Negative and Positive DCAD and Why It’s Important
The dietary cation-anion difference (DCAD) is determined by the charge balance of major cations (sodium and potassium) and anions (sulfur and chloride) in the ration. The original manipulation of DCAD in dairy cows in the 1970s was to reduce milk fever cases.
Feeding a negative DCAD diet has been known to prevent milk fever in transition cows. The negative DCAD is used to create a mild metabolic acidosis, which the animal will need to counter by promoting bone mobilization to maintain electrical neutrality of the blood, since bone acts as a buffer against excessive acidity. During the bone mobilization, Ca is released, along with increased intestinal absorption from the diet, therefore preparing the animal for the suddenly increased Ca demand for milk production once she calves.
In comparison, we have the opposite goal once the cow has freshened. The diet DCAD level should be increased to positive DCAD after parturition because a low DCAD diet may negatively affect feed intake, dietary fiber digestibility, as well as lactation performance. Although DCAD has not been as heavy of a focus for lactating cows as close-up dry cows, literature suggest that DCAD level has significant effects on intake, milk production and composition, digestion, and feed conversion efficiency in lactating dairy cows. A recent meta-analysis found that a 100 mEq/kg increase in DCAD resulted in respective increases of 0.10%, 36 g/d, 0.032 pH units, 1.5% NDF digestibility, and 0.013 FCM/DMI units in lactating cows (Iwaniuk and Erdman, 2015).
Lactating cows, early-lactation in particular, may need more potassium in the diet (thus higher DCAD), because the normal metabolism after calving tends towards acidosis. The diet with a positive DCAD tends to buffer the rumen and raise the ruminal pH, and neutralize the acids that build up in the blood of the animal, thus decreasing the incidence of rumen acidosis. A
DCAD in the range of 30 to 40 mEq/100g DM would be optimal for early lactation cows. An effective way to increase diet DCAD is by adding sodium bicarbonate (NaHCO3) and potassium carbonate (K2CO3).
In conclusion, DCAD value of a diet is an important indicator for whether a diet is properly balanced depending on the physiological and nutritional needs of the dairy cows. Origination LLC manufactures proprietary DCAD products, K-Carb Plus (positive DCAD) for lactating cows and MegAnion (negative DCAD) for transition dry cows in both bags and totes. Let us be a trusted partner for your DCAD needs. Please reach out to your salesperson for more information or contact us at email@example.com.
Fei Sun, PhD, PAS
Dairy Product Technical Manager, Origination LLC.
Iwaniuk, M. E. and R. A. Erdman. 2015. Intake, milk production, ruminal, and feed efficiency responses to dietary cation-anion difference by lactating dairy cows. J Dairy Sci 98:8973-8985.