Calves that become chilled at birth and don’t immediately ingest colostrum have poor survival rates. If a calf fails to nurse, it doesn’t obtain energy (for keeping warm) or antibodies to protect against disease.

A calf’s ability to absorb antibodies from colostrum diminishes as its body temperature becomes colder. Even if you force-feed colostrum a few hours after birth, absorption rate will be less than that of a warm calf. Any stress – from cold or a difficult birth – can interfere with optimum absorption, leading to problems with scours, pneumonia and other infections.

Robert Callan, professor of clinical sciences in the College of Veterinary Medicine at Colorado State University, says a newborn calf’s temperature is about 103° F. It drops to a “normal” of 101.5-102° within a few hours. “But if it drops below l01°, this means the calf can’t thermo-regulate and keep itself warm,” Callan says. If calves are born in cold, windy weather, their temperature drops faster.

You can tell when calves are really cold, and you can usually tell when calves will be alright, but borderline calves can be hard to evaluate, says Russ Daly, South Dakota State University Extension DVM. “Many ranchers stick a finger in a calf’s mouth to see how cold he is [if he hasn’t nursed, the inside of his mouth is cold], but I encourage use of a rectal thermometer. Any calf with a rectal temp below 100° will benefit from being warmed up and a supplemental dose of colostrum,” he explains.

A normal calf has a tremendous ability to thermo-regulate, especially if the cow licks him off quickly and helps him get dry, Callan says. A wet calf continues to chill (especially in a breeze) due to evaporation of moisture and more rapid heat loss.

“High-risk calves also chill quickly. These include calves that suffered prolonged birth, twins, and calves born to sick cows or cows in poor body condition. Cows deficient in energy and protein may give birth to weak calves that don’t have much reserve, and those cows’ colostrum has less energy and fewer antibodies,” Callan says. Calves born to well-nourished cows burn through glucose reserves, glycogen and fat more slowly than calves born to cows with inadequate nutrition.

“If a calf doesn’t nurse, it starts depleting its blood glucose within 30-60 minutes. Its body tries to replenish this from liver glycogen stores but these can be used up within 4-6 hours, after which the calf becomes hypoglycemic. If calves fail to receive proper nutrition, they deplete their brown-fat reserves in 1-6 days and are starving,” Callan says.

Protein and energy are crucial, and supplying supplemental fat to cows during late gestation will help calves be better prepared to handle cold weather, he adds. Cows with adequate protein levels also produce better colostrum.

Colostrum is important. Timely ingestion of colostrum is a big factor in handling cold weather. A calf that nurses soon after birth stays warmer.

“There’s much more to colostrum than antibodies. It contains much higher levels of fat and protein than regular milk,” Daly says.

“Any calf with a temperature below 100° needs assistance and warming,” Callan adds. “First and foremost, the calf needs milk to produce its own body heat. Provide it by bottle or tube, whether it is milk or colostrum directly from the cow, warm milk replacer or warm homogenized milk. Feed at least a quart. If it’s too cold to suck, give it by tube.”

Without milk, the calf has no energy source and will continue to go downhill. “Re-check a cold calf every few hours to make sure his temperature is rising. The energy provided by one feeding can be used up in 4-6 hours and it will need more,” Callan says.

Don’t forget shelter. Be prepared for cold weather, with windbreaks, shelter and bedding for calves, rather than just trying to deal with cold calves, says Charles Stoltenow, North Dakota State University Extension livestock program director.

“As far north as we are, we must get calves off frozen ground. If there’s no old grass, they need bedding. It’s often better to sacrifice some old hay than feed it to cows. Think preventatively. After calves suffer frostbite, or have been in the rain for three days, it’s too late,” Stoltenow says.

“Watch the weather and get calving cows out of the elements,” Daly says. Take care of any calves born outside as quickly as possible. While newborns can handle relatively cold temps, wind or precipitation can quickly sap body heat. They must be dried off as soon as possible, he says.

A “warm” windy day can be deceptive, he adds, and you may not realize that drying a newborn calf is an emergency. “I’d worry more about 32° temperature with wind and precipitation than a much colder day with no wind,” Daly says.

Warming a calf. Some people use a warm-water bath because it warms the calf’s extremities and body surface quickly, but this is labor intensive because you must completely dry it afterward.

You can reverse frostbite with warm water if the calf hasn’t been cold too long. “The key is warm water, not hot. And don’t rub him very much because tissues may be damaged from freezing and you could damage them worse,” Daly explains.

Warm water on freezing extremities will warm them faster than using warm air, but getting warm air into the lungs is beneficial for raising a calf’s core temperature more quickly.

Callan likes to use a warming box. “A small ceramic electric heater in a small, enclosed crate – where you can regulate temperature – works well. The calf is breathing warm air into the lungs, and all his blood is going through the lungs. A warming crate can be very beneficial for hypothermic calves,” Callan says.

Boxes should be cleaned and disinfected between calves. “We’ve seen situations in which I suspect the (lack of) warming-box sanitation led to increased calf scours,” Daly says. “Pay attention to materials and design, making sure the box can be cleaned easily. You need good ventilation, and some way to remove humidity. If it’s too humid, you’ll have problems with respiratory diseases as well as buildup of pathogens.”

Weak-calf syndrome. Several decades ago, some early-calving ranchers were losing calves to “weak-calf syndrome.” Studies in the 1970s determined it was primarily a problem in calves from young cows (two- and three-year-olds), caused by deficiency in dietary protein during late gestation.

Robert Loucks (Lemhi, ID, Extension agent, now retired) worked with an interdisciplinary team studying weak-calf syndrome for 15 years.

“In 1971-72, a research group from the University of Idaho led by Richard Bull collected and analyzed thousands of blood and tissue samples from healthy calves and weak calves, and samples from their dams, and found that weak calves – born from protein-deprived dams – were not physiologically normal,” Loucks says.

The calves didn’t absorb antibodies from colostrum efficiently. And, if the newborn’s immune system is compromised due to protein deprivation in the dam, likelihood is high that the calf will develop weak-calf syndrome and die.

The researchers worked with four cooperating ranches (150- to 1,100-head cowherds) that had history of weak-calf syndrome.

Protein levels for young cows were increased on two ranches, using higher-quality forage or protein supplement. Weak-calf syndrome was virtually eliminated on those two ranches, while incidence remained the same on the other two ranches.

“Bull demonstrated through subsequent studies that protein requirements of two-year-old cows in the last 45 days of gestation was 1.81 lbs. of crude protein (CP)/day. As a result of his research, the National Research Council increased its protein recommendation for young cows. The general recommendation today is 7% CP for mature cows, and 10% for young cows,” Loucks says.

When calving early – as many western ranchers do, to have calves born and cows bred before going to public range – cows are on harvested feeds or supplements rather than green grass during the last crucial weeks of pregnancy. This, combined with cold stress, can put calves at risk, Loucks says.
-- Heather Smith Thomas for BEEF magazine