The Sweet Spot for Oral Calcium Supplementation
Many dairies administer calcium boluses to fresh cows in an effort to boost systemic calcium levels and stave off milk fever.
But a group of Cornell University researchers recognized that this “blanket” approach actually has shown little research-confirmed success in increasing milk production and minimizing adverse health events in fresh cows. Pointing to recent research that reductions in blood calcium at 4 days in milk produce more negative outcomes than low blood calcium at 0 and 24 hours postpartum, they developed a study to evaluate an adjusted approach to oral calcium supplementation.
In the study, published recently in the Journal of Dairy Science, they hypothesized that delaying oral calcium bolus administration to 2 and 3 days postpartum (compared to standard administration at 0 and 24 hours postpartum) would result in improved milk production, decreased disease incidence, and improved blood calcium in the early postpartum period.
The study included data from Holstein cows from 4 commercial New York dairies. Each of the dairies milked at least 1,000 cows 3 times a day; fed a TMR and prepartum DCAD diet; and used DairyComp 305 for herd recordkeeping, including daily milk weights. In total, 998 cows were enrolled First-calf heifers were not included in the study; all cows enrolled were parity 2 and older.
Treatments included: (a) a non-treated control group with no calcium supplementation (343 cows); (b) a 43-gram oral calcium bolus administered at 0 and 1 day postpartum (330 cows); and (c) a 43-gram oral calcium bolus administered at days 3 and 4 postpartum (325 cows).
Milk production and disease events were monitored via DairyComp 305 records from each herd. Blood calcium levels were measured by analyzing blood samples collected at 1 and 4 days in milk from all enrolled cows.
Overall, the researchers found no significant difference between treatment groups for milk production, health events, or blood calcium concentration. However, they did uncover a significant difference in milk yield when data was broken out by parity. Parity 3 cows produced significantly more milk in weeks 5 and 10 of lactation than parity 2 or parity 4+ cows, when they received the oral calcium supplement on days 2 and 3 postpartum.
Interestingly, those parity 3 cows showed no significant change in blood calcium levels compared to their cohorts, leading to researchers to believe that they channeled the supplemental calcium to the mammary gland to support additional milk production, rather than to restore blood calcium concentrations.
Conversely, cows at parity 4 and greater showed no significant change in milk production, even though their blood calcium concentrations were lower for the parity 4+ cows in the day 2 and 3 treatment group.
The initial hypothesis that delaying oral calcium supplementation would improve milk production, disease incidence and blood calcium levels across the board in the early postpartum period proved to be false.
However, the researchers concluded that it could be beneficial to target specific cohorts of cows with prophylactic oral calcium. In parity 3 cows, delaying the treatment until days 2 and 3 postpartum was, indeed, more effective in boosting milk production.
Furthermore, they said the varying responses revealed in previous studies of oral calcium supplementation administered at days 0 and 1 postpartum could be due to the varying nature of calcium dynamics in the early lactation period.
