the causes and implications of subclinical hypocalcemia

Hypocalcemia!

It’s Not Just Milk Fever Anymore!!!

Jesse Goff

Iowa State University

Lactation #

Ca

(mg/

dl)

0

2

4

6

8

10

12

0 1 2 ≥3

Normal

Sub-clinical

Milk Fever

25%

0.7%

54%

2%

53%

5%

Incidence of hypocalcemia in USA confinement herds

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

1st 2nd ≥3rdLactation

NE

FA

(m

M)

Ca < 8.0 mg/dl

Ca 8.0 mg/dl≥

Mastitis

Retained FetalMembranes and Metritis

Ketosis/Fatty Liver

Milk Fever

Displaced Abomasum

Lameness

Decreasing DMIDecreasing DMI

Around Calving Calving

Insufficient Vitamins, Trace Minerals, or Anti-Oxidants

High DCAD or

Low Mg diets

Negative Energy + Protein Balance Increasing NEFA

Immune Suppression Hypocalcemia Lost Muscle Tone

Insufficient Dietary Effective Fiber

Rumen acidosis

Normal Blood Calcium Concentration= 9-10 mg/100ml

Extracellular Ca Pool ~11 g

Serum Ca pool ~ 3.5 g



Urine Ca0.2 - 6 g *

Endogenous Fecal Loss

5-8 g Ca



Urine Ca0.2 - 6 g *

Lactation- 20-30 g Ca

Colostrum –2.3 g Ca/ LMilk – 1.1 g Ca / L

Endogenous Fecal Loss

5-8 g Ca



Bone ~ 8 Kg Ca

Bone Fluid ~ 9 -15 g Ca *

Osteoclast recruitment &

activation

Urine Ca0.2 - 6 g *



PTH Endogenous Fecal Loss

5-8 g Ca

Parathyroid Hormone



Bone ~ 8 Kg Ca



activation

Urine Ca0.2 - 6 g *




5-8 g Ca

Trabecular

Co

mp

act

Co

mp

act

A B

Figure 50.5

OCLOb

ObOcyte

Blood vessel

Marrow Cavity

H

Bone spicule Figure 50.4

Parathyroid Hormone



Bone ~ 8 Kg Ca



activation

Urine Ca0.2 - 6 g *




5-8 g Ca

Section thru compact Bone

Ca++

Osteocytic Osteolysis Ca in bone fluid surrounding each cell pumped into blood

Parathyroid Hormone



Bone ~ 8 Kg Ca



activation

Urine Ca0.2 - 6 g *

Diet Ca = 45- 150 g**Passive Ca Transport




5-8 g Ca

Ca++

Ca++

Passive Transport of Ca Across Intestine

Ca++Ca++

Ca++Ca++

Ca++Ca++

Ca++

Ca++

Passive Transport of Ca

Ca++Ca++

Ca++Ca++

Ca++

Ca++

Ca++

Ca++


Ca++Ca++

Ca++

Ca++

Ca++

Ca++

Ca++

Ca++


Ca++Ca++

Ca++

Ca++

Ca++ Ca++

Parathyroid Hormone



Bone ~ 8 Kg Ca



activation

Urine Ca0.2 - 6 g *

Kidney 25-OH vit D

Diet Ca = 45- 150 g**

1,25(OH)2D

Active Ca Transport

Passive Ca Transport




5-8 g Ca

Ca++

Ca++ 1,25-vitD

VDR

Vitamin D-dependent Active Transport of Ca

Ca++ Ca++

Ca++

Ca++1,25-vitD

VDR-1,25-vitD


Ca++ Ca++

Ca++

CaBP

Ca++


Ca-ATPase pump

Ca++ Ca++

VDR-1,25-vitD

TRPV-6

Ca++

CaBP

Ca++

-CaBP


Ca++

Ca ATPase pump

Ca++ Ca++

Ca++

Ca++-CaBP

Ca -ATPase Pump


Ca++

Ca++ Ca++

Ca++

CaBP

Ca -ATPase Pump


Ca++

Ca++ Ca++

Ca++

Parathyroid Hormone



Bone ~ 8 Kg Ca



activation

Urine Ca0.2 - 6 g *

Kidney 25-OH vit D

Diet Ca = 45- 150 g**

1,25(OH)2D

Active Ca Transport

Passive Ca Transport




5-8 g Ca

A. pH=7.35 Normal Mg

Cyclic AMP

PTH

Receptor

C. pH=7.35 Hypomagnesemia

PTH

Receptor

B. pH=7.45 Normal Mg

Receptor

PTH

Adenyl cyclase complex



Mg++

Cyclic AMP Cyclic AMP

Mg++

2 Eq of each anion source fed

5.5

6.0

6.5

7.0

7.5

8.0

8.5

HC

lN

H4 c

hlor

ide

Ca

chlo

ride

Ca

sulf

ate

Mg

sulf

ate

Ele

men

tal S

ulfu

r

Uri

ne p

H

H2S

O4

Minerals/DCAD for Close-up Diets

Phos at .30-.37%Mg at .4% to use passive absorption!!S between .22 and .4%Ca at .85-1.3% ??Na at .1-.15%K as close to 1% as possibleEnough Chloride to urine pH.

