Scours is the single biggest killer of calves under three weeks old on most cow-calf operations. The frustrating part is that by the time a calf looks sick, you are already behind. A calf can go from bright and nursing at sunrise to flat and dehydrated by dark. The producers who lose the fewest calves are not the ones with the best drugs — they are the ones who treat prevention as a year-round job and catch sick calves in the first six hours.

This is a working protocol drawn from what holds up in the pasture and the calving barn, not a textbook chapter. It assumes you have a small to mid-size herd, limited labor, and need decisions you can make at 2 a.m. with a flashlight.

Why Scours Kills Calves So Fast

A newborn calf is roughly 75 percent water. When scours hits, that water leaves through the gut at a stunning rate — a 90-pound calf can lose 8 to 10 percent of its body weight in fluids inside 12 hours. The killer is almost never the pathogen itself. It is dehydration, metabolic acidosis, and the electrolyte crash that follows. By the time the calf is too weak to stand, blood pH has dropped and the heart is struggling. You are no longer treating diarrhea. You are treating shock.

Understanding this changes how you respond. The pathogen matters for prevention, but the treatment is largely the same regardless of cause: replace fluids, correct acidosis, keep the calf warm, and keep nutrition going. Get those four right and most calves recover.

The Main Pathogens You Are Up Against

Knowing what is causing scours on your place changes your prevention strategy. The big four:

  • E. coli (K99) — Hits in the first four days of life. Watery yellow scours, rapid dehydration. Vaccinating cows pre-calving is highly effective.
  • Rotavirus and coronavirus — Usually 5 to 21 days old. Pale, pasty scours. Spread fast in crowded calving areas.
  • Cryptosporidium — 7 to 28 days. Hard to treat, hard to kill in the environment, and zoonotic — wear gloves.
  • Coccidia — Usually older calves, three weeks and up. Bloody or dark scours, straining, often after weather stress or pen moves.

If you keep losing calves and do not know which pathogen, send a fresh fecal sample (or a freshly dead calf) to your state diagnostic lab. The cost is modest and the answer reshapes your whole prevention plan. Guessing burns calves.

The most expensive scours treatment is the one you give a calf you could have prevented from getting sick. Prevention dollars beat treatment dollars roughly five to one.

Prevention Starts Before the Cow Calves

Almost every prevention lever is pulled before the calf hits the ground. The five that matter most:

  • Cow body condition at calving — Aim for BCS 5 to 6 on mature cows, 6 on first-calf heifers. Thin cows produce thin colostrum.
  • Pre-calving vaccination — Scour-guard type vaccines given to cows 3 to 6 weeks before calving boost antibodies in colostrum dramatically.
  • Calving ground rotation — The Sandhills Calving System (moving pregnant cows to fresh ground every 7 to 10 days while pairs stay behind) breaks the pathogen load cycle. It works.
  • Mineral and trace mineral status — Selenium, copper, and zinc deficiencies in late gestation directly weaken calf immunity. Test, do not guess.
  • Clean calving area — Mud, manure pack, and old bedding are pathogen factories. If you calve in a barn, strip and re-bed between calves whenever you can.

Tracking which cows calve where, when they were vaccinated, and which calves got sick is the difference between "we always lose a few" and "we figured out it was the second pen." Keeping a simple field log — cow ID, calf birth date, calving location, any treatments — lets you see patterns by the third year. Tools like Barnsbook let you log this from your phone in the pasture without service, which matters when calving ground is a mile from the house.

Colostrum: The Single Biggest Lever You Have

If a calf does not get enough good-quality colostrum in the first six hours of life, no vaccine, no antibiotic, and no electrolyte program will fully compensate. The numbers to remember:

  • Volume — A calf needs 10 percent of its body weight in colostrum within the first 12 hours. For a 90-pound calf, that is roughly 4 quarts (about 4 liters).
  • Timing — Gut absorption of antibodies drops sharply after 6 hours and is essentially closed by 24. Half the colostrum should be in by hour 6.
  • Quality — A Brix refractometer reading of 22 percent or higher means good-quality colostrum. Under 18 percent is poor and should be supplemented.

If you assist a calving, watch a weak calf, or pull a backwards calf, do not wait to see if it nurses. Tube it. A clean esophageal tube and 2 quarts of colostrum (fresh, frozen-and-thawed at body temp, or a high-quality replacer) is cheap insurance. Frozen colostrum from a healthy older cow on your own place is the gold standard. Keep a few bags in the freezer.

Ready to put this into practice? Download on the App Store — it’s free and works offline.

