Research Summary - 4
Haptoglobin, milk yield, reproduction, and herd removal: Evaluating the impact of calcium supplementation in early lactation dairy cows
| Date/Time: |
9/13/2025
14:45
|
| Author: |
Kathryn Bach |
| Clinic: |
Cornell University |
| City, State, ZIP: |
Ithaca, NY 14853 |
Julia Poggi, BS
1
;
Jackson A. Seminara, BS
2
;
Kathryn D. Bach, MS, VMD, PhD
2
;
Jessica A. A. McArt, DVM, PhD, DAVBP (Dairy Practice)
2
;
1College of Agriculture and Life Sciences, Cornell University, Ithaca, NY, 14853
2Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853
Introduction:
Elevated inflammatory biomarkers early postpartum have been associated with negative downstream events, but treatments to reduce the impact of excessive inflammation remain lacking. Oral calcium supplementation is commonly used to improve lactational outcomes despite inconsistent research supporting its application. We evaluated whether oral calcium supplementation to multiparous dairy cows at 2 and 3 d in milk (DIM) would differentially impact outcomes of cows of varying inflammatory statuses at 2 DIM, assessed using serum haptoglobin concentrations. We hypothesized that cows with elevated haptoglobin would have increased average daily milk yield through 15 wk of lactation, reduced time to pregnancy, and increased time to herd removal after calcium supplementation compared to less inflamed cows.
Materials and methods:
We based our analysis on a previous field trial in which 535 multiparous Holstein cows from 4 commercial dairy farms in NY were randomized to 2 postpartum treatment groups: 1) 43 g oral calcium bolus administered at 2 and 3 DIM (n = 269), or 2) no bolus control (n = 266). Haptoglobin concentrations were measured from 2 DIM stored serum samples, and average daily milk yield for the first 15 wk of lactation, breeding outcomes within 100 days of the voluntary waiting period, and herd removal data were collected from farm records.
For the milk yield outcome, we created linear mixed models using the fixed effects of haptoglobin concentration, parity group (2, ≥3), treatment group, farm, time, a quadratic haptoglobin term, and biologically relevant 2- and 3-way interactions as well as the random effect of cow. A backwards stepwise elimination process was used to test and remove any variables where P > 0.1. We stratified results by parity group, given its importance in the model. For the time to pregnancy and time to herd removal outcomes, we created Cox proportional hazards models using the same variables noted above. Outcomes were calculated from the final models for an average cow at low (LO = 0.4 g/L) or high (HI = 1.1 g/L) haptoglobin concentrations.
Results:
Data from 535 cows were used including n = 219 parity 2 and n = 316 parity ≥3 cows. On average, across 15 wk postpartum, LO cows supplemented with oral calcium did not differ in milk yield compared to control cows in either parity group 2 or ≥3 (both P > 0.1). There was evidence that parity 2 cows with HI inflammatory status had a reduced mean milk yield when supplemented with oral calcium (control = 47.2 kg/d, 95% CI = 45.1 to 49.3 kg/d; treatment = 44.7 kg/d, 95% CI = 42.3 to 47.0 kg/d; P = 0.1), whereas HI cows of parity ≥3 supplemented with oral calcium produced more milk (control = 45.9 kg/d, 95% CI = 43.8 to 48.0 kg/d; treatment = 49.0 kg/d, 95% CI = 47.4 to 50.6 kg/d; P = 0.02). An average LO cow supplemented with calcium was no more likely to get pregnant at any time within 100 days following the end of the voluntary waiting period than a control cow [hazard ratio (HR) = 0.9, 95% CI = 0.7 to 1.0; P = 0.6], whereas an average HI cow supplemented with calcium was 30% more likely to get pregnant at any point during that time (HR = 1.3, 95% CI = 1.0 to 1.7; P = 0.02). An average LO cow supplemented with calcium had comparable hazard of herd removal to a control cow (HR = 0.8, 95% CI = 0.5 to 1.4; P = 0.5), whereas an average HI cow supplemented with calcium was 50% less likely to be removed from the herd (HR = 0.5, 95% CI = 0.3 to 1.0; P = 0.04).
Significance:
Our findings suggest that oral calcium administration at 2 and 3 DIM to cows with elevated inflammation improves milk yield in parity ≥3 cows across the first 15 wk of lactation but might impair milk yields in parity 2 cows. Interestingly, this treatment improved pregnancy and herd removal outcomes for cows in both parity groups. Although on-farm assessment of inflammatory status remains a challenge, oral calcium administration to overly inflamed cows has the potential to ameliorate consequences associated with excessive postpartum inflammation.
