Prevent Scours in Young Calves

by Heather Thomas

George Barrington of Washington State University says two major strategies for disease prevention are to:

1. 1. Reduce introduction of infectious disease agents into the herd (external biosecurity), and
2. 2. Reduce transmission of disease that is already present (internal biosecurity).

An example of the first strategy would be to never buy dairy calves to raise on cows that lose their calves, as doing so might introduce salmonella, cryptosporidia or Johne's disease. An example of the second strategy would be to make sure cows calve on new, clean ground — rather than in your winter feeding area — to minimize newborn calves' contact with fecal material.

The Sandhills calving method, in which cows that have not yet calved are moved to new, clean pasture every two weeks is one way to help prevent scours.

"You want to keep pathogens away from the youngest calves, and keep these babies away from the pathogens," Barrington explains.

Most disease agents causing diarrhea in young calves are normal inhabitants of the gastrointestinal (GI) tract of healthy mature cattle. These organisms exist in low concentrations and without clinical signs of infection, Barrington says. "Most cattle are exposed to continuous, low doses of pathogens, shed by subclinically infected or immune herdmates. When young, immunologically naïve calves are exposed to low doses, they too can develop immunity and not show signs of disease."

"However, if young calves are exposed to high doses, they develop clinical disease and become 'super shedders,' releasing billions of viral particles per gram of feces. This contaminates the environment very quickly and puts other calves at much higher risk for disease," he explains. Younger calves that have less resistance or that become exposed to a high level of pathogens are most at risk.

"There are some nasty bacteria — like salmonella — that you don't want to bring into your herd, but most of the others are already there. Rotavirus, coronavirus, protozoa (especially coccidia, and sometimes cryptosporidia) and even many E. coli are usually present. Preventing scours in young calves is mainly a matter of minimizing exposure of young, immuno-naïve calves to these pathogens," Barrington explains.

Some exposure is beneficial because this stimulates the calf to start building immunity. Calves become sick when exposed to an overwhelming level of pathogens. Since most pathogens we're concerned about are passed in feces (from adults and older calves that have come into contact with pathogens and might be scouring), keep young calves in a relatively clean pasture. Group calves according to age.

"Realizing calves will get exposed, it's a matter of controlling the level of infection in their environment. We know the pathogens are there, so we try to spread the calves out and minimize grouping/congregating them in small areas," he says.

"Feedbunks or round-bale feeders should be moved often. If you feed on the ground, keep moving to new areas," he says.

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