Spotting Scours Early: The Six-Hour Window

The single biggest skill in keeping calves alive is recognizing dehydration before it shows up as obvious illness. Walk through the calves twice a day during scours season. What to watch for, in order of how early they appear:

  • Behavior change — Calf is laying alone, not following the cow, slow to get up. This often shows up before any visible scours.
  • Suckle response — Stick a clean finger in the calf's mouth. A healthy calf has a strong, warm suck. A weak, cool, or absent suck means trouble.
  • Skin tent — Pinch the skin on the upper eyelid or neck. If it snaps back instantly, hydration is fine. A 2-second tent is 6 to 8 percent dehydrated. A 4-second tent is severe.
  • Eye position — Sunken eyes mean 8 percent or worse dehydration. By the time you see this, the calf needs IV fluids, not oral.
  • Gum color and warmth — Cool, tacky, or pale gums signal poor circulation.
If you only learn one field test, learn the suckle response. A calf that has lost the will to suck has lost the will to live within hours. That is your alarm bell.

A Treatment Protocol That Works

Once you have identified a sick calf, the protocol is straightforward. The goal is fluids, electrolytes, energy, and warmth. Antibiotics are secondary and not always needed.

  • Mild case (calf still standing, suckling, mild scours) — Give 2 quarts of oral electrolytes between milk feedings. Do not replace milk with electrolytes — the calf needs the calories. Space them at least 2 hours apart from nursing.
  • Moderate case (calf depressed, weak suck, 6 to 8 percent dehydrated) — Tube 2 quarts of high-quality electrolyte solution containing sodium, glucose, an alkalinizing agent (acetate or bicarbonate), and an amino acid like glycine. Repeat in 4 to 6 hours. Continue letting the calf nurse if it will.
  • Severe case (down, sunken eyes, cold mouth) — Oral fluids will not be absorbed fast enough. The calf needs IV fluids, ideally from a vet. If you are trained and equipped, lactated Ringer's or a 1.3 percent sodium bicarbonate solution at 1 to 2 liters over 30 minutes can save the calf. Warm the fluids first.
  • Antibiotics — Use only when a bacterial cause is suspected (blood in the stool, fever, septicemia signs) and ideally on a vet's call. Reflexively dosing every scoured calf with antibiotics breeds resistance and does not help viral or protozoal cases.

Keep sick calves warm. A calf jacket, deep dry bedding, and a heat lamp safely suspended out of reach can be the difference between recovery and death overnight. Hypothermia compounds dehydration fast.

When to Call the Vet, and What to Have Ready

Call the vet when:

  • The calf cannot stand or has a sunken-eye appearance
  • You see blood, mucus, or a foul-smelling dark stool
  • You have lost more than one calf in a week to scours
  • Oral electrolytes are not improving the calf within 12 hours
  • You are seeing scours in calves under 3 days old — that pattern points to E. coli or septicemia and needs aggressive treatment

When you call, have ready: calf age in days, time symptoms started, color and consistency of stool, whether the calf is standing, suckle response, eye appearance, and any treatments already given. A vet can triage twice as fast with that information, and over the phone they can often guide you through IV fluids if you have the supplies on hand.

Build the Records That Prevent Next Year's Outbreak

The producers who slowly drive their scours rate down are the ones who write things down. After every sick calf, log the cow ID, calf age in days, where the pair was when symptoms started, what the stool looked like, and what treatment was given and when. After calving season, look at the patterns. Is it always the heifers' calves? Is it always the back pen? Is it always day 8 to 10? Those patterns drive next year's prevention plan and tell you whether your colostrum, vaccination, or environment is the weak link.

This is the same record-keeping discipline that pays off across livestock and other small-ag operations. Whether you are tracking sick calves with Barnsbook, planting records and harvest logs in CropsBook, or hive inspections in HiveBook, the principle is the same: capture the data when it is fresh, review it before the next season, and let the patterns guide your decisions instead of your memory. Memory is generous. Notes are not.

Every dead calf is information. The producers who use that information stop losing calves. The ones who do not, keep losing the same calves to the same problem every spring.

The Bottom Line

Calf scours is preventable far more often than it is curable. Get cows in the right body condition, vaccinate before calving, rotate calving ground, get 4 quarts of high-quality colostrum into every calf in the first 6 hours, and walk the calves twice a day looking for the early signs. When a calf does get sick, treat fluids and warmth before anything else, save antibiotics for when they are actually needed, and call the vet early on the bad ones. Keep records honest enough that next spring is a little easier than this one.

Scours season is hard. It is also the season where small habits — a Brix reading, a skin tent check, a logged note about which pen the sick calf came from — pay back more than any other work you do all year.