Hypocalcemia, DCAD, Hypomagnesemia

What are some C/S of hypocalcemia or hypomagnesemia?

Older fresh cows ataxic or recumbent shortly after calving

Older fresh cows seem ok but are observed leaking milking after leaving parlor

Incidence of metritis is higher than usual but our retained placenta, dystocia, and twinning rates are not higher

We are experiencing several down mid-lactation cows that are not responding to IV CMPK

There have been several sudden death in beef cows just before and after calving

What can hypocalcemia lead to?

Immunosuppression, mastitis, retained placenta metritis, DA, smooth muscle issues, clinical hypocalcmia

What does clinical hypocalcemia lead to?

Skeletal injury

Compartment syndrome

Decubital ulcers

Pressure necrosis

What are C/S of clinical hypocalcemia?

Afebrile, ataxia, flaccid paralysis, death

What increases risk of clinical hypocalcemia?

Older

When does subclinical hypocalcemia OR clinical hypocalcemia occur?

Just prior to parturition to 72 hours to parturition

What is the occurrence of clinical hypocalcemia?

5% of older cows and rare in first lactation animals

What is the occurrence of subclinical hypocalcemia?

50% older cows and 25% of first lactation animals

T/F clinical hypocalcemia is a gateway disease?

True

What are the intervention level guidelines for hypocalcemia?

Older cows: >1% clinical or >25% subclinical

Heifers: >12% subclinical

What controls calcium levels?

PTH (will respond to very minute changes in blood Ca concentration)

What causes hypocalcemia?

1. Direct result of metabolic alkalosis due to a positive DCAD die from dietary POTASSIUM

2. Can occur secondarily to hypomagnesemia

How do you prevent clinical hypocalcemia?

1. Minimize pre-calving dietary calcium to <20g/day (cannot balance here though so not done anymore)

2. Zeolite

3. Injectable vitamin D

4. Dietary cation anion difference diet (DCAD)

What is zeolite?

Dietary supplement that binds to Ca, Mg, and P in the rumen to reduce absorption (basically reduces Ca in the diet)

What is the problem with zeolite?

Also prevent absorption of Mg so you need to really increase Mg levels

How does vitamin D prevent clinical hypocalcemia?

Daily injections >10 days to 30 days before calving leads to hypocalcemia prevention level at or close to Vit D toxic level

NOT RECOMMENDED

What is a DCAD diet?

balance diet for <1% to 1.5% K on dry matter basis and Mg level to 0.4%

Goal is to have 0-+10 mEq/100m to prevent clinical cases

What is the goal of a DCAD diet?

Prevent both clinical and subclinical cases

When do you want to feed a negative DCAD diet?

10-21 days prior to calving, acidification will occur in 3-5 days

T/F you can do a DCAD diet for the entire dry period but do not due to cost?

True

Why do some people think they need to pull salt from a DCAD?

They think Na is a cation and will mess it up but it is NaCl so it balances out

What is a sign that NaCl is deficient in th ediet?

Pica (animals licking or drinking urine off the ground)

How do you monitor DCAD management?

Urine pH of 8-12 cows with the mean 6.2-6.8

What happens if urine pH is <5.5 on a DCAD diet?

Uncompensated metabolic acidosis causing very poor fresh cow health and cows will start lactation very poorly

When can you use oral treatment for hypocalcemia?

Clinical but still standing and swallow reflex is present or risk of aspiration pneumonia

Takes 30 minutes to be effective

how do you prevent hypocalcemia orally?

Oral calcium gel/bolus at calving repeated 24 hours later

How do you treat hypocalcemia SQ?

CMP (not effective if severely hypocalcemic or dehdyrated)

Do not use glucose solutions as SQ abscesses are likely

When does blood Ca return to normal after SQ hypocalcemia tx?

30 minute lag time and normal in 6 hours

When should you treat hypocalcemia IV?

Recumbent animals using CMPK starting with 500mL slowly (do not give more)

Auscultate during administration to stop flow rate if arrhythmias occur

Why does homeostasis of Mg rely on dietary intake and solubility?

There is not available Mg storage pool

What does carb consumption depend on?

