Changes

Also known as: '''''Grass staggers — Grass tetany'''''

Also known as: '''''Grass Staggers — Grass Tetany'''''

==Introduction==

==Introduction==

Magnesium requirements are influenced by production. Therefore '''rapidly-growing and lactating''' animals have a higher requirement than non-lactating slow-growing animals. Cows in their third to fifth lactation have an increased risk of developing hypomagnesaemia due to increased production and reduced age-related mobilisation of magnesium from bone.

Magnesium requirements are influenced by production. Therefore '''rapidly-growing and lactating''' animals have a higher requirement than non-lactating slow-growing animals. Cows in their third to fifth lactation have an increased risk of developing hypomagnesaemia due to increased production and reduced age-related mobilisation of magnesium from bone.

Ruminants may survive for a few days by using residual magnesium in their soft tissues, but other than this, they cannot store magnesium effectively. A '''continuous supply of magnesium in the diet''' is therefore essential to avoid hypomagnesiaemia.

Ruminants may survive for a few days by using residual magnesium in their soft tissues, but other than this, they cannot store magnesium effectively. A '''continuous supply of magnesium in the diet''' is therefore essential to avoid hypomagnesaemia.

==Clinical signs==

==Clinical Signs==

===Acute form in cows===

===Acute form in cows===

Magnesium plays a critical role in '''neuromuscular transmission''' and signs include: depression and dullness, stiffness, excitability, '''tremors''', chewing, hypersalivation, blinking of the third eyelid, ear flapping, collapse, '''tetanic muscle spasms''', coma and death.

Magnesium plays a critical role in '''neuromuscular transmission''' and signs include: depression and dullness, stiffness, excitability, '''tremors''', chewing, hypersalivation, blinking of the third eyelid, ear flapping, collapse, '''tetanic muscle spasms''', coma and death.

===Hypocalcaemia===

===Hypocalcaemia===

'''Hypocalcaemia''' may occur concurrently, as hypomagnesaemia influences calcium metabolism by reducing the secretion of PTH and tissue sensitivity to PTH which is important for calcium absorption.

'''[[Hypocalcaemia]]''' may occur concurrently, as hypomagnesaemia influences [[Calcium|calcium metabolism]] by reducing the secretion of PTH and tissue sensitivity to PTH which is important for calcium absorption.

==Diagnosis==

==Diagnosis==

On '''postmortem''' examination, gross changes, such as petechiationg, are non-specific.

On '''postmortem''' examination, gross changes, such as petechiationg, are non-specific.

Fluid analysis can be used to confirm the diagnosis:

Fluid analysis can be used to confirm the diagnosis:

 

:'''Blood''': magnesium concentrations at which clinical signs appear are usually predictably below 0.5mmol/l.

'''Blood''': magnesium concentrations at which clinical signs appear are usually predictable, usually below 0.5mmol/l.

:A blood sample should be taken before treatment of an affected cow in case it does not respond.

 

:Other fluids which provide information on magnesium levels include: [[Cerebral Spinal Fluid - Anatomy & Physiology|'''CSF''']], '''urine''' and '''ocular fluids'''.

A blood sample should be taken before treatment of an affected cow in case it does not respond.

 

Other fluids which provide information on magnesium levels include: '''CSF''', '''urine''' and '''ocular fluids'''.

 

Given that ruminants are usually managed in large similarly-fed groups within similar production systems, there is a high risk of '''subclinical hypomagnesaemia''' in apparently unaffected individuals in a group where clinical hypomagnesaemia has occurred. Consequently, '''screening''' other members of an affected group for evidence of low blood levels of magnesium is the best method of confirming disease and investigating distribution and severity.

Given that ruminants are usually managed in large similarly-fed groups within similar production systems, there is a high risk of '''subclinical hypomagnesaemia''' in apparently unaffected individuals in a group where clinical hypomagnesaemia has occurred. Consequently, '''screening''' other members of an affected group for evidence of low blood levels of magnesium is the best method of confirming disease and investigating distribution and severity.

==Treatment and prevention==

==Treatment==

===Treatment===

Animals with the acute form of the disease require '''urgent treatment''' as their condition may deteriorate rapidly and success rates decline with time from the onset of clinical signs.

Animals with the acute form of the disease require '''urgent treatment''' as their condition may deteriorate rapidly and success rates decline with time from the onset of clinical signs.

Animals may have to be '''sedated''' to control the tetany, and affected animals should always be handled quietly and calmly to avoid aggravating the condition.

Animals may have to be '''sedated''' to control the tetany, and affected animals should always be handled quietly and calmly to avoid aggravating the condition.

===Control===

==Control==

Prevention of clinical hypomagnesaemia depends upon both reducing risk factors and ensuring daily intake:

Prevention of clinical hypomagnesaemia depends upon both reducing risk factors and ensuring daily Mg intake:

Avoid the use of '''potassium-containing fertilisers''' including slurry at critical periods, especially when grass is growing rapidly in the spring.

Avoid the use of '''potassium-containing fertilisers''' including slurry at critical periods, especially when grass is growing rapidly in the spring.

 

[[Category:Vascular Fluid]]

[[Category:Vascular Fluid]]

[[Category:To Do - Manson]]

[[Category:Neurological Diseases - Cattle]]

[[Category:To Do - Helen]]

[[Category:Neurological Diseases - Sheep]]

[[Category:To Do - Review]]

[[Category:Expert Review - Farm Animal]]