Colostrum management, calf health, and what the latest research means for your farm

The preweaning period is the riskiest time in a dairy calf’s life. Disease and death are most concentrated in these first weeks, and the consequences reach far beyond what’s visible at the time. Early-life illness doesn’t just create short-term costs — it fundamentally changes what that animal becomes.

Calves that experience illness before weaning don’t just cost more to raise. Research consistently shows they grow slower, convert feed less efficiently, produce less milk as adults, get sick more often, are harder to treat, and are significantly more likely to be culled or die prematurely. The economic and welfare implications are compounding, farm-wide, and often invisible until the damage is already done.

When we assess calf programs, there is rarely one glaring failure. More often, it’s a series of small oversights — an inconsistent colostrum volume here, a timing gap there that accumulate into poor outcomes. This is the signal that calf health management must shift from reactive treatment toward proactive prevention. Calfhood health is not a youngstock issue. It is a lifetime profitability issue.

New Research Quantifies the Problem

A recently published study from the University of Guelph (Edwards et al., 2026) provides some of the clearest farm-level evidence to date on what drives preweaning illness in dairy calves. Researchers followed 2,349 Holstein calves from birth to 56 days of age across 9 commercial dairy farms in Ontario, Canada. Farm-recorded health data were analyzed alongside birth weight, colostrum feeding records (number, volume, and quality of feedings), calving ease, and birth date. Blood sampling and thoracic ultrasound were used to detect both clinically apparent and subclinical disease.

The findings were striking:

• 61% of calves experienced at least one health event before weaning
• 23% were treated for diarrhea; 48% were treated for respiratory disease
• More than 50% had lung consolidation on ultrasound — often with no outward signs of illness
• 3.2% of calves died before 56 days of age, with a median age at death of 19 days

The presence of subclinical lung consolidation in over half of calves is particularly important for producers and veterinarians to internalize. These calves are not visibly sick, they are not being treated, and yet structural lung damage is occurring — damage that will silently reduce respiratory capacity, feed efficiency, and productivity for the rest of that animal’s life. Ultrasound screening reveals a disease burden that farm records alone will never capture.

What Made the Difference: Season and Passive Immunity

Season of birth was associated with the incidence of neonatal calf diarrhea, bovine respiratory disease, lung consolidation, and mortality. Additionally, excellent transfer of passive immunity was associated with lower odds of BRD, lung consolidation, and mortality.

Season of calving is a real and meaningful risk factor, but it is largely outside a producer’s control. It will vary based on region, climate, and barn design. Transfer of passive immunity (TPI), however, is the most important controllable factor influencing calf health, survival, and future productivity — and it remains an area where most farms have room to improve.

In this study, calves with good or excellent TPI:

• Had fewer cases of bovine respiratory disease (BRD)
• Showed significantly less lung damage on ultrasound
• Had lower preweaning death loss

While this study did not find a statistically significant link between poor TPI and increased treatment for diarrhea, this is likely a function of study size. Larger population studies — including Dubrovsky et al. (2019) — have consistently demonstrated that relationship. The absence of a finding is not the absence of an effect.

Why Colostrum Is Still the Most Important Tool You Have

A newborn calf is born without functional circulating immunoglobulins due to the structure of the bovine placenta. From the moment of birth, that calf is immunologically vulnerable until colostrum-derived antibodies are absorbed. Colostrum is not a box to tick — it is the calf’s first functional feed and first line of immune defense.

The 4 Qs of colostrum management — Quick, Quantity, Quality, Squeaky Clean — are well established, but this research reinforces a critical fifth:

QUANTIFY.

Getting colostrum into calves is necessary but not sufficient. Knowing whether calves are actually absorbing enough antibodies to achieve meaningful protection is what separates a colostrum program that exists from one that works.

The gold standard for measuring this is serum immunoglobulin G concentration (g IgG/L serum) tested in calves between 24 and 48 hours of age. Lombard et al. (2020) established the benchmark tiers — poor, fair, good, and excellent — that are now widely used to assess passive transfer status and predict disease risk. These thresholds give farms a measurable, repeatable standard to work toward.

The target: ≥70% of tested calves achieving good (18–24.9 g IgG/L) or excellent (≥25 g IgG/L) passive transfer. Hitting this benchmark means your colostrum program is not merely adequate — it is optimized for calf health, survival, and long-term productivity.

Regular testing also gives farms something invaluable: the ability to detect when something changes. A shift in colostrum quality, a new person feeding calves, a change in timing — all of these will show up in passive transfer results before they show up in your treatment records.

Practical Takeaways for Veterinarians and Producers

Every farm is different. Genetics, barn design, calving management, housing, nutrition, and staffing all shape calf outcomes. But the evidence from Edwards et al. and the broader literature is consistent: no matter what else varies, colostrum management remains the single most modifiable lever for improving preweaning health.

Key action points:

1. Feed colostrum within 1–2 hours of birth. Gut closure begins rapidly; timing directly affects IgG absorption efficiency.
2. Feed adequate volume. Current evidence supports feeding 8.5–10% of birth body weight at the first feeding to reliably achieve excellent TPI.
3. Test colostrum quality. Use a Brix refractometer — target ≥25% Brix for fresh colostrum, ≥50 g IgG/L.
4. Keep it clean. Bacterial contamination in colostrum directly impairs IgG absorption. Total plate counts should be <100,000 CFU/mL; coliform counts <10,000 CFU/mL.
5. Test your calves. Serum total protein via refractometer (target ≥8.4 g/dL) between 24–48 hours is a practical, low-cost proxy for IgG status. Aim for ≥70% of calves in the good-to-excellent range.
6. Consider ultrasound screening. The prevalence of subclinical lung consolidation found in this study (>50%) suggests farms may be significantly underestimating their respiratory disease burden. Incorporating thoracic ultrasound into calf health assessments provides a more complete picture.

The Bottom Line

This research from the University of Guelph does not overturn what we know — it sharpens it. Transfer of passive immunity remains the strongest modifiable predictor of whether a calf will get sick, how severely, and whether it will survive. Season matters, but we can’t change the calendar. Colostrum management is where every farm, regardless of size or system, can make a measurable difference.

The question is no longer whether colostrum matters. It’s whether your program is working well enough and understanding you can’t manage what you don’t measure.