Macromineral disorders in dairy cattle

Question 1

Both Milk fever and grass tetany are characterised as

Answer 1

decreased levels of blood Ca and Mg together with clinical signs.

Hence, the therapy of these diseases is intravenous infusion of calcium in milk fever and magnesium in grass tetany.

Question 2

magnesium homeostasis is mainly
regulated by (2)

Answer 2

the absorption rate of Mg from rumen and the excretion rate through kidneys.

Question 3

the most typical clinical
sign of milk fever is?
whereas during grass tetany the cow has?

Answer 3

the most typical clinical sign of milk fever is paresis, whereas during grass tetany cow has muscle tremors.

Question 4

When does Milk fever usually occur?

Answer 4

Milk fever occurs usually 1 day before – 1-2 days after parturition.

Question 5

Dairy cows will secrete ? g of calcium in the production of colostrum and milk in the early stages of lactation.

Answer 5

Dairy cows will secrete 20–30 g of calcium in the production of colostrum and milk in the early stages of lactation.

Question 6

What stimulates PTH?
& What does PTH stimulate?
What does vit D do?

Answer 6

decreased blood concentration of Ca+ stimulates PTH

PTH in turn stimulates
- Ca release from bones (osteoclast activity), - kidney reabsorption (increases phosphate
excretion)
- activates vit D (cholecalciferol) into active calcitriol in kidneys

vit D3/calcitriol increases Ca and Phos absorption from the GI tract,
promotes renal resorption of Ca+

Question 7

what infections can cause secondary milk fever?

Answer 7

during mastitis and severe endotoxemia, the calcium pathways are modified and hypocalcemia and paresis can occur

even severe diarrhea can also cause this due to a lack of Ca+ absorption in diarrhea.

Question 8

Why do some cattle not respond to PTH around the onset of lactation?

Answer 8

When dry cow feeding management is off-balance, and the diet contains a lot of K+.

High K levels in the diet expose dairy cows to metabolic alkalosis, which alters the conformation of PTH receptors leading to tissues less sensitive to this hormone.

(cations (primarily K and Na) are alkalinizing because they are positively charged ions, when they are absorbed and metabolized, they tend to raise the pH of the blood, making it more alkaline.)

Under normal conditions (blood pH 7.35), in response to hypocalcemia, PTH is released and successfully works.

Under alkalotic conditions (blood pH ≥ 7.45), the shape of PTH receptors change.

Question 9

Why does K+ in feed cause a metabolic alkalosis?

Answer 9

cations (primarily K and Na) are alkalinizing because they are positively charged ions, when they are absorbed and metabolized, they tend to raise the pH of the blood, making it more alkaline.

Thus, feeding anions (primarily chloride [Cl] and sulphate [SO4 2]) are acidifying because they are negatively charged ions, when anions are metabolized, they tend to lower the pH of the blood, making it more acidic.

Question 10

How is hypomagnesemia related to
hypocalcemia?

Answer 10

Severe hypomagnesemia can inhibit PTH function in response to hypocalcemia.

Moderate hypomagnesemia affectshow PTH functions.

PTH can still bind to its receptors, but it can’t initiate production of second messengers without Mg.

So, in case of hypomagnesemia, the signal from PTH receptor isn’t sent forward and there is no response to PTH hormone in the body or kidney cells.

Thus, Hypocalcemia can occur.

Question 11

what % of all the dairy cows have mild
hypocalcemia (<8 mg/dL) 24 h post partum as a physiologic respond to high milk production?

Answer 11

50% of all the dairy cows have mild
hypocalcemia (<8 mg/dL) 24 h post partum as a physiologic respond to high milk production?

This doesn’t necessarily have to cause any
problems.

Question 12

Why are older cows more prone to suffering from milk fever? (3)

Answer 12

3 or more parturitions-cows

the number of vit D receptors in the GI tract is decreased in older cows

Ca+ release from bones is decreased as well (just not as efficient)

the number of PTH receptors in the kidneys is decreased too

Question 13

name 3 cow related factors predisposing to milk fever

Answer 13

age (number of lactations, 3+)
milk yield (high yielders are more prone)
breed (e.g. jerseys are more prone)

Question 14

name 5 diseases or conditions that predispose to milk fever

Answer 14

hypomagnesemia
hypophosphatemia (phos and ca metabolism are related)

ketosis
fatty liver
endotoxemia

Question 15

name 3 environmental factors that predispose to milk fever

Answer 15

• Dry cow feeding strategy & management
• Sick cow management
• decrease K content of the diet – avoid a metabolic alkalosis

Question 16

Effects of Subclinical hypocalcemia (min.3)

Answer 16

Hypocalcemia stimulates mobilization of body fat – increased NEFA concentrations in blood – increased risk of ketosis.

