Mulder, RiaanFosgate, Geoffrey TheodoreTshuma, TakulaLourens, D.C. (Dirk Cornelius)2018-06-142018-06-142018Mulder, R., Fosgate, G.T., Tshuma, T. & Lourens, D.C. 2018, 'The effect of cow-level factors on colostrum quality, passive immunity and health of neonatal calves in a pasture-based dairy operation', Animal Production Science, vol. 58, no. 7, pp. 1225-1232.1836-0939 (print)1836-5787 (online)10.1071/AN16689http://hdl.handle.net/2263/65148A study of 95 cows (19 primiparous and 76 multiparous) and their offspring was performed on a pasture-based dairy in the coastal region of South Africa. Collected data included weight changes during the dry period, colostrum immunoglobulin G (IgG) and calf serum IgG at 24–48 h after birth. Colostrum and serum IgG concentrations were measured using radial immunodiffusion and colostrum was regarded as having adequate IgG concentration if the amount was 50 g/L. Calf serum IgG concentration of 10 g/L was considered an adequate transfer of passive immunity. The median (range in parentheses) colostrum quality for cows with weight loss during the dry period was 23.1 g/L (9.0, 108.1) compared with 61.9 g/L (10.9, 200.0) in cows without weight loss. The median serum IgG of calves from cows with weight loss was 9.9 g/L (0.5, 44.6) compared with 14.0 g/L (0.5, 76.3) in calves from cows that did not lose weight during the dry period. Cows experiencing weight loss were four times more likely to have colostrum with lower concentrations of IgG (OR = 0.25; 95% CI, 0.07–0.88; P = 0.030). Lactation number was also significantly associated with colostrum IgG concentration (P < 0.001), with younger cows tending to have higher IgG concentrations. Failure of passive transfer did not have a significant effect on any calf-health or production variables measured in the study. The effect of dry-cow feeding on colostrum IgG concentration is poorly understood and inadequate pasture management could have an impact on colostrum quality in pasture-based dairy herds.en© CSIRO 2018Dry cowDry periodNutritionWeight lossColostrum qualityPassive immunityHealthNeonatal calvesPasture-based dairyPostprint Article