under 1%, but 30% of affected animals will die- cost of 4 million pounds. 

grazing in the spring and autumn. but can occur at any time of the year, as long as magnesium levels are not sufficient to meet demands

- also occurs in suckler cows when fed poor forages

the majority of magnesium is found in the bone ( 60-70%) with 30-40% in the soft tissues and less than 1% in the extracellular fluid. 

there are no homeostatic controls for magnesium levels. 

thus is dependent on: 

1. absorption from the GI tract-rumen and omasum, low absorption

2. reqirement for milk production, tissue and endogenous losses

3. excreteion by the kidneys- excess dietery magnesium is removed via urine

the majority of magnesium is found in the bone ( 60-70%) with 30-40% in the soft tissues and less than 1% in the extracellular fluid. 

there are no homeostatic controls for magnesium levels. 

thus is dependent on: 

1. absorption from the GI tract-rumen and omasum, low absorption

2. reqirement for milk production, tissue and endogenous losses

3. excreteion by the kidneys- excess dietery magnesium is removed via urine

 [image]

- levels in blood dependent on inflow and outflow

a) how much magnesium is eaten

b) how much passes straight through the gut ( absorption)

c) Transport of mag from gut to tissue via the extracellular fluid/plasma

1. Soil levels

2. pasture species: legumes, weeds contain more magnesium

3. daily dry matter intake

4. pottassium: high levels disrupt absorption of mag, and also decrease the levels of sodium in the rumen

5. sodium: required to carry mag, across the rumen wall, thus sodium deficiency leads to poor absorption of magnesium from the diet

6. Rumen PH: rumen ph rises, magnesium solubility declines

7. Ammonia: high levels inhibit magnesium absorption

8. dietary energy: energy levels reduced, mag reduced

9. fats

10. dietary fibre: lush spring pastures are low in fibre, which increases time passed through rumen, lowering absorption time for minerals

11.Genetics

12. Redistribution of magnesium within the body: stress and high levels of insulin ( lead to rapid fall in magnesium levels)

peracute

acute

subclinical/chronic

nervousness, twitching the muscles, high head carriage, incoordination. 

- rapid progression into lateral recumbancy, convulsions leading to coma and death. progression into convulsions may be precipitated by stress. 

relapses common after treatment

goes unrecognised.

cows may appear slightly nervous. reluctant to be milked, depression of DMI and loss of milk yield. 

- other main sympom is hypocalcaemia 

in contrast to adult cattle, calves absorb magnesium very efficiently from the intestine. but falls rapidly by 2 mo. of age. thus calves that are reared for prolonged periods on whole milk diets without magnesium supplementation are prone to developing acute hypomagnesaemia. very rare 

history: lactating cows at grass during spring and autumn, and in suckler cows

clinical signs: acute onset, with signs of convulsions

bio chem: 

normal magnesium plasma level is 0.8

Post mortem: magnesium levels in CSF- below 0.6

- no magnesium in the urine

- magnesium levels in vitreous/aquous humour- below 0.25- these are stable for 48 hrs post mortem

calcium/magnesium ratio in bone- used to diagnose milk tetany in calves 

cases of acute staggers is an emergency

- remember that sudden stimulus may precipitate fatal convulsions

- take a blood sample prior to treatment in case further diagnostics are needed. 

- admin 400ml of 40% calcium borogluconate, 5% magnesium hypophosphite by slow IV injection

- admin 400ml of 25% magnesium sulphate by SUBCUT injection, warmed and given at 3-4 separate sites to improve absorption

- control seizures ( petobarb, xylazine, ACP

- TLC - keep comfortable

- ensure adequate dietary intake- relapse common because injection only lasts 6-12 hours- may need further subcut injection

- prognosis is not very good, a 1/3 will die- tell farmer before giving treatment

- check herd- blood sample a bunch

1. magnesium supplementation

2. General preventative measures

a lactating cow atleast requires 5g of magnesium from the diet to balance these losses. 30g of magnesium daily, taking into account absorption and losses, should provide 5g. 

- include in concentrate rations: target to use 60g magnesium oxide per cow per day. 

- medication of water supply: soluble magnesium salts- but problems such as palatibility, insufficient amount, toxicity problems

- mineral supplements

- dusting/spraying of pastures- dusted, but what if it rains

- intra-ruminal boluses: slow release over 4 wk period-but release small amounts

managing the factors influencing the availability of magnesium:

- soil levels

- pasture species

- DMI

- sodium

- ammonia

- Dietary energy

- fats- avoid excessive fat

- dietary fibre

- stress

nearly always occurs after lambing ( first 6 weeks after lambing), in ewes rearing twins at peak lactation

similar to cows

frequently presents as sudden death in adult ewes

serum magnesium below 0.6. 

fresh CSF and urine concentration below 0.6

fresh aqueous humour magnesium concentrations below 0.4 ( within 12 hours of death) 

- provision of extra magnesium to ensure intake of 7g magnesium per ewe per day. 

- ewes in lactation at grass- put in concentrates

- magnesium boluses

- extra forage to increase magnesium absorption

- reduce stress- shelter