Experts are warning that reduced mineral levels in grass following one of the wettest winters on record could result in livestock deficiencies and production losses.

Lisa Hambly, head of grassland and forage agronomy at Mole Valley Farmers and Dr Alison Bond, technical services manager for Nettex and Rumenco, explained the impact the weather has had on soil mineral levels.

Dr Bond said any ground underwater this winter could see its mineral content affected.

“Ground that has been underwater can affect the oxygen level and the uptake of minerals by the plant. We can also see an increase in the number of heavy metals, such as molybdenum and iron, taken up by these plants. These can interfere with the availability of other minerals and can impact the availability of other major elements such as calcium, magnesium and phosphorous.”

Iron levels can also increase where there is compaction, which acts as an antagonist and can prevent other minerals from being available to the animal. “Areas known for high levels of molybdenum could see exacerbated levels caused by the overwinter conditions,” she said. “For cattle close to calving, those levels are extremely important.”

The minerals available in grass may be further hampered by fast-growing spring grass, which can dilute the concentration of minerals available.

Ms Hambly added: “Testing fresh grass is absolutely vital, and it will give you an idea of how well that soil profile is being taken up within the crop. Soil tests should also be looked at – preferably a broad-spectrum test or an animal health soil test. If you know the soil has an underlying issue of over or under supply, take action to prevent any problems.”

Dr Bond said magnesium levels can also be diluted by fast-growing grass.

“If that grass is also relatively low dry matter, so it’s moving through the rumen quite quickly, the animal won’t be able to take up all the available magnesium. This can be compounded by high nitrogen and potassium levels, commonly seen on ground that’s been well treated with slurry.

“Blood tests can demonstrate in the short term what is going on in that animal before any physical signs are picked up. They can help understand how available some of those elements are in grass,” added Dr Bond.

Signs of mineral deficiency in livestock include:

  • Reduced performance
  • Poor fertility
  • Darker coloured animals and pigmentation issues in the case of copper deficiency
  • Twitching and nervousness
  • White muscle disease

Mineral supplementation options include free access in blocks or buckets and inclusion in compound feeds or through individual boluses. Bespoke minerals can be formulated where a mineral audit has been conducted.

By performing a mineral audit by testing soils, fresh grass, slurry, and blood samples from animals, farmers can assess what is available and then match that with what the animal needs.

Dr Bond added, “What an animal needs today might be very different from what it needs in six months, depending on what you are trying to do with those animals. Are they breeding animals or growing animals? Those change their requirements. It’s about looking at supply versus what they actually need.”

Ms Hambly says a slurry analysis can tell a lot about the mineral balance. “Having studied a lot of slurry analysis, you can see a massive difference with what is coming through the diet. If something appears in the slurry but does not show up in the soil analysis, it is being fed in the diet.

“Oversupply can be just as important as undersupply. Minerals that can’t be stored will just come out of the back end. Phosphorous is a prime example of this, which becomes a pollutant you have paid for,” added Ms Hambly.