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Sudden Death in Suckler Cows on Grass

Topic of the Month

Over the last month the practice has seen several sudden deaths in suckler cows out on grass only.

As none of them were sent to our local AHVLA for post mortem, a tentative diagnosis of grass tetany/staggers/magnesium deficiency was made.

Other causes of sudden deaths include: calving related deaths, downer cow syndrome, metritis, blackleg/clostridial diseases, acute bloat, acute haemorrhage, ecoli mastitis, anthrax, poisoning, lightning...

Magnesium should be supplemented at high risk periods where there is lush grass growth which is low in fibre (soil is low in magnesium)

A cow needs a minimum of 60g magnesium oxide per day "as prevention is better than cure". Here are a few options on how to supplement magnesium:

  • Magnesium can be supplemented in the water in the form of magnesium chloride (Epsom Salts). It can be added at 60g per cow per day. The dose must be split and added to water twice daily because the cattle don't like the taste. So the Epsom Salts need to be added over 2–3 weeks.

  • Pasture dusting with magnesium oxide at the rate of 60g per cow per day. Apply powder early in the morning and strip graze through the week.

  • High magnesium licks. Ensure to follow the manufacturers instructions concerning the number of cows per block. I would always use licks in conjunction with another magnesium supplementation.

  • Intraruminal magnesium boluses give a slow release of magnesium over a period of about four weeks.

  • Feeding concentrates with magnesium can also be used as a supplement.