Calf Scours

What is Calf Scours?

Calf scours (neonatal diarrhea) is the most common and deadly disease in young calves, accounting for 50–60% of all pre-weaning deaths in dairy herds. Scours is not a single disease — it's a clinical sign caused by multiple pathogens that attack the intestinal lining, causing fluid loss, dehydration, and electrolyte imbalance.

The primary pathogens causing calf scours include: Rotavirus (most common, 30–40% of cases), Coronavirus (20–30% of cases), Cryptosporidium parvum (10–20% of cases, resistant to most disinfectants), E. coli (10–15% of cases, typically in calves <5 days old), and Salmonella (5–10% of cases, often associated with fecal-oral transmission). Multiple pathogens can infect simultaneously, making treatment challenging.

Scours typically occurs in calves 1–21 days old, with the highest incidence at 3–10 days. Calves are most vulnerable during the first week of life when passive immunity from colostrum is declining and the gut is still developing. Calves that fail to receive adequate colostrum (>22% Brix within 2 hours of birth) are 3–5x more likely to develop scours.

The economic impact is severe: each case of scours costs $50–150 in treatment, labor, and lost growth. For a herd with 100 calves born per year and 25% scours incidence, the annual cost is $1,250–3,750 — not including the 5–10% mortality rate in severe cases.

Scours Prevention: The 3 Pillars

Pillar 1: Colostrum management. Calves must receive 3–4 liters (>10% of body weight) of quality colostrum (>22% Brix) within 2 hours of birth. Colostrum provides passive immunity (IgG antibodies) that protects the calf for the first 2–3 weeks of life until its own immune system develops. Calves with adequate passive transfer have 50–60% lower scours rates. Test every batch with a Brix refractometer before feeding. Pillar 2: Hygiene. Scours pathogens spread through the fecal-oral route — contaminated navel, bedding, feeding equipment, and handler hands. Clean and disinfect calving pens between every cow (lime or Virkon S). Dip navels with 7% iodine immediately after birth. Feed colostrum and milk in clean buckets or bottles — never use the same equipment for multiple calves without sanitizing. Change bedding daily in the first week. Wear clean gloves when handling newborns. Pillar 3: Environment. Calves need clean, dry, draft-free housing. Wet, muddy, or overcrowded conditions increase scours risk 2–3x. Target 1 calf per hutch or pen with adequate ventilation. Maintain bedding depth of 6+ inches of clean straw or shavings. Ensure water is available but not shared between pens.

Treating Scours: The 7-Step Protocol

Step 1: Assess dehydration. Check skin tent (pinch skin on the neck — >2 seconds return = dehydrated), eye socket (sunken = dehydrated), and mucous membranes (dry, tacky = dehydrated). Mild dehydration (<5%): alert, suckling well, skin tent <2 seconds. Moderate (5–8%): depressed, weak suckle, skin tent 2–4 seconds, sunken eyes. Severe (>8%): lethargic, unable to stand, skin tent >4 seconds, very sunken eyes, cold extremities. Step 2: Isolate immediately. Move the sick calf to a clean, warm, dry pen away from healthy calves. Step 3: Oral rehydration. Administer electrolyte solution (oral rehydration salts) via bottle or esophageal feeder. Give 2–4 liters initially, then 1–2 liters every 4–6 hours. Electrolytes should contain sodium, potassium, chloride, glucose, and glycine. Step 4: Continue milk feeding. Do NOT withhold milk during scours — calves need energy to fight infection and maintain body temperature. Feed half the normal milk volume every 12 hours alongside electrolytes. Step 5: Antibiotics (if bacterial cause suspected). Consult a veterinarian for antibiotic selection. Common choices: oral neomycin or oxytetracycline for E. coli; systemic antibiotics (ceftiofur, enrofloxacin) for severe cases. Do not use antibiotics for viral scours — they are ineffective. Step 6: Monitor. Check calf every 4–6 hours. Watch for improvement (increased alertness, returning suckle) or deterioration (unable to stand, cold extremities). Step 7: Prevent spread. Disinfect all equipment, bedding, and handler clothing between calves. Review and improve prevention protocols.

Vaccination and Prevention Programs

Maternal vaccination: vaccinate pregnant cows 4–6 weeks before calving with rotavirus, coronavirus, and E. coli vaccines. This stimulates antibody production in colostrum, providing passive protection to the calf. Studies show maternal vaccination reduces scours incidence by 40–60%. Scour vaccines for calves: oral vaccines (scour boluses) containing live rotavirus, coronavirus, and Cryptosporidium can be given at 1–3 days of age. These stimulate gut immunity before the calf is exposed to pathogens. Effectiveness varies — 50–70% reduction in scours when combined with good colostrum and hygiene. Navel dipping: dip the navel with 7% tincture of iodine immediately after birth. This disinfects the entry point for bacteria and reduces navel infections and joint ill. Colostrum testing: test every batch with a Brix refractometer. Discard colostrum below 18% Brix (poor quality). Use colostrum replacer for calves whose dam's colostrum is inadequate.