Reports of autumn grass staggers in freshly calved cows and white muscle disease in calves highlight the importance of checking forage quality and ensuring livestock receive the right balance of minerals and trace elements.
Nia Williams, livestock specialist at Nettex, said the business has heard from farmers reporting cases of grass staggers in freshly calved cows this October, which is unusually late in the season for a condition more commonly associated with the spring flush of grass.
Following a very dry summer and a warm, wet autumn, grass growth has accelerated. However, while grazing may be plentiful, its appearance does not necessarily reflect its nutritional value, making it important for farmers to understand exactly what their stock are receiving through their diet, warns Ms Williams.
“Although the grass is still growing, that doesn’t necessarily mean it is providing everything livestock need. Mineral and trace element levels can vary, so farmers should look at the nutritional value of both fresh grass and conserved forage rather than assume animals are getting everything they require.”
Grass staggers, also known as hypomagnesaemia, is caused by low magnesium levels in the blood. Lactating cows are particularly vulnerable because of their high magnesium requirements.
Unlike calcium, cows are unable to mobilise magnesium from bone, meaning they are dependent entirely on supply from the diet to meet requirements. Rapidly growing grass is often low in magnesium, while high moisture, protein and potassium levels can reduce its absorption. The condition can progress rapidly, sometimes resulting in convulsions and sudden death.
Farmers who suspect grass staggers should contact their vet immediately and review magnesium provision across the wider herd, as other animals may also be at risk.
Don’t overlook trace elements
Last October, the Animal and Plant Health Agency (APHA) reported cases of white muscle disease in calves through its disease surveillance in England and Wales.
The condition, caused by a deficiency of selenium, vitamin E or both, damages muscle tissue and can lead to weakness, muscle tremors, stiffness, difficulty standing and, in severe cases, sudden death.
Selenium levels in grass and forage can vary depending on soil conditions and temperature, and may decline as the season progresses, as selenium is concentrated mainly in the leaf portion of plants. Farmers should therefore not assume grazing or conserved forage is providing enough.
Where sulphur fertilisers are being used to address low soil sulphur, it is also worth considering selenium status, as high sulphur levels can reduce plant uptake of selenium under certain conditions.
“Testing is always something we recommend, but even more so in a year like this, when we’ve had such extreme weather,” Ms Williams said.
“The starting point must be to analyse fresh grass and conserved forage to understand what they are providing, then work with your vet or nutritionist to ensure the whole ration is balanced for energy, protein, minerals and trace elements. It’s important farmers aren’t supplementing blindly.”
Ms Williams explained that while products such as EnduraBol boluses can provide a baseline supply of selected trace elements and vitamins, supplementation needs to be appropriate to the animals’ requirements and the rest of their diet.
“If the ration is lacking energy or protein, this also needs to be addressed to support optimal performance. This is why it’s vital to understand your stock’s nutritional requirements and ensure these are being met by the diet,” Ms Williams said.
“Having grass available is one thing, but knowing what it is providing allows farmers to make informed decisions about their livestock’s nutritional needs.”
