Effects of replacing inorganic salts of trace minerals with organic trace minerals in the diet of prepartum cows on quality of colostrum and immunity of newborn calves

Our objectives were to evaluate the impact of supplementary trace mineral (TM) form-inorganic salts (STM; Co, Cu, Mn, Zn sulfates, and Na selenite) or organic (OTM; Co, Cu, Mn, Zn proteinates, and selenized yeast)-in the prepartum diet on quantity and quality of colostrum, passive immunity, antioxi-dant biomarkers, cytokine responses to lipopolysac-charide (LPS), health, and growth of newborn calves. Pregnant heifers (n = 100) and cows (n = 173) were enrolled at 45 d before calving, blocked by parity and body condition score, and allocated randomly to STM (50 heifers; 86 cows) or OTM (50 heifers; 87 cows) supplementation. Cows in both treatments were fed the same diet, except for the source of supplementary TM. Within 2 h of calving, dams and calves were sepa-rated, colostrum was harvested, the yield was mea-sured, and a sample was saved for posterior analyses of colostrum quality. A subgroup of calves (n = 68) had a blood sample collected before colostrum feeding. After colostrum feeding, all samples and data collection were limited to 163 calves (STM = 82; OTM = 81) fed 3 L of good quality (Brix% >22) maternal colostrum via nipple bottle minutes after harvesting. Concentration of IgG in colostrum and serum was determined 24 h after colostrum feeding using radial immunodiffusion. Concentration of TM in colostrum and serum were performed by inductively coupled plasma mass spectrometry. Activity of glutathione peroxidase, ferric reducing ability of plasma, and concentration of superoxide dismutase were evaluated in plasma by colo-rimetric assays. Ex vivo whole blood stimulation with LPS was performed on d 7 of life to evaluate cytokine responses in a subgroup of 66 calves. Health events were recorded from birth to weaning, and body weight was recorded at birth (all calves) and on d 30 and 60 (heifers only). Continuous variables were analyzed by ANOVA and binary responses were analyzed by logis -tic regression. Complete replacement of STM by OTM in prepartum diet resulted in greater concentration of Se (461 vs. 543 +/- 7 mu g/g; +/- SEM) but did not alter the concentration or total mass of other TM and IgG in co-lostrum. Female calves of the OTM group had greater concentration of Se in serum at birth (0.23 vs. 0.37 +/- 0.05 mu g/mL), were lighter in weight at birth (40.9 vs. 38.8 +/- 0.6 kg) and weaning (93.2 vs. 89.7 +/- 1.6 kg) than those of the STM group. Maternal treatments did not affect passive immunity or antioxidant biomarkers. On d 7, basal concentrations (log10 of concentration in pg/mL) of IFN gamma (0.70 vs. 0.95 +/- 0.083) and LPS-stimulated concentrations of CC chemokine ligand 2 (CCL2; 2.45 vs. 2.54 +/- 0.026), CC chemokine ligand 3 (CCL3; 2.63 vs. 2.76 +/- 0.038), IL-1 alpha (2.32 vs. 2.49 +/- 0.054), and IL-1 beta (3.62 vs. 3.86 +/- 0.067) were greater in OTM than in STM. Supplementation with OTM in pregnant heifers, but not in pregnant cows, reduced the incidence of preweaning health problems in their calves (36.4 vs. 11.5%). Complete replacement of STM by OTM in the prepartum diet did not cause major changes in colostrum quality, passive immunity, and antioxidant capacity, but increased cytokine and che-mokine responses to LPS on d 7 of life and benefited preweaning health of calves born to primiparous cows.