Blame Mother Nature. Within the first few hours of a calf's life, it gets up, looks for the udder, and sucks on everything from the cow's brisket to the tail. In the process of responding to this most basic of instincts, the calf picks up every pathogen (bacteria, virus or organism that can cause disease) that's clinging to the cow. As a result, the calf gets diarrhea — otherwise known as scours.

Bethany Lovaas, beef cow-calf management veterinarian at the University of Minnesota North Central Research and Outreach Center (NCROC) in Grand Rapids, estimates that 90% of pathogens are transmitted in this manner.

Which is why cleanliness, to prevent scours, is a major critical control point of a calf's life.

“Since we know exactly the time when the calf picks up the bug, we can then determine which bug it is by taking note of the calf's age at the time the scours finally shows up,” Lovaas explains.

Field diagnosis is very easy, she says, and is based upon calf age. It begins by understanding the three major types of infectious scours:

  • Bacterial — E. coli (most prevalent), Clostridia and salmonella (rare in beef cattle herds). Bacterial-caused scours infections are evident within 0-5 days of a calf's life.

  • Viral — rotavirus and coronavirus. Rarely causing serious scours, these viruses impact a calf's immune system, allowing other organisms to cause bigger problems. Rotavirus is present from 4-14 days of age; coronavirus, 7-30 days.

  • Protozoal — coccidia (Eimeria spp.) and cryptosporidium. Cryptosporidium is very consistent (8-16 days of age), and all calves typically get sick on the same day (i.e., 11 days of age). Coccidiosis takes longer (21 or more days) to develop. The delay is due to the coccidians completing an entire life cycle before clinical signs affect the calf.

These pathogens cause damage to the lining of the gut, making it difficult to absorb fluids. Dave Smith, University of Nebraska-Lincoln Extension veterinarian explains the gut is damaged in two ways: bacteria-produced toxin forces cells to secrete fluids rather than absorb fluid (secretory diarrhea); or viruses and bacteria destroy cells causing fluids to pass straight through the calf (malabsorption diarrhea).

Stop it before it starts

“Prevention of calf scours starts with the cow,” Lovaas says. The cow is the source of the pathogen, and as a result of not getting over its own infection, becomes an asymptomatic carrier. Lovaas says vaccination for increased colostral immunity against pathogens is helpful, but not enough.

“All the best vaccine/colostrum in the world isn't going to be able to combat a monumental exposure,” Lovaas says. She recommends cleanliness.

In her experience at NCROC, scours was a huge problem. It was typical to lose 6-8 calves/year due to scours, with every calf in the herd receiving some form of treatment. Under her guidance, in 2007 the NCROC herd didn't lose a calf to scours and only treated five calves.

“The secret is clean calving pastures, clean cows and a clean barn,” Lovaas says, noting the Sandhills Calving System is an ideal method (see “Victory Is In The Planning,” page 22) to calve cows. Unfortunately, it's not always conducive to all soil types and operation sizes. If challenges present themselves, Lovaas tells producers to be forward thinking, consult others, and be ingenious to keep cows from making a mess of themselves and their environment.

Vets have a difficult time quantifying how many pathogens are too much. “We know we're at a dangerous pathogen load when calves are starting to get sick,” Smith says, noting that all calves on a ranch are exposed to some level of pathogens.

Weather plays a role, too, either increasing the transmission of pathogens, or a weakening a calf's immune system (hyperthermia/hypothermia).

When temperatures are extreme, cattlemen compensate by providing artificial shelter for cows (windbreaks, barns, leantos, shade), all of which promotes congregation of cattle. As cattle lie down, manure clings to hair on legs and udders — readily available pathogen sources for when the calf nurses. Wet, muddy conditions provide ample opportunities for calves to drink out of puddles, which also favors pathogens getting into a calf's mouth.

“I can't stress enough how important it is to keep your cows and calving areas clean,” Lovaas says.

Feces identification

There are times when it's necessary to evaluate the fecal material to gain insight on confusing cases of calf scours. For example, if the calf is too old for cryptosporidium, but too young for coccidiosis, the feces can help identify the cause. Once the source of the pathogen is identified, it makes for more accurate diagnosis and treatment. Here's the scoop on identifying poop:

  • Cryptosporidium will have the color of butterscotch pudding, and a very distinctive, foul odor.

  • Coccidiosis will have undigested blood in the feces.

  • E.coli and salmonella will sometimes produce blood in the feces, but calf age differentiates it from coccidiosis.

  • Acidotic feces is grey, a result of scours where bicarbonate is lost along with fecal material. The calf has limited means of replacing its bicarbonate, otherwise known as the body's buffer.

“Scours that are very grey or white in color are not necessarily distinctive for any one cause of scours, but are more a result of an ongoing problem,” Lovaas says. If there's grey spattering from calves, she recommends including bicarbonate (baking soda) in the fluid therapy plan.

Supportive therapy

If producers have done everything they can to keep things clean but still have scours, Lovaas says treatment needs to be centered around fluid therapy. Hydration is key, as dehydration often causes the death of calves, not the bug.

“The big challenge is to keep those calves hydrated with enough fluids for the dehydration and ongoing loss of fluids,” Smith says. A 100-lb. calf that is 10% dehydrated will require 10 lbs. of fluid to correct dehydration, and another 10-15 lbs. of fluids/day for ongoing needs.

Calves going through scours are not only losing fluid, but also bicarbonate and electrolytes such as potassium, Smith says. Which is why he cautions that any supplementation for calves have those elements in it.

“That's the most critical thing; taking care of the fluid and electrolyte losses, keeping that calf hydrated and balanced for electrolytes and bicarbonate while it gets over the infection,” Smith says.

A typical calf will scour 2-3 days before looking better. In the worst case, calves that are treated extensively with antibiotics end up with fungal infections in the gut. That's because antibiotics have eliminated bacteria in the gut, Smith says, which causes the fungi to overgrow and calves end up scouring for weeks, if they don't die.

Lovaas cautions producers that antibiotics have very limited utility in treating calf scours because they're only effective on bacteria. Scours caused by bacterial infections are usually manifested in very young calves (0-5 days). Lovaas says sulfa drugs (antibiotics) have activity against cryptosporidium and coccidian, and amprolium is an effective coccidoistat, which are the anti-infectives she keeps on hand for dealing with calf scours.

Foster calves

Some of the biggest scours wrecks that Glenn Selk, Oklahoma State University Extension animal reproduction specialist, has seen originated with the purchase of a foster calf. “The calf is carrying some scours organisms that we didn't see,” Selk says of calves that are purchased to graft onto a cow that's lost its calf. “We just bought ourselves a whole bunch of trouble because of it.”

If producers are bent on purchasing foster calves, he recommends isolating the newly formed pair for 30 days. Remember, newborn calves (and their mamas) exposed to outside pathogens have no immune defenses.