It’s a lot easier to put together any dairy ration when multiple studies form consistent conclusions on some of the most important details. And this is exactly what’s happening with prepartum ration recommendations when balancing for negative DCAD.

The latest research aligns on many key points, including optimum dietary calcium levels, as well as targeted urine pH values and DCAD concentrations. The studies also sync with our long-held recommendations by suggesting that:

• Dietary calcium does not need to be elevated and can be as low as 0.4 percent of total dry matter (although we would still recommend a minimum of 0.5 percent to account for any variation in the ingredients).
• Urine pH does not have to be less than 6.0, either for desired outcomes of postpartum productivity and disease reduction or for blood calcium levels that minimize the risk of hypocalcemia.
• Choosing calcium carbonate to increase dietary calcium (or magnesium carbonate to increase dietary magnesium) could result in adding more anions than needed as the carbonate can buffer the urine.

The Journal of Dairy Science published research in August on the effects of negative DCAD and calcium on milk production, blood calcium and health. The conclusion: Cows fed positive DCAD prepartum had higher adverse health score and somatic cell count, and lower blood calcium indicating hypocalcemia, than cows fed negative DCAD.¹

Additionally, two separate presentations at the 2020 American Dairy Science Association conference arrived at similar conclusions. One indicated no difference in feed intake or metabolic acid-base status among dietary calcium carbonate at 0.2%, 1.2% and 1.8%, while the other concluded the target urine pH should be between 6.0-7.0.^2,3

As mentioned, these findings sync with our longstanding recommendation to target DCAD concentration between -8 to -12 mEq/100g and urine pH between 6.0-6.8, and to feed dietary calcium at 0.5 to 0.6 percent of dry matter. We find no rationale for feeding higher calcium levels, since increasing calcium carbonate in diets will end up requiring even greater DCAD concentrations to get desired results.

When sifting through the latest DCAD research, it’s important to remember that behind the data, researchers have one outcome in mind: Put prepartum cows in the best possible position to succeed. That has always been your goal and ours—and it always will be.

To discuss these and other strategies for optimizing your prepartum rations, contact your ARM & HAMMER representative.

1  JDS Aug: Negative dietary cation-anion difference and amount of calcium in prepartum diets: Effects on milk production, blood calcium, and health K. M. Glosson, X. Zhang, S. S. Bascom, A. D. Rowson, Z. Wang, and J. K. Drackley
2 Effects of calcium carbonate supplementation rate on metabolic acid-base status and feed intake of cows with compensated metabolic acidosis. H. Fujan, T. Brown, L. K. Mamedova, B. J. Bradford. 2020 ADSA Abstract. 
3 The association of prepartum urine pH, and plasma total calcium at calving in Holstein dairy cows. P. Melendez, J. Bartolome, C. Roeschmann, B. Soto, A. Arevalos, J. Moller. 2020 ADSA Abstract.