Within its first 24 hours of life, a beef calf is most likely to die from one of two things: a difficult birth or cold stress. Cold stress, or hypothermia, isn't just something producers north of the Mason-Dixon need to be concerned about. It can occur even with temperatures well above the freezing mark, especially if precipitation is present.
Chris Shelley, livestock Extension agent with Colorado State University, keeps it simple. "A wet calf is a cold calf," he said. And when environmental conditions are poor, it is a literal race against the clock to keep a calf's body temperature from dropping.
"Calves are born covered in fluid, and that will decrease their body temperature as it evaporates. Ideally, a good mother will lick the calf and remove most of this fluid. That stimulates blood flow and gets the calf to stand," Shelley said.
It's not just what goes on outside of the calf that matters. Russ Daly, South Dakota State University Extension veterinarian, said what's going on inside the calf is every bit as important, if not more so.
"Colostrum plays a significant role in helping a calf generate its own heat. We tend to think of colostrum in terms of antibodies, but it is higher in fat and protein than regular milk. That means instead of a newborn calf needing to burn off the brown fat he's born with, he can begin to generate his own body heat and recover more quickly thanks to the colostrum," he explained.
From the time a calf is born, Daly said the window for intervention in the event of cold temperatures is a short four to six hours. Normal body temperature for a calf (taken rectally) is 101 to 103F. As that temperature begins to drop, it's a sign hypothermia is setting in. Once the calf's body temperature reaches 96 or 97F, it is often a condition from which the animal cannot recover.
SIGNS OF COLD STRESS
Colorado's Shelley added that cold calves may not shiver, and there can be few to no physical signs of cold stress. Some studies point to pale, cold hooves, a cold nose, problems standing and nursing, clumsiness and erratic behavior as visible signs of a problem. The only way to know for sure if hypothermia is setting in, however, is by taking the calf's temperature. Shelley stressed it's important to remember to wash thermometers between uses to prevent scours and other disease transmissions.
Having established hypothermia exists, warming the calf takes priority. There are multiple ways to do this. Dry the calf using towels, hair dryers, space heaters or warming boxes. When using a warming box, Daly added, it's important to keep it clean between calves. The boxes can be excellent incubators for bacterial growth.
Another proven warming method is to submerge the calf in a warm water bath to bring up its core body temperature. Heat from the warm water transfers through the skin via the calf's blood vessels. It is a very efficient means of treating a cold-stressed calf. Be careful the water is not too hot to the touch; keep it around 100 to 108F.
Glenn Selk, Oklahoma State University beef specialist, reported water warming was compared with air warming (infrared heat lamps) in a study by University of Alberta animal scientists. Calves started with rectal temperatures of 86F. Those calves immersed in the warm water (100F) regained normal body temperature most rapidly with minimal metabolic effort.
Once cold-stressed calves have recovered, there are generally no lingering issues with the exception of frostbite. Veterinarian Daly said there is some evidence cold-stressed calves don't absorb antibodies from colostrum well, which may put them at more risk for health issues the first few weeks of life. So they do bear watching. Long term, however, there are no indications they can't do well in a feedlot, on a pasture or as a replacement. The one exception would be if the calf suffered frostbite to its feet.
"Frostbite on an extremity, and it's often the back feet, will become evident within a couple of weeks of the calf being stressed," he said. "If that is the case, those injuries to the back feet are often severe enough to consider euthanasia. Frostbite on the tips of ears or tails, however, usually will not impact the animal in any way other than its appearance."
Hypothermia in newborn calves is not just something that happens when snowdrifts are piling up at the door. In the right conditions, temperatures in the 30s or 40s, in combination with precipitation, can be enough to plunge a newborn calf's body temperature into the danger zone.
Several steps taken before cold weather sets in can help the herd and any newborns survive the elements.
-- Construct windbreaks to protect against winter winds.
-- Ensure bedding is ample and replenished often to help insulate from the cold.
-- Plan ahead for areas and supplies needed to get a newborn calf reheated quickly. This may include a heating crate, warm water bottles, a calf-sized tub with access to warm water, hair dryers, space heaters and heating pads. Heating crates, also called hot boxes, should be used with caution, not allowing temperatures to exceed 105F, and being sure ventilation is good. These boxes need to be cleaned between uses.
-- Keep a calf-care kit in the farm truck and a second one in the area designated for reheating. Each of those kits should include a digital thermometer, dry towels, blankets, tubing, powdered colostrum and water.
-- Consider keeping heifers close to areas where calves can be warmed quickly, as these females are more likely than experienced mama cows to have delivery problems.
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