New work demonstrates benefits of fully acidified, high-calcium diet

Growing South Dakota
Farm Forum

Dietary Cation-Anion Difference (DCAD) diets have been a component of a strong dry cow program for generations, as producers have sought to optimize blood calcium levels of dairy cows following calving to maximize their herd’s health and milk production. Not all DCAD diets are created equal, however, so a team of researchers, led by Dr. James Drackley of the University of Illinois, recently investigated the effects of feeding three commonly fed prepartum strategies on health and production of early-lactating dairy cows. The findings of this study suggest that minor adjustments to pre-fresh diets can impact cow health and productivity.

New Recommendations for Calcium Intake

Eighty-one Holstein cows were utilized in a three-treatment study and followed through 10 weeks of lactation. The prepartum dietary treatments were:

• a control diet (non-acidogenic, low calcium, 0.40% calcium);

• a fully acidogenic, low-calcium diet (urine pH < 6.0, 0.40% calcium); and,

• a fully acidogenic, high-calcium diet (urine pH < 6.0, 2.00% calcium).

Results of the study demonstrated:

1. Cows fed the control diet (non-DCAD, low-calcium) had lower ionized and total blood calcium concentrations following calving compared to cows fed either of the fully acidogenic diets.

2. Typical of properly formulated negative DCAD diets, prepartum DMI was only slightly reduced in cows fed the fully acidogenic diet with high dietary calcium (1.47% of BW) compared to DMI of cows fed the non-DCAD diet (1.51% of BW).

3. Flux of calcium through the exchangeable calcium pool was significantly increased (as indicated by urinary calcium excretion) in cows fed the fully acidogenic diet with high dietary calcium (11.98 g/d) compared to cows fed either a fully acidogenic low calcium diet (9.49 g/d) or cows fed a non-acidogenic diet (0.94 g/d).

4. Adverse health score (a financially weighted, cumulative aggregate of various health events) was significantly reduced in cows fed fully acidogenic diets compared to cows fed non-acidogenic diets.

“The conclusions from this study reinforce the importance of building a solid foundation for dairy cow success that starts with a properly balanced prepartum acidogenic diet,” says Kristen Glosson, Dairy Technology Manager, Phibro Animal Health Corporation. “Results from this study, as well as many others, reinforce the concept of feeding acidogenic diets to help enhance fresh cow health and milk yield compared to a strategy of feeding a non-acidogenic diet. Feeding a prepartum acidogenic diet is the better choice and a less challenging strategy than feeding a low-calcium prepartum diet, which can be tricky to formulate and to consistently implement.”

Low Urine pH, High Productivity

One of the most significant findings from this study was that cows fed the fully acidogenic diet with high dietary calcium had a significantly greater turnover of the available calcium pool compared to cows fed the fully acidogenic, low-calcium diet. “We’ve known for years that cows fed an acidogenic diet will have an increased turnover rate of the calcium pool compared to cows fed a non-acidogenic diet. By turning over the available calcium pool more frequently, more calcium is made available at the beginning of the peripartum period. The cow is more readily able to adjust for the high demand of calcium beginning with colostrogenesis and through the first few days of lactation. This work demonstrates the additional or additive benefit of feeding high dietary calcium, compared to low dietary calcium, under a program of full acidification,” explains Dr. Ken Zanzalari, Animate® Product Director, Phibro Animal Health Corporation. This recommendation is an adjustment to the existing dogma that prepartum acidogenic diets are most beneficial when dietary calcium is kept low.

Additionally, results of this study demonstrate that feeding a fully acidogenic prepartum diet with high dietary calcium (> 1.6% calcium) does not depress DMI below a fully acidogenic, low- calcium diet.

Zanzalari suggests, “For fully acidogenic diets to be effective, you must feed a source of anions, which is palatable. This will allow you to target and maintain a urine pH range between 5.5 and 6.0. Most sources of anions do not allow you to target and maintain this level of acidification without some negative effects, such as prepartum DMI depression.”

Phibro Animal Health Corporation has invested significant resources to better understand the effects of levels of dietary acidification and calcium on transition cow health and performance, as well as the relationships between them.

“Dairy producers can keep transition-cow productivity high with a low urine pH,” advises Glosson. “Our recommendation of maintaining urine pH between 5.5 and 6.0, together with feeding high dietary calcium levels, may be the best approach to enhancing postpartum blood calcium status. Maintaining blood calcium status helps support transition cow health and performance.”