FAC42: Hypomagnesaemia (Grass Staggers) Flashcards
What is magnesium essential for?
Activation of enzymes and biological processes
Neurological function - synaptic transmission
How is magnesium controlled/maintained in the body
There are no hormonal control mechanisms for regulation of magnesium levels!
Input: absorption from gut
Output: requirements for milk and tissues and excretion via kidneys
What is the availability of magnesium in the cow dependent on?
Intake - dietary levels and amount eaten
Absorption from the guy
Transport to the tissues
Describe the pathogenesis of hypomagnesium.
- Level of magnesium in the soil
- Pasture species
- DM intake
- Potassium levels (if you increase the metal ions and acidify the blood, there wont be as much absorption of magnesium in the blood)
- Sodium levels
- Ammonia levels
- Energy content of the diet
- Fat content
- Dietary fiber
- Genetics
- Redistribution of magnesium within the body
- Stress
- Increased mobilisation of fat
Which animals usually get acute hypomagnesaemia?
Beef cows with suckled calves at foot in spring
What is a common clinical sign of acute hypomagnesaemia?
Tetanic spasms
Sudden death
Can calves get hypomagnesaemia?
Yes, it is called milk tetany and is the result of not enough Mg in the milk with no supplements.
What biochem do you see in a cow with hypomagnesaemia?
Plasma Mg below 0.8
Post mortem: CSF below 0.6 and Fresh aqueous humour below 0.25
How do you treat acute hypomagnesaemia?
EMERGENCY
Minimise handling and stress (can induce fitting states)
- Control convulsions with pentobarbitone, xylazine, acepromazine
- 400 ml Ca borogluconate with added Mg
- SubQ 400 ml of Mg sulphate
- TLC (relapses common - usually a whole herd problem)
What are the daily Mg requirements of a cow?
Daily requirements of a cow giving 25L of milk is 5g Mg
Target value is 30g of dietary Mg per day (which may be insufficient if poor absorption)
What methods are there supplementing Mg for control and prevention of hypomagnesaemia?
- Inclusion in concentrate feeds
- Medicated water supply
- Mineral supplements (Mg salts are not palatable)
- Dusting of pasture
- Intra-ruminal boluses
How do you diagnose hypomagnesaemia in sheep?
Serum Mg below 0.6
Fresh aqueous humour below 0.4
How do you treat hypomagnesaemia in sheep?
20 mls Ca borogluconate/Mg IV
50 mls Mg sulphate subQ
How do you control against hypomagnesaemia in sheep?
Dietary supplementation with Mg and general preventative measures
What are some general preventative measures against hypomagnesaemia (not artificial supplementation)?
Pasture species
Adequate sodium
Fertilizer use (potash (k) and nitrogen (NH3))
Nutritional - energy and ERDP levels, fat inclusion
Provision of fiber in diet
Reduce stress
