Treating scours in calves starts with replacing lost fluids, continuing milk feedings, and keeping the calf warm and dry. Most cases of calf scours resolve with oral electrolytes and supportive care alone, but severe dehydration or signs of systemic illness require veterinary intervention. The speed of your response matters: a scouring calf can lose up to 7 liters of fluid per day, and dehydration can become life-threatening within hours.
Assess Dehydration First
Before you decide how aggressively to treat, you need to know how dehydrated the calf is. Two simple physical checks give you a reliable picture. First, pinch a fold of skin on the neck and release it. If the skin snaps back in under 3 seconds, dehydration is mild. If it takes 3 seconds or longer, the calf is roughly 4 to 5 percentage points more dehydrated than one with a quick snap-back. Second, look at the eyes. If they appear sunken into the skull by even a small amount, the calf is about 3.5 percentage points more dehydrated than one with normal-looking eyes.
Combine those observations with behavior. A calf that still stands, walks around, and has a suckle reflex is a candidate for oral treatment at home. A calf that can’t stand, won’t suck, or feels cold to the touch is in serious trouble and needs IV fluids from a veterinarian. Loss of the suckle reflex is one of the clearest signs that oral electrolytes alone won’t be enough.
Oral Electrolytes: Your Primary Tool
Oral electrolyte solutions are the backbone of scours treatment. They replace water, sodium, potassium, and buffering agents that the calf loses through diarrhea. Commercial electrolyte packets mixed with warm water are the easiest option and are widely available at farm supply stores.
For a mildly dehydrated calf, offer electrolyte solution two to three times per day between milk feedings. A good starting target is 2 liters per feeding. For moderate dehydration, you may need to increase that to 3 or 4 feedings of electrolytes daily. The general guideline for daily fluid needs is 80 to 100 mL per kilogram of body weight for maintenance, plus whatever the calf is losing through diarrhea. For a 45-kilogram (100-pound) calf, that means at least 3.5 to 4.5 liters per day just for maintenance, with additional fluid on top to replace ongoing losses.
Some electrolyte products contain gelling agents that slow the passage of fluid through the gut, which can reduce the severity of diarrhea within hours of feeding. These products may also coat the inflamed intestinal lining, giving it some protection while it heals.
Keep Feeding Milk
One of the most common mistakes is pulling a scouring calf off milk. Decades of veterinary research show this does more harm than good. Oral electrolytes alone cannot provide enough calories to maintain the calf’s body weight or fuel its immune system. The glucose concentration in electrolyte solutions has to stay low to keep the fluid properly balanced for absorption, so they simply don’t deliver the energy a sick calf needs.
A University of Illinois study compared three approaches: electrolytes only for two days with milk slowly reintroduced over a week, partial milk feeding with electrolytes, and full milk feeding alongside electrolytes. Fecal scores (the severity of diarrhea) were the same across all three groups. But calves that received their full milk allotment throughout treatment maintained significantly more body weight. The takeaway is straightforward: keep feeding milk on the normal schedule and give electrolytes as separate feedings in between. Space them at least 2 hours apart so the electrolyte solution doesn’t interfere with milk clotting in the stomach.
Warmth and Clean Bedding
A scouring calf burns through energy fast and loses body heat quickly. Calves under 3 weeks old start needing extra energy to stay warm when temperatures drop below 68°F. For calves over 3 weeks, that threshold is around 50°F. A calf that’s already sick and dehydrated hits these limits even sooner.
Deep-bedded straw is the best option. Unlike sawdust, straw allows calves to nest, creating a pocket of warm air around their body. The University of Wisconsin Veterinary School developed a simple nesting score: if you can’t see the calf’s rear legs when it’s lying down, the bedding is deep enough (score of 3). If the legs are fully visible, you need more straw. Sawdust absorbs moisture well but does little to insulate a calf during cold weather. Using it alone in winter is not recommended.
If temperatures are low and the calf is weak, a calf jacket or a heat lamp (positioned safely) can make the difference between recovery and decline. Move sick calves to a dry, draft-free area away from healthy animals to limit pathogen spread.
