Production Diseases: HypoCa, HypoMg, HypoP Flashcards
when do hypoCa, hypoMg, hypoP occur during the dairy cow cycle
what are the functions of calcium
Essential mineral component of skeleton
Ionized calcium involved in muscle contraction, blood coagulation, enzyme activity, neural excitability and hormone secretion
98% of Ca is in skeleton
2% in extracellular fluid, around half bound to plasma protein (albumin) and around half ionized in soluble form
Must maintain ionized Ca in blood for normal nerve and muscle function
what is the total blood Ca in a normal adult cow
2.1-2.5 mmol/L
what occurs at the onset of lactation
degree of hypocalcemia 12-24h postpartum
calcium homeostasis mechanisms kick in and restore circulating levels
what are the calcium homeostasis mechanisms
what 3 hormones manage calcium homeostasis
- parathyroid hormone (PTH)
- 1,25-dihydroxyvitamin D
- calcitonin
how do the 3 hormones maintain blood calcium levels
what is the calcium status during the transition period
what is subclinical hypocalcemia total blood levels
1.38-2.0 mmol/L
what does subclinical hypocalcemia predispose the cow to
Increases risk of:
Ketosis
DA
Mastitis
Metritis
Fatty liver
what effect does subclinical hypoCa have on production
decrease fertility, milk yield, immunity
at what blood Ca level is milk fever
<1.4 mmol/L
when does milk fever occur
dystocia
still births
RFM
uterine prolapse
what is milk fever
clinical disorder
Availability of calcium rather than true deficiency
Life threatening to cow
Increases risk of other diseases (metabolic and infectious)
Age
Breed
what is the prevalence of milk fever
increasing prevalence as increasing lactation number
Up to 50% of herd could have subclinical hypocalcemia near parturition
what are the clinical signs of stage 1 of milk fever
Excitability
Nervous
Weak
Shift weight and shuffle hind feet
what are stage 2 milk fever clinical signs
Sternal recumbency
Moderate to severe depression
Partial paralysis
Lying down with head turned into their flank
what are stage 3 milk fever clinical signs
Lateral recumbency
Completely paralyzed
Bloated
Severe depression to coma
what are the general clinical signs of milk fever
Protrusion of tongue
Thermoregulation ability loss
Cutaneous circulation depressed — cold extremities (cold ears and dry muzzles)
Rumen stasis
Increased heart rate
Absence of PLR
how are stage 1 clinical signs of milk fever treated
Oral calcium
- Calcium chloride 50g
- Calcium propionate 75-125g
- Calcium chloride + calcium sulphate fat-coated bolus
SC 23% calcium solution
- Divided for at least 4-5 sites ~75ml each
- May be ineffective in dehydrated cows
how are stage 2 and 3 milk fever cows treated
IV calcium (jugular vein)
- 500ml of 23% calcium borogluconate (10g calcium)
- 400ml of 40% calcium borogluconate (12g calcium)
- Slow administration (5-10 min)
Sudden increase in heart rate
Arrhythmia
Stop!
If relapses 12-18h later then:
- oral calcium: once the cow is alert and able to swallow + 12h later
- Or SC calcium (may be ineffective in severe cases and dehydrated cows)
Palliative care! Down cow
what are early signs of treatment responsiveness to milk fever
Tremors
PLR
Wet muzzle
Eructation
Urination
Defecation
how is hypoCa prevented using nutrition pre calving
Low-calcium diet at pre-partum (less 100g)
Nutritional antagonists/binders of Ca (zeolite)
Vitamin D supplementation
Assurance dietary magnesium supply (0.4%)
Slight acidification of blood reducing ratio of strong cations (Na+ + K+) to strong anions (Cl- + S2-) to increase PTH activity (DCAD diet) —> metabolic acidosis
- Monitor urine pH (loss H+)
- Decrease palatability
Calcium supplementation at calving
Monitor calcium in blood (24-48h post-partum)
how is hypoCa prevented/controlled using good management
Avoid stress
No overcrowding
No group movement
Social factors
Feed management (low K silage)
Etc
what are the risk factors of hypoMg
Older cows
- Decrease ability to absorb dietary magnesium
Rapid changes of diet
- Lush grass (moving fields)
- Low fibre (straw can slow rumen transit)
- Weather (rain leaching)
- Diet restriction (inadequate supply/ration access)
High levels of potassium and ammonia
