Role of sulfur and chloride in the dietary cation-anion balance equation for lactating dairy cattle.
Ten Holstein cows averaging 120 d in lactation were arranged in replicated 5 x 5 Latin squares with 3-wk periods to evaluate the role of sulfur (S) in the dietary cation-anion balance equation. Diets were based on corn silage in Exp. 1 and sorghum silage in Exp. 2. Supplemental S and chloride (Cl) from the double sulfate of potassium and magnesium and CaCl2 were used to manipulate dietary cation-anion balance from 0 to +30 meq when expressed as meq [(Na + K)-(Cl + S)]/100 g diet DM and from +19 to +49 meq when expressed as meq [(Na + K)-Cl]/100 g diet DM. Blood pH was not affected by cation-anion balance, although both S and Cl supplementation tended to lower pH. Blood HCO3- and urine pH decreased and plasma calcium (Ca) and urinary Ca excretion increased as anion was added to the diet. Milk fat production tended to be increased by the low S supplementation. Dietary Cl and S had similar effects on acid-base status. Therefore, we suggest that S be included with Cl in the dietary cation-anion balance equation for lactating dairy cows as follows: meq [(Na + K)-(Cl + S)]/100 g diet DM. Although response of acid-base status to S and Cl was similar, as more data comparing the acidogenicity of S vs Cl become available, it may be necessary to include a modifying coefficient for S in the equation to adjust for differences between S and Cl in acid-generating potential. This coefficient may be further dependent on the dietary source of S.
Tucker
W B
WB
Anim. Sci. Dept., Oklahoma State University, Stillwater 74078.
Hogue
J F
JF
Waterman
D F
DF
Swenson
T S
TS
Xin
Z
Z
Hemken
R W
RW
Jackson
J A
JA
Adams
G D
GD
Spicer
L J
LJ
D000136:Acid-Base Equilibrium; D000821:Animal Feed; D000818:Animals; D002118:Calcium / Q000097:blood / Q000652:urine; D002417:Cattle / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism* / Q000652:urine; D004435:Eating; D005260:Female; D007774:Lactation / Q000378:metabolism*; D008892:Milk / Q000737:chemistry / Q000378:metabolism; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood / Q000652:urine; D013455:Sulfur / Q000378:metabolism*
D002712:Chlorides; D013455:Sulfur; D012964:Sodium; D011188:Potassium; D002118:Calcium