Na, K, and Cl for the close-up dry cow.

Keep diet Na at .10-.15%

Keep diet K as close to 1.0% as you can get.

THIS IS ALL YOU NEED TO DO TO PREVENT MILK FEVER IN HOLSTEINS!!!!

TO REDUCE SUBCLINICAL HYPOCALCEMIA YOU WILL NEED TO ADD CHLORIDE TO COUNTERACT K.

HOW MUCH Chloride do I add to the diet?

Enough to bring urine pH between 6.2 and 6.8 the week before calving. (Jersey target= 5.8-6.2)

When urine pH is below 5.3 in the cows you may have caused an uncompensated metabolic acidosis = trouble!!!!!

Thumbrule

% Chloride needed = % K - 0.5

Example -If diet K is 1.3% then bring diet to 0.8 % Cl and check urine pH to fine tune diet

Interpreting urine pHCollect ten samplesScenario 1- average pH = 6.3 + .6

- good shape, compensated metabolic acidosisScenario 2-average pH= 7.4 + .5

Add more anion – 0.25 lb incrementsScenario 3 – average pH 5.2 + 0.5

-reduce anion by 0.5 lbScenario 4 – 4 cows at 5.2, 6 cows at 7.8

-reduce anion by 0.5 lbs and start increasing back in after 4-5 days by 0.25 lb increments

150

200

250

300

350

400

DC

AD

0.0

0.5

1.0

1.5

2.0

2.5%

of

DM

Con

trol 50

100

150

Chloride (lbs/acre)

Potassium

Calcium

Chloride

DCAD

A. pH=7.35 Normal Mg

Cyclic AMP

PTH

Receptor

C. pH=7.35 Hypomagnesemia

PTH

Receptor

B. pH=7.45 Normal Mg

Receptor

PTH




Mg++

Cyclic AMP Cyclic AMP

Mg++

Hypomagnesemia

Blood Mg < 1.9 mg/dl within 12 hrs of calving indicates inadequate dietary absorption of Mg.

-secondary hypocalcemia

-Depressed feed intake, depressed rumen fermentation (Ammerman, et.al., 1971)

-Tetany in grazing dairy ( below 1.2 mg/dl).

MagnesiumAdult Ruminants absorb Mg across rumen wall ! Mg insoluble at rumen pH is NOT available.

- Active transport process efficient with low diet Mg BUT EASILY POISONED BY DIET K AND NITROGEN

- Second passive transport system exists, but requires high concentration of ionized Mg in rumen fluid to work

Keep diet Mg at 0.4% prepartum and early post-partum to take advantage of passive transport of Mg across rumen wall

MAKE SURE Mg Source is AVAILABLE to the cow. Finely ground, not overly calcined!

Magnesium sources

Pre-calving - using MgSO4 or MgCl2 as “anions” also supplies readily available, soluble Mg.

-The better anion supplements on the market include Mg in this form to remove Mg worries pre-calving.

Post-calvingMagnesium Oxide – supply Mg and act as rumen alkalinizer.

- my experience low Mg = primary cause of mid-lactation milk fevers

Testing Magnesium Oxide Availability

Weigh out 3 g MgO into large vessel.

Add 40 ml of 5% acetic acid (white vinegar) slowly!!

Cap container and shake well and let sit 30 minutes. Check the pH.

Vinegar will be pH 2.6-2.8!

The best MgO will bring the pH up to 8.2.

The worst to just 3.8.

pH is a log scale so this represents >10,000 fold difference in buffering action.

Milk Fever PreventionMilk Fever Prevention1. Avoid very high potassium forages for

close-up cows; practiced by most dairies in US.

2. Add anions (Cl or Sulfate) to diet to reduce blood and urine pH; various forms practiced.

3. Diet Mg = 0.4% and available

4. Reduce diet Ca to stimulate parathyroid hormone release well before calving.

Milk Fever PreventionMilk Fever Prevention1. Avoid very high potassium forages for

close-up cows; practiced by most dairies in US.

2. Add anions (Cl or Sulfate) to diet to reduce blood and urine pH; various forms practiced.

3. Diet Mg = 0.4% and available

4. Reduce diet Ca to stimulate parathyroid hormone release well before calving.

-zeolite makes this possible!!??

Milk Fever - UnknownsMilk Fever - Unknowns

1. Is it necessary to raise diet Ca when using ‘anionic” diets?

2. Is there any advantage to combining preventatives? Low K + Low Ca + Anions, + IV or oral Ca?

3. Is partial acidification better than no acidification?

the causes and implications of subclinical hypocalcemia

Education

g ca lmilk

25oh2ddiet ca

gserum ca pool

mg100mlextracellular

g ca lpthendogenousfecal

g ca lendogenousfecal

parathyroid hormonediet

g cacolostrum