Due to ca+ involvement in muscle contraction.
- Predisposes to displaced abomasum?
- Causes decreased milk yield

+ lowers the immunity,
reduces the fertility,
increases the risk of fatty liver
and retained placenta.

Question 17

Ruminants are more prone to hypomagnesemia than monogastric
animals.

The variation in Mg metabolism among species is mainly because of

Answer 17

anatomic and physiologic differences in digestive tracts.

Species differences in Mg metabolism are attributable to variation in both absorption efficiency of Mg from the gut and reabsorption of Mg by the kidney tubules.

Ruminants absorb Mg less efficiently than nonruminants (35% vs 70% of intake).

The rumen is the main site of absorption but Absorption from the large intestine occurs with high Mg intakes.

In nonruminants, the small intestine is the main site of absorption.

Question 18

Maintenance of normal plasma Mg levels is
dependent on

Answer 18

continuous dietary Mg supplementation!

Mg absorption from rumen depends on the Mg concentration in the ruminal fluid and the integrity of Mg transport mechanism (Na-linked active transport).

Question 19

What Plasma Mg level will inhibit the
secretion of Mg to urine?

Answer 19

Plasma Mg level <1.8 mg/L will inhibit the
secretion of Mg to urine.

Question 20

the main risk factors for developing of
hypomagnesemia? (6)

Answer 20

Diet related factors such as
- low Mg content in diet (needs to be supplemented!)

• high K content in diet (high K+ will inhibit Mg absorption from rumen)
• high content of unsaturated fatty acids in diet (high FA inhibit Mg absorption)
• increased rate of ingesta passage (Mg doesn’t have time to absorb adequately)
• high ruminal pH >6.5 (inhibits Mg absorption)

Of course, reduced dry matter intake as well.

Question 21

Milk fever stages.

Answer 21

stage 1: still ambulatory but with tremors etc.

stage 2: no longer standing, cold extremities, tachy etc.

stage 3: loss of consciousness, severe bloat, unresponsive etc.

Question 22

Normal serum Ca?
Normal serum Mg?

Answer 22

Normal serum Ca is 8.0-10.0 mg/ dL.

Normal serum Mg is 1.8-2.4 mg/ dL

Note however, the serum Ca and Mg concentrations are individually
different – cows can develop clinical disease at very different serum
concentrations.

Question 23

Treatment plan for milk fever:

Answer 23

Intravenous calcium infusion
 Dose 9 g / 600 kg = 1-2 g/ 100 kg

 Given slowly during 15-20 min.

 Nsaids (ketoprofen, meloxicam)

Mg is often added to Ca solutions as it protects the heart from cardiotoxic effects of Ca. arrythmias and bradycardia, if you give the Ca infusion too fast.

Question 24

When is subcut Ca appropriate?

Answer 24

Previously used in treatment/prevention of
hypocalcemia and is an approved route for
administration on product labels.

However, absorption of Ca from subcutaneous tissue needs adequate
peripheral perfusion which is decreased in cows with hypocalcemia.

+ dehydration can worsen perfusion

Subcutaneous Ca is irritating and can cause necrosis especially, if it contains glucose – risk of abscessation.

Also only keeps the blood Ca level high for only about 6 hours.

Thus, we only give Ca intravenously!

Question 25

Oral calcium supplements are used in the
treatment of (3)

Answer 25

subclinical hypocalcemia,
after treatment of milk fever or
as prophylactic therapy for cows in risk groups.

Question 26

Oral Ca supplement options: (3)

Answer 26

calcium chloride
calcium propionate
calcium carbonate

Question 27

What’s the difference between
calcium chloride
calcium propionate
calcium carbonate

Answer 27

1. Calcium chloride
    Fast absoprtion (30 min) of 50 g bolus – high bioavailability.
    Caustic to oral and pharyngeal tissues if given uncovered and repeatedly.
    Acidic response – cow starts to use it’s own Ca stores.
2. Calcium propionate
    Slower absorption (1 h) of 75-125 g bolus
    Less injurious to tissues
3. Calcium carbonate
    Can’t be absorbed from acidic environments or if contractions of
   digestive tract are slow

 Does not increase blood Ca concentrations – poor bioavailability

 Alkalotic agent – keep in mind the effect for PTH

 However, is cheap – can be used in diet to meet long-term Ca needs.

