Calcium Management in Dairy Cattle Flashcards
describe calcium
- important in many pathways:
-skeletal and smooth muscle function
-immune function - tight regulation of serum Ca concentration in the blood!
-too low = release PTH and vitamin D
-too high = release calcitonin - serum calcium values:
-normocalcemia: 9-10mg/dL total calcium
-subclinical hypocalcemia: <8.0mg/dL, subclinical effects on gut and immune systems
-clinical hypocalcemia: <4.5mg/dL; unable to rise, gut slows, immune dysfunction
describe the effects of hypocalcemia
clinical:
1. death
2. lateral recumbency
3. unable to rise
4. S shaped neck
5. muscle tremors
6. cool extremities
subclinical (also happening if see clinical signs!!):
1. immune dysfunction
2. retained placenta
3. decreased DMI
4. decreased milk production
5. higher risk of: dystocia, metritis, mastitis, ketosis, displaced abomasum
describe how calcium relates to retained placenta
- cattle have cotyledonary placentation
- the immune system digests the glue between the cotyledon and caruncle
- the immune system needs calcium
- too little calcium = glue stays and placenta is retained
- high incidence of retained placenta = herd level calcium issues
do NOT give oxytocin!! just monitor cow until placenta rots out and falls away
-also do NOT pull!!
describe where calcium is normally found in the body
- stored in bones
- very little in blood
- uptake from the gut
- excreted in the urine and milk
normal calcium turnover:
1. bone turnover is a slow process to increase serum calcium
2. GI absorbs calcium to add to serum calcium
3. colostrum and milk production and urinary calcium excretion decrease serum calcium
describe calcium balance at calving
- very sudden need for calcium because of very high milk production in early lactation
-plenty of total calcium still (in bones) - but the calcium metabolism engine is not warmed up before that sudden demand so = issues
- serum contains approx 2.5g Ca at any time
-dry period and fetal bone needs approx 10g per day
-at calving, cow dups 30g Ca into colostrum - increased PTH and vitamin D in response to low calcium causes
-intestinal absorption
-renal tubular absorption
-bone resorption by osteoclasts
what are risk factors for periparturient hypocalcemia in cows
- age: older cows more trouble
- breed: jerseys have more trouble
- milk production
- diet
- feed intake
what are the types of calcium dynamics?
- normocalcemia: eucalcemia
-increased feed intake, lower disease risk, increased fertility - transient subclinical hypocalcemia: eucalcemia
-increased feed intake, decreased disease, increased milk yield, and increased fertility - persistent subclinical hypocalcemia: discalcemia
-decreased feed intake, increased disease risk, decreased fertility - delayed subclinical hypocalcemia: dyscalcemia
-decreased feed intake, increased risk of disease, decreased milk yield, decreased fertility - clinical hypocalcemia: dyscalcemia
describe management to prevent hypocalcemia
- feed enough calcium:
-not usually possible and cows can’t absorb it that fast - increase calcium metabolism/turnover
-feed very little calcium (meh not great)
-negative DCAD (dietary cation anion difference) diet
describe altering calcium balance through diet
- before the sudden demand at calving, feeding a diet with more negative ions (negative DCAD) induces a SLIGHT metabolic acidosis
- this causes urinary acidification and hypercalciuria (dumping calcium in urine)
- losing calcium in urine makes osteoclasts more active and ready to deliver calcium to the blood
-warms up the system - excreting acid into urine = calcium co-transported and also excreted
-can measure urine pH as proxy for calcium urine levels
-want 6-7 urine pH
describe DCAD diet management
- analyze all foraged for K (+), Na (+), Cl (-), and S (-)
- select low K, palatable forages
-ideally, forages with higher Cl as well - select grains/by-products that are lower in K
- balance rations for negative DCAD (-5 to -10mEq/100g DM)
-magnesium sulfate
-calcium sulfate
-ammonium sulfate
-calcium chloride
-ammonium chloride
-hydrochloric acid - monitor the COWS not just the rations!
-test close-up urine pH on approx 10 cows 1-2x/week
-allow 48-72 hr after ration change
-desired range of 6.0-6.8 for all cows, not just the average!
-monitor group feed intake and potential for sorting (particle size)
-monitor periparturient diseases: milk fever, clinical ketosis, RP’s, DA’s, metritis
-adjust ration as needed, using urine pH and forage analyses
describe over-acidification of the pre-partum diet
- add more anionic salts just to be sure it’s working but
- adding more anionic salts costs money
- metabolic acidosis decreases feed intake
-lower calcium intake
-higher risk for metabolic disease (energy)
describe hypocalcemia treatment
- IV calcium: SLOW, 1 bottle per cow
-500ml of 223% calcium gluconate
-fast 10.7g of calcium (4x normal serum)
-rebound hypocalcemia thanks to calcitonin release (willing to risk in a down cow because will definitely die if not) - subcutaneous calcium
-slower admin = less risk of rebound hypocalcemia - oral calcium
-bolus:
–43g calcium
–calcium chloride = fast absorption
–calcium sulfate = slow absorption
-oral calcium as part of oral electrolyte drench or oral gel
NO standing cow gets IV calcium, but a DOWN cow is an EMERGENCY
-remember: just because the cow needs calcium doesn’t mean giving it won’t also mess up the whole system!
what if clinical hypocalcemia cow does not respond to treatment?
- probs not give more calcium, could wait longer to see if respond
- really, look for other issues:
-injury
-nerve damage
-magnesium
-compartment syndrome
