Production diseases: HypoCa, Mg, HypoP

What is calcium regulation controlled by?

Hormones

__ requirement for calcium on the 1st day of lactation?

3x

What is the difference between hypocalcemia and milk fever?

Hypocalcemia is just a serological finding, milk fever is a clinical presentation

What is ionized calcium involved with in the body?

muscle contraction, blood coagulation, enzyme activity, neural excitability and hormone secretion

What is a normal total blood calcium in an adult cow?

2.1-2.5 mmol/L

What is the calcium need for a dry dairy cow?

10-12 grams

What is the calcium need for a fresh lactating dairy cow?

30 grams or more

What is the normal blood value for ionized calcium in a dairy cow?

1 mmol/L or higher

What is calcium homeostasis controlled by specifically?

parathyroid hormone (PTH), 1,25 dihydroxyvitamin D, Calcitonin

How does PTH and 1,25 dihydroxyvitamin D control blood calcium?

increases it

How does calcitonin control blood calcium?

lowers it

What are the active sites of PTH after secretion?

Bone and kidneys

How does the kidney impact calcium homeostasis when stimualted by PTH?

Increases activation of vitamin D and decreases calcium excretion

In a normal adults cow at the onset of lactation what occurs 12-24 hours postpartum?

degree of hypocalcemia → calcium homeostasis

In subclinical hypocalcemia what happens during the periparturient period in 50% of older cows?

increased risk of ketosis, DA, Mastitis, Metritis, Fatty liver + decreased fertility, milk yield, and immunity

What is the total blood calcium level that we see in subclinical hypocalcemia?

1.38 to 2.0

How should we do calcium monitoring in our dairy cows?

Regular blood sampling, esp multiparous cows 1-4d post partum

What type of hypocalcemia can be explained by a simple physiological Ca deficit?

transient hypocalcemia

What type of hypocalcemia is considered a maladaptation of the Ca homeostatic system?

Peristent or delayed hypocalcemia

What is the alarm level of parturient hypocalcemia in multiparous cows????

≥30%

Where does 50% calcium live in the body?

bound to proteins such as albumin

Hows does 42-48% of calcium exist in the body?

ionized form (biologically active)

How does total serum proteins affect total calcium levels vs ionized calcium levels?

hypoalbuminemia could result in low total calcium in the blood and relatively normal levels of ionized calcium

What levels indication hypocalcemia in total blood calcium?

<2.0 mmol/L

What levels indication hypocalcemia in ionized blood calcium?

<1.0 mmol/L

Lack of calcium homeostasis with total Calcium levels of 1.4mmol/L leads to what?

Milk fever

Milk fever leads to what signs at calving?

dystocia, still births, RFM, uterine prolapse

When does milk fever typically occur in the production cycle?

24 hours prepartum to 72 hours postpartum

In exceptional situation when can milk fever occur?

several weeks postpartum

Is milk fever a deficiency of calcium?

NO

What is milk fever truely?

clinical hypocalcemia due to lack of availability of calcium

What are the clinical signs of milk fever in stage 1?

excitability, nervous, weak, shift weight and shuffle hind feet

What are the clinical signs of milk fever in stage 2?

sternal recumbency, moderate to severe depression. partial paralysis, lying down with head turned into their flank

What are the clinical signs of milk fever in stage 3?

lateral recumbency, completely paralyzed, bloated, severe depression to coma

What are general clinical signs of milk fever throughout all stages?

protrusion of the tongue, thermoregulation ability loss, cutaneous circulation depressed (cold extremities and dry muzzle), increased HR, absence of PLR, rumen stasis

How do you treat stage 1 milk fever?

oral calcium - calcium chloride 50g, calcium propionate 75-125 g, or calcium chloride + calcium sulphate fat coated bolus

sc 23% calcium solution - divided for a least 4-5 sites ~75 ml each, may be ineffective in dehydrated cows

How do you treat stage 2/3 milk fever?

IV calcium (jugular vein) - 500ml of 23% calcium borogluconate (10g calcium) OR 400 ml of 40% calcium borogluconate (12g calcium)

What are early signs of treatment responsiveness of milk fever stage 2/3?

tremors, PLR, wet muzzle, eructation, urination, defecation

How do you treat stage 2/3 milk fever if she relapses 12-18 hours later?

IV calcium (jugular vein) - 500ml of 23% calcium borogluconate (10g calcium) OR 400 ml of 40% calcium borogluconate (12g calcium) + oral calcium once the cow is alert and able to swallow +12 hours later OR SC calcium (may be ineffective) + palliative care

How do you prevent milk fever?

diet formulation and presentation, early detection of diseases, access to feed/water, cow comfort and environment

What diet formulation precalving helps prevent milk fever?

low calcium diet (less 100gr), nutritional antagonists/binds of calcium (zeolite), vitamin D supplementation (25000-50000 IU), assurance dietary magnesium supple (0.4%), slight acidification of blood reducing ratio of strong cations to strong anions to increase PTH activity (monitor urine pH → mild metabolic acidosis)

How does anionic salt - DCAD diet help prevent milk fever?

metabolic acidosis → decreased urine pH → increase urinary calcium excretion → increased calcium availability postpartum

What is the composition of DCAD diet?

low potassium base diets, anionic supplements (ie MgCl2), supplement MgS or MgCl

partial - 0 to -100 mEq/kg of DM

full - -100 to -150 mEq/kg of DM

What is good management practices to help prevent milk fever?

avoid stress, no overcrowding, no group movement, social factors, feed management (low K silage), etc.

