Magnesium Disorders in Ruminants

Moredun-logoSummary written by Neville Suttle BSc PhD

Taken from Moredun Foundation Newsheet Volume 2 No. 19 (1998)



  • ewe-with-twinsMagnesium (Mg) deprivation continues to cause significant losses amongst lactating sheep and cattle and is not always avoided or best treated by providing Mg supplements.
  • Mg disorders occur primarily when stock are turned onto lush pastures in spring and autumn because of poor absorption of Mg from both potassium (K)-rich pasture and Mg supplement.
  • In sheep, two-fold improvements in Mg absorption should be attainable on many farms by delaying, restricting or redistributing K applications in fertilizers and slurries.
  • Cattle are more vulnerable than sheep to Mg-disorders because they absorb Mg far less efficiently from fresh or conserved pasture even when K is low.
  • For sheep and cattle, the target should be spring pasture with no more than 2.5% K in the dry matter.
  • For sheep and cattle, earlier but gradual introduction of spring grazing reduces the challenge from K.
  • For cattle, the culling of susceptible cows will slowly increase the inherited efficiency of Mg absorption in the herd.
  • By using less magnesite, risks of hypocalcaemia (acute calcium deprivation) scours and urinary calculi may be reduced.



sheep cover2 smMore information on managing your flock can be found on the DVD 'Managing Your Flock for Peak Health' - programme 2 in the series 'Sheep on Your Smallholding'.








The full news sheet for any of the disease summaries can be ordered from the Moredun Foundation by using the following request form. The first news sheet title requested is free*, further news sheet titles are charged at £5.00 per copy (including postage).

*offer limited to one news sheet title per postal address in any one year. After that each news sheet will be charged at the standard price of £5.00 (including postage).


Click here for more information about Moredun Foundation News Sheets


  Moredun Membership Scheme

Moredun runs a membership scheme which aims to keep farmers and their vets up to date with the latest developments in animal health research. If you are interested in becoming a member of the Moredun Foundation, please click here.