This document discusses hypocalcemia, also known as milk fever, in dairy cows. It provides information on the incidence of hypocalcemia in US dairy herds, risk factors, and physiological mechanisms. The key strategies for preventing milk fever that are discussed are: 1) avoiding high potassium forages, 2) adding anions like chloride to the diet to reduce blood and urine pH, 3) ensuring adequate dietary magnesium intake, and 4) potentially reducing dietary calcium pre-calving to stimulate PTH release. The document also raises some unknowns about combining prevention strategies and the need to raise calcium levels when using anionic diets.
4. Mastitis
Retained
Fetal
Membranes
and Metritis
Ketosis/
Fatty Liver
Milk Fever
Displaced Abomasum
DDeeccrreeaassiinngg DDMMII
Around CCaallvviinngg
Lameness
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
Rumen acidosis
Insufficient Dietary Effective Fiber
5. Normal Blood Calcium Concentration= 9-10 mg/100ml
Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
6. Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
Urine Ca
0.2 - 6 g *
Endogenous
Fecal Loss
5-8 g Ca
7. Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
Urine Ca
0.2 - 6 g *
Lactation- 20-30 g Ca
Colostrum –2.3 g Ca/ L
Milk – 1.1 g Ca / L
Endogenous
Fecal Loss
5-8 g Ca
8. Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
Bone
~ 8 Kg Ca
Bone
Fluid
~ 9
-15 g
Ca *
Osteoclast
recruitment &
activation
Urine Ca
0.2 - 6 g *
Lactation- 20-30 g Ca
Colostrum –2.3 g Ca/ L
Milk – 1.1 g Ca / L
PTH
Endogenous
Fecal Loss
5-8 g Ca
9. Parathyroid Hormone
Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
Bone
~ 8 Kg Ca
Bone
Fluid
~ 9
-15 g
Ca *
Osteoclast
recruitment &
activation
Urine Ca
0.2 - 6 g *
Lactation- 20-30 g Ca
Colostrum –2.3 g Ca/ L
Milk – 1.1 g Ca / L
PTH
Endogenous
Fecal Loss
5-8 g Ca
12. OCL
Ob
Ob
Ocyte
Blood vessel
Marrow
Cavity
H
Bone spicule Figure 50.4
13. Parathyroid Hormone
Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
Bone
~ 8 Kg Ca
Bone
Fluid
~ 9
-15 g
Ca *
Osteoclast
recruitment &
activation
Urine Ca
0.2 - 6 g *
Lactation- 20-30 g Ca
Colostrum –2.3 g Ca/ L
Milk – 1.1 g Ca / L
PTH
Endogenous
Fecal Loss
5-8 g Ca
14.
15. Osteocytic Osteolysis
Ca in bone fluid
surrounding each cell
pumped into blood
Ca++
Section thru compact Bone
16. Parathyroid Hormone
Diet Ca = 45- 150 g**
Passive Ca
Transport
Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
Bone
~ 8 Kg Ca
Bone
Fluid
~ 9
-15 g
Ca *
Osteoclast
recruitment &
activation
Urine Ca
0.2 - 6 g *
Lactation- 20-30 g Ca
Colostrum –2.3 g Ca/ L
Milk – 1.1 g Ca / L
PTH
Endogenous
Fecal Loss
5-8 g Ca
21. Parathyroid Hormone
Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
Bone
~ 8 Kg Ca
Bone
Fluid
~ 9
-15 g
Ca *
Osteoclast
recruitment &
activation
Urine Ca
0.2 - 6 g *
Kidney
25-OH vit D
1,25(OH)2D
Diet Ca = 45- 150 g**
Active Ca
Transport
Passive Ca
Transport
Lactation- 20-30 g Ca
Colostrum –2.3 g Ca/ L
Milk – 1.1 g Ca / L
PTH
Endogenous
Fecal Loss
5-8 g Ca
29. Parathyroid Hormone
Extracellular Ca Pool ~11 g
Serum Ca pool ~ 3.5 g
Bone
~ 8 Kg Ca
Bone
Fluid
~ 9
-15 g
Ca *
Osteoclast
recruitment &
activation
Urine Ca
0.2 - 6 g *
Kidney
25-OH vit D
1,25(OH)2D
Diet Ca = 45- 150 g**
Active Ca
Transport
Passive Ca
Transport
Lactation- 20-30 g Ca
Colostrum –2.3 g Ca/ L
Milk – 1.1 g Ca / L
PTH
Endogenous
Fecal Loss
5-8 g Ca
30. A. pH=7.35
Normal Mg
PTH
Cyclic AMP
Receptor
C. pH=7.35
Hypomagnesemia
PTH
Receptor
B. pH=7.45
Normal Mg
PTH
Receptor
Adenyl
cyclase
complex
Adenyl
cyclase
complex
Adenyl
cyclase
complex
Mg++
Cyclic AMP Cyclic AMP
Mg++
31.
32. 2 Eq of each anion source fed
5.5
6.0
Urine pH
6.5
7.0
7.5
8.0
8.5
HCl
NH4 chloride
Ca chloride
H2SO4
Ca sulfate
Mg sulfate
Elemental Sulfur
33. 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 possible
Enough Chloride to urine pH.
34. 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.
35. 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
36.
37. Interpreting urine pH
Collect ten samples
Scenario 1- average pH = 6.3 + .6
- good shape, compensated metabolic acidosis
Scenario 2-average pH= 7.4 + .5
Add more anion – 0.25 lb increments
Scenario 3 – average pH 5.2 + 0.5
-reduce anion by 0.5 lb
Scenario 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
39. A. pH=7.35
Normal Mg
PTH
Cyclic AMP
Receptor
C. pH=7.35
Hypomagnesemia
PTH
Receptor
B. pH=7.45
Normal Mg
PTH
Receptor
Adenyl
cyclase
complex
Adenyl
cyclase
complex
Adenyl
cyclase
complex
Mg++
Cyclic AMP Cyclic AMP
Mg++
40. 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).
41. Magnesium
Adult 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!
42. 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-calving
Magnesium Oxide – supply Mg and act as rumen
alkalinizer.
- my experience low Mg = primary cause of mid-lactation
milk fevers
43. 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.
44. MMiillkk FFeevveerr PPrreevveennttiioonn
1. 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.
45. MMiillkk FFeevveerr PPrreevveennttiioonn
1. 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!!??
46. MMiillkk FFeevveerr -- UUnnkknnoowwnnss
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?