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The objective of this study was to evaluate the associations of serum markers for systemic inflammation, liver, mineral, and energy status, and blood neutrophil counts with the function of circulating neutrophils in postpartum dairy cows. Blood samples were collected from 21 healthy Holstein cows at 5, 10, 14, and 21 d postpartum. Serum samples were used to measure concentrations of total calcium, phosphorus, magnesium, total protein, albumin, globulin, cholesterol, urea, glucose, gamma-glutamyl transferase, aspartate aminotransferase, glutamate dehydrogenase, haptoglobin (Hp), β-hydroxybutyrate, non-esterified fatty acids (NEFA), and insulin-like growth factor-1. The shift of percentage of activated neutrophils for phagocytosis (PPC) and oxidative burst (POB) and the median fluorescence intensity (MFI) for PC (MFIPC), OB (MFIOB), and endocytic and proteolytic degradation measured via DQ-ovalbumin (MFIDQ) were evaluated using flow cytometry. Mixed linear regression models were used to assess the associations of serum concentrations of metabolites and blood neutrophil counts with each neutrophil function assay outcome accounting for d postpartum, parity, and body condition score. Pearson correlation tests (r) were used to describe the relationships of metabolites and neutrophil counts with neutrophil function assays that were significant in the regression models. Greater serum concentrations of Hp were associated with lesser OB function (POB and MFIOB; r = -0.2 for both), but greater PPC and MFIDQ (r = 0.3 for both). Greater serum NEFA and cholesterol were associated with lesser (r = -0.3) and greater (r = 0.2) POB function, respectively. Blood neutrophil counts were associated with PPC (r = -0.2) and MFIDQ (r = -0.3). At 5 d postpartum, greater serum total protein was associated with greater OB function (POB and MFIOB; r = 0.4 for both). Other markers were not associated with neutrophil function. Some metabolic and inflammatory markers in healthy postpartum dairy cows were associated with circulating neutrophil function. However, these associations only explained a small proportion of the variance in neutrophil function. Serum Hp concentration was most associated with neutrophil function changes but had opposite directions of association with OB- and PC-related functions. Future studies should focus on understanding the mechanisms by which Hp and other metabolic indicators affect neutrophil function in healthy and diseased postpartum dairy cows., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Systemic inflammation (SI) is increasingly studied in several species because it may be central in many metabolic disturbances and be a risk factor for clinical disease. This proof-of-concept study evaluated the effects of the anti-inflammatory drug meloxicam on markers of SI and energy metabolism, polymorphonuclear neutrophil (PMN) function, and endometritis in clinically healthy postpartum dairy cows. Cows received meloxicam (0.5 mg/kg of body weight; n = 20) once daily for 4 days (10–13 days postpartum) or were untreated (n = 22). Blood samples were collected −7, 1, 3, 5, 7, 10, 11, 12, 13, 14, 18, 21, 28, and 35 days relative to calving to measure serum concentrations of metabolic and inflammatory markers. Function of peripheral blood PMN were evaluated at 5, 10, 14, and 21, and proportion of PMN in endometrial cytology were performed at 5, 10, 14, 21, 28 and 35 days postpartum. Meloxicam decreased serum haptoglobin from the second until the last day of treatment, and improved indicators of energy metabolism (lesser β-hydroxybutyrate and greater insulin-like growth factor-1 during treatment, and greater glucose at the end of treatment than control cows). This improved PMN function at 14 days postpartum, but the endometrial inflammatory status was not affected. [ABSTRACT FROM AUTHOR]

Our objectives were to evaluate the effect of the form of supplementary trace minerals—inorganic salts (STM: Co, Cu, Mn, and Zn sulfates and Na selenite) or organic (OTM: Co, Cu, Mn, Zn proteinates, and selenized yeast)—fed at 100% of recommended levels in both pre- and postpartum diets on in vitro phagocytic activity of neutrophils, and in vivo IgG responses to an ovalbumin challenge during the transition period. In addition, we investigated the associations of these immunological responses with incidence of postpartum clinical diseases and the dynamic changes of metabolic markers during the transition period. Pregnant heifers and cows (n = 273) were enrolled at 45 ± 3 d before expected calving, blocked by parity and body condition score, and allocated randomly to STM or OTM supplementation. Cows in both treatments were fed the same diet, except for the form of supplementary trace minerals. Automatic feeding gates were used to assign treatments to individual cows. Blood was collected on d −7 ± 3 and 7 ± 3 relative to calving in a subgroup of cows (n = 131 and 133, respectively) to measure phagocytic activity of neutrophils in vitro using flow cytometry. Subcutaneous immunization with 0.5 mg of chicken egg ovalbumin was performed in a subgroup of cows (n = 181) on d −45, −21, and 3 relative to calving. Concentration of anti-ovalbumin IgG in serum was measured by ELISA on d −45, −21, 3, 7, and 21. Trace mineral concentrations in blood were measured by inductively coupled plasma mass spectrometry on d −45, −21, −7, 0, 7, and 21 relative to calving. Selected metabolites were measured on d −21, −10, −3, 0, 3, 7, 10, 14, and 21 relative to calving. Treatment did not affect the percentage of neutrophils performing phagocytosis on d −7 or 7 but the median fluorescence intensity of phagocytosis on d 7 was greater for OTM than STM. We found no differences between treatments in the level of anti-ovalbumin IgG in serum on any of the sampling days. Changes in neutrophil function from prepartum to postpartum were associated with incidence of postpartum clinical disease, postpartum feed intake and milk production, concentrations of Ca, K, Se, Mn, Co, and total protein in serum. Immunoglobulin G responses to ovalbumin injections were not associated with incidence of postpartum clinical disease but were associated with body weight, feed intake, energy balance, and concentrations of nonesterified fatty acids, aspartate aminotransferase, gamma-glutamyl transpeptidase, albumin, Na, P, and Cu in serum. In conclusion, replacement of STM by OTM improved one measure of phagocytic capacity of neutrophils in vitro, which was also greater in cows that did not develop postpartum clinical disease. The associations of innate and acquired immune responses with feed intake, energy balance, and circulating concentrations of key macro and micronutrients reinforce the importance of nutritional management for the health of dairy cows during the transition period. [ABSTRACT FROM AUTHOR]