Our objectives were to evaluate the association of subclinical hypocalcemia (SCH) dynamics with the risk of early lactation disease, removal, and milk production. We conducted a prospective observational cohort study in 407 Holstein cows in 2 dairy herds in New York. Cows were stratified by parity group (144 primiparous, 263 multiparous) and classified into 1 of 4 groups based on postpartum plasma Ca concentrations previously associated with improved milk production or increased risk of disease: normocalcemic (NC; primiparous [Ca] >2.15 mmol/L at 1 and 2 d in milk, n = 67; multiparous [Ca] >1.77 at 1 d in milk and 2.20 mmol/L at 4 d in milk, n = 109); transient SCH (tSCH; primiparous [Ca] ≤2.15 at 1 d in milk and >2.15 mmol/L at 2 d in milk, n = 25; multiparous [Ca] ≤1.77 at 1 d in milk and >2.20 mmol/L at 4 d in milk, n = 50); persistent SCH (pSCH; primiparous [Ca] ≤2.15 mmol/L at 1 and 2 d in milk, n = 33; multiparous [Ca] ≤1.77 at 1 d in milk and ≤2.20 mmol/L at 4 d in milk, n = 34); or delayed SCH (dSCH; primiparous [Ca] >2.15 at 1 d in milk and ≤2.15 mmol/L at 2 d in milk, n = 19; multiparous [Ca] >1.77 at 1 d in milk and ≤2.20 mmol/L at 4 d in milk, n = 70). Evaluated outcomes were development of an adverse event [hyperketonemia (blood β-hydroxybutyrate concentration ≥1.2 mmol/L at 3, 5, 7, or 10 d in milk), metritis, displaced abomasum, or herd removal in the first 60 d in milk] and average milk yield per day across the first 10 wk of lactation. Multivariable Poisson regression was used to analyze the adverse event outcome and generalized linear mixed models for milk yield analysis. Primiparous cows with tSCH were no more likely to have an adverse event than NC cows [risk ratio = 1.3; 95% confidence interval (CI) = 0.5 to 3.2], whereas multiparous cows tended to have a higher risk for an adverse event than NC cows (risk ratio = 1.4; 95% CI = 0.9 to 2.1). However, pSCH cows were 4.1 (95% CI = 2.1 to 7.9, primiparous) and 1.8 (95% CI = 1.2 to 2.7, multiparous) times more likely, and dSCH cows 3.2 (95% CI = 1.5 to 7.0, primiparous) and 1.9 (95% CI = 1.3 to 2.6, multiparous) times more likely, to have an adverse event than NC cows. Primiparous and multiparous cows with tSCH made more milk per day than NC, pSCH, or dSCH cows across the first 10 wk of lactation. Primiparous cows averaged 28.5 ± 0.7, 31.9 ± 1.1, 29.7 ± 0.9, and 28.7 ± 1.2 kg/d, and multiparous cows averaged 44.6 ± 0.7, 49.1 ± 1.1, 46.4 ± 1.3, and 41.4 ± 0.9 kg/d for NC, tSCH, pSCH, and dSCH cows, respectively. Our results suggest that cows with tSCH adapt well to early lactation, develop fewer disease or removal events than pSCH or dSCH cows, and make more milk than NC, pSCH, or dSCH cows. Cows with pSCH or dSCH, regardless of parity group, are at an increased risk for early lactation disease or removal events.

