Neonatal calf diarrhea: Understanding and treating a common threat

By Dr. Luiza Stachewski Zakia, University of Guelph

Neonatal calf diarrhea (NCD) is a persistent challenge for dairy producers and calf raisers worldwide. It is one of the most common health issues in young calves, particularly during their first few weeks of life. Diarrhea not only reduces the growth potential of calves but also increases the risk of death, making it a significant concern for both animal welfare and farm profitability.

Effective management of NCD requires understanding its clinical signs, identifying which calves are at risk for severe illness, and deciding when to use treatments like oral electrolytes, antimicrobial drugs (AMD), and non-steroidal anti-inflammatory drugs (NSAIDs). Calves with NCD often experience dehydration, but not all cases are equally severe. A subset of diarrheic calves may develop bacteremia, a condition where bacteria enter the bloodstream, leading to systemic infection. In a recent study from the University of Guelph, 37 per cent of calves with diarrhea were found to be bacteremic. Identifying bacteremic calves is critical, as they require immediate and targeted treatment to prevent severe outcomes.

Recognizing systemic illness and bacteremia

To identify calves with bacteremia, key indicators include scleral injection (redness in the whites of the eyes – Figure 1), sunken eyes despite the calf receiving oral fluids, and an inability to stand. An absent suckle reflex, combined with an increased rectal temperature, also strongly suggests systemic illness. These observable signs allow producers to quickly assess which calves are most at risk and prioritize their care. Laboratory findings can further support clinical observations. The same study showed that bacteremic calves often had lower blood pH (acidosis) and elevated inflammatory markers. While these tests may not be practical for everyday use on farms, they highlight the physiological changes underlying severe diarrhea and reinforce the importance of clinical vigilance.

Timing antimicrobial treatment: Key findings from a randomized trial

One of the most debated aspects of NCD management is when to start AMD treatment. A recent randomized trial conducted by a research group at the University of Guelph compared two approaches: treating calves with AMD at the onset of diarrhea versus only treating if they presented systemic signs of disease, such as scleral injection, increased rectal temperature, dehydration despite oral fluids, absent suckle reflex or inability to stand (Figure 2).

Calves treated with AMD at the first sign of diarrhea did not experience shorter diarrhea duration or improved average daily gain compared to those treated later. Moreover, these calves faced higher risks of mortality. Premature treatment may interfere with the calf’s natural ability to recover, potentially weakening its overall health. On the other hand, delaying treatment until systemic signs proved more effective. This approach ensures that only calves in genuine need receive AMD, reducing unnecessary drug use and helping to combat antimicrobial resistance.

Practical recommendations for producers

1. Monitor closely for clinical signs of systemic illness: Producers should regularly observe calves for signs such as scleral injection, sunken eyes, absent suckle reflex, and increased rectal temperature. These signs indicate the need for immediate veterinary attention.
2. Prioritize hydration and supportive care: For calves with diarrhea but no systemic signs of bacteremia, rehydration and nutritional support should be the first line of treatment. Ensuring the calf maintains hydration and energy levels is often enough for recovery. NSAIDs can also be beneficial in reducing inflammation and improving the calf’s comfort.
3. Use antimicrobial drugs selectively: Not all diarrheic calves require AMD. Reserving AMD for those showing systemic signs reduces the risk of resistance while ensuring effective treatment for calves in need.
4. Collaborate with your veterinarian: Developing a tailored treatment protocol with a veterinarian can help producers make informed decisions about when and how to intervene.

Take home messages

Managing NCD effectively requires balancing prompt action with careful judgment. The decision to treat calves with AMD should not be taken lightly, as unnecessary use can have long-term consequences for both animal health and farm sustainability. By focusing on clinical signs and targeted treatments, producers can improve the health and survival of their calves while reducing costs and safeguarding the efficacy of AMD. The studies reviewed here highlight the importance of a practical, evidence-based approach to NCD management. With these tools, producers can navigate the challenges of calf diarrhea more effectively, ensuring healthier animals and a more productive operation.