Understanding and solving colostrum quality challenges

By Dr. Cynthia Miltenburg on behalf of the Bovine Ontario Animal Health Network

It’s essential that calves ingest adequate volumes of high-quality colostrum in the first hours of life to achieve transfer of passive immunity. Testing on-farm Immunoglobulin G (IgG) concentration ensures the volume fed delivers adequate total IgG to the calf. A Brix refractometer can be used to estimate IgG concentration, recognizing that higher values are generally associated with better outcomes. Test results can guide feeding decisions in real time. If the dam’s colostrum does not meet targets, it can be enriched with a colostrum replacer powder or replaced with high-quality frozen, stored colostrum.

Colostrum with ≥50 g/L IgG (approximately 22 per cent Brix) is considered high quality. However, this threshold may not be sufficient in all situations. When feeding three litres at the first feeding, aiming closer to 24 per cent Brix may be necessary to achieve the goal of delivering at least 200 g of IgG. Higher Brix readings reflect substantially greater IgG concentrations – for example, values around 25.8% predict ≥100 g/L IgG. Many producers are therefore targeting higher Brix values and reporting improved transfer of passive immunity, calf health, and performance.

What happens if too many cows are producing colostrum that does not meet quality standards? Individual, seasonal, environmental, nutritional, and management factors can all influence colostrum yield and IgG concentrations. In these cases, a herd-level review might be in order. To guide this process, key factors associated with colostrum quality are reviewed below.

Confirm this is truly a quality problem

The first goal is to confirm it’s a true quality problem, not a measurement error or due to delayed sampling. Questions we would ask are:

• Are Brix readings taken immediately after first harvest? Pooled colostrum from multiple milkings can result in lower readings
• Has the refractometer been calibrated? Distilled water should be used to obtain a reading of 0 per cent on optical refractometers or use the zeroing function for digital refractometers
• If using a colostrometer, is colostrum at the right temperature? These tools require colostrum to be at 22°C to be accurate

Look for patterns in at-risk cows

Reviewing which cows have poor vs. adequate colostrum readings can tell us who is at risk of failing. While individual cow factors, including genetics, may play a role, the goal is to identify any herd-level patterns. Multiparous cows generally produce higher IgG concentrations. If failure is disproportionately affecting primiparous cows, targeted support through nutrition or pen management may be needed. A higher incidence of stillbirths has also been associated with reduced colostrum IgG. Some studies suggest higher colostrum quality in cows delivering male calves or twins, although this finding is inconsistent and may relate more to calf size than sex. Reviewing affected groups can help identify common risk factors.

Assess the season and risk for heat stress

Research shows a complex relationship between season, environmental conditions such as exposure to light and heat stress, and colostrum quality. Several U.S. studies report reduced IgG concentrations during summer months (June to August), but seasonality varies in other global studies. These effects may relate to temperature and humidity or a disruption of hormone signalling. Other colostrum components vary seasonally: fat tends to be higher in spring, protein higher in fall and winter, and lactose tends to be lower in the summer.

Late gestation heat stress affects both the cow and the developing bovine fetus, resulting in lower birth weights, reduced immune function, reduced transfer of passive immunity, and increased disease risk. Regardless of the month on the calendar, where cattle are exposed to heat stress, heat abatement strategies have been shown to influence colostrum production. Cooled cows produce more colostrum with an elevated IgG concentration compared to heat-stressed cows. While reduced feed intake contributes, it does not fully explain colostrum losses, reinforcing the importance of thermal management of dry cows. If poor quality results are linked with seasonal temperatures, review heat abatement in dry cows.

Prepartum management, metabolic status, and nutrition

Shortening the dry period has been shown to reduce colostrum yield, but its effect on IgG concentration is less consistent. To support cows through a successful transition, reviewing the experience of the cow in the dry cow pen, including time there and stocking density, is worthwhile. Management stress likely matters more than exact dry period length.

Over-conditioning may negatively impact colostrum quality. Increasing dietary starch prepartum has been associated with lower IgG concentrations, higher insulin levels, and altered fatty acid profiles. In contrast, fat supplementation appears to have minimal effect. Younger cows may benefit from additional metabolizable protein to support mammary epithelial cell turnover in the dry period, but overall, protein over-supplementation does not seem to be a reliable strategy to improve colostrum quality. Similarly, the evidence for improvements in IgG concentration from specific vitamins or minerals is limited.

An altered metabolic or inflammatory state of cows in late gestation has been linked to reduced colostrum quality. Prepartum blood profiles on cows in the close-up dry period may provide insight on herd-level trends for glucose, albumin, calcium, and indicators of inflammation or reduced liver function. However, these relationships are complex and may reflect broader transition cow challenges, rather than a colostrum-specific issue. As such, results should be interpreted in the wider context of transition cow performance, including health events and milk production outcomes.

Harvest timing and handling

Post-harvest practices can reduce measurable IgG if poorly managed. Delayed collection, particularly when not harvested until six to nine hours post-calving results in dilution of IgG as colostrum transitions to milk. If many samples are just below the 22 per cent Brix cut off, harvest timing may be the root cause.

Colostrum composition varies across individual cows, herds, and seasons. Colostrogenesis begins three to five weeks before calving, emphasizing the importance of supporting cows throughout the dry period, especially during the hot summer months. Improving colostrum quality through prepartum nutrition and management is an achievable goal but closely linked to overall transition cow health. Aim to harvest high-quality colostrum in ≥90 per cent of samples tested. Effective troubleshooting begins with the who, when, and how it was harvested. If you are not meeting your targets, talk to your herd advisors.

Key areas for investigation:

1. Harvest timing and verify first milking
2. Proper refractometer use
3. Parity distribution
4. Heat stress and seasonal management
5. Late gestation metabolic health

References available upon request.

The Bovine Ontario Animal Health Network is a group of veterinarians and specialists working in government, university research and laboratory, and in beef, dairy, and veal practice who meet regularly to monitor and discuss disease trends in Ontario. Our goals are to facilitate coordinated preparedness, disease prevention, early detection, and response to animal health risks in Ontario. For our recent reports or more information visit www.oahn.ca.