This year’s silage samples has shown variations in grass mineral levels and an increase in dry matter content, according to analysis by ForFarmers of 2.600 samples harvested in 2025 across Great Britain.
It has been reported that this summer’s widespread drought has led to lower forage stocks for many farmers
ForFarmers product manager, Bruce Foreshaw explained the changes in minerals from the samples, advising farmers on how to manage these mineral levels in dairy cow diets.
Mineral levels
He said: “This year’s grass silages have been lower in chloride which we would expect to reduce the dietary cation anion balance (DCAB), but because potassium and sodium are higher than in 2024, the DCAB has increased.
“It is not a big shift but one to be aware of if you are relying on low DCAB diets to control milk fever.”
The samples were found to have reduced levels of magnesium, copper and zinc, which has been a trend over the last three years.
ForFarmers reported that copper levels were 8mg in 2023, 7mg in 2024, and 6mg in 2025 while zinc was 32mg in 2023, 28mg in 2024, and 27mg in 2025.
However, ForFarmers stated that “if 12kg (DM) of this average silage was fed alongside a compound with a standard winter mineral pack”, both copper and zinc would be “over supplied”
Drought conditions
Foreshaw highlighted that the drought this summer has also impacted the mineral levels within the silage samples.
He added: “We have also seen cobalt levels lower in 2025; this mineral is essential in the production of B12, which in turn is needed for energy metabolism.
“Drought can affect cobalt uptake as lack of moisture reduces the solubility of the cobalt ions in the soil.”
This year’s drought also affected iron levels according to ForFarmers, with the dry harvest conditions leading to lower soil contamination among the silage samples
Within ForFarmers’ analyses of silage samples, it outlined that the iron levels for 2025 “averaged 258 mg/kg DM, in contrast to 2023’s wet summer, when iron averaged 473mg/kg DM”.
ForFarmers
Speaking on the reduced iron levels, Foreshaw commented: “It could be argued that as iron is an antagonist, although copper levels are lower, the mineral could be more available to the cow.
“Providing the right vitamins and minerals is essential to support optimal milk yield and herd health, but more isn’t always better.
“Even a mild oversupply of nutrients can increase production costs, while significant excesses may lead to subclinical toxicity or, in extreme cases, serious health issues.”
