Magnesium Disorders in Ruminants
Summary written by Neville Suttle BSc PhD
Taken from Moredun Foundation Newsheet Volume 2 No. 19 (1998)
- Magnesium (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.
More 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'.
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