Systematic review and meta-analysis of biomarkers measured in colostrum and transition milk of beef and dairy cows following maternal dietary supplementation during the dry period.
Systematic Review
Maternal nutrition during the dry period impacts colostrum quality, as well as cow and calf health. Despite the potential of biomarkers, in evaluating preventive interventions, their systematic identification remains limited. The objective of this study is to synthesize and identify biomarkers in colostrum and transition milk and, quantify the variation in response to dietary supplementation during the dry period. A comprehensive literature search was conducted across animal sciences interfaces, including studies from 1949 to 2024. Eligible studies focused on cows receiving dietary supplementation during late pregnancy measuring biomarkers in colostrum and transition milk. Study quality was assessed using a risk of bias tool. We identified 70 studies, all on experimental farms. The overall quality of the evidence was considered good, with 41 % of the studies had a low risk of bias. However, almost all studies lacked a plausible rationale for biomarkers selection. A total of 47 distinct biomarkers were identified, and categorized into biomarkers of dietary exposure (n = 38; e.g., lipids), health (n = 47; e.g., SCC), and status (e.g., protein). To explore the variation of colostrum IgG concentration in response to dry period supplementation, a random-effects meta-analysis was performed on 22 studies, including 19 in dairy cattle and 3 in beef cattle. Despite non-explicit pathways, we found a significant mean difference of 8.7 g/L of IgG between the treatment and control groups. In conclusion, in order to improve the selection of biomarkers in the longitudinal studies, we recommend to reflect on the supposed causal pathway. The link between exposure and health can be documented with appropriate biomarkers available in colostrum and milk matrices.
