Discipline: calf rearing; Keywords: dry cow, dry period, nutrition, IgG, weight loss.
Weight loss of cows during the dry period has several consequences, mostly associated with reproduction and subsequent lactation. What is not generally considered is the success of colostrum production and its quality. This formed the basis of the study by the authors cited below.
The authors performed a study on 95 cows and their offspring on a pasture-based dairy farm in the coastal region. The data collected included weight changes during the dry period, colostrum immunoglobulin G (IgG) and calf serum at 24 to 48 hours after birth. Colostrum and serum IgG concentrations were measured using radial immune diffusion and colostrum was regarded as having adequate IgG concentration if the amount was equal or more than 50 g per litre. Calf serum IgG concentration of equal to or more that 10 g per litre was considered an adequate transfer of passive immunity.
Results showed that the median colostrum quality for cows with weight loss during the dry period was 23.1 g per litre (9.0 to 108) compared with 61.9 g per litre (10.9 to 200) in cows without weight loss. The median serum IgG of calves from cows with weight loss was 9.9 g per litre (0.5 to 44.6) compared with 14.0 g per litre (0.5 to 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 (p = 0.3). 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, but this may be due to large variation.
It was concluded that 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.
R. Mulder, G.T. Fosgate, T. Tshuma & D.C. Lourens., 2018. The effect of cow-level factors on colostrum quality, passive immunity and health of neonatal calves in a pasture-based dairy operation.