Calf Diarrhea: From Signs to Deadly Scours

Calf scours, commonly known as neonatal calf diarrhea, is a widespread disease that affects young calves across the globe. This condition is marked by sudden diarrhea, which can lead to dehydration, electrolyte imbalances, and even death if not addressed promptly. For livestock producers, calf scours is a major concern because it impacts calf health, slows growth, and reduces overall herd productivity. In this blog, we’ll explore every key aspect of calf scours—its causes, who it affects, how it develops, and how to manage it. Our goal is to provide a clear, professional, and easy-to-read guide to help you tackle this challenge effectively.

Etiology: What Causes Calf Scours?

Calf scours is a complex disease with multiple causes, often involving both infectious agents and environmental factors. Here’s a breakdown of the main culprits:

Infectious Agents

• Bacteria: Escherichia coli (E. coli) is a leading cause, especially the enterotoxigenic type (ETEC), which releases toxins that upset the gut. Other bacteria, like Salmonella species and Clostridium perfringens, can also trigger scours.
• Viruses: Rotavirus and coronavirus are major players. They attack the intestinal lining, causing poor nutrient absorption and diarrhea.
• Parasites: Cryptosporidium parvum and coccidia (Eimeria species) are common parasitic causes, particularly in calves older than a week.
• Mixed Infections: It’s not unusual for calves to be hit by more than one pathogen at once, making diagnosis and treatment trickier.

Non-Infectious Factors

• Poor Colostrum Intake: Colostrum, the first milk from the cow, is packed with antibodies. Calves that don’t get enough soon after birth lack this vital protection.
• Nutrition Issues: Bad feeding practices or sudden diet changes can weaken a calf’s system.
• Environmental Stress: Overcrowding, dirty conditions, or harsh weather can increase the risk.

Knowing these causes helps producers target their prevention and treatment efforts effectively.

Host Susceptibility: Who’s at Risk?

Calf scours mainly strikes newborn calves, with certain factors making some more vulnerable than others:

• Age: Calves are most at risk from 1 to 4 weeks old. Their immune systems are still maturing, and the protective antibodies from colostrum start to fade during this time.
• Colostrum Intake: Getting enough colostrum right after birth is critical. It provides antibodies that shield calves from pathogens. Without it, they’re far more likely to get sick.
• Nutrition: Calves that are malnourished or fed improperly have weaker defenses.
• Environment: Dirty or stressful surroundings, like crowded pens or wet bedding, make calves more prone to infection.

While some breeds might be slightly more susceptible, age and colostrum are the biggest factors by far.

Incubation Period: How Long Before Symptoms Show?

The incubation period—the time from exposure to symptoms—depends on the pathogen involved:

• Bacterial Infections: For E. coli, symptoms can appear in just 12 to 24 hours.
• Viral Infections: Rotavirus and coronavirus usually take 1 to 3 days to show up.
• Parasitic Infections: Cryptosporidium parvum might need 3 to 7 days before signs emerge.

In real-world settings, mixed infections or varying conditions can mean symptoms start anywhere from a few hours to several days after exposure.

Clinical Signs and Symptoms: What to Look For

The main sign of calf scours is diarrhea, but its severity and look can vary:

• Mild Cases: Loose, pasty stools that might be yellow or greenish.
• Severe Cases: Watery, profuse diarrhea that could be yellow, white, or mixed with blood and mucus.

Other signs include:

• Dehydration: Sunken eyes, dry mouth, and skin that doesn’t snap back when pinched.
• Weakness: Calves may seem tired or unsteady.
• Loss of Appetite: They stop eating or drinking as much.
• Weight Loss: Growth slows down.
• Severe Cases: Cold body temperature, lying down a lot, or even death.

The symptoms can hint at the cause:

• E. coli often leads to quick, intense dehydration.
• Rotavirus and coronavirus cause absorption problems.
• Cryptosporidium tends to produce long-lasting, watery diarrhea.

Spotting these signs early can make a big difference in saving the calf.

Morbidity and Mortality: How Bad Can It Get?

