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what is the biologically active form of calcium? what % of total calcium does this represent?
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what is relationship between blood pH and ionized Ca?
- acidosis increases ionized/free Ca (less bound to albumin)
- alkalosis decreases ionized/incr. bound Ca
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what is the role of Ca with neurons? what is the result of low Ca?
- dampens/inhibits Na channels to prevent hyperexcitability
- -hypoCa: muscle fasciculations
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what is role of Ca with muscles? what is result of hypoCa?
- enhances release of Ach for muscle contraction
- hypoCa: muscle weakness/flaccid paralysis, poor cardiac contractility/rebound tachycardia, GI stasis
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What role does Ca have with glucose? what role does it have with CNS?
- Ca needed for insulin release -w/o it, no insulin so hyperglycemic
- Ca needed for norepinephrine/Ach release in CNS - w/o it can lead to coma
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what is main storage pool for calcium?
primary is bone (GI also important source)
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why is excess P in the diet a problem for Ca homeostasis?
P competes w/Ca for absorption in GI (duodenum)
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how does Ca homeostasis relate to chronic renal disease?
chronic loss of Ca - deficits
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what is main component of bone mineral compound?
calcium to form hydroxyapatite
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what is relationship of Mg with Ca homeostasis?
Mg needed for PTH release
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low ionized Ca stimulates release of PTH. What is role of PTH? 5
- promotes bone resorption
- promotes GI absorption of Ca and P
- promotes retention of Ca
- promotes excretion of P in urine/saliva
- promotes active Vit D
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what is active form of vit D and what is its role in Ca homeostasis?
- 1,25 di-(OH) D3
- promotes bone resorption
- promotes absorption of Ca and P from GIT
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what is calcitonin and when is its release stimulated?
- released in face of excess Ca
- *promotes deposition* of calcium into bone
- promotes loss of Ca through urine
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Parturient Paresis is primarily a problem in beef or dairy? When is it most likely to be a problem?
- dairy (esp. Channel breeds-jersey)
- within 48 hours of calving
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how does age and number of previous parturitions relate to likelihood of developing milk fever?
- older (>3yr): can't activate stores as quickly
- increases w/parity (rare in heifers)
- incr. if higher milk producer
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if beef cow suffers from milk fever, when during gestation/parturition period is this likely to occur?
- late gestation when fetal demands are high (demands for Ca for colostrum not as high in beef)
- *also the case w/small ruminants
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what is normal calcium in grams in adult vs how much is required for fetal growth/colostrum production?
- normal: 3grams
- post-parturition: 30grams (10xs!)
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Although often missed by farmer, what are signs of stage 1 milk fever? 8
what is calcium level at this point?
- excitable
- muscle fasciculations
- anorectic
- weak
- tachycardia
- slight hyperthermia
- tongue protrudes
- firm feces
- 7-8.5mg/dl (normal is 9-12)
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what are signs of stage 2 milk fever? 6
what is Ca level at this point?
- recumbent, weak
- GI stasis
- tachycardia (<90bpm)
- constipation
- cool extremities/Low temp
- flaccid neck muscles; "S"
- decr. PLR
- 4.5-6.5 mg/dl
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what are signs of stage 3 milk fever?3
what is Ca at this point?
- lateral recumbency, near coma/death
- severe bloat
- inaudible heart sounds or up to 120bpm
- <3mg/dl
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It's often not necessary to use blood work results to diagnose milk fever, but why should you collect samples anyway?
helpful if the cow doesnt respond to treatment as expected
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With milk fever, what are expected magnesium levels (hi or low)? phosphorous? glucose?
- Mg: normal to high
- P: normal to low (PTH stims P loss thru urine/saliva)
- hyperglycemia (can't release insulin)
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what are some complications associated w/milk fever?
- asperation pneumonia
- bloat
- skeletal, muscle, nerve injury/compression
- (peroneal nerve damage
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PTH has decreased efficiency in alkaline situations. What are two common reasons the cow will be alkaline?
- displaced abomasum
- eating forage high in K
- (therefore decr. response to low serum Ca)
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how is stage 1 vs stage 2/3 milk fever treated?
- 1: oral calcium gels or SQ Ca gluconate
- 2/3: IV ca salts (23% Ca borogluconate IV/SC)
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will oral CaCl induce acidosis or alkalosis?
- acidosis - promotes incr. ionized Ca
- (caution: oral erosions)
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how much Ca should you administer and how do you administer it to avoid cardiotoxicity?
- 1g per 45kg
- IV slowly over 10-20minutes (don't hold higher than cow's head)
- monitor for bradycardia/arrhythmia
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About 1/3 will relapse after treatment. Who is most likely to relapse?
- older
- hypoCa that happened prepartum
- cows deficient in Mg, K, or PO4
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what is seen as positive response to treatment for milk fever?
- eructation, increased alertness, defecate/urinate
- normalized HR
- (shiver, sh*t, shuffle to their feet)
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how is diet managed to prevent milk fever?
- -*low Ca diet* during last 3-4 wks parturition so PTH/vit D stimulated to start mobilizing Ca
- -*add anionic salts* since Ca is mobilized w/acidosis
- -ensure *adequate Mg*; needed for PTH release
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what happens to calcium in bone and urine when diet is acidified?
- resorbed from bone
- excreted in urine
- (incr. vit D formation)
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what is goal urine pH with diet acidification for Jerseys vs. Holstein?
- 6-6.5 for Holsteins (may be adequate for jersey)
- 5.5-5.99 is optimum for Jerseys
- (below 5.5 excessive)
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what are some uses of phosphorous in the body? 6
- cell membranes
- RBC metabolism
- reproductive tissues
- energy metabolism (ATP)
- acid/base regulation
- mineralization of bone
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