Question 28

By dosing animal with large amounts of very soluable Ca, it’s possible to..?

? g Ca per dose

Given when?

Answer 28

By dosing animal with large amounts of very soluble Ca, it’s possible to force Ca from intestines to blood by means of passive diffusion.
 Old cows
 High yielding cows in earlier lactations

 50-125 g Ca per dose

 Given (12 h before calving), at calving and 12 + 24 h later (4 times total).

Question 29

Prevention of hypocalcemia and milk fever?

Answer 29

Previously, low Ca diet during the dry period was recommended for prevention but thats difficult and also counterintuitive since nowadays we know that an alkalotic state causes PTH resistance.

Thus, we should ensure, that metabolic alkalosis doesn’t develop by decreasing K+ in the diet.

control of hypocalcemia is not successful if diet contains more than 1.8 % of K.

Dietary cation-anion difference is the point, add anion salts to the diet so that blood pH would decrease.

Question 30

Why are cations like K+, alkalinizing?
Why are anions like Cl-, acidifying?

Answer 30

cations like K+ and Na+ are alkalinizing because they are positively charged ions, when they are absorbed and metabolized, they tend to raise the pH of the blood, making it more alkaline.

anions like Cl- and SO42- are acidifying because they are negatively charged ions, when anions are metabolized, they tend to lower the pH of the blood, making it more acidic.

Question 31

Major cations in cows feed: (4)

Answer 31

Na +, K +, Ca 2+, Mg 2+

Question 32

Major anions in cows feed: (4)

Answer 32

Cl -, SO42-, phosphate

Question 33

The difference between the number of cation and anion particles determines the

Answer 33

blood pH
 mEq/kg

DCAD = (mEq Na+ + mEq K+) – (mEq Cl- + mEq S-)

However, these are not only cations/anions presented in the diet, so the expression should be more complex.

Question 34

There are Fixed amounts of Ca, Mg, Na and P in the diet – so instead we can manipulate

Answer 34

the amounts of K and Cl in the diet.

There’s gonna be K+ in cow’s diets anyway - Cl- anions should be added to counteract the blood alkalinity.

The concentration of Cl required in the diet to acidify the cow is 0.5 % less than the concentration of K.

High amounts of Cl reduce DMI – palatable Cl products should be used.

Question 35

When to give the adjusted DCAD diet?

Answer 35

2 weeks before calving but not earlier as the kidneys will begin buffering and the effect is lost.

then confirm if its working by checking urine pH

Question 36

normal cow urine pH?
optimal urine pH on adjusted DCAD diet?

Answer 36

normally 7.5- 8.7

on DCAD diet pH 6.5-6.8

Question 37

heart on auscultation in grass tetany?

Answer 37

Really strong heart beat and tacchycardia

Question 38

Treatment of grass tetany:

Answer 38

IV magnesium infusion 2-3 g of Mg / cow slowly over 15-20 min.

+ Nsaids

Question 39

Are there any oral Mg products available?

Answer 39

 Oral Mg products can be used after IV treatment to maintain optimal Mg concentration or to prevent hypomagnesemia in cows in risk.

1. Magnesium oxide 100 g PO

or

2. 50 % Magnesium sulfate 200-400 ml PO
    More available for absorption than Mg oxide.

Oral Mg salts are unpalatable – they should be given with other palatable components (molasses etc.)

Question 40

Recommendations to prevent the
occurrence of hypomagnesemia: (4)

Answer 40

Stepwise familiarization on to new pasture

Supplement minerals

Feed analysis

Treat the cows in risk groups with oral Mg

Question 41

even After two IV Ca+ treatments for milk fever, What if the cow still doesn’t stand up aftertreatment of milk fever?

Answer 41

Other macromineral disorders are rare reasons for downer cows.

But are Usually disorders of potassium (K) and phosphorous (P).
 Hypokalemia
 Hypophosphatemia (7% of milk fever cows also need phosphate)

So next step is to evaluate for one or both of these and treat them.

