The results of a year-long, large-scale study feeding negative DCAD diets to prepartum cows on commercial dairy farms in Canada are in. Feeding a negative DCAD diet for 21 days prepartum significantly improves cow health and boosts milk production. These benefits more than pay for the cost of feeding the anionic supplement.
University of Guelph researchers (Serrenho et al., 2021a & Serrenho et al., 2021b) completed the study on 4 commercial dairy farms in southwest Ontario. All farms had free-stall barns, and each had one dry cow pen enrolled in the study. Cows were moved to the close-up dry pen about 21 days before calving. Using a pen-level randomized design, pens switched every 3 months between control and treatment diets. Farm personnel were blind to which protocol the cows were on. Dry cows on treatment received a negative DCAD diet (-108 mEq/kg of dry matter) using SoyChlor. Cows on the control diet received a positive DCAD diet (+105 mEq/kg of DM).
“The goal of the negative DCAD diet was to create a slight compensated metabolic acidosis with a urine pH between 6.0 to 6.5,” explains Stephen LeBlanc, senior project leader, veterinarian and professor at the Ontario Veterinary College at the University of Guelph. “This slight acidosis allows cows to respond more quickly to the drop in blood calcium that occurs at calving.”
Research has shown that this drop in blood calcium is not bad for the cow as long as it is not excessive or prolonged. A quick return to normal calcium homeostasis is important for cow health and productivity, which is how negative DCAD diets help give cows a smoother transition.
A total of 1,086 cows were included in the final analysis of clinical outcomes and milk production. Urine pH averaged 6.3 for cows on treatment (negative DCAD diet) and 8.1 for cows on the control diet. Both multiparous cows and first-calf heifers were used in the study, and possible effects of parity and body condition on treatment were checked. The majority of effects from feeding a negative DCAD diet prepartum were seen in multiparous cows. Significant effects include:
Greater milk production (7.0 and 5.5 lbs/day, respectively) by multiparous cows on their first and second monthly test days. Energy-corrected milk was 5 lbs/day greater on the first test day.
Less milk fever in over-conditioned (≥ 3.75 BCS) multiparous cows: 1.8% vs. 13%.
Fewer multiparous cows with 2 or more disease events during the transition period: 13.9% vs. 22.5%.
Greater pregnancy rate in multiparous cows, with the percentage of multiparous cows pregnant at first A.I. increased: 42% vs. 32%.
Less culling. Percentage of multiparous cows removed from the herd by 305 days in milk was reduced: 21.3% vs. 31.7%.
Displaced abomasum incidence was reduced in all cows: 1.7% vs. 3.6%.
Increased the number of days for first-lactation cows to become pregnant by 21 days.
In terms of practical application, LeBlanc and team recommend a targeted approach to feeding negative DCAD diets to multiparous cows whenever possible.
A 3:1 Return
Decades of research and on-farm use have proven the biological benefits of negative DCAD diets, but some still question the economics of feeding an anionic supplement. The cost/benefit of using any anionic supplement will vary by farm, region and country, explains Tim Brown, director of technical support for SoyChlor. By using the data from this recent large-scale study, combined with a reasonable estimate of milk price in the U.S. and the cost of health events as modeled by Liang et al. (2017), Brown calculated a conservative cost-benefit relationship for feeding the negative DCAD diet used in the research. Only results that were statistically significant (P ≤ 0.05) were considered in the economic evaluation.
During the study, SoyChlor was fed at a rate of approximately 2 lbs/cow/day to achieve a target urine pH between 6.0 and 6.5. In the U.S., SoyChlor was estimated to cost about 40 cents/lb. For the 21-day prepartum period, the purchase cost of SoyChlor was about $17/cow. However, since SoyChlor also contains 20% true protein from canola meal and bypass soybean meal (SoyPlus), the true cost of feeding it is less than its purchase cost because you can reduce the amount of other protein and energy supplements needed in the diet. So, when the value of the protein and energy supplied by SoyChlor are accounted for, the actual cost of feeding the anionic supplement for 21 days prepartum would be closer to $12/cow.
Milk production in this study was measured at monthly DHIA tests. Prepartum nutrition did not affect milk production of first-lactation cows. However, multiparous cows fed SoyChlor prepartum produced 7.0 lbs/day and 5.5 lbs/day more actual milk on the first and second test days, respectively. Using the median days of milk production of 27 days and 38 days for first and second test days, respectively, each treated multiparous cow produced an additional 398 lbs of milk.
There was also a difference in milk components. While milk protein percentage was the same for all cows; milk fat percentage on the first test day was lower (3.7% vs. 3.9%) and tended to be lower at the second test (3.3% vs. 3.4%) for all treated cows. But greater milk production from multiparous cows fed negative DCAD resulted in an additional 0.09 lbs/day of milk fat on both test days and an additional 0.22 and 0.16 lbs/day of milk protein on the first and second test days, respectively. However, since treated first-lactation cows did not have increased milk production, they produced less milk fat, 0.12 and 0.08 lbs/day on the first and second test days, respectively. Using milk component pricing information from Dairy Farmers of America for December 2020 of $0.35/cwt, $1.54/pound and $3.03/pound for milk volume, fat and protein, respectively, the net extra value of milk resulting from the negative DCAD prepartum nutrition becomes $28.99. In this study, the increase in milk production from multiparous cows generates a return that is twice the cost of feeding SoyChlor to all of the cows in the close-up pen.
Now let’s look at health events. In the Serrenho research, milk fever incidence for over-conditioned multiparous cows was reduced (1.8% vs. 13%) by feeding a negative DCAD diet prepartum. With 30% of multiparous cows with BCS ≥ 3.75 as in the study, the benefit in this subset of the herd equals 2 fewer milk fever cases for every 100 cows and heifers that calved. Using Liang’s modeled milk fever cost (minus milk loss) of $240 per case, a savings of $480 can be attributed to the negative DCAD diet.
Feeding a negative DCAD ration prepartum also cut the incidence of displaced abomasum for all cows by nearly half. Again, using Liang’s modeled disease cost (minus milk loss), that’s an additional benefit from feeding a negative DCAD diet of $620 per 100 cows and heifers that calved.
For heifers, feeding a negative DCAD diet prepartum had another negative; an additional 21 days to become pregnant during their first lactation. First-parity cows comprised 33% of the study. Using an estimated cost of $1 per additional day open, this would require a subtraction of $693 from the values in this 100-cow example. Despite the negative results for first parity cows, the benefits of feeding SoyChlor to multiparous cows prepartum are compelling.
Take a moment to think about the cost and benefits of feeding SoyChlor in this study. Just the extra milk produced by multiparous cows was enough to pay for the negative DCAD diet for all cows and first-calf heifers in the close-up pen by a 2 to 1 margin. Add in the value of fewer milk fevers and fewer displaced abomasa, and the return from feeding SoyChlor rises to nearly 3 to 1. When you put any kind of dollar value on the additional benefits of keeping 10% more mature cows for another lactation, treating fewer cows for multiple health issues and having a higher percentage of mature cows becoming pregnant on the first insemination, the economic benefits of feeding SoyChlor cannot be denied.