| RENO, Nev. (Feb. 6) — Cattlemen’s College® attendees heard from veterinary experts on calf scours and bovine viral diarrhea (BVD) during the PR 103 session titled, “Developing a Disease Control Plan for Your Ranch.” David Smith of the University of Nebraska, Lincoln outlined the Sandhills Calving System and how it can help reduce instances of calf scours. Dan Givens from Auburn University spoke about detecting and preventing instances of persistently infected (PI) BVD cases. The academics were followed by Montana producer Tom Hougen, who talked about his personal experience with BVD.
Calf Scours prevention with Sandhills Calving System
Smith equated calf scours to dominos: Once the first one falls they all tumble down. However, there are three ways to prevent this domino effect. First, producers could eliminate the agent, which would keep the first domino from falling. The second option is to increase the host’s resistance, making them less likely to fall. Or producers could prevent effective contact with the disease. This would have the same effect as spreading the dominos out; when one falls it couldn’t hit another.
“The first option is not possible,” Smith said. “The agents of scours, including bacteria, viruses, protozoa and fungi, are present in every herd.”
So it becomes a battle between exposure and immunity. Smith says there is a window of vulnerability from 1 to 3 weeks of age in which calves are very susceptible to scours. This is also the same age when they can transmit the disease to other calves.
The second option of increasing resistance can be monitored by ensuring calves drink sufficient colostrum after birth. However, prevention of spreading also must be explored. Smith found that there was a greater risk of calf scours as the calving season progressed. This makes sense because the potential for exposure is multiplied, especially by the presence of older calves. A new calving system concept emerged from this problem.
“Let’s have eight one-week calving seasons instead of one eight-week calving season,” Smith said. The system he described is the Sandhills Calving System. In this program the first group of females that calve are left in the first pasture, while the remaining bred females are moved on to the next pasture. This pattern continues on a weekly basis, with pairs being left as the heavies move on to a new pasture each week. This limits potential for exposure because all calves in a pasture are born within a week of one another.
“This is the number one thing we’ve done over the years that has benefited us economically,” says Terry Clements, a Nebraska rancher who implemented the Sandhills system. Clements and others have found that the calving system dramatically reduces death loss from scours and minimizes the need for antibiotic use.
PI BVD
Grooms said the good news about BVD is that, unlike calf scours, its agents aren’t naturally present in the environment. This makes the goal for most farms to become completely BVD-free very reasonable.
Calves can become persistently infected in utero during the first five months of gestation. By following these tips, Grooms said instances of BVD-PI cattle can be eliminated from an operation.
The first step is to test to identify and remove PI animals.
“Testing tells you if you need to practice biosecurity or biocontainment,” Grooms said. Biocontainment is preventing a disease on the farm from spreading to other individuals; whereas, biosecurity is preventing the disease from even entering the farm.
Grooms’ second recommendation is producers should not let cattle lacking BVD testing onto their farms, especially within the first five months of the breeding season.
“The greatest danger is movement and mixing of cattle,” Grooms said.
To go along with this, Grooms said to avoid cattle coming into contact with cattle from outside herds off of the farm. If this is not possible, he recommended a 21-day quarantine for nonpregnant animals when they return to the farm. If a female in the first five months of her pregnancy comes in contact with outside cattle, Grooms recommended isolation until the calf is born and tested.
Grooms’ fourth recommendation was preventing people wearing boots and coveralls that may have been around other herds from coming in contact with the cattle.
“You can kill BVD with dishwashing detergent,” Grooms said. This is all it would take to remove the pathogen from clothes. But without cleaning, contamination from another herd is a real possibility.
Fifth, Grooms told ranchers they shouldn’t allow dirty or contaminated equipment or vehicles from other herds to come in contact with their cattle. This especially applies to ranchers who share equipment with other producers.
Grooms sixth recommendation was fly control and his seventh was to limit wildlife contact, especially deer.
BVD-PI ranch biocontainment
Hougen, owner of the Hougen Ranch in Melston, Mont., experienced BVD firsthand.
Starting in fall 2002, Hougen was experiencing sick calves and unexplained abortions. In January 2003 he happened to attend a producer meeting on BVD.
“Then one day after treating four or five heifer calves it was like something hit me in the head,” Hougen says of his fall 2003 realization. “One of those calves looked like the pictures of BVD calves I’d seen.”
Hougen called his veterinarian out to take samples. As he suspected, many of the calves tested positive for BVD-PI. A feeder he sold steers to tested and found similar results.
“I’m assuming we lost at least 20 calves that fall between the two of us,” Hougen said.
Up to that point, Hougen hadn’t been vaccinating for BVD. Going into 2004, he set up a modified-live virus (MLV) vaccination program. He also put together a plan to PI test all the calves born on the ranch. Of the 1,320 calves tested, 39 calves tested positive. Between branding in mid-May and weaning in early November, 20 of the PI calves died. Hougen isolated the 19 remaining PI calves, 14 of which died due to adverse weather or other stressful situations during the winter.
By following a strict vaccination-and-testing protocol, Hougen said he is fairly certain he no longer has any BVD-PI cattle on his ranch. However, the experience did leave behind some useful lessons he shares with other producers.
“We need to be aware as ranchers that there is that critical time, and we need to know where our cows are in that time,” Hougen said. “If you suspect you have a problem, whole-herd test,” he recommends. If these test results come back PI positive Hougen says that there is no question what needs to be done.
“Once a PI, always a PI,” he said. “So you just need to get rid of them.”
|