The Causes and Implications of Subclinical Hypocalcemia
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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.
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The Causes and Implications of Subclinical Hypocalcemia
- 1. Hypocalcemia! It’s Not Just Milk Fever Anymore!!! Jesse Goff Iowa State University
- 2. Incidence of hypocalcemia in USA confinement herds 12 10 dl) Normal mg/8 Sub-clinical 25% (Ca 6 4 Milk Fever 0.7% 2 0 Lactation # 54% 2% 0 1 2 ≥3 53% 5%
- 3. 0.90 0.85 Ca < 8.0 mg/dl Ca ≥ 8.0 mg/dl mM) 0.80 0.75 (NEFA 0.70 0.65 0.60 0.55 0.50 Lactation 1st 2nd ≥3rd
- 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
- 10. Trabecular Compact Compact A B Figure 50.5
- 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
- 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
- 17. Passive Transport of Ca Across Intestine Ca++ Ca++ Ca++ Ca++ Ca++Ca++ Ca++ Ca++
- 18. Ca++ Ca++ Passive Transport of Ca Ca++ Ca++ Ca++Ca++ Ca++ Ca++
- 19. Ca++ Ca++ Passive Transport of Ca Ca++ Ca++ Ca++ Ca++ Ca++ Ca++
- 20. Ca++ Ca++ Passive Transport of Ca Ca++ Ca++ Ca++ Ca++ Ca++ 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
- 23. Vitamin D-dependent Active Transport of Ca Ca++ Ca++ Ca++ VDR Ca++ 1,25-vitD
- 24. Vitamin D-dependent Active Transport of Ca Ca++ Ca++ Ca++ VDR-1,25-vitD Ca++ 1,25-vitD
- 25. Vitamin D-dependent Active Transport of Ca Ca++ CaBP Ca++ Ca- ATPase pump Ca++ Ca++ VDR-1,25-vitD TRPV-6
- 26. Vitamin D-dependent Active Transport of Ca Ca++ CaBP Ca++ Ca++ -CaBP Ca ATPase pump Ca++ Ca++ Ca++
- 27. Vitamin D-dependent Active Transport of Ca Ca++-CaBP Ca -ATPas e Pump Ca++ Ca++ Ca++
- 28. Vitamin D-dependent Active Transport of Ca CaBP Ca -ATPas e Pump Ca++ Ca++ Ca++ Ca++ 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++
- 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
- 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
- 38. 400 350 300 250 200 150 DCAD 2.5 2.0 % of DM 1.5 1.0 0.5 0.0 Control 50 Potassium Calcium Chloride 100 150 DCAD Chloride (lbs/acre)
- 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?