Identifying the Cause by Age and Symptoms
Scours isn’t a single disease. It’s a symptom caused by different pathogens depending on the calf’s age. Knowing which pathogen is likely helps you anticipate the course of illness and decide whether additional treatment is warranted.
- E. coli (enterotoxigenic): Hits calves under 3 to 5 days old. Produces profuse, watery feces. Progresses rapidly and can be fatal without fast fluid replacement.
- Rotavirus and coronavirus: Most common in calves 5 to 15 days old but can affect calves up to several months. Feces are voluminous, soft to liquid, and often contain large amounts of mucus.
- Cryptosporidium: Peaks in the second week of life, seen from 5 to 35 days old. Causes persistent diarrhea that typically does not respond to standard therapies, including antibiotics. Supportive care with fluids and nutrition is the main approach.
- Coccidiosis: Usually affects older calves, often around 3 weeks and beyond. May produce bloody diarrhea. Unlike the pathogens above, it responds to specific medications.
If you see blood or mucus in the stool, or if diarrhea persists despite fluid therapy, a fecal sample can help your veterinarian identify the pathogen and tailor treatment.
When Antibiotics Are Warranted
Most cases of calf scours are caused by viruses or protozoa, which don’t respond to antibiotics. For a calf with diarrhea but no fever, a normal appetite for milk, and no signs of systemic illness, antibiotics are not recommended and won’t speed recovery.
Antibiotics become appropriate when a scouring calf shows signs of bacterial infection spreading beyond the gut: fever, depression, complete refusal to eat, or a toxic appearance. These calves need systemic (injectable) antibiotics, not oral ones. Your veterinarian will select a broad-spectrum option based on the calf’s condition. Giving antibiotics to calves that don’t need them increases the risk of antibiotic resistance and disrupts beneficial gut bacteria, potentially making the diarrhea worse.
Treating Coccidiosis Specifically
If fecal testing confirms coccidiosis, targeted treatment shortens the course of illness and reduces transmission to other calves. Amprolium given orally for 5 days is one of the most commonly used options and is available over the counter in many areas. Sulfadimethoxine, given as a drench or in water for 5 days (a higher dose on the first day, then a lower dose for the remaining four), is another standard choice approved for use in cattle in North America.
Single-dose treatments like toltrazuril or diclazuril are also effective and more convenient. When one calf in a group is confirmed, treat the entire group since the parasite spreads rapidly through fecal contamination of shared environments.
Probiotics as a Supplement
Adding a probiotic (direct-fed microbial) to electrolyte feedings shows promise as a complementary treatment. In one controlled study, scouring calves given electrolytes plus a Bacillus-based probiotic had less severe diarrhea, lower rates of needing IV fluids, and reduced shedding of harmful gut bacteria by day 7 compared to calves given electrolytes alone. Total treatment costs during the first two weeks were also lower in the probiotic group. Calves that received the probiotic were less likely to experience a second bout of scours after recovery.
Probiotics aren’t a replacement for electrolytes or milk, but they appear to be a useful add-on that reduces severity and may lower your overall treatment costs.
Prevention Starts With Colostrum
The single most important factor in preventing scours is making sure every calf gets enough high-quality colostrum within the first hours of life. Calves are born with essentially no immune protection. They rely entirely on antibodies absorbed from colostrum to fight off the pathogens that cause scours.
High-quality colostrum contains at least 50 mg of immunoglobulin G (IgG) per milliliter. You can check colostrum quality on the spot with a Brix refractometer: a reading of 22% or higher generally indicates adequate IgG for dairy cattle (18% or higher for some breeds). Calves should receive 10% of their body weight in colostrum within the first 6 hours, with the first feeding ideally within 1 to 2 hours of birth. A calf whose blood serum later tests below 10 mg/mL of IgG has failed passive transfer and is significantly more vulnerable to scours and other infections.
Beyond colostrum, keeping calving areas clean, avoiding overcrowding, and separating calves by age group all reduce pathogen load. Vaccination of pregnant cows against rotavirus, coronavirus, and E. coli in the weeks before calving boosts the antibody levels in their colostrum, giving newborns a stronger starting defense.