Building the future of your herd: Best practice colostrum management

Date published: 12 December 2025

Calf rearing is one of the most valuable investments on your farm, accounting for up to 20% of a dairy farm’s annual production costs. The care, nutrition and management a calf receives in her first few months directly influences lifetime productivity, fertility and health. Having a strategic and well thought out rearing plan, which focuses on key performance indicators, can positively impact not only herd health but also profitability. It typically takes 1.5lactations for a heifer to recoup her rearing cost and so critiquing management practices must be viewed through a long-term economic lens. With the average age at first calving in Northern Ireland at 28.5 months, reducing this to a target age of 24 months will significantly reduce rearing costs as daily costs are accounted for at £2.30 per head per day over 24 months of age. While many factors influence successful calf rearing, the lifetime impact of these decisions begins at birth.

The First Hours

Management during the first few hours of life will have a direct impact on calf immunity and health. There is limited placental transfer of immunity between cows and their calves, meaning that calves do not receive significant amounts of antibodies from the dam during pregnancy and are born with undeveloped immune systems. Reliance of immunity comes from active absorption of immunoglobulin G (IgG) through the gut wall into the bloodstream which is got from colostrum.  Alongside high quality colostrum steps such as disinfecting the navel, housing calves in a clean, dry pen and ensuring timely colostrum intake are simple but effective steps which promote established robust calf health.

When considering colostrum management, following the “Three Q’s” of ‘Quality’, ‘Quantity’ and ‘Quickly’ is an effective way to ensure passive transfer of immunity.

Quality

High quality colostrum contains a minimum of 50g/L IgG. A sample of farm colostrum should be measured each calving season to establish if dry cow management is effective on farm. This can be measured using a refractometer; by cleaning and calibrating using distilled water, then placing a few drops of colostrum onto the refractometer you can look through the eyepiece to see the scale, good quality colostrum will show a reading of a minimum 22% Brix, with lower readings indicating poor quality. The refractometer should be calibrated and cleaned thoroughly after each sample to ensure accurate results. Hygiene also plays an important role, Emma explains that feeding equipment must be cleaned and disinfected after every use, poor hygiene during colostrum collection and feeding introduces pathogenic bacteria while the calf’s immune system is still immature. This can lead to gut inflammation, impaired villi and papillae development and ultimately reduced nutrient absorption. Early-life gut health has a major impact on feed efficiency, growth rates and milk production later in life, calves with well-developed rumen papillae and balanced microbiota tend to have better dry matter intake and conversion efficiency as heifers. 

Where colostrum is tested and produces a result below 22% Brix on a refractometer, it should not be used, poor quality colostrum will increase the risk disease susceptibility and mortality, while also potentially reducing growth rates due to illness and poor nutrient absorption.

Quantity

The quantity of colostrum intake is essential for calf health, supporting optimal growth rates and development of the gastrointestinal tract. It is recommended to feed 4 litres of colostrum (or 10% of the calf’s bodyweight) within two hours of birth and following up with a second feeding of 2 litres within the next 12 hours. 

Quickly

Newborn calves should receive colostrum within two hours of birth as the gut is highly permeable and efficiency of IgG transfer across the gut wall is highest immediately after birth. The rate of IgG absorption is highly time-sensitive, there is a 33% decrease within six hours of birth and continues to fall rapidly over time. By 24 hours after birth the calf’s gut wall loses the ability to absorb these large protein molecules into the bloodstream and becomes ineffective. Do not delay the first feeding or rely on the calf to suckle the dam as this will lead to failure of passive immunity transfer and will increase the calf’s susceptibility to disease and mortality.

Milk feeding routine

Once colostrum feeding is complete, a consistent milk feeding routine should be established. Calves should be fed 10-15% of their initial body weight in milk daily, split into a minimum of 2 feeds per day to reduce digestive stress, with energy intake adjusted for age, weight and temperature. Consistency is key as calves are sensitive to changes, even small variations in milk temperature or concentration will upset digestion and affect growth rates. Fresh water and a palatable, high-quality calf starter should be offered from one week of age to promote early rumen development. Target growth rates are 0.7-0.9kg/day in the pre-weaning phase and it is important to supply sufficient energy in the diet for maintenance, thermoregulation and growth.

Skimmed milk-based and whey-based milk replacers differ in their protein sources, fat content, and digestibility for dairy calves. Skimmed milk replacers use casein-rich proteins derived from whole milk with the fat removed, offering slower digestion and a clot-forming effect in the abomasum, which mimics natural whole milk feeding. They typically contain higher fat levels and are ideal for calves needing sustained energy release. In contrast, whey-based replacers use proteins from the liquid by-product of cheese production, primarily whey protein, which digests faster and supports early rumen development. Whey replacers often have lower fat content and lack fibre but are more cost-effective and suitable for accelerated growth programs. Neither replacer contains fibre inherently, so fibre must be introduced via starter feeds. Whole milk remains the gold standard for digestibility and nutrient balance but poses challenges in consistency, hygiene, cost and disease management, particularly regarding the risks surrounding Johne’s disease transmission. Choosing between replacers depends on calf age, growth targets, farm economics, and feeding systems.

Sustainability benefits

Gold standard calf rearing practices contribute significantly to the sustainability of dairy farming in Northern Ireland. Healthy, fast-growing calves reach breeding age earlier, and improve lifetime productivity. Efficient growth means fewer resources are needed per litre of milk produced, lowering the farm’s carbon footprint. Strong early-life health also reduces antibiotic use and disease losses, improving welfare standards.

Investing in calf rearing is an investment in the future of your herd. By reviewing your management practices on colostrum, hygiene and feeding practices, you will raise healthier, more productive animals while improving sustainability and profitability. Small changes made in early life, lead to lasting benefits – stronger immunity, faster growth and better lifetime performance. Prioritising best practice today builds a resilient, efficient dairy herd for tomorrow.