Source: Ontario Ministry of Agriculture, Food and Rural Affairs
How was your calving season? It’s the most exciting time of the year on most Ontario beef cow-calf farms! When calving is in full swing and the crop of wobbly calves struggling to keep up with the herd, the mood on the farm is positive. With good momma cows, good management and good weather, your production season was off to a great start. Oh, did I say good weather? Excellent point … while we know our cows and are confident in our management ability, the weather remains remarkably unpredictable. While we expect extremely cold temperatures in February, March should give us a break. However this year, the first week of March brought -30C in north eastern Ontario, while in Walkerton, in the south central part of the province, overnight lows touched -25C! These were much colder than the normal overnight lows for these locations for this time of the year, which are -12C and -9C respectively.
With this kind of cold snap, if calving occurs outside of a warm structure, the calf will die of hypothermia if it is not quickly retrieved and warmed up. Cattle have not evolved to calve in these frigid conditions. Wild populations of similar animals such as moose, deer and bison, would not even think about calving in March (or even April) under our climatic conditions! They wait until May and June, when temperatures are warm and feed is plentiful and nutritious. As well, their births are not attended by obstetrical staff. Even so, they are usually able to deliver their newborn and get it mothered up without help.
Back to the barn. If we choose to calve in winter or early spring, we have to be prepared. Sheltered, well bedded calving barns or pens are a must (warmed with at least cattle body heat). This is especially true when the conditions turn ugly, like extremely cold temperatures, strong wind chill values, freezing rain, or the dreaded liquid rain at +1C. Why are these conditions so devastating? The answers lie in physiology, geometry and the physics of heat flow.
Compared with adult cattle, calves are relatively small animals. Due to the mathematical relationship between volume and surface area, small animals have a much greater surface area relative to their volume than do large animals. Heat loss is directly related to surface area, but heat production is related to body volume. This means that small animals are at an extreme disadvantage in cold conditions.
Compared to large animals, they lose heat to the environment at a much faster rate, relative to their ability to produce heat from normal metabolism. When wind becomes a factor, heat loss is exaggerated as the constant stream of cold air pulls heat away from the calf’s surface. When it rains in cold weather, the effect doubles. A wet hair coat loses its insulative properties, and moisture evaporating from the calf consumes a remarkable amount of body heat in the process. Combine any two of: cold air temperature, wind, or a wet calf and you have the recipe for hypothermia and death.
Since calves are born covered with fluid, they are already prone to chilling. Attentive mothers will immediately lick their calf to dry it off, stimulate blood flow, and encourage it to get up and start nursing. Any time lag between birth and drying puts the calf at risk … and even the best mom can’t deal with -30C or severe wind chill.
So what can you do to combat chilled calf syndrome? Researchers at the University of Alberta1conducted experiments to determine the best methods of warming a chilled calf. The calves were experimentally chilled to a rectal temp. of 28C. Then the calves were placed in a 20C room, and rewarmed using one of four methods. These included: a warm water bath; vigorously rubbing the calf dry and wrapping it in a blanket; or vigorously rubbing the calf dry and warming it with two 250 watt heat lamps. They found that the warm water bath was the most effective treatment, taking about 1 hour and 20 minutes to bring rectal temperature back to normal (38C). Both the blanket method and the heat lamps were effective at raising the calves’ body temperature, but these methods were slower, taking about 2 hours and 20 minutes.
Although the water bath method was most effective, it is also the most difficult to manage. You need to start off with cool water and gradually add warm water to achieve a water tem-perature of 38C. The calf needs constant attention to make sure it doesn’t drown. The researchers recommend the water bath method for severely hypothermic calves or for those born prematurely and mildly chilled. For mildly hypothermic calves, the blanket or heat lamp methods should be adequate.
Many variations of “calf warming boxes” have been tried over time, with variable results. Extension specialists at the University of Nevada2 reviewed a number of studies and concluded that in order to be safe and effective, these devices need to have a circulating fan, a thermostatically controlled heat source, and a ventilation port in the top which allows super humid air to escape. Without these features there is a significant risk of scorching the calf, overheating the calf and subjecting the calf to high humidity, which predisposes it to pneumonia.
Saskatchewan experts3 suggest using a rectal thermometer to help pick out mildly hypothermic calves. They note that chilled calves are not able to effectively absorb fluids, so warming the calf before feeding is a must. With a mildly hypothermic calf, feed warmed colostrum when it is alert and able to suck. With severely chilled calves, you may have to tube feed them with an esophageal feeder even after they are well on the way to warming up. They may also benefit from a commercial oral electrolyte designed to counteract acidosis.
Always consult your veterinarian for recommendations specific to your situation.
Happy Calving !
- University of Alberta, Dairy Research Center publication, Rewarming Chilled Calves, by Barry Robinson, Ph.D., Great Northern Livestock Consulting Ltd. [with Dr. Bob Christopherson and Dr. Bruce Young, University of Alberta]
- Adapted with permission of University of Nevada Cooperative Extension from its publication, Care of Hypothermic (Cold Stressed) Newborn Beef Calves by Ron Torell, Bill Kvasnicka, Ph.D.; and Ben Bruce, Ph.D., University of Nevada Cooperative Extension specialists, CL 788.
- Adapted with permission of the Farm Animal Council of Saskatchewan from its publication, Cattle FACS: Calf Scours Overview, General Principles.