Surveys show that 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. Slow and difficult births (dystocia), and cold stress (hypothermia), are the leading cause of death during this first 24-hour period of life. Fully realizing that prevention is the best cure, this paper concentrates on the care and treatment of the hypothermic or cold stressed calf. Specifically, we will review a case study conducted in Elko County, which examined the use of calf warmers as a tool to overcome hypothermia.
Types of Hypothermia
There are two types of hypothermia, exposure (gradual) and immersion (acute). 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 of hypothermia affects all classes of livestock, but particularly affects young, old, and thin animals.
Immersion hypothermia is the rapid loss of body heat through conditions of saturated hair coat in a cold environment. Immersion hypothermia is often brought on during the birthing process where the calf is born saturated with birthing fluids. Other causes of immersion hypothermia of newborns may include being born in deep snow or wet ground, falling into a creek or being saturated from heavy rains followed by chilling winds.
Symptoms of Hypothermia
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 100ºF 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 newborn calves, severe shivering may interfere with its ability to stand and suckle. This sets the calf up for severe hypothermia. Behaving erratically, confused and clumsy, are all signs producers often refer to as a dummy calf. These are often signs of mild hypothermia.
Figure 1. Roy-L-Heat Calf warming and drying box.
Severe hypothermia results as the body temperature drops below 94ºF, shunting of blood continues, manifesting cold and pale nostrils and hooves. This is 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 begins to slow as the body core cools to 88ºF.
Below core temperature of 94ºF, the vital organs are beginning 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 86ºF 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.
Treatment of Hypothermia
Returning the calf’s core body temperature to normal (100ºF for newborn calves) is the immediate concern. Maintaining the normal core body temperature is a secondary objective. “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, are all methods which have been used over the years by producers.” State Ron Torell, UNR Extension Livestock Specialist and study coordinator. Warming and drying boxes have been used over the years with limited success. Some producers refer to them as ‘death boxes’. Most early warming boxes were a 4 foot by 3 foot plywood box that the hypothermic calf could be placed in 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”, Torell concluded.
The use of a thermometer is essential to determine hypothermia according to Dr. Bill Kvasnicka, UNR Extension Veterinarian. “Oftentimes a calf does not appear to be hypothermic, however upon taking its temperature you 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 hypoxia (lack of oxygen) situation. The calf being hypoxic, is slow to dry off and nurse, allowing hypothermia to set in”.
“Feeding the hypothermic calf warm Colostrum as soon as possible speeds recovery and increases the probability of full recovery,” says Dr. Ben Bruce, UNR Extension Livestock Specialist. “Breathing the warm air from the calf warmer along with consumption of Colostrum, warms the calf from the inside out and provides the needed energy to overcome the trauma they just went through,” concluded Bruce.
Recent design improvements have overcome the problems encountered in the early handmade versions of the warming boxes. In the winter of 1996, 3 Elko County Nevada ranchers cooperated in a case study, which evaluated the effectiveness of using commercial calf warmers to revive hypothermic calves.
The "ROY-L-HEAT" calf warming and drying box (Figure 1)1 features a 110-volt heater equipped with a circulating fan and automatic shutoff thermostat. The circulating warm, dry air moves under the wet calf, (the calf sits on a mesh screen elevated 4 inches off the floor) up the sides of the calf and is recirculated through the heater. The accumulated moisture escapes through the attic vent. The heater is protected in a separate enclosure attached to the rear of the box and removes easily to make rinsing and disinfecting simple. The box is made of high-density polyethylene. Its interior size provides adequate space for calves to lay down or stand up. Opposite the heater is a rubber “head boot” which permits the calf to breathe outside air when desired, yet holds the warm air in at all times.
Cooperator Ed Sarman, owner and manager of Lee Livestock in Lamoille, Nevada, uses the “ROY-L-HEAT” calf warming box predominately with his first-calf heifers. “We calve our heifers in late February, one heat cycle prior to the mature cow herd. 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. The calf-warming box saves us time and labor. We place the cold calf in the box and are able to go on and do other things while the calf recuperates. We used to have to baby-sit the calf for fear of scorching. We find ourselves placing mild hypothermic calves, that we used to let recuperate on their own, at a slower pace, in the box for a short period of time. Getting the edge off of these slightly-stressed calves gets them off to a better starts.”
Cooperator Tom Barnes of Jiggs, Nevada, collected data on a few of the hypothermic calves he treated with the “ROY-L-HEAT” calf warming box. “I was impressed with the recovery of one calf in particular,” says Barnes. “I found this calf at 1:00 a.m. on February 27th. There was 6 inches of frozen snow on the ground and it was 10ºF. This calf was flat out, his body temperature was 86ºF. I placed him in the warmer for 6 hours. This calf weaned off at 525 pounds this fall. I know he would have died if I had not had the calf warmer.” Barnes’ data collected is outline in Table 1.
Table 1. Calf Warmer and drying box data collected on Barnes’ Ranch in winter of 1996.
|Time||2:00 a.m.||6:30 a.m.||1:00 a.m.|
|Outside Temp||-5º F||-8º F||10º F|
|Snow and Moisture Condition||Clear, 6” snow||Clear, 6” snow||Frozen, 6” snow|
|Calf Body Temp Before||93º||91.5º||86º|
|Calf Body Temp After||Normal||Normal||Normal|
|Calf Condition Prior||Good||Poor||Poor|
|Calf Condition Post||Vigorous||Vigorous||Good|
|Calf Birth Weight||90-100 lbs||85 lbs||70 lbs|
|Time in Box||3 hrs.||41/2 hrs.||6 hrs.|
|Time||6:00 a.m.||6:00 p.m.|
|Outside Temp||5º F||28º F|
|Snow and Moisture||Clear, snow||Wind, Wet|
|Calf Body Temp Before||94º||94º|
|Calf Body Temp After||Normal||Normal|
|Calf Condition Prior||Good||Good|
|Calf Condition Post||Vigorous||Vigorous|
|Calf Birth Weight||70 lbs||80 lbs|
|Cow Age||3||5-8 Yrs|
|Time in Box||2 hrs.||3 hrs.|
Kvasnicka stresses early treatment of hypothermic calves. “The severe hypothermic calf can be revived and saved. However, they often are set back from the experience and their body defense system can be compromised. This sets the calf up for pneumonia, scours, and other calf hood problems.”
The authors believe that the incidence and severity of hypothermic calves can be reduced through preventive measures. A separate paper on preventing hypothermia in beef calves is available by calling 702-784-1624.