Good Veterinary Practices for Managing the Colostral Period in Dairy Calves to Improve Their Immune Competence-A Systematic Review.

Passive transfer of immunoglobulin G (IgG) through colostrum is essential for early immune protection in dairy calves. This systematic review synthesizes the most relevant evidence on colostrum quality, feeding practices, storage methods, and post-feeding assessment. High-quality colostrum (≥50 g/L IgG and low bacterial contamination) can be reliably assessed using Brix refractometry (≥22%) or radial immunodiffusion. Early administration is critical: feeding within 1-2 h after birth maximizes IgG absorption. Providing 8.5-10% of body weight (≈3-4 L) at first feeding, followed by a second feeding within 8-12 h, significantly reduces failure of passive transfer. Pasteurization at 60 °C for 60 min and controlled freezing maintain immunological integrity while reducing microbial load. Monitoring passive immunity using serum total protein (5.0-5.5 g/dL) or serum Brix (8.1-8.5%) offers practical field diagnostics aligned with the IgG ≥ 10 g/L threshold. Integrated colostrum management protocols-combining quality evaluation, timely feeding, hygienic handling, and trained personnel-are essential to improve passive immunity, health, and overall performance of dairy calves.