Cold Stress and Newborn Calves
Michelle Arnold, DVM (UKVDL) Dr. Michelle Arnold, Large Ruminant Extension Veterinarian, University of Kentucky. Dr. Arnold is a member of the US YAKS Science Committee and the Health Committee.
When the weather is predicted to be bitterly cold, producers should take extra care of newborn calves to ensure their survival. A calf’s body temperature often falls below normal in extremely cold conditions due to a slow or difficult birth (dystocia) followed by delayed standing and nursing.
Returning the calf’s core body temperature to normal (100° F for newborn calves) is of immediate concern then maintaining that core temperature is of secondary importance. If at all possible, bring close-up cows indoors to calve in a heavily bedded, clean pen. If calving outdoors, make sure there is dry, clean ground available for the cows to calve without a large amount of manure. If the cow calves outdoors, bring the calf in until warm and dry if the calf is showing signs of hypothermia or if there are no natural windbreaks available.
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 breathing, 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 due to a wet, saturated hair coat in a cold environment. Immersion hypothermia often occurs after the birthing process because the calf is born soaked with uterine fluids. Other causes of immersion hypothermia of young calves 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.
Signs of Hypothermia
Faced with a cold environment, the body defends 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. Cold nostrils 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. Erratic behavior, confusion and a clumsy gait, are all signs of mild hypothermia. Producers often refer to these as “dummy” calves. Severe hypothermia results as the body temperature drops below 94° F. Shunting of blood continues, manifesting as cold and pale nostrils and hooves. Paleness is due to poor oxygenation of the tissues near the body surface. Decreased blood circulation in the muscles of extremities results in a buildup of acid metabolites (waste products). After the shivering stops, it is replaced by muscle rigidity. The pulse and respiration rates begin to slow as the body core cools to 88° F. Below core temperature of 94° F. , 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 to 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 is often the actual cause of death.
Treatment of Hypothermia
The two most important factors in calf survival are warmth and colostrum. Before giving colostrum, a chilled calf first needs to be warmed as these newborns are typically too weak to suckle. Karo syrup (dark is preferred) delivered by mouth to a weak calf is a quick source of readily available energy and is rapidly absorbed through the mucosa in the mouth into the bloodstream. Effective methods to warm a calf include:
Floor board heaters of pickup trucks.
Submersion of wet calves in a warm bath-you must support the calf to prevent drowning. The water should be gradually warmed to 100° F and will need to be changed to keep it at that temperature.
Placing calves next to the heater in the house and/or using a blow dryer to dry and warm the hair coat. Never leave calves unattended next to a portable space heater.
Placing the calf under a heat lamp-be careful to cover the lamp with a screen so the calf will not get burned as it becomes more active.
Warm blankets-These should not be so hot that they can cause skin burns. Change the blankets as needed to maintain a consistent temperature and not allow the calf to cool off.
Hot box or warming box-the temperature should not be so high that burns could result. Some type of venting is necessary to prevent buildup of carbon monoxide and moisture. Air movement is also important to ensure thorough warming of the calf and prevent hot spots in a warming box.
Warm IV fluids may be administered by a veterinarian.
Once the calf has been warmed, provide colostrum and maintain body temperature. Colostrum is a concentrated source of protein, vitamins, minerals and energy and also contains antibodies to diseases or vaccines that the dam has been exposed to. If the calf is unwilling to suck, use of an esophageal feeder is recommended to deliver colostrum. If it is not possible to milk the dam, commercial powdered colostrum replacement products are available. Calves should be fed colostrum as soon as possible after the suckle reflex has returned-generally within the first 6 hours after birth but ideally within 1-2 hours after birth. Once the calf is warm and fed, move it back to its mother. It is important that they have a place to get out of the wind; a draft free place to go during extreme wind chill days/nights.
Other Tips on Dealing with Livestock in Extreme Cold:
Water is critical. Livestock need water to maintain their health and immune system. Lactating animals have a higher need for water than young stock and mammals in their dry period. Livestock will reduce their consumption of feed and produce less milk if they don’t have water available. Check your water source several times a day. It’s vital for the health and production of your animals. In addition, consumption of salt without water available can result in salt poisoning which often results in death of the animal.
Cold temperatures will increase maintenance energy needs. Producers either need to increase their animals’ feed intake or increase the energy density of the diet by feeding higher quality hay or adding grain to the ration. Consider separating younger and thinner animals that may not have the same internal insulation as conditioned older animals and supplement them accordingly or offer them higher quality forage if available.
Take care of yourself too. Keep an extra set of clothes and a blanket in your truck. If you get wet while doing chores, being able to change into dry clothes quickly could be the difference between finishing chores with just a nuisance – or getting hypothermia. An extra pair of dry boots is a great plan too. Let someone know when you are going out and always take a cell phone in the event of an emergency. If you get into trouble, then you can’t be the caregiver of your livestock that you want to be.