Poor weather conditions, lush grass growth and high potash levels are being blamed for a recent spike in hypomagnesemia cases in beef cattle.
SAC Consulting warns cows which are most at risk of developing the disorder are lactating cows, older cows and cows under nutritional stress.
Robert Ramsay, SAC senior beef consultant, says: “This year grass covers are good on paddock grazing systems and supplementary feeding may seem unnecessary. However, advice to producers is to use magnesium licks or buckets and make sure stock has access to them at all times."
He says this is particularly important when turning cattle onto new paddocks with lush grass. Lush grass in autumn can be low in magnesium and its fast rate of passage through the animal means there is less time for absorption.
He explains that magnesium is not stored in the body and must therefore be available daily in the diet.
The target for daily intake is about 25g/day and the levels of magnesium provided by grass can be variable, but on average, it contains about 1.6g/kg dry matter.
However, there are a number of factors that can impact on the absorption of magnesium.
Mr Ramsay explains that high levels of ammonia in the rumen, produced by excess protein in lush grass, can interfere with magnesium absorption.
Poor weather can be a stress trigger, along with low pasture covers. During periods of bad weather, cows may also eat less, resulting in a lower intake of magnesium.
When supplementing magnesium, Mr Ramsay says hi-mag rolls can be a good solution and will also provide energy when grass supplies are short. Mag buckets are an option, but be sure to allow enough buckets or blocks for the number of animals.
He adds that mineralising your own cereals can be cheaper, but wastage must be accounted for to ensure there is an adequate supply.
Other options include molasses fortified with magnesium or treating the water supply.
SAC’s top tips to avoid hypomagnesemia