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Causes of calf scours can be difficult to identify

There is no simple test to be able to identify what causes scours in calves

Scours is the most common illness and cause of death in young calves. Some years are worse than others for scours outbreaks, and there are many causes including certain kinds of bacteria, viruses or protozoa. Whether calves get sick depends on many factors including exposure (contact with pathogens, either by coming in contact with a sick animal or from a contaminated environment), and each calf’s level of immunity.

Stress reduction — protecting calves from bad weather and not confining them too much during calving season — can help reduce the incidence of scours, since stress hinders the immune system.

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Determining a cause

Producers often want some way to try to figure out the cause of diarrhea so they would know how best to treat it, but it’s not easy to tell just by looking at the calf or the feces. There are several pathogens that can cause scours.

“There have been various tests that people have come up with over the years with the intent of enabling producers to get a feces sample to do some on-farm testing, but none of these have ever been very effective,” says Steve Hendrick, a veterinarian with Coaldale Veterinary Clinic, just east of Lethbridge, Alta.

The calf’s age can give a clue, however. “Bacterial scours might occur within the first couple of days of life, particularly if the source is something like E. coli. We generally don’t see viral scours until calves are one to two weeks old.”

Protozoal pathogens take a longer incubation time. Cryptosporidiosis generally won’t occur until a calf is at least seven to 10 days old or older, and generally won’t show up in calves until about two weeks of age. Coccidiosis takes closer to four weeks before enough intestinal damage is done and the calf has diarrhea.

“The hard part in trying to diagnose scours by age, however, is that there’s usually some overlap,” Hendrick says. “A calf that’s two weeks old might have viral scours and a concurrent bacterial infection as well. It also depends on how early in life a calf was exposed and infected.”

A calf born nose-first into a puddle contaminated with feces in a muddy corral might pick up protozoa at birth and break with scours from crypto by the time it’s five days old.

Many producers think that colour and consistency of the feces can be a clue, but this is not always true.

“When we see blood in the feces we suspect coccidiosis, but these calves may not always have evidence of blood,” Hendrick says. The feces may just be brown and watery. With some other kinds of intestinal infection they may be grey, yellow, or greenish or nearly white.

“We can’t say for sure what type of infection it might be, just by the colour or consistency of the feces. If there are multiple calves with scours, have your veterinarian take a fecal sample to see what the cause might be — especially if that knowledge can help you treat additional cases more effectively. When we experience an outbreak of scours, there are often multiple ‘bugs’ involved.”

Keep them hydrated

Unless you know what you are dealing with, the best thing to do is just give the calf adequate fluids/electrolytes (usually every six to eight hours) and consult your veterinarian for advice on any additional treatment. A broad-spectrum antibiotic might be needed, especially if there is a chance it might be bacterial or complicated by a secondary bacterial infection.

“I can understand why people reach for a scour bolus because it’s easy, but it doesn’t always help,” Hendrick says. “Using electrolytes and keeping the calf hydrated are much more important.” The more severely dehydrated the calf, the more often you’ll need to give fluids.

However, if there is too much gut damage the calf will have trouble absorbing oral fluids and electrolytes and will need IV fluids. Usually if the calf can still stand up and move around, it can be given oral fluids, but if it is too weak to stand, and no longer has a suckle reflex, oral fluids won’t do it any good. Blood circulation to the gut is too compromised and the only way you will save it is with IVs — administered as soon as possible.

In an outbreak situation, scours is generally due to a management problem. The cattle may be too confined in a contaminated environment. “There are generally many factors that come together to create the problem,” Hendrick says.

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