Our objectives were to perform a proof-of-concept study to assess the association of a prolonged inflammatory state (based on a continually elevated haptoglobin concentration at the end of the first week after parturition) with mineral, protein, and energy balance markers in the first 2 wk after parturition, and milk production in the first 60 d of lactation in clinically healthy cows. We conducted a cohort study in 1 herd in west Texas that was milking Jersey and Jersey-Holstein crosses. Only multiparous Jersey cows were eligible for enrollment. Cows were classified as having or not having elevated haptoglobin concentrations based on plasma concentrations evaluated on d 4 and 7 postpartum. We used median concentrations of haptoglobin in the reference population (i.e., before the exclusion of cows diagnosed with clinical diseases) as the limits for categorizing cows into 2 groups: cows with plasma haptoglobin concentrations greater than the median values on both d 4 (0.49 g/L) and 7 (0.35 g/L) had continually elevated haptoglobin (with eHp); and cows with plasma haptoglobin concentrations lower than or equal to the median values of the reference population on d 4 or 7 did not have continually elevated haptoglobin (without eHp). Next, cows with clinical diseases in the first 2 wk of the postpartum period were excluded, so that 233 cows remained for the final analyses. Evaluated outcomes were average daily milk production across the first 60 d of lactation, plasma Ca, Mg, and glucose concentrations on d 1, 2, 3, 4, 5, 7, 10, and 14 postpartum, and β-hydroxybutyrate (BHB), nonesterified fatty acids (NEFA), fructosamine, albumin, urea, and creatinine concentrations on d 3, 5, 7, 10, and 14 postpartum. Rectal temperatures measured on d 4, 7, and 10 postpartum were also analyzed. We performed statistical analyses using linear mixed models while accounting for the repeated effect of sampling time (plasma analytes and rectal temperature models) and weekly milk test (milk production model). Cows with eHp had lower plasma Ca concentrations in the first 2 wk after calving, but no differences in Mg, BHB, NEFA, glucose, or rectal temperatures compared to cows without eHp. Cows with eHp had lower plasma fructosamine, albumin, and urea concentrations in a time-dependent manner. They also had lower milk production (2.3 kg/d less than cows without eHp in the first 60 DIM). Our study demonstrated that 25% of cows without clinical disorders in the first 2 wk after parturition had continually elevated haptoglobin concentrations at d 7 after parturition relative to d 4, suggestive of a prolonged, low-grade systemic inflammatory state. More observational studies are needed to more fully characterize the duration of prolonged postpartum subclinical inflammation in cows without clinical diseases, as well as its long-term effects, and to evaluate the use of other potential markers of systemic inflammation to describe this disorder.

Our objectives were to examine the stability of (1) serum and plasma total calcium (tCa) after delayed separation of bovine whole blood stored at 4°C, and (2) frozen serum and plasma tCa stored at -80°C. Whole blood was collected from 19 cows into vacutainer tubes (Becton Dickinson, Franklin Lakes, NJ) containing no additives (serum) or lithium heparin (plasma). Baseline tCa concentrations (0-h tCa) were determined on serum and plasma harvested within 2 h of blood collection. To evaluate the effect of prolonged whole blood storage at 4°C, serum and plasma were harvested from samples after 6, 24, 48, 72 h, and 7 and 14 d of storage. For evaluation of the stability of frozen serum and plasma stored at -80°C, samples were stored for 7 d and 1, 3, 6, and 12 mo. The median 0-h tCa concentration for serum and plasma was 2.25 mmol/L (range: 1.58 to 2.60 mmol/L) and 2.28 mmol/L (range: 1.60 to 2.65 mmol/L), respectively. The average difference in tCa from 0-h samples ranged from -0.02 to 0.03 mmol/L for all samples stored at either 4 or -80°C. The median within-cow variability for whole blood samples stored at 4°C was 1.1 and 1.0% for serum and plasma, respectively, and for serum and plasma stored at -80°C was 1.1 and 1.3%, respectively. When whole blood was stored at 4°C, no differences in serum or plasma tCa concentrations were observed across the evaluated time points as compared with 0-h concentrations. Similarly, frozen serum and plasma stored at -80°C remained stable up to 12 mo. Therefore, our findings show that whole blood samples may be stored for at least 14 d at 4°C in vacutainer tubes containing no additives or lithium heparin without biologically important changes in tCa concentrations beyond expected analytical variation. Additionally, serum or plasma may be stored at -80°C for up to 12 mo with no effect on tCa concentrations.

Summary: Proposed mechanisms linking (1) systemic inflammation during endotoxemia (i.e., presence of lipopolysaccharide in the bloodstream) to hypocalcemia, and (2) systemic inflammation during a sterile inflammatory response to hypocalcemia. Of note, hypocalcemia in the context of this review is defined as a state of significantly reduced blood Ca concentration when Ca concentrations are compared with healthy cows within the same age and stage of lactation (i.e., subclinical hypocalcemia). The reduction of the Ca set-point is defined as the extracellular Ca concentration at which secretion of parathyroid hormone is half-maximal. CaSR = Ca sensing receptor; 25(OH)D3 = 25-hydroxyvitamin D₃; 1,25(OH)2D = 1,25-dihydroxyvitamin D₃; ROS = reactive oxygen species. Figure created with BioRender.com.

