It’s well known that fresh cows need a higher dietary cation-anion difference (DCAD) and supplemental potassium to correct potassium imbalances and buffer blood acids. This helps to allow the cow to rapidly increase dry matter intake postpartum and maximize milk and milk component production.
Two recent studies presented at the 2014 American Dairy Science Association Annual Meeting offer additional, compelling evidence of DCAD’s influence on lactating cow performance and health. The data also show that many nutritionists and dairies currently feed rations with insufficient DCAD levels – and are missing opportunities to positively impact productivity and profitability.
A University of Maryland meta-analysis looked at data from 1965 through 2011 to determine if there is a linear response to DCAD over a wide range of studies.
“We examined hundreds of treatments across 44 studies that had been conducted over a long period of time and essentially performed a re-analysis,” explains Dr. Rich Erdman, University of Maryland professor of animal science. “It’s been at least 25 years since the last major review of the research literature. Our confidence level regarding the results is extremely high due to the large dataset.”
Results of this analysis showed a linear response (P less than 0.001) to increasing DCAD levels for a number of key production parameters. For example, each 10-point increase in DCAD increased:
- Milkfat percentage by 0.1 percent
- Milkfat grams per day by 0.35
- Rumen pH by 0.033
- Neutral detergent fiber digestibility by 1.5
- Fat-corrected milk (FCM)/DMI by 0.013
“The first incremental increase in DCAD is probably where you’ll get the most bang for your buck,” Erdman says, adding that it’s currently unknown if there is an upper limit to DCAD’s impact. The results do indicate, however, that a significant number of dairies are missing an opportunity by not increasing DCAD levels, especially in early lactation.
“We have a lot of data to support higher ration DCAD levels and also can conclude that the amount of feed additives used to influence DCAD are likely being fed at insufficient levels in most cases,” he says. “We don’t know that there’s an upper limit at this point, but most herds can increase lactating cow ration DCAD levels as an opportunity to increase milkfat production, for example.”
Focus on feed efficiency
The University of Maryland researchers also conducted follow-up research to 2013 data to determine the optimal dietary DCAD level needed to maximize lactating cow feed efficiency.
- Increasing DCAD from 250 to 400 milliequivalents per 100 grams of dry matter (24 to 40 per 100 g DM) resulted in linear increases in milkfat percentage, FCM and DMI, but an optimal level was not found since the response was a straight line – it just kept going.
- This means individual cows (not groups or herd averages) that are about 100 days in milk (DIM) or later and are producing about 85 pounds of milk would likely optimize their feed efficiency with a DCAD between 300 and 400 meq per kg (30 to 40 meq per 100 g).
- In other words, DCAD should not be a fixed number for all stages of lactation.
The researchers concluded that DCAD can be used to increase feed efficiency to help dairy producers reduce feed costs and improve profitability.
Both studies strongly support feeding lactating cow rations with higher levels of DCAD. “Increasing postpartum ration DCAD levels has a tremendous amount of upside potential that’s not being taken advantage of on many farms,” concludes Erdman. “Look at it as an opportunity to increase cow productivity rather than just a tool to prevent losses.”
Use these five steps to balance high-producing dairy cow rations for DCAD:
1. Analyze forages and byproduct commodity feeds known to vary in DCAD minerals for sodium (Na), potassium (K), chloride (Cl) and sulfur (S) by wet chemistry. Keep in mind that water can contribute additional minerals as well, so test water supplies, too.
2. Remove as many chloride and sulfate salts as possible from the diet. This step alone increases DCAD.
3. Add a potassium carbonate source to achieve a dietary K level of at least 1.7 percent of the total DM during non-heat-stress periods. Increase the amount fed to at least 2 percent of DM just prior to and during heat-stress periods.
4. Adjust DCAD to your target level by adding a sodium buffer. Total dietary sodium can be raised to as much as 0.8 percent of ration DM. This would add the rumen buffering required as well as give you the ability to fine-tune DCAD.
5. Adjust dietary magnesium such that the ratio between K and Mg is between 4-to-1 and 5-to-1. PD
Gene Boomer is manager of field technical services and a nutritionist at Arm & Hammer Animal Nutrition. Contact him by email.
References omitted due to space but are available upon request. Click here to email an editor.
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