.

We are often guilty as an industry of making assumptions and looking for a quick fix to a problem. This can cause issues with over supplementation, which is not only costly to the pocket but may also have a detrimental impact on the environment as well. In addition, over supplementation can sometimes be just as harmful as feeding too little. Thought needs to be given to all the sources of mineral (powdered minerals, buckets, boluses, mineralised feeds etc) that are being fed as well as background levels coming from the base ration.

Look for evidence that cattle are deficient. A good starting point would be to blood test some animals and check the forage mineral content. The source of elements is also important, for example selenised yeast has been shown to improve colostrum quality in dairy cows with them having twice as much selenium in colostrum compared to cows supplemented with inorganic selenium (i.e. sodium selenite).

Take a measured, logical approach to supplementing minerals, in many situations we over supply by too much. For example a common myth is that high phosphorus is needed for fertility when in reality excess to animal requirements is simply excreted.

In most situations 4% phosphorus in a mineral meets the needs of a lactating suckler cow at grass. If you are purchasing a mineral of 8% phosphorus then up to 50% may be wasted. As phosphorus currently costs about £22/% it adds up. An open mind to think more sustainably towards how we feed minerals is required and being aware of the negative effects feeding too much can also have.

Iodine is a trace element often talked about as being deficient and applied on the flanks of cattle for extra supplementation through skin absorption. It can often be found in breeding minerals at very high rates. In reality a mineral with a low level of 250mg/kg of iodine, fed at 100g/day still supplies 5 times the requirement of a dry cow coming up to calving.

Mineral interactions within the animal are complex and it is a matter of assessing the risk versus the reward. It is really important to base buying decisions on the facts of what is required, rather than basing it on assumptions of what is perceived to be required and good marketing.