Term
| What are the common names for hypomagnesemia in the cow? |
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Definition
-grass tetany or Spring tetany
-winter tetany
-wheat pastrue tetany
-milk tetany
-lactation tetany
-transport tetany |
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Term
| What is the purpose of intracellular Mg2+? |
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Definition
| -cofactor for enzymatic rxns |
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Term
| What is the purpose of extracellular Mg2+? |
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Definition
-normal nerve conductance
-muscle function
-bone mineral formation |
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Term
| Where do cows get magnesium? |
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Definition
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Term
| What are the components of endocrine regulation that control Mg2+? |
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Definition
-PTH
-aldosterone
-thyroxine |
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Term
| Describe the incidence of hypomagnesemia in cattle? |
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Definition
-1-3% of cattle in US die of hypomagnesemia
-highest incidence in lactating beef cattle
-usually within 60 days of calving |
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Term
| What is the etiology of hypomagnesemia in cows? |
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Definition
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Term
| What are some predisposing factors for cow hypomagnesemia? |
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Definition
-dec Mg in feedstuffs: inc K resuts in dec Mg and Ca uptake by plant
-dec Mg absorption by reticulorumen epithelium: inc K nand N2 in forages (rumen pH > 6.5)
-lush high-moisture pasture dec GI transit time (like wheat pasture)
-stressors = inc catecholamines |
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Term
| What kind of animals get bovine hypomagnesemia? |
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Definition
-adults
-periparturient: lactating most susceptible
-thin or overconditioned |
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Term
| What kind of environment and weather predispose cattle to hypomagnesemia? |
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Definition
-lush forages, heavily fertilized, or wheat pastrue
-no Mg supplementation
-cloudy, misty, cool weather |
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Term
| What is the cause of grass tetany with bovine hypomagnasemia? |
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Definition
| -beef cows grazing on spring/fall lush pastrue |
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Term
| What is the cause of milk tetany with bovine hypomagnasemia? |
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Definition
| -calves fed only milk > frist 2 months of life |
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Term
| What are the clinical signs of moderate bovine hypomagnasemia? |
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Definition
-anorexia
-nervousness
0hyperesthesia
-erect ears
-dec milk pdn |
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Term
| What are the clinical signs of severe bovine hypomagnasemia? |
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Definition
-muscle fasciculations
0irritability, aggressiveness
-0incoordination, spasticity
-tachycardia but LOUD, tachypnea
0hyperthermia
-recumbency
-convulsions, opisthotonus, paddling
-rapid/repeated blinking, nystagmus
-DEATH |
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Term
| What do we see on clin path with bovine hypomagnasemia? |
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Definition
-low magnesium lelvels
0inc CPK and AST in downer cow
-/+ HypoCa, hypoP |
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Term
| Where do we test [Mg] in postmortem bovine exam for hypomagasemia? HOw long after death is this test reliable? |
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Definition
-vitreous humor
-24-48 hours |
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Term
| How does hypomagnesemia cause tetany? |
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Definition
-dec central and peripheral nerve membrane potential
-inc ACh release at neuro-mascular jcts
-dec intracellular ATPase activity
-low Mg: Ca ration in ECF => affect neuromuscular excitability |
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Term
| Where in the digestive system does poor Mg absorption occur that leads to hypomagnesemia in cows? |
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Definition
| -rumen > omasum >>> intestines |
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Term
| How do we treat hypomagnesemia in cows? |
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Definition
-EMERGENCY!
-slow IV Ca gloconate soln
-SC Mg sulfate
-oral Magnagel paste but can aspirate
-enema of Mg chloride
-response to treatment/expectations: 20-30% |
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Term
| How do we prevent bovine hypomagnesemia? |
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Definition
-Mg oxide added to ration
-Mg feeding blocks
-high Mg mineral (salt based): at least 10% Mg
-hay supplementation
-remove from offending pastre |
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Term
| What are the clinical signs of milk tetany in calves? |
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Definition
-irritable
-tetany
-prolapse third eyelid
-convulsions |
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Term
| How do we treat milk tetany in calves? |
|
Definition
-MgSO4 10% soln SC
-oral Mg (gel)
-alfalfa hay
-starter ration |
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Term
| What cows get lactation tetany? |
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Definition
-4-7 years old lactating dairy cows > beef cows
-within first 2 months of lactation: loss of Mg in milk |
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Term
| What are the risk factors of lactation tetany in cows? |
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Definition
| -grazing on lush spring grass pastrue without hay or mineral supplementation |
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Term
| What are the clinical manifestations of lactation tetany? |
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Definition
-Acute: unusual alertness, hyperesthesia, staggers, convulsions
-Subacute: exaggerate limb mvts, spasmodic urination, tremor
-Chronic: dullness, unthriftines, paresis |
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Term
| Which cows are more predisposed to transport tetany? |
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Definition
-late term pregnancy: cows and ewes
-also fleshy lambs |
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Term
| What are the conditions seen with transport tetany? |
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Definition
-long transportaition: stressful, feed restrictions
-weather extremes
-off feed |
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