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what is the biologically active form of calcium? what % of total calcium does this represent?
what is relationship between blood pH and ionized Ca?
- acidosis increases ionized/free Ca (less bound to albumin)
- alkalosis decreases ionized/incr. bound Ca
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
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
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
what is main storage pool for calcium?
primary is bone (GI also important source)
why is excess P in the diet a problem for Ca homeostasis?
P competes w/Ca for absorption in GI (duodenum)
how does Ca homeostasis relate to chronic renal disease?
chronic loss of Ca - deficits
what is main component of bone mineral compound?
calcium to form hydroxyapatite
what is relationship of Mg with Ca homeostasis?
Mg needed for PTH release
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
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
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
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
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
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
what is normal calcium in grams in adult vs how much is required for fetal growth/colostrum production?
- normal: 3grams
- post-parturition: 30grams (10xs!)
Although often missed by farmer, what are signs of stage 1 milk fever? 8
what is calcium level at this point?
- muscle fasciculations
- slight hyperthermia
- tongue protrudes
- firm feces
- 7-8.5mg/dl (normal is 9-12)
what are signs of stage 2 milk fever? 6
what is Ca level at this point?
- recumbent, weak
- GI stasis
- tachycardia (<90bpm)
- cool extremities/Low temp
- flaccid neck muscles; "S"
- decr. PLR
- 4.5-6.5 mg/dl
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
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
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)
what are some complications associated w/milk fever?
- asperation pneumonia
- skeletal, muscle, nerve injury/compression
- (peroneal nerve damage
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)
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)
will oral CaCl induce acidosis or alkalosis?
- acidosis - promotes incr. ionized Ca
- (caution: oral erosions)
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
About 1/3 will relapse after treatment. Who is most likely to relapse?
- hypoCa that happened prepartum
- cows deficient in Mg, K, or PO4
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)
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
what happens to calcium in bone and urine when diet is acidified?
- resorbed from bone
- excreted in urine
- (incr. vit D formation)
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)
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