Flashcards in Mineral disorders-adult animals postpartum Deck (48)
When approaching a downer cow, what are the 5 M differentials?
What is the cause of hypocalcemisa in cattle?
decreased blood ionized calcium concentration (biologically active fraction is ionized calcium)
What are the clinical signs of severe hypocalcemia (periparturient hypocalcemia/paresis)
5% dairy cows/year
What are the clinical signs of subclinical hypocalcemia?
1. decreased feed intake (poor rumen/intestinal motility), poor productivity
2. increased susceptibility to other diseases like DA
3. up to 50% in older cows
4. channel island breeds more susceptible
Why do we worry about hypocalcemia?
Clinical case=334$ (2%, 150 cow, 1 002/yr)
subclinical case=$220 (30% incidence, 150 cow, 10 000/yr)
What are is the pathophysiology of hypocalcemia?
1. 99% Ca stored as hydroxyapatite
2. blood calcium 2.-2.5mmol/L (ionized calcium bbound to albumin)
3. lowest levels 12-24hr post partum
4. parathyroid hormone increases bone mobilization,!!!! (and renal tubular reabsorption)
5. 1, 25-dihydroxyvitamin D: generated in response to PTH, increases Ca dietary absorption
6. Hypocalcemia occurs when Ca loss to milk > bone mobilization
What are the factors involved in predisposing to hypocalcemia?
1. metabolic alkalosis
How does metabolic alkalosis predispose to hypocalcemia?
1 more cations than anions
2. decreaseed PTH receptor senstiivity to PTH (receptor changes conformation at higher pH)
3. decreased ionized calcium
How does hypomagnesemia predispose to hypocalcemia?
1. decreased PTH secretion
2. decreased tissue PTH sensitivity (Mg is a cofactor of the receptor)
What factors in small ruminants predisposes to hypocalcemia?
1. forced exercise
2. long distance transport
3. food deprivation
4. oxalate toxicosis
What are the stages of hypocalcemia?
What are the features of stage 1 of hypocalcemia?
1. animal standing
2. brief episodes of excitement and tetany
3. hypersentivity and muscle tremor
What are the features of stage 2 of hypocalcemia?
1. sternal recumbence
3. cool extremities
4. uterine prolapse
What are the features of stage 3 hypocalcemia?
1. lateral recumbency
3. complete flaccidity (flaccid paresis)
What are lab findings of hypocalcemia?
low seum total Ca
What is the treatment for hypocalcemi?
1. intravenous calcium gluconate
-only to recumbent cows
1g/45kg body weight as a rule of tumb
500ml bottle contains 8-11g Ca
Ca is cardiotoxic--administer slowly
Why should you be careful with Ca administration
cardiotoxic, dysrythmia--monitor heart rate if dysrhythmias occur, admin rate should be decreased and atropine considered
Why do animals become hypocalcemic after Ca therapy IV?
because calcitonin increases and then animal becomes hypocalcemic again
What should be done to prevent animals becoming hypocalcemic after initial Ca therapy?
1. oral calcium supplementation for cows that are still standing or that have just been treated IV
calcium proprionate more acidic, works better than calcium chloride?
2. subQ can be good (but not put in multiple sites! slower absorption if put in one site
How is hypocalcemia prevented?
1. dietary cation-anion difference (DCAD)
2. oral calcium at calving
What are the features of diatry anion-cation difference?
The general principle is decrease absorbable cations and/or increase absorbable anions in ration
compensated metabolic acidosis--increase affinity of PTH for receptor
cations: Na, K, Ca, Mg
Anions: Cl, SO4, PO4
Organic acids rapidly metablizee
DCAD=(Na + K + Ca + Mg) - (Cl + SO4 + PO4)
Aim for negative DCAD
How do you practically applicate DCAD?
1. treat K and CL as the variables
2. keep K close to NRC requirement if possible 8.5g/kg
3. add Cl to 5g/kg less than K levels
4. evaluate urine pH after 3-4 days (holsteins 6.2-6.8), (channel islands 5.8-6.3)
5. add chloride as needed to reduce urine pH (ensure palatability HCl most palatable)--
What are issues with changing Na, P or S in diet?
Na: udder edema
P-blocks renal 1,25-OH vit D
Why doesn't everyone use a DCAD diet?
get 11.5% drop in dry matter intake
works if excellent management, intakes monitored, urine pH of transition cows monitored
usually top 25% of herds will do?
What can you do at calving to prevent hypocalcemia?
1. calcium chloride: acidogenic so mobilizes Ca, 25-50g Ca needed, formulations in gel are less effective
2. calcium propionate: non-acidogenic 75-125g Ca?????
3. calcium carbonate: limestone, alkalinogenic, drives Ca down
4. calcium boluses (not currently in canada)--steady Ca
Is oral Ca economic if cows on low DCAD program?
What doses of Ca (oral) can be cardiotoxic?
Why should you not give calcium to cows that have dystocia (potentially)
they do better without
What are the features of feeding a Ca deficient diet?
1. negative Ca balance increases PTH seccretion
2. bone resoprtion and 1,25-OH vit D production
3. works during metabolic aklaosis
4. need high caclium diet post-partum
5. can be difficult to reduce calcium levels enough (50%