Dairy producers know calcium metabolism in their cows is important prior to calving to help avoid a nutrient deficiency or milk fever. Now, a new study from the University of Illinois shows that cows benefit from even more calcium than what has long been the industry standard recommendation.
"We are saying that you need to go to -20 milliequivalents and up to 2% of dietary dry matter for calcium (in negative DCAD diets)," explains Phil Cardoso, associate professor in the Department of Animal Sciences, in a news release. DCAD stands for dietary cation-anion difference.
Traditionally, producers using a negative DCAD strategy acidify a cow’s diet by taking it to only -5 milliequivalents and not adding calcium or by adding it at only 1% of dietary dry matter.
During the study, Cardoso’s team fed 76 multiparous Holstein cows one of three diets in the month before calving. These were: a control, non-acidified DCAD diet with no added calcium; an acidified DCAD diet (-24 milliequivalents per 100 grams of dry matter) with no added calcium; and an acidified DCAD diet (-24 milliequivalents) with added calcium at 2% of dietary dry matter. The DCAD formulation was mixed with typical forages and corn silage in prepartum diets.
After calving, all cows were switched to a typical postpartum diet with 1% of dietary dry-matter calcium.The researchers then monitored changes in the blood, uterus, ovaries, and pregnancy status at two weeks and four weeks post-calving.
"There was a tendency for cows fed the negative DCAD + calcium diet to get pregnant at a higher rate than cows fed the control diet, but we need to test that in a larger population to be sure of that result," Cardoso reports.
Research shows increased calcium use also lessens the rates of uterine infection and improves cows’ speed-of-return to ovulation.
Cows fed the calcium-added diet also had more favorable disease-fighting antioxidants in the blood and more glands in the uterine lining, which keep the uterus clean and produce hormones that can kick-start ovulation. "That could be why we saw better pregnancy rates," Cardoso says.
Either way, he says the research outcome validates that a negative DCAD diet with added calcium can help improve herd health and future pregnancy outcomes.