If you already do a good job with feeding management and monitoring pre-fresh cows, then implementing a moderate negative dietary cation-anion difference (DCAD) diet is just adding some minerals. Cows on a moderate DCAD diet are mildly metabolically acidified with a urine pH of 6 to 7, which gives you a little safety measure if DCAD drift occurs.
Brown tim
Director of Technical Support / Dairy Nutrition Plus

With moderate DCAD, you don’t have to worry about adding a lot more work or more management time to care for the cows. It really is simple, and it works.

Decades of research demonstrate that negative DCAD diets do more than just prevent milk fevers. A recent meta-analysis showed negative DCAD diets improve transition cow health and productivity. Cows fed a negative DCAD diet during the close-up period also have reduced incidence of retained placenta and metritis, and multiparous cows have increased yields of milk and milk components.

How to get started

Step 1: Make the decision

Understand that for best results, you should create a two-group dry cow system – far-off and close-up. And if you have the space to feed close-up first-calf heifers separately, do so. They really don’t benefit from the extra anions, but they do need the extra metabolizable protein (MP) that should be in close-up diets.


For cows to receive the benefit of a moderate DCAD diet, they only need to be mildly acidified for the last 21 days before calving. Research in 2018 showed feeding cows negative DCAD diets for more than 21 days might be detrimental. The study showed cows fed negative DCAD diets for 42 days had reduced milk production, shorter gestations and tended to have more open days.

So while some producers do decide to feed negative DCAD the entire dry period because of space constraints, understand that doing so may be slightly detrimental to milk production. But regardless of duration, moderate DCAD will still reduce the incidence of milk fever and other common health issues during transition. Sometimes compromise is necessary because of limitations with facilities, and that’s OK. Just make the decision with all of the facts in hand.

Step 2: Identify and test forage sources

Make a list of available forage sources, test using wet chemistry analysis and request the DCAD mineral package from the lab you use. When negative DCAD diets are used, the diet is balanced to provide more negative anions than positive cations. This creates a mild compensated metabolic acidosis, which helps the cow absorb more calcium from the gut and pull calcium from bones to meet its calcium needs at calving.

That’s why having a consistent or dedicated supply of low-potassium forage with accurate lab analysis is so important. A change in the mineral content of forage can quickly change the diet DCAD. Wheat straw, corn silage and some warm-season grass hays are generally lower in potassium than alfalfa, oat straw and cool-season grass hay.

Step 3: Talk to your current nutritionist

I can’t stress this enough. Make sure your nutritionist has your best interests in mind. Ask the hard questions.

  • Do you believe the 30-plus years of research and on-farm application that have proven the benefits of negative DCAD diets?

  • Are you willing to help me move forward with my transition cow management?

  • Do you have experience balancing negative DCAD diets?

In order to get good results from a moderate DCAD diet, there are several ration-balancing considerations to tend to. Your nutritionist should be knowledgeable of these and eager to help you. After all, when your cows perform well, the nutritionist looks good.

After the conversation, if you believe your nutritionist is on board, give them the feed inventory with mineral analysis for the forages and ask them to formulate a moderate negative DCAD diet for the close-up cows. A calculated DCAD of -10 milliequivalent (mEq) per 100 grams diet dry matter is a good starting point.

Step 4: Check feeding and cow management

Your feeding management and cow management should be top-notch, whether you do DCAD or not. But implementing a moderate DCAD diet doesn’t add much additional work. It never hurts to review protocols before starting a new project. It also will give you time to share with employees the change you are making, why and give them positive feedback.

For feeding management, examine the TMR, check how closely the feeder follows the mix sheets, confirm scale accuracy and monitor frequency of feed push-up. For cow management, review protocols for pen stocking rates, timing of pen moves, monitoring cows during labor and care of just-fresh cows, including treatment if necessary. Make sure the training for all employees is up-to-date. And check to make sure they keep accurate records.

Step 5: Start feeding a moderate negative DCAD diet and check urine pH

Three days after you start feeding a moderate DCAD diet, check urine pH. The size of your close-up group will determine how many cows’ urine needs to be tested for pH. In larger herds, 10 cows can provide a representative sample. In smaller herds with only a few pre-fresh cows, just spot-check urine pH in a couple of cows.

If the average urine pH is between 6 and 7, congratulations; you’re doing moderate DCAD. If urine pH is a little high, increase the dose of anions a little, and if pH is a little low, vice versa. With some more diluted anionic products, adjusting the anionic supplement rate straight from the bag allows you to adjust acidification level. Once you initially get your urine pH in the right ballpark, move to step 6.

Step 6: Monitor cows

With a moderate DCAD program, there is no need to constantly monitor urine pH. Yes, you need to check it when you first start to make sure cows become mildly metabolically acidified. But once you get cows in that sweet spot with a urine pH of 6 to 7, then you only need to test urine pH after a known change in forage or if you notice something “off” in the cows.

For example, you have a case of milk fever (DCAD drifted higher) or see a drastic reduction in feed consumption (DCAD drifted lower) or notice slow labor and delivery during calving. All are things an astute staff will naturally notice. And while re-testing forages will ultimately help you understand the reason for any DCAD drift, the important thing is to get cows back to a urine pH of 6 to 7.

Step 7: Relax and enjoy the benefits of moderate DCAD

After the initial start-up, there really isn’t extra work to do. Your normal feed intake monitoring and cow observations should alert you if DCAD gets out of bounds. Whenever you start a new forage source, even a different bag or bunker of silage, proactively test to determine mineral content. Adjust the ration if needed.

The beauty of moderate DCAD is the built-in safety factors. If drift occurs – most often from an undetected change in forage mineral content – and cows become more acidified than expected, there is a lot of room before they become overly acidified. With moderate DCAD, there is no need for knee-jerk reactions to a small change in urine pH or to constantly check urine pH. Moderate DCAD is simple.

Weigh the benefits

Moderate DCAD diets reduce the incidence of milk fever, subclinical hypocalcemia, retained placenta and metritis, and result in more milk. On-farm observations confirm mildly acidified cows are healthier, birthing proceeds more rapidly, and calves are born with more vigor and get up to drink colostrum sooner. As a veterinarian in Ireland once told me, “Since starting with moderate DCAD, the cows aren’t lazy at calving anymore.”

Moderate negative DCAD is simple and effective. Isn’t it time you gave it a try? The result could be healthier, more productive transition cows.  end mark

Tim Brown