Assessment of passive immunity transfer in dairy calves using integrated immunological and molecular approaches in a...

In bovine species, the epitheliochorial placenta prevents prenatal transfer of immunoglobulins, rendering calves dependent on colostrum intake for passive immunity. Efficient passive immunity transfer (PIT) is critical for neonatal health, yet conventional assessments primarily focus on immunoglobulin quantification without evaluating structural integrity.

This pilot study aimed to comprehensively evaluate PIT in a cohort of Holstein calves using an integrated approach combining field-based diagnostic tests, quantitative protein assays, and molecular validation techniques.

A total of 13 Holstein cow-calf dyads were initially enrolled in this study. However, two calves were excluded from the longitudinal serum analysis due to mortality. Consequently, the final cohort for the longitudinal assessment comprised 11 calves and their respective dams. Serum samples were collected from the 11 cows during the pre-partum period (3 and 2 weeks before calving, and at parturition) and from the 11 surviving calves at 0, 48, and 72 h postpartum. Immunoglobulin concentrations were assessed using sodium sulfite precipitation and zinc sulfate turbidity (ZST) tests. Protein concentration of the immunoglobulin-enriched fraction was determined using the bicinchoninic acid (BCA) assay. Structural integrity and immunoreactivity were evaluated using SDS-PAGE and Western blotting. Colostrum quality was assessed via density measurement. All subsequent immunological, molecular, and statistical analyses were performed on this final cohort (n = 11).

Maternal IgG concentrations declined progressively approaching parturition. In the neonates, serum IgG levels increased significantly following colostrum ingestion, with 100% of the longitudinally tracked surviving calves (n = 11) successfully surpassing the critical passive immunity transfer threshold (>10 mg/mL) by 48-72 h postpartum. Electrophoretic and immunoblot analyses confirmed the presence and structural integrity of the transferred immunoglobulins. Statistical analysis using a repeated-measures ANOVA revealed a highly significant effect of time on serum immunoglobulin levels (P = 0.001).

The findings suggest adequate passive immunity transfer within the study cohort and highlight the potential value of integrating quantitative and molecular approaches for a more comprehensive assessment of neonatal immune status. Given the exploratory nature of this pilot study and the lack of standardization in colostrum administration, these results provide a foundational model for future, larger-scale investigations into the structural and functional aspects of PIT.