Why do some calves thrive in cold weather while some, given the same conditions, just want to die? Sometimes we say the calf has no "heart to live" or the cow is simply not a "good mother." But, Ron Torell, University of Nevada Extension livestock specialist, says that might be a cop-out.

It probably has more to do with management of the cow and the calf's ability to trigger thermogenesis -- the creation of heat, he says. In the case of the latter, it's the ability of a newborn wet calf to dry off, warm up and bring its core temperature to normal -- even with a wet hide and in the face of a cold, howling wind.

"Shivering helps the body generate heat," Torell says. "The skeletal muscles create the shivering and there's a little muscle on each hair that helps to create a better blanket."

More important is the brown fat, or adipose tissue, prevalent in healthy, well-fed newborns that exhibit non-shivering thermogenesis to regulate their body temperature. Torell says the brown fat is located around blood vessels and major organs. When triggered into activity, the brown fat causes warming of the blood, which is circulated throughout the body to spread the warmth.

"If a calf is born from a thin cow, chances are the calf lacks an adequate amount of this stored brown fat tissue to warm itself," Torell says. "On a cold day with the wind blowing, you may have a dead calf if the calf lacks this brown fat."

A calf can have "heart" and "will to live," but if it has no fat storage, hypothermia may take its toll primarily due to a lack of brown fat adipose tissue in the calf. That is the manager's fault, Torell says.

"It all goes back to 12 months of cow herd management," he says. Preservation of body condition, adequate nutrition of the brood cow, good management, a mineral program, good genetics, mothering ability, calving in an area that offers protection and calving in synch with Mother Nature, these factors all contribute. Other factors such as dystocia, first-calf heifers, delayed delivery, oxygen deprivation at birth -- can all contribute to hypothermia and impede thermogenesis.

A thermometer is essential to determine the degree of hypothermia, Torell adds. "Often, a calf doesn't appear hypothermic but, upon taking its temperature, you find its body temp is below normal."

Early treatment of hypothermic calves is important. The severe hypothermic calf can be revived and saved. However, the experience often sets them back and their body defense system can be compromised. This sets the calf up for pneumonia, scours and other calfhood problems. -- Clint Peck