Preventing scours in calves
February 1, 2019
The most common illness in young calves is scours. According to George Barrington, Washington State University, diarrhea results in the greatest economic loss in this age group. In beef calves, one study showed 5.5 percent of calves die from diarrhea during the first three weeks of life.
There are many causes for intestinal infection and diarrhea including bacteria, viruses or protozoa. Whether calves get sick is often related to multiple factors including exposure (contact with pathogens, and the "dose" of pathogens), level of immunity, and stress. Good weather, clean ground and stress reduction (shelter from bad weather, minimizing confinement) can help reduce incidence of scours.
Barrington said the two major strategies for prevention are 1. reducing the likelihood of introducing a disease agent into the herd (external biosecurity — not bringing new cattle into the herd that might expose your cattle to new pathogens), and 2. reducing the likelihood of transmitting a 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. A dairy calf might bring Salmonella, Cryptosporidia, or 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 in the winter feeding area — to minimize newborn calves' contact with fecal material and contamination.
The Sand Hills calving method, in which the 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," he said.
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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 without clinical signs of infection. "Most cattle are probably exposed to continuous, low doses of these pathogens, shed by sub-clinically 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," he said.
"However, if young calves are exposed to high doses, two things can happen. First, these calves typically develop clinical disease. Second, they become 'super shedders' and release billions of viral particles (or bacteria) per gram of feces. This super shedding contaminates the environment quickly and puts other calves at a much higher risk for disease," Barrington said. Younger calves with less resistance, or that 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 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, immuno-naive calves to these pathogens," he said.
It doesn't hurt to have some exposure, because this stimulates the young calf to start building immunity against the pathogens. Calves become sick when they are exposed to an overwhelming level of these 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.
"Calves get exposed, so it's a matter of controlling the level of infection in their environment. We know the pathogens are there, so we try to spread calves out and minimize grouping/congregating them in small areas," he said. Then they don't encounter a high level of contamination. Summer calving, with cows spread out on clean pasture, greatly reduces risk for scours. Whenever the cows with young calves have to be fed, this groups them in a smaller area and presents more challenge with contamination.
"If our feeding pattern can help spread them out, this can minimize problems. A feeding area can become contaminated very quickly when space is limited or ground is wet. If you use feed bunks or round bale feeders, you need to move them often. If you are feeding on the ground, keep moving to new areas," he said.
"It helps to feed some distance away from water so cattle have to travel between feed and water and don't stay all the time in the same small area, with more manure buildup. The most important thing is to never calve in your winter feeding area because it is highly contaminated," Barrington said.
"This is where the Sand Hills method is beneficial, rotating the cows to a new pasture every couple weeks. Grouping calves based on age really helps," he said. The older calves have already begun shedding pathogens in their feces, and if you can have the younger, more vulnerable calves in a new, clean place, they won't be exposed so quickly, nor to such an overwhelming load.
Chris Clark, large animal medicine, Western College of Veterinary Medicine, University of Saskatchewan, said a healthy cow with good colostrum gives the calf the best protection. "There must be a high level of antibodies in the cow's colostrum and the calf must nurse enough colostrum, very quickly after birth, to be adequately protected," he said.
"You want to make sure your cows are vaccinated for scours, up-to-date on their vaccinations, and vaccinated relatively close to when they start calving. Then the cow will have the highest possible level of antibodies in her blood, which means she will then have high levels in her colostrum," he said.
Also make sure the cow is in good body condition before calving, with proper levels of nutrients when she gives birth. "This will also ensure that she can produce the best and largest amount of colostrum. As a rule of thumb, heifers' colostrum is never quite as good," Clark said. They haven't had as much chance to become exposed to as many things and to build as strong immunity as an older cow.
"If you need to give a calf colostrum (if he can't nurse for some reason), it should be as much colostrum as possible and as fast as possible. This means about 6 pints in the first six hours and another 6 pints in the following six hours, to give him the best opportunity to absorb adequate antibodies." You might use frozen colostrum or some from another cow, or milked from the calf's own mother if for some reason he is unable to suckle her.
"If you don't have any colostrum available, consider using one of the high quality commercial substitutes. Make sure it's a good quality — one that is made from colostrum rather than one that was made by extracting antibodies from milk or blood," Clark said.
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. If a calf can't nurse or doesn't nurse on time to absorb those antibodies, however, you've wasted your money on the vaccine.
"There is no one vaccine that will halt all problems, and trying to depend too much on vaccines won't resolve a scour problem," Barrington said. No vaccine can make up for poor management, but vaccination can augment good management in a prevention program.
There are some good vaccines, and they keep changing. Which ones you select should depend on your own situation and needs, with recommendations from your veterinarian. "These may include rota-corona vaccines, E. coli vaccines and some of the clostridia (such as C. perfringens Type C&D)," Barrington said. Which brands and types you select may depend on your needs and timing — when it is most feasible to vaccinate the pregnant cows in your particular operation.
Birth is stressful for the calf, but even more stressful if it's a difficult birth or he's born in cold temperatures. "Shelter is important, but calving in a barn can also be a problem. We've stopped many scours outbreaks just by spreading the animals as far and wide as possible rather than putting them into a barn," Barrington said.
If cows must calve in a barn, make sure the stalls are always clean, for each cow, and never leave the new pair in the barn for more than 12-24 hours. "If you congregate the cows to calve near the barn it takes a tremendous amount of work to deal with the contamination," he said.
Even if you aren't calving in winter, a late spring storm may necessitate shelter so you need to be set up to provide it with the least amount of stress and contamination. "We can't control the weather but we can address things like crowding by spreading out the feeding or moving the cattle to clean areas." This helps make sure calving cows are not lying in fresh manure and that young calves are not exposed to feces from older scouring calves. With the Sand Hills system the cows calve in small separate groups and are not co-mingled until the youngest calves are about a month old and past the most critical age for scours. ❖
— Smith Thomas is a cattle rancher, horseman, freelance writer and book author, ranching with her husband near Salmon, Idaho. She can be reached at firstname.lastname@example.org.