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Hypomagnesemic Tetany - Coggle Diagram
Hypomagnesemic Tetany
ddx
rabies
nervous ketosis
milk fever
lead poisoning
polioencephalomalacia
enterotoxemia
salt toxicity/water eprivation
tetanus
nervous coccidiosis
listeriosis
general info
alternatively known as
grass staggers
lactation tetany
wheat pasture poisoning
winter tetany
green-oat poisoning
barley poisoning
grass tetany
Mg deficiency of blood and CSF
highly fatal
only affects ruminants
low occurence
outbreaks
up to 20% affected
usually early lactation animals
lush pastures in spring and fall
may occur in milk-fed 2-4mo calves and lambs (milk tetany)
multifactorial
normal plasma Mg >2 mg/dL
treatment
restraint with acepromazine
immediate MG and CA
IV CBG
SQ CBG + Mg-sulfate
response is slow; don't disturb for 3-5 hours
Mg-sulfate enema
avoid relapse w/oral salt slurry
start supplementing herd/flock immediately
clin path
hypomagnesemia <1.2 mg/dl
CSF hypoMg
after death
urine hypoMg
reflects current diet
hypoCa
hypoP
hypoK
increased AST, CPK
etiology
develops when Mg output exceeds input
high Mg output, early lactation
low Mg in diet (<0.2% of dry matter)
cool season grasses contain less Mg (wheat)
cool wather (spring/fall) reduced plant tissue Mg uptake
high moisture content of rapidly growing pasture (spring/fall) = low Mg
example crops with low Mg
early growth cereals
barely
wheat
green oat
corn stalk stubble
inadequate Mg absorption across rumen
high dietary K
interferes with Na-linked transport
lush, high moisture pasture
rapid passage
less opportunity to absorb Mg
rumen Ph
greater >6.5pH decreases soluability
age
older animals can only absorb Mg through rumen and LI
calves
low Mg in milk diet
can absorb through SI
as they age, less able to absorb
risk factors
usually first 0-8w of lactation
high producers
ewes suckling multiple lambs
over or underconditioned
environmental/management stress + low Mg diet
onset of lactation
sudden weather changes
transport
feed deprivation
sudden feed changes
MG homeostasis :cow:
70% in bones and teeth
30% soft tissues
stores not v laile
milk production removes 0.15g Mg/L milk
require at least 20g/day
must be supplied almost entirely by diet
diagnosis
necropsy
submit
serum
CSF
urine
enucleated eye
bone Ca:Mg ratio
often diagnosed after 1-2 animals "found dead"
history
early lactation
lush pasture
disturbed soil due to convulsions
2-4mo old/lamb fed whole milk (milk tetany)
response to Mg and Ca treatment
low urine/blood Mg levels in 5-10 herdmates
results of hypoMg
depleted from CSF and ECF
deficiency lowers central and peripheral nervous membrane potentials closer to threshold
hyperexcitability
convulsions
dysmodulation of CA effect on Ach release ay myoneural jxn
excess release of Ach
Mg-dependent ATP-ase dyregulation
difficulty to relaxation phase of mm contraction
sustained myofibril contractions/tetany
less of neuromuscular fxn
reduced PTH scecretion
affects Ca homestasis
hypocalcemia
CS
early (Plasma [Mg] 1.1 - 1.8mg/dl)
reduced feed intake
nervousness
decreased milk production
mm twitching
irritability
isolationg from herd
spastic, stiff
frequent urination
bellowing
hypersensitive to stimuli
advanced
can be rapid progression
plasma Mg <1/1 mg/dl
tetanic mm spasms
staggering, falling
lateral recumbency
convulsions
tachycardia
tachypnea, pyrexia
nystygmus
rapid progression
prevention
manipulate pasture Mg content
reduce stressors