When Prevention Pays Off
It is now well-known that a properly formulated and managed negative DCAD diet is still the best solution to counteract hypocalcemia phenomena.
As Jesse Goff (Emeritus Professor and Coordinator of the Veterinary Medicine Program at Iowa State University) states, intravenous calcium treatment for a cow has become an increasingly rare event in modern dairy farms. However, this metabolic disorder is still a significant problem; in fact, 50% of multiparous cows develop subclinical hypocalcemia, and nearly 3% of these cows require treatment for milk fever. This has a considerable impact on farm profits.
In this article, we will review some studies by Professor Goff, delving into how a partially negative DCAD diet is a key factor for achieving high performance while maintaining herd health.
The day before calving, a cow needs about 20 grams of dietary calcium for maintenance and fetal development, whereas on the day of calving, the same cow requires approximately 52 grams of this macroelement.
An additional 32 grams of calcium are needed to produce colostrum and prevent hypocalcemia. The endocrine system of cows, based on parathyroid hormone (PTH), signals the body to restore calcium homeostasis; consequently, the kidneys stop excreting calcium in the urine, vitamin D is activated and improves the absorption of dietary calcium, and bones release calcium into the bloodstream.
In cows fed an alkaline diet, blood pH, and consequently urine pH, is elevated (urine pH > 7.50), which means that bone and renal tissues are less sensitive to PTH, and many cows cannot mobilize the additional 32 grams of calcium needed and develop hypocalcemia.
Conversely, when cows are fed an acidogenic diet, they enter a state of mild metabolic acidosis (compensated metabolic acidosis) that increases tissue responsiveness to PTH signals. This is why acidified cows can immediately release more calcium from their bones into the bloodstream compared to non-acidified cows; it also accelerates the absorption of dietary calcium.
Properly acidified cows generally mobilize the calcium needed to meet the additional 32 grams required by colostrum and milk production the day after calving. The DCAD level of the diet determines blood pH, which is reflected in urine pH. Research has shown that the optimal urine pH is between 6.0 and 6.8 –
“My ideal level is between 6.2 and 6.3,” says Goff. This should be the average value for the examined group, characterized by a low standard deviation. This indicates that there are no selection or feeding competition issues. Dry matter intake varies within a group of cows, and even a difference of just 1 kg can alter urine pH. With a group average urine pH between 6.2 and 6.3, all cows are in a state of compensated metabolic acidosis.
On the other hand, if aiming for a value between 5.5 and 6.0, some cows might be excessively acidified, showing a decrease in intake (since eating less in an extremely acidified diet is the only way cows can avoid over-acidification).
From all the research and on-farm experience to date, “I see no advantage in lowering urine pH below 6.0,” emphasizes Goff. “I don’t want to risk excessively acidifying them and consequently causing them to stop eating”.
Calcium
The amount of dietary calcium provided also affects urine pH, being a cation and therefore alkaline. If a negative DCAD diet is used to produce mild metabolic acidosis and at the same time high levels of dietary calcium are provided in the form of calcium carbonate (exceeding 1% of dry matter in the diet), that extra calcium acts as an antagonist to anions.
When aiming for a urinary pH below 6.0, feeding high levels of calcium in the diet can protect cows from excessive acidification. However, this also means spending more on providing extra calcium that cows do not need, and paying more for additional anions needed to achieve the desired urine pH, says Goff. This cannot be the preferred strategy. Current research recommends a calcium range of 0.7 to 1.0% of dry matter.
In the diets formulated by Prof. Goff, he maintains the calcium level at the lower end of the range, with urine pH between 6.2 and 6.4. “I am still surprised when I visit a farm that does not implement measures for controlling and preventing hypocalcemia,” says Goff.
“Calcium solutions are administered intravenously to cows against milk fever, but there are no proven control measures to prevent hypocalcemia, such as: a negative DCAD diet, adequate space so that all cows can eat simultaneously, good comfort, and excellent cow management.”
What Does an Anionic Diet Cost and What Is Its Economic Return?
When you have a good transition management protocol for dairy cows that includes a negative DCAD diet, it is money well spent.
The return on investment is 3:1, says Goff. Using production data from the meta-analysis by Santos et al. in 2019, acidified cows show an increase in milk production of 1.5 kg/day, or an additional 450 kg of milk per cow for a 305-day lactation. Considering the milk price at the barn of €0.60/kg, this amounts to approximately €270 of additional milk income from cows fed a negative DCAD diet. You might spend up to €85 per cow on prevention and still achieve a 3:1 return.
Anionic supplementation costs between €32 and €40 per cow. Even if a couple of calcium boluses are administered to multiparous cows after calving at €10 each, that’s an additional €20 per cow. The total spent on prevention is €60, with a profit of €190 per multiparous cow. Add the value of better cow health, including fewer puerperal collapses, fewer retained placentas, and displaced abomasums, and it will make the negative DCAD diet a cornerstone of the farm’s nutritional program.
Experts Recommend:
Anion Booster
A blend of sulfate and chloride ions from fermented glutamic acid and soluble from corn fermentation. Its unique drying process gives it a coffee-like aroma. Research indicates that close-up rations should have a difference between cations and anions (DCAD) between -5 and -15 mEq/100 gm of dry matter. ANION BOOSTER helps reduce DCAD to the desired level while maintaining calcium levels in the transition diet at an optimal level.
Cow Dry Plus SE
Supplements the vitamin and trace mineral needs of dry cows and those in pre and post-calving stages. The high intake of essential polyunsaturated fatty acids (omega-3) positively stimulates fertility. Choline and methionine enhance liver activity.
Close Up HA
Mineral feed for dairy cows in the dry period.
PROF. JESSE GOFF
DVM, PhD, Professor and Director of the Veterinary School at Iowa State University, Ames, IA USA
His research has focused primarily on hypocalcemia in cattle and calcium metabolism in many species. In subsequent years, he studied the interaction between the bovine immune system and metabolic diseases around calving. This has led to improvements in hypocalcemia prevention using low DCAD diets and oral calcium therapies to prevent milk fever.
To stay updated on all our news, follow us on Instagram or on Facebook.
