Sandhills Calving System shows calf health improvement
When veterinarians, including veterinary epidemiologist David Smith of the University of Nebraska-Lincoln, began to take a look at how to manage cows to prevent disease and improve productivity, the result was the Sandhills Calving System.
The Sandhills production system is so named because of its implementation on several ranches in western Nebraska’s Sandhills where ranchers have been able to cut calf scours to nonexistent levels.
“To work, ranchers have to make the decision to change management practices, particularly to minimize risk for scours,” says Smith. “For the Sandhills ranches to move to nonexistent calf scours was a real accomplishment because their herds weren’t always like that.”
Smith says when he explains the Sandhills principles to vet students he uses dominoes as an example. “The problem with domino ranching is the dominoes fall down, and the closer you put them together the more they knock each other down and the more rapidly the spread of domino disease,” he illustrates. “Once you understand that you can start to think about how you’re going to keep the dominoes from falling down.”
Any production system that prevents other dominoes from falling down is a biocontainment strategy – the actions taken to prevent the spread of infectious agents within a population. “It’s about knowing they’re out there and managing animals so they don’t get the disease,” says Smith.
One way to prevent spread is to prevent effective contacts by physically separating animals or minimizing contact time. Another is to increase host resistance. “For calf scours, that typically means we’re going to vaccinate the cow so her colostrum provides protection to the calf or make sure the cow has been exposed to the pathogens so she can provide the protections,” says Smith.
A third biocontainment strategy is to remove the agent or prevent its introduction to the population in the first place. “This strategy isn’t very effective in calf scours because the pathogens exist in the herds and there’s not much opportunity to eliminate them,” explains Smith.
“Calf scours are important because of death loss of calves, performance losses occurring in surviving calves, treatment costs in labor and medication and the human toll we don’t often talk about,” says Smith. “There’s a huge sense of frustration ranchers experience when they’re dealing with scouring calves after spending days and nights getting live calves on the ground.”
In addition, Smith says there are public health concerns with calf scours, like salmonella. “There’s a risk to human health from those pathogens.”
“The agents that cause scours are numerous. There are a number of bacteria and we sometimes see fungal infections after we treat scours,” he explains. “These scours agents exist on all cattle operations and they’re waiting for opportunity to cause disease.”
Smith says there’s a battle between a calf’s immunity and resistance and the level of exposure to pathogens. “When we think about the principles of calf scours, this is the thing we need to be thinking about – the immunity of the calf and its challenge level of exposure.”
“The battle begins at birth, so the calf acquires protection by absorbing antibodies from his dam’s colostrum. Although it can’t have an immune response immediately, the calf eventually acquires the ability to resist pathogens,” he says.
Between the colostrum’s protection and the calf’s development of resistance there is left a period of time when it is more susceptible to infection. “If the level of exposure is high enough, there’s a time period when the calf is more susceptible to disease,” says Smith. In herds experiencing scours, most illnesses and deaths occur in calves between two and three weeks of age. “That’s the window of vulnerability,” he says.
That’s also the age when calves become infective. “Calves become infective to other calves when they’re two or three weeks in age, and the greatest risk to a newborn calf is a calf two or three weeks old, now infective and shedding pathogens at higher levels,” says Smith.
In their investigations of calf scour outbreaks, Smith says one herd, consisting of 402 cattle managed as a single group in an intensive grazing system, illustrates most of his points about calf scours.
The ranch calved in May and June, moving to fresh pastures every two or three days. “They made the decision that, because of ongoing problems with scours, their labor investment was better spent taking care of cows and not treating sick calves,” says Smith. That year they didn’t treat any calves with scours, resulting in 48 deaths.
“We took the information we knew about the calves that did and didn’t get sick to explain what it was about the calves that did get sick that made them more susceptible,” explains Smith.
One thing, which isn’t new news, was the age of its dam. “If it was born to a two-year-old heifer, it had a greater probability of dying than if it was born to a three-year-old or older,” says Smith. “Heifers don’t have the same quality of colostrum and offer passive protection. There are a number of things to explain that relationship.”
Because of the intensive grazing, the cows had learned to go through the gate immediately upon its opening. “The cows often left their calves behind to eat fresh pasture and came back to pick up their calves,” says Smith. “We wondered if there was a relationship between deaths and calves born and left alone that day without the same care they would have received had the gate stayed shut.”
Smith says researchers found calves born the day the gate opened were almost twice as likely to die from scours than a calf born another day.
“Most of the calves died between one and two weeks of age,” he says. “Very few died after three weeks of age because they were acquiring their own immune response by then.
Regardless of when in the calving season calves were born, they consistently died in the two- and three-week age range. However, if a calf was born in the early part of the calving season it had lower probability of ever dying from scours. “The later a calf was born, the greater its probability of dying from scours,” says Smith.
In answer to this, Smith says the more calves hit the ground, the more pathogens multiply. “The cows are the reservoir of the pathogens from one year to the next. Many ranchers believe certain pastures are contaminated, but I doubt that,” he says. “In Nebraska there are winters cold enough, and summers hot enough the pathogens don’t survive. The pathogens live in the GI tracts of the adult cows. The calves, being susceptible, grow those pathogens to greater and greater numbers.”
“Things look really good at the beginning of calving and then deteriorate, so we tried to recreate conditions that exist at the beginning of the season – a clean calving area and no older, more infective calves as a source for exposure,” says Smith. “We move pregnant cows every week into a new pasture to minimize exposure and start in a clean environment. It also gives us the opportunity for more maternal bonding because we’re not messing with the cows every day trying to move pairs.”
Another result of moving pregnant cows every week leaves pairs in the pasture in which the calves were born, creating pastures where all the calves are within a week of age, leaving out the older, infective calves.
“In herds where we’ve collected data this system is extremely effective with significantly less death and illness due to scours, and minimal to no antibiotic use because we don’t have calves to be treated,” Smith comments.
Ranchers who’ve implemented the system say it’s the number one thing they’ve done over the years benefiting them economically.
“The point is that actions we take for biocontainment through these management systems can be very effective,” says Smith. “When I talk with ranchers about employing these systems in their own environments, the important thing is to use the principles here and to not make so many compromises the system doesn’t work any more.”
Christy Hemken is assistant editor of the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.