Low levels of sodium
when does hypoMg occur
4-8 weeks postpartum beef cattle
peracute cases
sudden death
how does hypoMg lead to increase risk for milk fever
Decrease secretion parathyroid hormone
Decrease tissue sensitivity to PTH
Mg has no hormonal control
what is the plasma levels of Mg in a normal adult cow
Plasma: 0.80 to 1.0mmol/L
CSF: ~1.0mmol/L
how is Mg homeostasis maintained
young calves: small intestine absorption
adult: rumen
- [Mg] in solution in rumen fluid
- Mg transport mechanism (Na vs K)
when should you blood sample cows to monitor for hypoMg
Within 12 hours postpartum — periparturient cow status
First week of lactation — lactating cow’s diet
at what plasma level does hypoMg tetany occur
Less than 0.5mmol/L
what does hypoMg tetany cause
Ataxia
Tetanic muscle spasms
Hyper excitability
Hyperesthesia
when do seizures and convulsions occur in hypoMg
less than 0.4 mmol/L
what are the treatment options of hypoMg
Mg IV
Mg + other macroelements
Mg SC
Mg enema
when should Mg IV be used
Seizures + convulsions
IV sedation
- Xylazine 0.05mg/kg
IV magnesium sulphate 20% (200-300ml)
Slow administration — cardiotoxicity
Respiratory distress
Excessive slowing or increase in heart rate —> stop admin
how is Mg and other macroelements IV + Mg SC used to treat hypoMg
Seizures & convulsions:
IV sedation
- Pentobarbitone 3mg/kg; xylazine 0.05mg/kg
IV magnesium sulphate (30ml 25% solution) combine with calcium borogluconate (400ml 40% solution)
- Remaining 370ml of 25% magnesium sulphate SC (over at least 4 sites)
how is Mg SC injection used to treat hypoMg
SC injection magnesium sulphate 50% solution (200ml — at least 4 injection sites)
how is Mg enema used to treat hypoMg
Rectal infusion of Mg salts
Magnesium chloride — up to 5 tablespoonful in 250ml warm water
how often do relapses occur after hypoMg treatment
Relapses 12 to 24h later
Assure dietary intake (40g)
- Ex. concentrates
how is hypoMg prevented/controlled
Potassium and sodium content in the diet
Molasses-based licks/buckets (Mg and Na)
Concentrates with Mg and Na
Water medicated with Mg salts
Intraruminal boluses containing Mg
Pastures dusted with calcined magnesite
Ensure adequate ration intakes!
what are the challenges with hypoP
Not fully understood
Similar mechanisms and links with calcium homeostasis
Sometimes difficult to distinguish clinically in diary cows with hypocalcemia
Can be observed as complication in milk fever cases
what are the causes of hypoP
Inadequate dietary P supply (diet or soil)
Excessive P losses
Compartmental P shifts (dextrose/insulin)
Combination of several mechanisms
- Increased milk production
- Decline of DMI
- Increase glucose and cortisol at parturition
- Renal losses
what are the normal serum levels in adult cattle
1.4-2.6 mmol/L
what are the normal serum levels in growing cattle
1.9-2.6 mmol/L
what are the considerations when blood sampling to measure levels of P
Site
Anticoagulants
Sample collection and processing
Pre-sampling factors
what are serum levels of clinical cases of hypoP
serum <0.5 mmol/L
when do acute hypoP cases occur in dairy
around parturition
early lactation
when do chronic hypoP cases occur i
grazing animals in arid regions - low P soil content
fast growing calves low P ration/milk
what are the clinical signs of acute hypoP
Muscle weakness
Recumbency
Intravascular hemolysis —> downer cow syndrome, periparturient hemoglobinuria
leads to:
Downer cow syndrome
Periparturient hemoglobinuria
what are the clinical signs of chronic hypoP
Bone demineralization
Impaired fertility
Anorexia
Pica (abnormal eating)
Poor growth or weight loss
Impaired milk production
how are anorexic cattle treated for hypoP
Oral supplementation:
- Sodium phosphate salts: 150 to 270g
- Monopotassium phosphate
- Monocalcium phosphate: 200 to 400g
how are recumbent cattle treated for hypoP
slow IV injection of sodium phosphate salts (extralabel)
- life-threatening hyperkalemia + oral supplementation
Slow IV injection:
- Calcium hypophosphite (400ml)
- 20% toldimphos (20ml)
- Sodium glycerophosphate
how is hypoP prevented/controlled
Grazing animals:
- Fertilizing soil with P
- Free access to high P minerals
- Water supplementation
