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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Ruminant Diseases and Immunology Research » Research » Publications at this Location » Publication #106040
Title: A DIETARY CATION-ANION DIFFERENCE EQUATION BASED ON URINE ACIDIFYING ACTIVITY OF VARIOUS ANIONIC SALTS: IMPLICATIONS FOR PREVENTING MILK FEVER

Author
item Goff, Jesse
item Horst, Ronald

Submitted to: International Conference on Production Diseases in Farm Animals
Publication Type: Abstract Only
Publication Acceptance Date: 8/25/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Metabolic alkalosis reduces tissue responsiveness to PTH, reducing the ability of the cow to maintain Ca homeostasis and increasing the risk of milk fever. Metabolic alkalosis is common because of the high cation content of forages fed to dairy cows. Adding anions to the diet can offset the effect of the high cation forages by inducing a milk metaboli i acidosis which restores the ability to maintain Ca homeostasis. The difference in mEq of dietary cations and anions (DCAD) is expressed as (Na+ + K+) - (Cl- + S--). This equation implies that dietary chloride a sulfate are equipotent in ability to alter acid-base balance of the cow. Using urine pH to monitor effects on acid-base balance, experiments were conducted to test the relative acifying activity of various sulfate and chloride anion sources added to the diet of nonpregnant, nonlactating Jersey cows. Chloride, supplied as hydrochloric acid, proved to have 4 fold the acidifying activity of sulfate, supplied as sulfuric acid. Ca and Mg, ignored by the common DCAD equation, had a small alkalinizing effect when accompanying an anionic salt. Rank of the anion sources tested, from most to least potent urine acidifier, was hydrochloric acid ammonium chloride, Ca chloride, Ca sulfate Mg sulfate and sulfur. These data form the basis for a new DCAD equation, (Na+ + K+ + .15 Ca++ + .15 Mg++) - (Cl- + .25 S-- + .5 P---). This equation suggests that milk fev would be better prevented using chloride salts than sulfate salts and th the alkalinizing activity of dietary Ca and Mg is relatively small. Whi this equation suggests phosphate could be an effective acidifier, increasing dietary phosphate is contraindicated because of direct effect of phosphate on vit D metabolism to actually induce milk fever.