Caring for cold stressed or hypothermic cattle
Hypothermia is a profound drop in body temperature. Animals less than 48 hours old or animals with a preexisting condition or disease are at the greatest risk for developing hypothermia, according to Dr.
Charles L. Stoltenow, North Dakota State University Extension veterinarian. Newborns are often hypoglycemic (low energy reserves) and have electrolyte imbalances. Animals with preexisting conditions (pneumonia, old age) have impaired body reserves and may succumb more readily to very cold and windy conditions.
“The delayed delivery often associated with heifers, and lack of experience to lick the calf and stand to let it nurse, all contribute to the increased incidence of hypothermic calves in our first-calf heifers,” according to extension specialists at University of Nevada-Reno.
Mortality in beef herds from birth to weaning range from 3 to 7 percent. The majority of this occurs within the first 24 hours of life, with slow and difficult births (dystocia) and cold stress (hypothermia) the leading causes of death.
There are two types of hypothermia, according to extension specialist Ront Torell, Dr. Bill Kvasnicka and Dr. Ben Bruce.
The first, exposure hypothermia, is the steady loss of body heat in a cold environment through respiration, evaporation and lack of adequate hair coat, body flesh or weather protection. This type affects all classes of livestock but particularly affects young, old and thin animals.
The second, immersion hypothermia, is the rapid loss of body heat due to saturated hair coat in a cold environment. Immersion hypothermia is often brought on during birth when the calf is born saturated with birthing fluids.
Other causes may include being born in deep snow or on wet ground, falling into a creek or being saturated from heavy rains followed by chilling winds.
Faced with a cold environment, the body tries to defend itself in two ways: shivering, to increase muscle heat production, and blood shunting, to reduce heat loss by diverting blood flow away from the body extremities to the body core.
Mild hypothermia occurs as the body’s core temperature drops below normal (approximately 100° F. for beef calves). In the early stages, vigorous shivering is usually accompanied by increased pulse and breathing rates. A cold nostril and pale cold hooves are early signs that blood is being shunted away from the body’s extremities. In the case of a newborn calf, severe shivering may interfere with its ability to stand and suckle. This sets the calf up for severe hypothermia. Erratic behavior, confusion and clumsiness are all signs of what producers often call “dummy calf.” These are signs of mild hypothermia.
Severe hypothermia results as the body tempera ture drops below 94° F.
Shunting of blood continues, manifesting cold and pale nostrils and hooves due to poor oxygenation of the tissues near the body surface. Decreased circulation also results in a buildup of acid metabolites (waste products) in the muscles of extremities. After the shivering stops, it is replaced by muscle rigidity. The pulse and respiration begin to slow as the body core cools to 88° F.
Below core temperature of 94° F, the vital organs begin to get cold. As the brain cools, brain cell metabolism slows, resulting in impaired brain function. The level of consciousness deteriorates from confusion to incoherence and eventual unconsciousness. Below 86° F, signs of life are very difficult to detect and the calf may be mistaken for dead. The pupils of the eyes will be dilated and fixed. The pulse may be undetectable. Occasional gasps of respiration at a rate as low as four or five per minute may be the only clue that the calf is still alive. Heart failure may be the actual cause of death.
Calves with hypothermia need to be warmed slowly, according to Stoltenow. The heat source should be about 105-108° F. Warmer temperatures may cause skin burns or shock. Sources of heat include a warm water bath, an electric blanket, heat lamps, or hot water bottles, plus a warming box. Supplying an energy source to these calves is essential. If the calf is newborn, colostrum should supplied within the first six to 12 hours of life. Milk or electrolytes with an energy source such as glucose are recommended. An esophageal feeding tube works quite well to supply these. Without fluids, the animal becomes acidotic as it warms up. An acidotic calf is predisposed to contracting scours or pneumonia.
The immediate concern is returning the calf’s core body temperature to normal (100° F for newborns). Maintaining the normal core body temperature is a secondary objective. For years, producers have used floor board heaters of pickup trucks, submersion of wet calves in a warm bath, placing calves next to the heater in the house, or placing the calf under a heat lamp. Warming and drying boxes have also been used over the years. Most early warming boxes were a four-foot by three-foot plywood box where the hypothermic calf could be placed to dry and warm. Heat sources were often a heat lamp or propane heater. There was usually no fan to circulate warm air. Ventilation was not considered in construction. As the hair coat dried, the moisture raised the humidity within the box, setting the calf up for pneumonia. Oftentimes, the calf would be left unattended and suffer from heat stress or scorching.
New improved models have been developed, offering a higher success rate.
The use of a thermometer is highly recommended. Often, a calf will not appear to be hypothermic. However, upon taking its temperature, you may realize that the calf’s body temperature is below normal. This is often brought on by dystocia (slow births) which may have put the calf in a hypoxic state (lack of oxygen).
A hypoxic calf is slow to dry off and nurse, allowing hypothermia to set in.
Feed the hypothermic calf warm colostrum as soon as possible to speed recovery and increase the probability of full recovery. Breathing the warm air from the calf warmer along with consuming colostrum will warm the calf from the inside out and provide the needed energy to overcome the trauma it just went through.
Areas suffering from frostbite should be warmed up quickly. Frostbite is the actual destruction of tissue. To prevent permanent damage, affected areas need to be restored with circulation as soon as possible. Again, the heat source should be about 105-108° F. Opposite to what you see in the movies, do not rub affected areas. They are already damaged and quite fragile. As the area warms up, it will be painful. Do not let the animal rub these areas, it will only make the situation worse. In severe cases, analgesics (pain killers) may be indicated. Consult your veterinarian.
Frostbite in teats and scrotums deserves special mention. Frostbitten teats may be difficult to detect. The first sign may be a thin calf. The actual teat end is affected and can slough. If this happens, the sphincter muscle of the teat may be lost. This makes mastitis a possibility. Also, an affected teat may cause that quarter to dry up since the cow won’t let the calf nurse. In addition, the frostbitten teat may go unnoticed until next year. At that time the calf is thin, and when the cow is examined, the actual teat is healed over with scar tissue. This teat will need to be opened.
Scrotums and testicles of bulls can suffer frostbite. Often these lesions go unnoticed. These lesions can cause transitory or permanent infertility. All herd bulls should have breeding soundness exams 45-60 days after the last severe cold spell. Your veterinarian can help you with these exams. — WLJ