Tech Seminar #02 – New Recommendations on Passive Immunity
This presentation was prepared in 2020 as Calf Note #217 and was adapted to Tech Seminar #02.
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Summary
In Tech Seminar #02 (Calf Note #217), Dr. Jim Quigley reviews new consensus recommendations on passive immunity in dairy calves, based on a forthcoming Journal of Dairy Science manuscript developed by a panel of calf health experts. Traditionally, passive transfer has been evaluated using a simple cutoff: failure of passive transfer (FPT) at serum IgG <10 g/L and successful passive transfer (SPT) at ≥10 g/L. While this approach significantly reduced calf mortality over the past decades, it did not meaningfully reduce overall morbidity. Reanalysis of 2014 NAHMS data showed that risk of disease and death declines progressively as serum IgG increases, prompting new, more refined herd-level targets that move beyond a simple “pass/fail” model.
The new recommendations emphasize improving overall immunity distribution within the herd—not just avoiding FPT. Higher IgG concentrations are associated with lower mortality and, importantly, lower morbidity in a largely linear fashion. Achieving these goals requires improved colostrum management (quality, quantity, and timing) and routine herd-level monitoring through blood sampling programs, often using serum Brix as a practical proxy for IgG. By shifting from minimum standards to higher performance targets, producers can improve calf health, reduce treatment costs, and enhance long-term productivity.
Take-Away Points:
Implement routine blood sampling (often via serum Brix) to monitor herd-level immunity and drive continuous improvement.
Move beyond “FPT vs. SPT” — immunity exists on a spectrum, and higher IgG means lower disease risk.
New herd-level targets:
- 40% ≥25 g/L
- 30% 18–24.9 g/L
- 20% 10–17.9 g/L
- ≤10% <10 g/L
Mortality declines as IgG increases; morbidity declines even more consistently.
Improve colostrum management: feed more, feed high-quality colostrum, and feed it earlier.