Weather is expected to become more changeable towards the end of the week, with rain and lower temperatures forecast.

As such, freshly-calved autumn cows grazing lush, low-dry matter grass will be at higher risk of developing grass tetany.

First-calved heifers, as well as thinner, older cows or those with twins, are the animals that will be at greatest risk.

Spring-calving cows with strong calves at foot will also be susceptible, so make sure animals are properly supplemented with magnesium from now until the end of the grazing season.


There are various methods of offering supplementary magnesium. All have merits and drawbacks.

Lick buckets tend to be the most common on suckler farms.

If buckets are in use, provide one bucket for every 10 cows in each grazing group and locate them at various points in each paddock.

Keep cows moving to fresh grass

Along with magnesium supplementation, move cows on to the next paddock as soon as grass covers start getting low.

Do not force cows to clean out paddocks tight to the ground in autumn. Swards can be cleaned off in the next rotation or by stores and sheep.

Holding cows on low covers at this stage of the year will reduce intakes and this can trigger nutritional stress, leading to the onset of tetany.

Offering some form of fibre via a few flaps of hay will slow down the cow’s digestion of lush grass, giving more time to absorb magnesium from forage.

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