Understanding DCAD Diets
As calving approaches, it’s time to consider the role of a DCAD diet in your calving herd. If you’re unsure how to go about it, putting it together can feel a bit intimidating. However, doing it right can reduce incidences of severe animal health issues such as milk fever, improve future production and save you money.
But first, what is a DCAD diet?
DCAD stands for Dietary Cation – Anion Difference.
Positively charged ions, called cations, act to increase the pH levels of a cow’s blood, making it alkaline. This can have a positive impact on milk production in lactating cows. Potassium (K) and sodium (Na) are cations.
Negatively charged ions known as anions, reduce pH levels in the blood, making it more acidic. This makes it less likely for a cow to get milk fever because the ability to mobilise stored calcium (Ca) is increased. Chloride (Cl) and sulphur (S) are anions.
Why is a DCAD diet important?
A DCAD diet is important because it can help to reduce milk fever, subclinical hypocalcemia and the incidence of displaced abomasum in newly calved cows.
Milk fever is a metabolic disorder that usually occurs at or around calving time. High producers and older cows are more susceptible.
It occurs as a result of severe hypocalcemia. Around calving, the demand for calcium in a cow’s body increases steeply. As a result, either calcium absorption from the gut is increased or the excess calcium is drawn from the bones of the animal. When the animal still fails to receive adequate calcium levels by these means, milk fever develops.
Milk fever can be fatal within 24 hours. Even if the cow recovers, it can impact her milk production going forward and puts her at increased risk of mastitis and other animal health issues.
How to formulate a DCAD diet
To feed your herd optimally according to a DCAD diet, it may in some instances be optimal to remove the herd from pasture four weeks prior to calving and offer a low-potassium forage instead. In addition, to increase chloride and sulphur you can supplement with anionic salts.
The equation to calculate your DCAD is: (sodium + potassium) – (chloride + sulphur)
Starting around four weeks before calving, you should aim for a DCAD of approximately -50 milli-equivalents (mEq)/kg DM.
After calving, you will need a DCAD of between 200 and 250 mEq/kgDM to keep the herd healthy and reducing the incidence of milk fever.
Also, remember that while you can certainly calculate your DCAD values yourself, it can be very helpful to talk to your nutritionist or farm consultant about getting your DCAD diet right, because an imbalance can severely impact animal health and business profitability.
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Planning and feeding out a DCAD diet is an excellent way to reduce the stress of calving. It will lead to better outcomes in terms of animal health, profitability, milk production and staff wellbeing, so it’s worth the effort to get it right!