Question 42

Describe Hypokalemia in cows.

Answer 42

Severe hypokalemia (< 2.5 mmol in serum) may develop, if cow is anorexic.

Lactating cows are in high risk during periods of inappetence, because K is lost in milk (1.4 g of K/L of milk).

Is a rare disorder → only consider when predisposing factors are present and the treatment of other diseases is ineffective.

Question 43

Describe Hypophosphatemia in cows.

Answer 43

The restriction of fertilizer with phosphorus containing compounds can lead to decreased intake of phosphorous in dairy cows. (too much phos is bad for soil)

7% of milk fever cows also need phosphate

Question 44

hypophosphatemia can be acute or chronic, explain

Answer 44

Chronic disease → rickets in young animals and osteomalacia in adults – the
clinical signs take years to develop.

When considering chronic hypophosphatemia → check the diet and
calculate the daily amount of Phosphate needed and check against the current intake.

Question 45

Clinical signs of either hypokalemia or hypophosphatemia?

Answer 45

Unthriftiness
Anorexia
Depression
Recumbency
Muscle weakness
Tachycardia
NB S-shaped neck! (characteristic)

Question 46

Clinical signs of hypokalemia?

Answer 46

GI stasis

Rhabdomyolysis (due to potassium’s critical role in muscle cell function, Without enough energy to maintain cellular functions, muscle fibers are damaged, leading to cell rupture and the release of muscle contents)

Question 47

Clinical signs of hypophosphatemia?

Answer 47

Intravascular hemolysis
Hemoglobinuria
Pica

Question 48

If cows’ diet contains a lot of potassium why do they get hypokalemia sometimes?

Answer 48

 Due to inappetence for any reason more than 2 days.

 Gastrointestinal stasis for any reason.

 Alkalosis (displaced abomasum)

 Renal disorders, acute renal failure

 Iatrogenic causes –Glucocorticoids
(isoflupredone/dexamethasone), diuretics (furosemide).

NB! In dairy cows with normal appetite,
hypokalemia is extremely rare!

Question 49

Why does hypophosphatemia contribute to paresis?

Answer 49

Phosphate is a part of energy-transferring molecules (ATP), therefore during
hypophosphatemia ATP molecules cannot be produced and energy is not transferred in muscle cells = paresis

Question 50

Why does hypophosphatemia cause intravascular hemolysis and hemoglobinuria?

Answer 50

In erythrocytes, lack of ATP leads to increased intracellular Na and cells
become rigid and rupture in small capillaries.

Remember the lack of ATP is because ATP-building needs phosphate too.

Question 51

Treatment of hypokalemia?

Answer 51

Oral potassium chloride 20– 30 g/100 kg → 60-120 g per cow q 12 h.

IV potassium chloride max 0.5 mEq/
kg/ hour.
 Dangerous and expensive
 risk of Arrythmias → ventricular fibrillation and death.

Question 52

Treatment of hypophosphatemia?

Answer 52

IV 6 g of P supplied by 23 g of monosodium
phosphate dissolved in 1 L saline

PO 40-60 g of P, commerical products avail.

NB! P is only absorbed from intestines,
so with rumen/abomasal problems, PO
administration of P may be pointless if the phosphate can’t reach the intestines.

Phosphorous supplementation can be a part of the treatment of the downer cows, but must be limited to the recumbent stage of the disease

Question 53

Blood test of BHB tells us what exactly?

Answer 53

the exact concentration of ketone

As opposed to cow-side tests for ketones which may not be so precise and only let you know of the presence of ketones.

Question 54

Metabolic alkalosis can induce the occurrence of hypocalcemia. What is the main cause for metabolic alkalosis?

Answer 54

high potassium level in the diet

Question 55

If the cow doesn’t stand up after the first calcium treatment,

Answer 55

second calcium infusion can be given intravenously after 6-8 h.

Question 56

Ketone bodies can be utilised as an energy source by the

Answer 56

heart and skeletal muscles and in some amount in the brain.

Question 57

Functions of extracellular calcium in the organism include (3)

Answer 57

blood clotting, muscle contractions, nerve impulse transmission

Question 58

Haemoglobinuria occurs during hypophosphatemia, because

Answer 58

because low phosphate levels lead to a reduction in red blood cell membrane stability, causing hemolysis (destruction of red blood cells), which releases hemoglobin into the bloodstream. The free hemoglobin is then filtered by the kidneys, leading to its presence in urine (hemoglobinuria).

