New research from Cornell University demonstrates that blood calcium concentration the first few days after calving is associated with dry matter intake and milk yield.
Veterinarian Jessica McArt’s research team conducted a retrospective analysis of 3 previously reported studies (Leno et al., 2017a, b; and Kerwin et al., 2019) to determine the association between blood calcium concentration/subclinical hypocalcemia status on postpartum dry matter intake and milk yield. Cows were classified by blood total calcium into 1 of 4 subclinical hypocalcemia (SCH) groups based on mean calcium concentrations of cows in the study: Normocalcemic >1.95 mmol/L at 1 DIM and >2.2 mmol/L at 4 DIM; transient SCH ≤1.95 mmol/L at 1 DIM and >2.2 mmol/L at 4 DIM; delayed SCH >1.95 mmol/L at 1 DIM and ≤2.2 mmol/L at 4 DIM; and persistent SCH ≤1.95 mmol/L at 1 DIM and ≤ 2.2 mmol/L at 4 DIM. Of the 78 multiparous Holstein cows used in the analysis, 36% were classified as normocalcemic, 34% as transient SCH, 22% as persistent SCH and 8% as delayed SCH. Results include:
All cows classified as persistent SCH were fed a positive DCAD ration prepartum.
In the 2 weeks leading up to calving DMI steadily decreased but did not differ by SCH group.
At 1 DIM feed intake for persistent SCH cows was already lower than the other 3 groups. At 2 DIM intakes began to increase for normocalcemic and transient SCH cows but intake of delayed SCH cows declined.
Average daily feed intake during the first 21 DIM was as follows: transient SCH, 46.7 lbs; normocalcemic, 45.8 lbs; delayed SCH, 41.0 lbs; and persistent SCH 38.8 lbs.
Transient SCH cows produced the most milk during the first 6 weeks of lactation, averaging 108.0 lbs; normocalcemic cows, 105.4 lbs; persistent SCH, 98.8 lbs; and delayed SCH 92.2 lbs.
Cow that experienced prolonged episodes of SCH also had reduced concentrations of blood magnesium and phosphorus.
The higher levels of DMI for normocalcemic and transient SCH cows combined with greater milk yield and elevated concentrations of blood calcium, magnesium and phosphorus suggest that these cows were able to successfully adapt to the metabolic challenges of lactation.