Changes in biomarkers of metabolic stress during late gestation of dairy cows associated with colostrum volume and immunoglobulin content

ABSTRACT: The objective of this observational study was to compare the metabolic status of dairy cows during the last 6 wk of gestation based on colostrum volume and immunoglobulin content. For this, healthy Holstein cows were randomly selected from 3 commercial herds in Michigan. In each farm, 4 cohorts of 21 cows (1 per season), stratified by parity, were enrolled (n = 228). Cows were blood sampled weekly during the last 6 wk of gestation, and biomarkers related to nutrient utilization, oxidant status, and inflammation were quantified in serum. Cows were milked within 6 h of calving, and the volume of colostrum produced was recorded and an aliquot collected. Concentration of IgG, IgA, and IgM were measured by radial immunodiffusion. Cows were grouped into high or low colostrum producer, high or low IgG, high or low IgA, and high or low IgM. For volume category, we arbitrarily defined 6 L of colostrum (4 L for first and 2 L for second feeding of calves) as the cutoff point, whereas for IgG we used the industry standard of ≥50 g/L. To create groups of low and high IgM or IgA, we used the median of these immunoglobulin as the cutoff point. Colostrum volume was lowest in winter, but no differences were observed among parity groups. Conversely, colostrum IgG concentration was highest in fall and winter, but colostrum IgM was lowest at these seasons. However, colostrum immunoglobulin content only showed a negative weak correlation with volume (Spearman's correlation coefficient < −0.28). Compared with low colostrum producer, high colostrum producer cows had higher concentrations of antioxidant potential and β-hydroxybutyrate, and lower cholesterol and oxidant status index. Cows with high IgG showed higher concentrations of glucose compared with low IgG. Cows with high IgA had higher concentrations of cholesterol, reactive oxygen and nitrogen species, oxidant status index, and total protein, whereas β-hydroxybutyrate and glucose were lower compared with low IgA. Biomarkers of metabolic stress were not significantly different between high IgM and low IgM. Nevertheless, the differences observed did not result in differences in inflammatory status between animals in any of the colostrum variable categories analyzed, suggesting that physiological homeostasis was not disrupted during late gestation in association with the colostrum variables studied. Overall, the great variability observed in colostrum variables suggests that colostrogenesis is a complex and multifactorial process. However, our results suggest that greater availability of antioxidants during late gestation could support the production of higher volumes of colostrum, which needs to be explored in future trials