Ration carbohydrate density and the total dry matter consumed by the animal

What molecule leads to acidosis?

Starch mostly

What happens with DMI increases?

Rumen pH decreases

How much saliva bicard is made a day?

7-9 days normally

Why do we add 0.25 lbs of bicarb to the diet a day?

To make us feel like we are helping prevent acidosis but it does not do much

Why is rapid absorption of acid from rumen important?

pH stability

What absorbs acid from the rumen?

Rumen papillae, longer length and more surface area means more absorption

What does chronic rumenitis and fibrosis do to rumen papillae?

Reduces absorption of acid due to shortening

How can you prevent SARA?

Feed a TMR

Feed available at least 20 hours a day

Appropriate ration formulation

Monitor forage dry matter content

Minimize diet sorting

Multiple feeding per day

Minimize time away from feed and water

Adequate bunk space and resting space

Minimize heat stress

Promote rumen buffering

Adapt rumen to lactation diet in closeup pen

Incorporate feed additives

Why is a TMR useful?

Prevents selective eating so every bite is balanced

Why should you have feed available 20 hours a day to prevent SARA?

Prevents slug feeding (rapid drop in pH from a big meal)

What happens when moisture increases in a diet?

Dry matter decreases leading to less cud and bicarb

How often should you check dry matter content?

Weekly

What type of feed do cattle prefer/

Fine particles (highly fermentable carbs)

What makes diet sorting worse?

Excessively dry

Excessive long hay particles over 2.5 inches

Incoporation of poor-quality forages

Why do we want multiple feedings per day?

Limits size and slug feeding and makes them more consistent

How can we minimize time from feed to prevent SARA?

Milk duration shorter and good stall maintenance

How much lying time will help prevent SARA?

12-14 hours

How can we promote rumen buffering to prevent SARA?

Endogenously with effective fiber

Exogenously with a positive DCAD diet

What are good feed additives to prevent SARA?

Yeast

Monensin

Replace some fermentable carbs with sugars

Can SARA occur in pasture fed animals?

YES

What is the main C/S of acute acidosis?

Death

What are the main C/S of SARA?

Poor production

Poor body condition

Laminitis

What causes PTH release?

Hypocalcemia

What is a normal pH?

7.35 in the blood

What does PTH do?

Helps Ca be released from bone and renal production of Vit D to increase Ca dietary absorption

What happens to PTH effectiveness during metabolic alkalosis?

PTH is less able to bind and is less efficient

What happens to PTH when there is hypomagnesemia?

Interacts tightly with kidney and bone blunting PTH ability in bone and renal production of Vit D

What are the major cations?

Na and K

What are the major anions?

S and Cl

What does it mean when we want pre-calves to be in a negative DCAD?

More anions than cations

What is the goal to prevent both clinical and subclinical?

-15 to 0

How much phosphorus do we want in a diet?

<0.25% because high P reduces Ca absorption

What is Soychlor?

Commercial DCAD diet with a hydrochloric acid base

Biochlor is an alternative

How do you assess if there is a issue with the DCAD diet after calving?

Ca and Mg from serum

If 20% of samples are <concern levels there is a problem

Why do you assess Ca and Mg together in down calves?

If primary Ca issue, Mg will be normal

If secondary Ca issue, Mg will be low

If primary Ca issue, P will also always be low

If you treat a cow for hypocalcemia and she is still not doing right what is the problem?

Hypophosphatemia, need to do an oral P source or a IV fleet enema product

If a cow is ataxic and not periparturient what is the top of the ddx list?

Hypomagnesemia

What causes hypomagnesemia / grass tetany in beef cattle?

Excessive dietary K causes reduced Na levels and Mg consumption

K reduces active ruminal Mg transport

How do you prevent hypomagnesemia in beef cattle?

Feed high Mg mineral that will allow for passive transport of Mg across rumen wall

What causes winter tetany / hypomagnesemia in beef cattle?

High forage diets with Mg solubility lower due to higher rumen pH

Older animals absorb less

How do you treat grass tetany?

IV Ca/Mg/K slowly

Will respond quickly so have a plan in place before you remove the halter