What is another name for hypomagnesemia?

grass staggers

What is the function of magnesium?

major intracellular cation - cofactor for enzymatic reactions

extracellularly - vital for nerve conduction, muscle function, bone mineralization

How is magnesium controlled in the body?

absorption depended on diet, no hormonal control

Who is more commonly affected by hypomagnesemia?

beef cattle, older cows

What can hypomagnesemia cause in cattle?

sudden death (4-8 weeks postpartum if peracute)

risk factor for milk fever

How does hypomagnesemia occur?

rapid changes of diet → lush grass, low fiber, weather (rain leaching), diet restriction (inadequate supply/ration access)

age change → decreased ability to absorb dietary mg

high levels of potassium or ammonia or sodium

How is hypomagnesemia a risk factor for milk fever?

decreased secretion of parathyroid hormone, decrease tissue sensitivity to parathyroid hormone

What levels of magnesium would result in dietary absorption in a cow?

plasma: 0.8-1 mmol/L

CSF/vitreous humor: ~1 mmol/L

Where does magnesium get absorbed from in a young calf?

small intestine

Where does magnesium get absorbed from in an adult cow?

rumen

How should you test cows you may suspect of hypomagnesemia?

blood sample 10 cows within 12 hours postpartum - periparturient cow status or first weeks of lactation - lactating cows diet

What is hypomagnesemic tetany?

less than 0.5 mmol/L in plasma

What are the clinical signs of hypomagnesemic tetany less than 0.5 mmol/L in plasma?

ataxia + tetanic muscle spasm + hyperexcitability + hyperesthesia

What are the clinical signs of hypomagnesemic tetany less than 0.4 mmol/L in plasma?

seizures and convulsions

What options do you have for hypomagnesemia treatment?

Mg IV, MG + other macroelements, Mg SC, Mg enema

What treatment should do you for hypomagnesemia with seizure and convulsions?

Mg IV + IV sedation (xylazine)

When should you stop administration of IV Mg?

if in respiratory distress or excessive slowing or increase in heart rate

What treatment should do you for hypomagnesemia with seizure and convulsions if previous treatment did not work?

IV sedation (pentobarbitone 3mg/kg + xylazine 0.05mg/kg), IV magnesium sulphate (30ml 25%) + calcium borogluconate (400ml 40%)

with remaining 370 ml of 25% magnesium sulphate SC (over at least 4 sites)

How do you administer Mg SC?

50% solution, 200 ml at least 4 injection sites

How do you give a Mg enema?

rectal infusion of Mg salts - magnesium chloride - up to five tablespoonful in 250 ml of warm water

How do you continue treatment of hypomagnesemia if relapses 12-24 hours later?

assure dietary intake (40 gr)

How do you prevent hypomagnesemia?

potassium and sodium content in 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 calined magnesite

What is the importance of phosphate in the body?

multiple biological functions

tissue, cellular and molecular levels (teeth/bone)

How is phosphate maintained in the body?

not fully understood, similar mechanism and links with calcium homeostasis

can be difficult to distinguish from hypocalcemia

What are some causes of hypophosphatemia?

inadequate dietary P supply (diet and soil)

excessive P losses

compartmental P shifts (dextrose/insulin)

combination of several mechanisms - increased milk production, decline in dry matter intake, increase glucose and cortisol at parturition, renal losses

What are normal phosphate serum levels in an adult cow?

1.4-2.6 mmol/L

What are normal phosphate serum levels in an growing cow?

1.9-2.6 mmol/L

Is P concentration in serum or plasma a reliable parameter for measuring?

no as it is predominantly an intracellular electrolyte

What considerations must you make when sampling phosphate?

site, anticoagulants, sample collection and processing, presampling factors

What levels indicate severe hypophosphatemia?

<0.5 mmol/L

When does acute hypophosphatemia occur in dairy cows?

around parturition and early lactation

Who does chronic hypophosphatemia affect?

grazing animals in arid regions - low P soil content

fast growing calves low P ration/milk

What are the clinical signs of acute hypophosphatemia?

muscle weakness, recumbency, intravascular hemolysis (reduction in ATP content) → downer cow syndrome and periparturient hemoglobinuria

What are the clinical signs of chronic hypophosphatemia?

bone demineralization, impaired fertility, anorexia, pica, poor growth or weight loss, impaired milk production

How do you treat hypophosphatemia in anorexic cattle?

oral supplementation

• sodium phosphate salts: 150-270 g

• monopotassium phosphate

• monocalcium phosphate: 200-400 g

slow IV injection of calcium hypophosphite (400 ml) and sodium glycerophosphate

How do you treat hypophosphatemia in recumbent cattle?

slow IV injection of calcium hypophosphite (400 ml) and sodium glycerophosphate

sodium phosphate salts + oral supplementation

**Can cause life threatening hyperkalemia

How do you prevent hypophosphatemia?

fertilize soils with phosphorus, free access to high phosphours minerals, water supplementation