– Dr. John Yost, Extension Educator, Agriculture and Natural Resources, Wayne County, Ohio State University Extension
I can’t say for sure, but I imagine that any cow-calf producer would trade frozen ground for mud. The downside of frozen ground and newborn calves is the chance for hypothermia. Cows aren’t stupid. When the weather turns cold the herd will congregate where it is dry and sheltered. Those cows that come into labor and look to isolate themselves are often left to go to the worst spot of the field to drop their calf. The sight of a new calf stretched out in a wet hole, will knot up your stomach and you know it is going to be a long night trying to get it warmed back up.
Newborn calves don’t benefit from heat generated by the rumen fermentation that helps their mother weather cold temperatures. When air temperature drops below 55 degrees Fahrenheit, a calf is reliant on metabolic heat from the small fat reserves that are deposited prior to birth. When a calf is born into an extreme cold environment, their normal 18-hour energy reserve can be quickly exhausted through shivering, leading to hypothermia.
A calf’s normal body temperature at birth should be between 101.5 and 102.5 degrees. As their core temperature decreases, the symptoms of hypothermia will set in. The body’s initial reaction is to preserve its core temperature by decreasing blood flow to the limbs, shortened breathing, and shivering. This biological response can delay a calf trying to stand and nurse, thus compounding the problem. If their core temperature drops to close to 88 degrees, breathing rate will drop to 4 to 5 breathes per minute and the calf may appear to be deceased.
Knowing the rectal temperature of a hypothermic calf is necessary to determine what supportive care is needed. Every cattleman should have a rectal thermometer as part of their newborn calf tool kit. You can also use a calf’s behavior to determine how much trouble it may be in. If their body temperature has just dipped below 100 degrees, and they are still able to hold a normal laying position, they may only need to be dried off and relocated to a sheltered space to regain their body temperature. Moving them to a well bedded barn with mom can get them headed back in the right direction. It is when their core temperature falls to the mid-90’s or below that more aggressive care is warranted.
Those calves that have a poor suckling response, will need to be provided an external heat source to begin raising their core temperature. It could be just putting them in the heated shop, sitting with them in the floor of the truck, or using a warming box. This will probably require you to take them away from mom and you will need to provide some initial nutrition. A calf needs to consume 4 to 6 quarts of colostrum during its first 24 hours of life. As you know, colostrum is essential for providing early immunity until their immune system develops around the time they are 1 to 2 months old. The more they can consume, earlier in that 24 hour period, the better off they will be. Ideally, you can milk out the mother but if not you can substitute a quality colostrum replacer of 100 igG.
If a calf’s temperature drops below 90 degrees, you will need to all of the available tools to give it a fighting chance. A recent study by Copeland et al., from Iowa State (http://doi.org/10.1111/jvim.17066) comparing forced air to water bath rewarming methods found that both systems were able to successful return a calf’s body temperature to normal range. The water bath method (64 minutes) worked twice as fast as a forced air system (123 minutes). If using a water bath, remember that you will need to support the calf’s head during the rewarming process. You will also need to use a stock tank heater to maintain the water temperature around 100 degrees. If you use a forced air system, like a torpedo heater, keep the heater far enough away from the calf as to not cause burns. Another point to is to get the calf off the floor when using forced air by laying them on a wooden pallet. Concrete and bare earth will continue to rob heat from the calf. These calves will need to be tubed every couple hours with about 24 oz of colostrum replacer. Researchers have looked at adding caffeine or sugar to these tube feedings, but the results have been inconclusive.
I am always amazed at the fight in some cold calves. There are times that I worked all day on a calf, not expecting it to make it, only to have it greet me at the shop door. This isn’t a battle that you can expect to win all the time. However, I am never surprised at the effort cattlemen and ranchers will put into resuscitating a cold calf. That is just who you are.