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Environment control key to scours prevention in calves

Heather Smith Thomas Published on 23 December 2011
Cattle in snowy field

The most common illness in young calves is scours.

According to George Barrington of Washington State University, diarrhea results in the greatest economic loss from disease in this age group.

A recent study showed that 5.5 percent of beef calves die from diarrhea during the first three weeks of life.

Some years are worse than others, and there are many causes. Intestinal infection can be due to bacteria, viruses or protozoa.

Whether or not calves get sick involves multiple factors including exposure (contact with pathogens and the “dose” of pathogens), level of immunity and stress.

Good weather, clean ground and stress reduction (which includes shelter from bad weather and minimizing confinement) can help reduce incidence of scours.

Biosecurity steps

Barrington emphasizes that the two major strategies for disease prevention are reducing the likelihood of introducing an infectious disease agent into the herd (external biosecurity – such as not bringing in cattle that might expose your cattle to new pathogens) and reducing the likelihood of transmitting a disease that is already present (internal biosecurity).

An example of the first strategy would be to never bring home dairy calves to raise on cows that lose their calves.

A dairy calf might bring salmonella, cryptosporidia or even Johne’s disease into a beef herd. An example of the second strategy would be to make sure your cows calve on new, clean ground – rather than your winter feeding area – to minimize newborn calves’ contact with fecal material and contamination.

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

“You want to keep the pathogens away from the youngest calves and keep these babies away from the pathogens,” explained Barrington.

The most frequently recognized disease agents causing diarrhea in young calves are normal inhabitants of the GI tract of most healthy mature cattle.

These organisms exist in low concentrations and don’t produce clinical signs of infection. “Most cattle are probably 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 can develop immunity and not show signs of disease,” he says.

“However, if young calves are exposed to high doses, two things happen. First, they develop clinical disease.

Second, they become ‘supershedders’ and release billions of viral particles per gram of feces. This supershedding quickly contaminates the environment and puts other calves at much higher risk for disease,” he explained.

Younger calves that have less resistance or become exposed to a high level of pathogens in the environment 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.

Most of the viruses (rotavirus, corona virus), protozoa (especially coccidia, and sometimes cryptosporidia) and even many E. coli are usually present in the herd.

Preventing scours in young calves is mainly a matter of minimizing exposure of young, immunologically naïve calves to these pathogens,” explained Barrington.

Low-dose exposure stimulates the young calf to start building immunity. Calves become sick when exposed to an overwhelming level of pathogens.

Since most of the pathogens we’re concerned about are passed in feces (from adult cattle and from older calves that have come into contact with these pathogens), we want to keep young calves in a relatively clean pasture.

Reduce contamination of the environment

“Realizing that calves will get exposed, it’s a matter of controlling the level of infection. We know the pathogens are there, so we try to spread calves out and minimize grouping or congregating them in small areas,” he said. This helps ensure that they don’t encounter a high level of contamination.

Feeding is often necessary when winter and early spring pastures are not nutritionally adequate for cows, but this concentrates them in a smaller area and presents more challenge with contamination.

“We can feed in a strategic manner, however, to promote more dispersal of animals and spread them out,” he said. “Sometimes a feeding area becomes contaminated very quickly (as when space is limited or ground is wet), and in other conditions more slowly.

But in general, we know contamination occurs in less than two weeks. If you use feedbunks or round bale feeders, move them often. If you are feeding on the ground, keep moving to new areas.

“This is where the Sand Hills method is beneficial: rotating calving cows to new pasture every couple of weeks.

Grouping the calves based on age really helps,” Barrington said. The older calves have already begun shedding pathogens in feces, and if you can have the younger, more vulnerable calves in a new, clean place, they won’t be exposed so quickly to an overwhelming load.

You can control the level of infection with your feeding and management practices.

Importance of colostrum

“Another important factor is increasing calves’ resistance, making sure they get off to a good start. This includes giving assistance at birth, if necessary, and making sure they nurse colostrum soon after birth.

On some ranches this is difficult, while in other situations it’s easier to drive through the calving heifers and cows several times a day to assist calves if needed. Making sure they are up and suckling within a couple of hours is very important,” he says.

“It’s also crucial to watch for mismothering. Sometimes a calf doesn’t get colostrum (or get it on time) because of mothering problems, especially in heifers, and they have more problems in a crowded environment.”

When cows are grouped or confined too much at calving, a calving cow may steal another’s newborn calf, and heifers may become confused and not bond very quickly with their calves. Whatever you can do to decrease these problems and facilitate better chances for proper bonding will help.

Vaccination

Certain vaccines, given at the appropriate time during pregnancy, stimulate the cow to produce antibodies against some of the pathogens the calf will encounter, and the calf receives this “instant immunity” by nursing her colostrum.

But even if you vaccinate pregnant cows, if a calf can’t nurse or doesn’t nurse on time to absorb those antibodies, you’ve wasted your money on the vaccine.

“There is no vaccine that will halt all problems, and trying to depend on vaccines won’t resolve a scours problem,” said Barrington.

“No vaccine will make up for poor management, but vaccination can augment good management in a prevention program.

The most time and effort should be put toward proper management versus dependence on vaccination. It’s a mistake thinking you can skimp on management practices because you vaccinate.”

Vaccines that can help augment good management will vary, depending on your situation. Which ones you select should depend on your needs, with recommendations from your veterinarian.

“These may include the rota-corona vaccines, the E. coli vaccines and some of the clostridia vaccines (such as C. perfringens Type C and D),” he said. Which brands and types you select may depend on when it is most feasible to vaccinate pregnant cows in your particular operation.

Minimize stress

Barrington said the fourth leg, addressing stress, can be a challenge. “Birthing is stressful for the calf, especially if it’s a difficult birth or the calf’s born in sub-zero temperatures,” he said.

“In cold conditions, shelter is important, but calving in a barn can also be problematic. We’ve put a stop to many scours outbreaks here just by spreading the animals as far and wide as possible rather than putting them into a barn.”

If a cow must calve in a barn, make sure the stalls are always clean for each new cow and never leave a new pair in the barn for more than 12 to 24 hours.

“If you are congregating the cows to calve in one area – near the barn – it takes a tremendous amount of work to deal with contamination.

You might think the labor would decrease (not having to drive out in a large area to check on the cows), but it actually increases your work tremendously to calve in a confined environment and try to keep it clean.”

Sometimes with a late spring storm you have no choice but to provide shelter, so you need to be set up to where you can do this with the least amount of stress and contamination.

We can’t control the weather but we can address things like crowding and bad surface conditions by spreading out the feeding or moving cattle to clean areas.

With the Sand Hills system, for instance, cows calve in separate groups and are not commingled until the youngest calves are about a month old and past the most critical age for scours.  end_mark

PHOTO:

Top: If hay is always fed in the same area it will become contaminated, so try to move hay to new, clean areas when feeding on the ground. Staff Photo

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