Unregulated, systemic inflammation negatively impacts health and production in dairy cows. Soluble mediators and platelets have been studied for their expansive role in mediating inflammation. Our objectives were to compare the plasma oxylipin and endocannabinoid profiles, and the platelet and plasma proteomic profiles of healthy cows to cows experiencing elevated systemic inflammation as indicated by plasma haptoglobin (Hp) concentrations. Postpartum cows at 3 DIM with plasma Hp concentrations \(\:\ge\:\) 0.50 g/L and no clinical disease were enrolled into the high-inflammation group (n = 8). Cows with plasma Hp concentrations \(\:\le\:\) 0.1 g/L and no clinical disease were enrolled into the low-inflammation group (n = 8). Targeted lipidomic analysis revealed differences in the plasma oxylipin and endocannabinoid profile between high- and low-inflammation cows. Cows in the high-inflammation group had increased plasma concentrations of the oxylipins 9(S)-HpOTrE, 9(S)-HOTrE, 13(S)-HpOTrE, and 9,10-EpOME, and the endocannabinoid anandamide. In-depth proteomic analysis of platelets between the high- and low-inflammation groups revealed significant differences in protein categories related to platelet granule release and cellular iron uptake. Proteomic outputs from plasma revealed 24 proteins to be different between high and low-inflammation groups, including proteins involved in autophagy and immune mediation. Together, our results indicate that cows experiencing an exacerbated systemic inflammatory response in the postpartum may have impaired disease resistance, and platelets could be contributors to their inflammatory state.

Research exploring specific associations of markers of negative energy balance and Ca in postpartum Jersey cows with lactation performance is lacking. Our objectives were to evaluate the associations of total Ca concentration (tCa) measured at 1 through 3 d in milk (DIM) and free fatty acids (FFA), β-hydroxybutyrate (BHB), and glucose measured at 3 DIM with (1) the risk of multiparous Jersey cows being diagnosed with early-lactation diseases and culling, (2) milk production in the first 9 wk of lactation, and (3) the risk of pregnancy in the first 150 DIM. A cohort study was performed in 1 dairy herd in Texas. Multivariable Poisson regression models were built to evaluate the association of the analytes of interest with the risks of early-lactation diseases and culling in the first 60 DIM (i.e., binary outcomes). Linear mixed models were used to evaluate the association of the analytes of interest with milk production within the first 9 wk of lactation, and a Cox proportional hazard model was built to assess the risk of pregnancy within 150 DIM. A total of 380 cows were used in the final analyses. Total Ca measured at 1 through 3 DIM was not associated with the risk of metritis. Cows with increased FFA and BHB had an increased risk of being diagnosed with metritis and clinical mastitis, respectively. Increased concentrations of glucose and FFA and decreased tCa at 3 DIM were associated with an increased risk of culling. Reduced tCa concentrations at 1 DIM (≤1.84 mmol/L) and 2 DIM (≤2.04 mmol/L) were associated with increased milk production across the first 9 wk of lactation compared with tCa concentrations above those thresholds. Total Ca was not associated with milk production when assessed at 3 DIM, whereas increased FFA (≥0.37 mmol/L) and decreased glucose (≤2.96 mmol/L) at 3 DIM were associated with increased milk production. None of the metabolites measured were associated with the risk of pregnancy in the first 150 DIM. Our results demonstrate that tCa concentration assessed in the first 3 DIM show temporary associations with milk production and culling in multiparous Jersey cows. Although increased concentration of FFA assessed at 3 DIM was associated with greater milk yield, it was a detrimental factor for the risk of metritis. This study attempted to better elucidate the relationship of tCa, FFA, BHB, and glucose assessed in early postpartum with health and performance of Jersey cows. Based on this study, assessments performed at 3 DIM using tCa concentration ≤1.99 mmol/L for increased risk of early-lactation culling and FFA ≥0.43 mmol/L for increased risk of metritis could be used as starting points. More studies evaluating the dynamics of energy balance markers and tCa in postpartum Jersey cows using a greater number of herds are needed to better inform dairy consultants on critical levels for exacerbated postpartum negative energy balance and subclinical hypocalcemia for the Jersey breed.