Calcium dynamics and associated patterns of milk constituents in early lactation multiparous Holsteins

Abstract

Immediately following parturition, physiological demands for calcium increase substantially to support the onset of milk production. As a result, transitioning dairy cows may experi­ence subclinical hypocalcemia (SCH) at some point during early lactation. Cows respond to this homeostatic challenge dynamically, such that serum total calcium concentrations (tCa) at 1 and 4 days in milk (DIM) can be used to classify cows into 4 calcium dynamic groups: normocalcemic (NC: SCH at no DIM), transient (tSCH: SCH at 1 DIM only), delayed (dSCH: SCH at 4 DIM only) and persistent (pSCH: SCH at both 1 and 4 DIM). Identifying cows in the pSCH and dSCH groups is important clinically because these groups are at greater risk of adverse health events compared to the NC and tSCH cows. Our objective was to describe the temporal patterns of milk constituents for cows in each calcium group using Fourier-transform infrared (FTIR) spectroscopic analysis of milk samples. Additionally, we hoped to ascertain whether these methods might be valuable as a diagnostic tool for grouping cows based on calcium dynamics at a clinically useful timepoint.