Mineral nutrition
Cobalt, copper, zinc and selenium: what each one does in the herd
They are required in milligrams and they decide in arrobas. Trace minerals do not fatten the animal: they make work the things that do.
Small amount, large job
On the label, macrominerals appear in grams and trace minerals in milligrams. The difference in unit is not one of importance: it is one of dose. They do not enter the animal's structure the way calcium enters bone. They enter as part of enzymes and of processes running all the time. A little missing stops a great deal.
That is why a trace mineral shortfall almost never has a face of its own. It shows up as performance below expectation, poorer use of the pasture, weak immunity, breeding that drags. The farmer sees the result; the cause sits further back.
Cobalt: the rumen uses it before the animal does
Cobalt is the clearest case of a mineral that works indirectly. The first user is not the animal: it is the rumen microorganisms, which turn it into vitamin B12. Cattle depend on that conversion, and the rumen flora keeps no store. Supply has to be continuous.
When it runs short the signal is treacherous: appetite falls. The animal eats less grass and loses condition even with pasture standing in front of it. It is a picture easily mistaken for worms or for lack of feed, and it leads the farmer to change everything except where the problem actually is.
Copper and zinc: immunity, coat and hoof
Copper takes part in enzymes tied to iron metabolism, to coat pigmentation and to the building of connective tissue. It is also the mineral most exposed to antagonism: excess molybdenum, sulphur or iron in the pasture and the water gets in the way of its uptake. In other words, there can be copper in the grass analysis and still be copper missing inside the animal.
Zinc works in the skin, the hoof, in wound healing, in immunity and in the fertility of the sire. The signs appear at the edges of the body, which is where a shortfall shows first: a rough, dull coat, lesions slow to close, poor hoof quality. It does not build up in any useful amount either, which brings back the same conclusion as cobalt: the trough has to be served every day.
Selenium, and why the label carries maximums
Selenium works in the body's antioxidant system, alongside vitamin E. It is tied to muscle integrity in young animals and to the period around calving. Its presence in the soil is uneven across Brazil, so the region weighs on the sum as much as the class of animal does.
Selenium and copper have a narrow margin between too little and too much. That is why they appear on the label as a maximum level, and why topping up minerals on your own account, mixing products at the trough, is a risky decision. With copper the difference is between species: what cattle tolerate can poison sheep at the same trough. Formulation and adjustment are the work of a qualified technician, with the pasture and the herd in front of them.
Where the figures come from
- 1Embrapa. Technical publications on mineral nutrition of cattle and trace mineral requirements. https://www.embrapa.br/gado-de-corte
- 2Brazilian Ministry of Agriculture and Livestock. Labelling rules and declaration of guaranteed levels in animal feed products. https://www.gov.br/agricultura/pt-br/assuntos/insumos-agropecuarios/insumos-pecuarios/alimentacao-animal
Further reading
Informational content. It does not replace guidance from a responsável técnico for your herd.
See all articles