Question 59

In older cows (three or more lactations), the risk of hypocalcemia is higher because

Answer 59

the uptake of calcium from the kidneys and intestines is reduced &
the response of bones to hypocalcemia is reduced.

Question 60

An owner calls you and complains, that he has found lesions around the mouth in some lambs in a few lambs. He took the photo and sent it to you. What is your first guess as a diagnosis?

A.
Foot and mouth disease

B.
Sheep ked

C.
Contagious pustular dermatitis (ORF)

Answer 60

The correct answer is:
Contagious pustular dermatitis (ORF)

Question 61

Phosphorous is a part of

Select one or more:

a.
ATP molecule

b.
adenosine triphosphate

c.
antioxidants

Answer 61

a.
ATP molecule

b.
adenosine triphosphate

Question 62

Which of the following diseases can cause hypocalcaemia as well?

a. interdigital phlegmon

b. endotoxemic metritis

c. Hoflund’s syndrome

Answer 62

b. endotoxemic metritis

Question 63

Calcium chloride is an oral calcium product, which is rapidly absorbed from the rumen. However, the downside of this product is

Answer 63

caustic effect to oral and pharyngeal tissues.

Question 64

Treatment of clinical hypomagnesemia includes

Answer 64

IV infusion of calcium and magnesium solution

or

IV infusion of magnesium solution and NSAID-s

Question 65

Cow has calved 5 days ago. The body temperature is 39,2 ̊C, cow has dry and pale mucous membranes. The milk in one udder quarter is yellowish and watery and the somatic cell count is increased. The heart rate is increased and the rumen motility decreased. Extremities (especially ears) are cold. Cow is recumbent. Such signs are most likely caused by

Answer 65

endotoxemic mastitis

Question 66

What is the main cause for decreased magnesium level in cows’ organism?

Answer 66

diet low in magnesium

Question 67

The main feeding strategy in preventing hypocalcemia incidences in fresh cows is

Answer 67

to keep the potassium level in the dry cow diet as low as possible.

Question 68

Calcium solutions containing phosphorous can be used in primary hypophosphatemia treatment if they…

Answer 68

if they contain phosphorous in the form of phosphate.

This is the biologically active form of phosphorous.

Question 69

Hyperthermia occurs during hypomagnesemic tetany because

Answer 69

extreme muscle contractions produce a lot of heat.

Question 70

The main body source for magnesium is…

Answer 70

There are no body sources for magnesium. If cow cannot get enough magnesium from the diet, magnesium level in the organism starts to fall in the end, because magnesium cannot be redistributed from tissues to blood.

Question 71

To prevent secondary recumbency due to ischemic necrosis and pain in the muscles, cows with milk fever should be

glucocorticoids?
NSAIDS?
Turning?
soft bedding?

Question 72

What could be a risk factor for development of fatty liver and ketosis?

Answer 72

Excessive body condition at parturition.

Question 73

Clinical signs of hypomagnesemia usually disappear in one hour after magnesium infusion because

Answer 73

that time is needed for normalisation of magnesium levels in the cerebrospinal fluid and brain

Question 74

Why is vitamin D important in calcium homeostasis?

Answer 74

active form of vitamin D stimulates the uptake of Ca2+ from the intestines

Question 75

Right after calving, recumbent cows with hypophosphatemia can be demerged from hypocalcemia by

Answer 75

the lack of response to calcium infusion.

Question 76

Besides of downer cow syndrome, hypophosphatemia can cause

Answer 76

post-parturient haemoglobinuria

Question 77

Hypophosphatemia may occur in hypocalcemic cows, because

Answer 77

Hypophosphatemia and hypocalcemia can occur together due to parathyroid hormone activity. If cow is hypocalcemic, PTH is secreted in increased amounts. Because phosphorous is mainly absorbed with same route as calcium from the intestines, increased PTH activity puts the calcium absorption first, leading to decreased absorption of phosphourous. Anyway, phosphorous is secreted through kidneys and in saliva, which is then not absorbed from intestines.

The correct answers are: increased secretion of parathyroid hormone increases the absorption of calcium from intestines,

phosphorous is secreted in increased amounts via kidneys, saliva and feces and

absorption of phosphorous from intestines is decreased .