# Impact of timing of a second colostrum feeding on serum immunoglobulin G dynamics in calves during the first week of life

## TL;DR

Feeding calves a second dose of colostrum earlier (12 hours after birth) improves their early immunity compared to feeding it later (24 hours).

## Contribution

This study shows that early second colostrum feeding enhances initial immunity in calves, while later feeding leads to longer IgG persistence.

## Key findings

- Calves fed colostrum at 12 hours had higher IgG and total protein levels in the first week.
- Calves fed colostrum at 24 hours showed greater IgG persistence despite lower peak levels.
- Early feeding improved passive immunity, while later feeding showed longer IgG duration.

## Abstract

Summary: In this study, all calves received the same high-quality colostrum at birth, followed by either an early second colostrum feeding at 12 or 24 hours postpartum (p.p.). Although serum ?-glutamyl transferase concentrations did not differ between groups, calves receiving the second feeding at 12 hours p.p. reached higher serum immunoglobulin G (IgG) and total protein concentrations throughout the first week of life. These calves also maintained higher circulating IgG levels over time, despite the physiological post-peak decline. In contrast, calves fed the second colostrum meal at 24 hours p.p. showed a greater apparent IgG persistence relative to their lower peak concentrations. Clinical variables and growth were not affected by treatment. Overall, advancing the timing of the second colostrum feeding improves early IgG status, whereas later feeding may result in marginally more persistent IgG profiles. BTM = bulk tank milk. Created in BioRender. Freiherr von Riedheim, M. (2025) https://BioRender.com/o9kf11e.

Summary: In this study, all calves received the same high-quality colostrum at birth, followed by either an early second colostrum feeding at 12 or 24 hours postpartum (p.p.). Although serum ?-glutamyl transferase concentrations did not differ between groups, calves receiving the second feeding at 12 hours p.p. reached higher serum immunoglobulin G (IgG) and total protein concentrations throughout the first week of life. These calves also maintained higher circulating IgG levels over time, despite the physiological post-peak decline. In contrast, calves fed the second colostrum meal at 24 hours p.p. showed a greater apparent IgG persistence relative to their lower peak concentrations. Clinical variables and growth were not affected by treatment. Overall, advancing the timing of the second colostrum feeding improves early IgG status, whereas later feeding may result in marginally more persistent IgG profiles. BTM = bulk tank milk. Created in BioRender. Freiherr von Riedheim, M. (2025) https://BioRender.com/o9kf11e.

•Early colostrum feeding is crucial for successful passive transfer of immunity.•A second colostrum feeding at 24 hours p.p. increased serum IgG by only 4%.•Lower serum IgG was linked to longer apparent persistence of IgG.

Early colostrum feeding is crucial for successful passive transfer of immunity.

A second colostrum feeding at 24 hours p.p. increased serum IgG by only 4%.

Lower serum IgG was linked to longer apparent persistence of IgG.

This study evaluated whether a high-IgG colostrum replacer administered at 24 h postpartum (p.p.) influences IgG absorption in neonatal calves. Twelve Holstein and crossbred calves were assigned to 2 groups: CCT (n = 6) received 2.5 L of colostrum replacer (100 mg IgG/mL) at 4 and 12 h p.p., followed by enriched bulk tank milk at 24 h p.p.; CTC (n = 6) received the same colostrum replacer at 4 and 24 h p.p., with enriched bulk tank milk at 12 h p.p. Enriched bulk tank milk was bulk tank milk supplemented with 27 g/L colostrum replacer, mimicking transition feeding. Serum IgG, total protein, γ-glutamyl transferase, and apparent efficiency of absorption (AEA) were measured. The IgG concentrations and AEA were compared at 24 h p.p. in CCT and on d 2 (32–38 h p.p.) in CTC to reflect the status after the second colostrum feeding in each group. At these time points, CTC calves had lower IgG (16.9 ± 1.1 vs. 23.3 ± 1.8 mg/mL) and AEA (11.7% vs. 16.8%), although IgG persisted longer. These findings clearly highlight the superiority of early colostrum feeding for achieving adequate passive immunity, while also revealing that lower initial IgG concentrations were accompanied by a relatively greater persistence during the first week of life.