Calf scours can hit a herd hard:

• Morbidity: During outbreaks, 50% to 80% of calves might get sick.
• Mortality: Death rates depend on care. With quick treatment, fewer than 5% may die. Without it, over 50% could be lost in bad cases.

Beyond losing calves, scours costs money through treatment, slower growth, and long-term effects on the herd’s output.

Pathogenesis: How the Disease Develops

Calf scours messes with the gut, leading to diarrhea and dehydration. Here’s how it happens:

• Infection: Pathogens attack the intestinal lining, causing inflammation and damaging cells. This stops the gut from soaking up water and nutrients, leading to runny stools.
• Toxins: Bacteria like E. coli release toxins that make the gut pour out fluids and salts, worsening diarrhea.
• Immune Reaction: The calf’s body fights back, but this can add to the damage.

Calf scours, or neonatal diarrhea, begins when infectious agents such as E. coli, Salmonella, rotavirus, coronavirus, or Cryptosporidium enter the calf’s body through contaminated feed, water, or contact with infected animals. These pathogens attach to and damage the intestinal lining, reducing the absorption of nutrients and fluids. Some, like rotavirus and coronavirus, destroy the villi in the small intestine, while others, like E. coli, release toxins that further impair gut function. The result is excessive fluid secretion into the intestines, leading to watery diarrhea.

This massive loss of fluids and electrolytes causes dehydration, electrolyte imbalance, and metabolic acidosis. If left untreated, the calf’s condition can rapidly deteriorate, with signs like weakness, sunken eyes, and cold extremities appearing. In severe cases, bacteria may enter the bloodstream, causing septicemia and potentially death. Calves with poor colostrum intake are especially vulnerable due to weak immune defenses.

How bad it gets depends on the pathogen’s strength, the calf’s health, and whether multiple bugs are involved.

Development Mechanisms

The pathogenesis of calf scours involves three major mechanisms, each linked to specific pathogens:

These mechanisms result from pathogen exposure, often from the dam, other calves, or the environment, leading to gut damage and subsequent diarrhea, which can escalate to dehydration and metabolic disturbances

Postmortem Findings: What’s Seen After Death

If a calf dies from scours, a necropsy (animal autopsy) might show:

• Dehydration: Sunken eyes, dry mouth, and skin that stays tented.
• Gut Changes: The intestines may be swollen with fluid. The lining could look red, swollen, or dead in spots.
• Specific Clues:
  • E. coli: Bloody gut inflammation, sometimes with signs of blood poisoning.
  • Rotavirus/Coronavirus: Shrunken intestinal villi (tiny nutrient-absorbing fingers).
  • Cryptosporidium: Tiny parasite eggs visible under a microscope in gut scrapings.
• Other Organs: In severe cases, the liver, spleen, or lymph nodes might show damage.

These findings help confirm what caused the death and guide future prevention.

Treatment: How to Manage Calf Scours

Treating calf scours focuses on support and tackling the root cause:

• Rehydration: The top priority is replacing lost fluids and electrolytes. Oral rehydration solutions (ORS) work for mild cases. Badly dehydrated calves may need IV fluids.
• Antibiotics: These help if bacteria are involved, but they’re not useful for viruses or parasites. Use them carefully to avoid resistance.
• Supportive Care: Keep calves warm and dry. Offer milk or special milk replacers made for scouring calves.
• Probiotics: These can help rebuild healthy gut bacteria and shorten diarrhea time.
• Prevention Tips (Key to Success):
  • Make sure calves get colostrum within hours of birth.
  • Keep calving areas and feeding gear clean.
  • Vaccinate pregnant cows to boost colostrum antibodies.
  • Separate sick calves to stop the spread.

Acting fast with a full plan can boost recovery and cut deaths.

Conclusion

Calf scours is a tough hurdle in raising calves, but it’s manageable with the right knowledge. By understanding its causes, spotting it early, and using solid treatment and prevention steps, producers can protect their herds. This guide covers everything you need to know—from why it happens to how to fix it—so you can keep your calves healthy and your operation thriving.