Choosing the Right Diet for Close-Up Cows

Multiple strategies exist to implement a successful DCAD program for transition cows, and nutrition should be tailored to each specific dairy. A number of factors can impact an individual transition cow’s program in different ways, including:

• Forages available.
• Management level of dairy and capabilities of staff and feeding system to provide consistent mix and delivery of feeds, especially if using an anionic supplement.
• Facilities available for grouping dry cows.
• Number of cows that will calve per month.
• The potential for overcrowding or increased stress during the transition period.

Milk fever, or hypocalcaemia, is bad enough on its own. But it also increases the risk of eight other diseases and is often considered the “gateway” disease process for poor transition performance, according Robert Van Saun, extension veterinarian at Penn State University.

Decades of research have demonstrated the negative effects of milk fever. And it’s not just the clinical milk fever that you have to be concerned with.

Newer studies show that subclinical milk fever can make multiparous cows more vulnerable to disease risk, lower milk production and increase the risk of involuntary culling.

Fortunately, milk fever is highly preventable. When you prevent low blood calcium you also minimize the health problems that often follow.

That’s why it’s important to reframe the action needed. Rather than treating sick cows, it’s critical to prevent the conditions that allow both clinical and subclinical milk fever to occur.

Reducing Prevalence of Milk Fever

A Pennsylvania dairy had milk fever prevalence upwards of 15% in multiparous cows. But blood analysis revealed the prevalence of subclinical hypocalcemia in multiparous cows was greater than 50%.

An investigation showed a change in the forages fed to the dairy’s dry cows. In addition, the dairy was using a mixture of nutritional practices, including a partial DCAD diet and feeding high dietary calcium.

To correct the problem, forages were tested for mineral content. The dietary DCAD was calculated at 0 mEq/kg dry matter, dietary magnesium was increased and dietary calcium was reduced to 0.95%.

After this adjustment, the prevalence of all transition diseases was dramatically reduced—milk fevers declined to less than 5%.

In fact, many nutritionists report they can achieve less than 3% milk fever prevalence and less than 20% subclinical milk fever using negative DCAD diets.

***Every dairy should evaluate their transition

cow program and ask if they can do better.****

DCAD Is Not One-Size-Fits All

For dairies with clinical and subclinical milk fever, research and on-farm use has clearly shown the many benefits of feeding negative DCAD diets to close-up cows, says Van Saun. Three simple nutritional strategies have emerged:

1. Not feeding an anionic supplement, but instead focusing on lowering the DCAD by feeding low potassium and low sodium forages.
   
   Producers in areas that can grow low potassium and low sodium forages may opt for reducing the dietary potassium load, with no anionic supplement.
   
   With this strategy, you should keep the dietary calcium level as low as possible, meaning little or no high-calcium forages, and no calcium supplements.
   
   This results in a calculated DCAD of about +100 mEq/kg of DM, which results in a urine pH of 8.3 to 8.5. This strategy may reduce clinical milk fevers, but subclinical milk fever often remains above desirable levels.
   
   
2. Feeding enough anionic supplement to reduce the calculated DCAD to about zero.
   
   Adding some anionic supplement, sufficient to reduce the calculated DCAD to about 0 mEq/kg DM, should result in a urine pH of about 7.5 and is a good intermediate step in the right direction toward reducing some transition cow issues.
   
   However, recent research by Koszewski and Goff (2018) suggests that transition cows don’t start experiencing benefits from added anions until the urine pH drops below 7.5.
   
   Producers should keep added dietary calcium to a minimum, keep dietary phosphorus at 35 grams/day or less and increase magnesium to 0.45%.
   
   This strategy is a small step that allows producers to try anionic supplements and see some reduction in clinical milk fevers.
   
   
3. Feeding enough anionic supplement to create a negative DCAD diet and induce a state of metabolic acidosis in the cow.
   
   The strategy that yields the most benefits to the cow is feeding an even lower DCAD diet that creates a mild, compensated metabolic acidosis with a urine pH of 6.0 to 6.5.
   
   For this strategy, the calculated DCAD is about -50 to -100 mEq/kg of DM. Between 60 and 120 grams of supplementary calcium per day can be used without negatively impacting feed intake.
   
   In addition, keep phosphorus intake under 35 grams per day and increase magnesium to 0.4 to 0.5%. Urine pH should be checked weekly and DCAD supplementation adjusted if needed.

Each Strategy Is Unique

Each of the three strategies requires a little bit more in terms of labor and management. That’s why it is important to understand the day-to-day requirements, cost and potential benefits of each before you try. Van Saun stresses that producers must stick with the strategy selected to see good results and shouldn’t try to mix the nutritional aspects of two different strategies. 

Work with your veterinarian and nutritionist about which strategy would be best to improve transition cow success on your dairy.

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The above article was originally published in an earlier issue of the Dairy Nutrition Plus newsletter, find it here.