DCAD Calculator for Dairy Cows
close-up and lactating cow diets.
Work out the dietary cation-anion difference (DCAD) of a ration from its sodium, potassium, chloride and sulfur, and compare it with the usual targets for close-up dry cows and lactating cows.
DCAD (mEq/kg DM)
10 × [(Na ÷ 0.023 + K ÷ 0.039) − (Cl ÷ 0.0355 + S ÷ 0.016)], minerals as % of dry matter.
Result
What DCAD Does
The balance of positive and negative minerals in the diet changes the cow's blood pH and calcium.
Sodium and potassium push DCAD up; chloride and sulfur pull it down. A negative DCAD close-up diet (anionic salts or an anionic product) makes the cow slightly acidic before calving, which helps her mobilise calcium and lowers the risk of milk fever. After calving, a positive DCAD supports intake, milk yield and milk fat.
On an anionic close-up diet, your veterinarian will set a urine pH target and check it. Urine pH is the best sign that the diet is working; the DCAD figure is a starting point.
How to use this calculator
- Choose the diet: close-up dry cows (the last 3 weeks before calving) or lactating cows. This sets the target range shown under the result.
- Enter sodium, potassium, chloride and sulfur for the whole ration, as a percentage of dry matter. If your feed report gives g/kg DM, divide by 10 (12.9 g/kg is 1.29%).
- Read the DCAD figure, the target under it and the message below the boxes.
- Look at the four mineral boxes to see which mineral moves the result most. Change one figure at a time to test an idea before you discuss it with your nutritionist.
Reading the result
DCAD is shown in mEq per kg of dry matter. The usual range used here is −150 to −100 mEq/kg for close-up cows and +250 to +400 mEq/kg for lactating cows. The sodium and potassium boxes are positive and the chloride and sulfur boxes are negative; added together they give the DCAD. Potassium is usually the largest positive figure, so a close-up DCAD that is too high often points to high-potassium forage. A result outside the range is a reason to review the ration with your nutritionist, not to add anionic salts on your own.
Common questions
Where do I get the mineral figures?
From a feed analysis of your forages and concentrates, combined in proportion to how much of each the cows eat. The Pro ration balancer works this out for a whole ration.
Why are calcium and magnesium not in the formula?
This is the common four-mineral DCAD equation (Na + K − Cl − S). Calcium and magnesium are still important for close-up cows; balance them separately with your nutritionist.
My nutritionist gives DCAD in mEq/100 g. How do I compare?
Divide this calculator's result by 10. For example, −120 mEq/kg DM is −12 mEq/100 g DM, and the close-up range of −150 to −100 mEq/kg is −15 to −10 mEq/100 g.
Can I just add anionic salts to bring DCAD down?
Anionic salts taste bitter and can cut feed intake if they are not mixed in well. They work best spread evenly through a mixed ration, with the amount set by your nutritionist and urine pH checked by your vet.
Does this apply to buffaloes?
The chemistry is the same, but the target ranges on this page come from work in dairy cows. Ask your vet and nutritionist before feeding an anionic close-up diet to buffaloes.
Decision support only. Not a substitute for your veterinarian.