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Feed right to fight calf scour

Calf scour is the main cause of death in young calves. Here, Emma Sargent MVB, ruminant veterinary area manager, MSD Animal Health, gives an overview of feeding young calves, and why getting milk-feeding practices right will pay dividends

Calving season is fast approaching, and a busy few months lie ahead on the farm. Disease outbreaks in the calf shed can be an unwelcome and costly problem. Calf scour is the number one cause of death in young calves, accounting for more than one quarter of all losses in the first month of life. Rotavirus and cryptosporidiosis are the two main culprits, together accounting for over 37 per cent of cases1.

A costly disease

Recent research estimates the economic impact of cryptosporidiosis at €195 per reared dairy heifer, with costs attributable to high mortality rates, increased rearing costs and reduced milk production in the first lactation2. Affected beef calves can weigh up to 34kg, less on average, than their healthy counterparts at six months of age, which translates to losses in direct sales of greater than €200 per calf at current trade. Given the significant long-term impacts that calf scour can have on the efficiency and productivity of our herds, it is wise to adopt a preventative approach to protect our youngstock.

Calf health is a balancing act

Calf health relies on maximising calf immunity while minimising infectious pressure i.e. exposure to disease. It is impossible to eliminate all pathogens on-farm, but good management practices can give your calves the best chance to fight off disease, as well as significantly reducing the build-up of infectious agents in the environment.

Focus on feeding

Pre-weaning nutrition is a critical component of calf health, as it directly influences immune system development, gut maturation, efficacy of scour vaccines and resilience to disease. In addition, feed conversion efficiency (FCE) is at its highest in the first weeks of life, when calves can convert feed into growth exceptionally well – up to one kilogramme of bodyweight for every two kilogrammes of feed. After this early window, FCE falls from roughly 50 per cent to around 36 per cent post‑weaning, and to under 10 per cent by adulthood. Maximising this period of efficiency with high‑quality, high-quantity colostrum and transition milk feeding delivers more growth per litre, builds stronger immunity and gut function, and sets calves up for better health and higher lifetime production. In short, what you feed your calves (and how you feed it) will pay dividends for the rest of their lives.

Colostrum

Colostrum is the first and most important feed for the calf; it contains protective antibodies which are essential for immunity. Each hour after calving, colostrum antibody levels reduce due to the dilution effect of further milk production. The calf’s ability to absorb antibodies also declines, so aim to feed at least three to four litres within two hours of birth. Colostrum quality can be assessed using a Brix refractometer – only colostrum reading above 22 per cent should be used or stored for the first feed. Colostrum management can be monitored by blood sampling healthy calves less than one week of age. Speak to your vet regarding testing.

Transition milk

Prolonged transition milk feeding (milk from the first six milkings) is an area of focus in recent years. Transition milk provides protection at a local level in the gut. Further proven benefits include increased energy intake, increased immunity, reduced antimicrobial use, increased benefit from pre-calving vaccination, improved average daily gain, promotion of gut development, reduced calfhood sickness and death and improved reproductive and lactation outcomes for dairy heifer calves3.

Pre-calving vaccination

Pre-calving vaccination has been successfully used for many years to protect calves against common scour pathogens. These vaccines work by raising specific antibodies in the dam before calving, which are passed to the calf through colostrum and transition milk feeding. For this reason, a high standard of colostrum management, as well as ongoing transition milk feeding, is essential to optimise vaccine efficacy.

MSD Animal Health offers the broadest neonatal calf scour vaccine portfolio, including both Bovilis Rotavec Corona (providing protection against rotavirus, coronavirus and Escherichia coli) as well as Bovilis Cryptium, the vaccine to protect calves against cryptosporidiosis scour. Bovilis Rotavec Corona may be administered as a single dose, three weeks to 12 weeks before calving. When calves are fed colostrum and transition milk for the first two weeks of life, the antibodies have been shown to reduce the incidence and severity of scour and calves also shed less rotavirus and coronavirus4. Bovilis Cryptium may be administered as a two-dose primary course, four to five weeks apart in the three-to-12-week period before calving. When calves are fed colostrum and transition milk for five days, the antibodies have been shown to reduce the clinical signs caused by Cryptosporidium parvum for up to two weeks. A single booster dose is required before all subsequent calvings. Conveniently, Bovilis Rotavec Corona and Bovilis Cryptium can be administered at the same time, at different sites. Speak to your veterinary practitioner to determine the best vaccination protocol for your herd.

Nutritional stress

Underfeeding can be a significant stressor for calves, as they require energy from milk to grow and keep warm. Well-fed calves are also better able to fight disease. Aim to feed a minimum of 15 per cent of the bodyweight of the calf per day in transition milk or good quality milk replacer. Increase amounts being fed by one litre for every 10-degree Celsius drop in temperature below 15 degrees Celsius to avoid energy deficits – a maximum/minimum thermometer in the calf shed is a useful tool to monitor this. Changes in feeding routine can also be a source of stress for young calves: keep time, temperature, volume and concentration of feeds consistent and do not withhold milk from scouring calves for best results.

Hygiene

It is important that colostrum and milk collection and feeding utensils (bucket, bottle, stomach tube, teats, etc.) are kept clean, as contamination here can act as a direct source of infection for the calf, as well as reducing colostrum quality and impacting absorption of antibodies. Fatty buildup on feeding equipment also provides the ideal medium for bacterial growth. Soaking equipment in a dilute peracetic acetic solution helps here, along with regular hot water and detergent scrubs.

Healthy calves grow into productive cows

By focusing on early nutrition and clean feeding practices, you’re not just avoiding disease, you’re investing in the future of your herd. Make colostrum a priority, continue transition milk feeding for as long as possible, keep feeding equipment clean and compliment your efforts with vaccination to give your calves the strong start they deserve.

References

  1. All Island Disease Surveillance Report 2023.
  2. Burger, B. 2025. Cost assessment of cryptosporidiosis in calves. European Buiatrics Conference, Nantes.
  3. Denholm, K. 2024. Benefits of extended colostrum feeding in dairy calves and how to implement it on farm. In Practice, 46: 380-387.
  4. Crouch, CF, Oliver, S & Francis, MJ. 2001. Serological, colostral and milk responses of cows vaccinated with a single dose of a combined vaccine against rotavirus, coronavirus and Escherichia coli F5 (K99). The Veterinary Record, 149(4), 105-108.
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