Hypothermia in Calves

Mark Z. Johnson, Oklahoma State University Extension Beef Cattle Breeding Specialist

 

Hypothermia (lower than normal body temperature), is one of the major causes of death in newborn calves.  With a significant winter storm on the way to Oklahoma this article addresses how to identify, prevent and manage cold stress in baby calves. Moderate environmental temperatures aren’t typically a problem for calves produced by cows with adequate milk/colostrum supply that are in good condition (Body Condition score of 5.5 – 6). Calves from cows that have had good nutrition during the last trimester of pregnancy have a layer of brown fat that serves as a rapidly mobilized energy reserve to make them vigorous at birth and quick to get up and nurse. On the other hand, calves from thin cows may not have the energy needed and are more susceptible to hypothermia. Wet and cold weather (below 50 degrees F) accompanied by wind will take a toll on calves especially if the calving process takes longer than normal. Dystocia (calving difficulty), increases the amount of time a calf will take to stand and nurse, which increases the potential of hypothermia. Calves maintain body temperature by converting food into body heat. Calves need to stand and nurse an adequate amount of colostrum as soon as possible after birth. If there is any question as to whether a calf has ingested an adequate amount, use a tube feeder or bottle to administer warm, high fat (up to 10%) colostrum. A practical rule-of-thumb is to feed 5% to 6% of the calf's body weight within the first four hours and repeat the feeding when the calf is about 12 hours old. For an 80-pound calf, this will equate to about 2 quarts of colostrum per feeding. Calves that nurse or are given colostrum within the first two to four hours after birth fare much better throughout their entire lives.

 

There are several ways to assist a hypothermic calf, the first step is knowing when to help. Normal rectal temperature of a newborn calf is 101.5 – 102.5 degrees F. A thermometer will help to know if a calf is at risk. If the temperature drops below 101 degrees F, help may be needed. Place a finger in the mouth to check for a suckling reflex. The mouth of a healthy calf will be warm and moist and the calf will attempt to chew or suck your finger. Lack of a suckling reflex is a definite sign that you are dealing with a cold stressed calf that needs assistance. When calves are cold, the body responds in two ways: shivering and diverting blood flow to their inner core. Shivering is an involuntary reflex that increases heat produced by the muscle, but it requires energy. Excessive shivering, erratic behavior, confusion and clumsy movement are all signs of hypothermia. Mild hypothermia is a calf temperature below 100 degrees F. Severe hypothermia, when internal organs start to cool is below 94 degrees F.

 

When rewarming a calf is necessary, there are two routes: internal and external. Administering colostrum should be the first step to warm the calf internally. Warm (100 – 102 degrees F), high quality colostrum is vital as it provides fat and energy that will be burned for internal heat. In some cases, administering colostrum or milk replacer may need to be repeated. Externally, the following steps should be followed to treat and prevent hypothermia in at risk calves.  

1. Dry calves immediately, remove all wetness with towels or a blow dryer.
2. Warm externally, use heat lamps, the floor board of your farm truck, a "hot box," or a warm water bath (around 100°F, gradually increasing). Remove heat source when calf’s temperature is up to 99 degrees F and monitor to ensure they are able to maintain their temperature.
3. Get calves off the cold ground, place calves on pallets or blankets to prevent heat loss.
4. Get calves to a warm, dry, sheltered area like a barn, garage or shop. 

 

References

Managing Hypothermia in Newborn Calves

 

The Importance of Colostrum. Cow-Calf Corner Newsletter. January 9, 2023.

 

Mark Johnson, OSU Extension beef cattle breeding specialist, discusses the importance of colostrum during the first 12 hours after a calf is born on SunUp TV from January 16, 2023 (Youtube). 

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Extra Supplement for Beef Cows during Cold Weather

Paul Beck, Oklahoma State University Cooperative Extension Breed Cattle Nutrition Specialist

 

Cold weather increases the nutrient requirements of beef cows, particularly energy. A common question during winter storms is: How much extra supplement is needed to get cows through these weather events?

 

Let’s consider a 1,200-lb pregnant beef cow in the third trimester consuming prairie grass hay that is 90% dry matter (DM), 7% crude protein (CP), and 56% total digestible nutrients (TDN). Under normal conditions, this cow requires approximately 1.85 lb of CP and 12.5 lb of TDN (DM basis) per day. She would be expected to consume about 24 lb of hay daily (1.8% of body weight on a DM basis).

 

In normal weather, feeding 24 lb of this hay plus 2 lb of a 20% protein range cube will meet the cow’s CP and TDN requirements. However, as temperatures drop below the cow’s lower critical temperature (LCT), energy requirements increase by approximately 1% for every degree below the LCT.

 

For a cow in good body condition (BCS 5) with a thick winter hair coat, the LCT is about 32°F. When temperatures fall to 20°F, her energy requirement increases by about 12%, raising her TDN requirement from 12.5 to roughly 14.0 lb per day. As additional supplement is fed, hay intake typically declines. To meet this energy shortfall, she would require approximately 3 additional pounds of range cubes per day, for a total of about 5 lb of cubes daily.

 

The situation becomes more critical for a thin cow (BCS 4) with a thin hair coat. These cows already need to gain body condition to improve the likelihood of rebreeding, so they may already be receiving around 4 lb of cubes per day. Their LCT is closer to 40°F. When temperatures drop to 20°F, energy requirements increase by about 20%, raising TDN needs from approximately 13.3 to 16.0 lb per day. This results in an energy deficiency of about 2.7 lb of TDN per day. To offset this deficit and prevent further body condition loss, approximately 7 additional pounds of cubes would be required, for a total of about 11 lb of supplement per day. Feeding this level of supplement is both expensive and difficult to manage.

 

Some of this energy deficiency can be offset by providing higher-quality hay during winter storms. However, these examples clearly illustrate the importance of maintaining cows in good body condition before severe winter weather occurs.

 

Producers are encouraged to contact their local Cooperative Extension office for assistance in developing a winter feeding program tailored to their cow herd.

 

Paul Beck discussed management of cattle in cold weather on SunUpTV from  February 6, 2021 - Cattle & Cold Weather and February 22, 2021 - How to Protect Your Cattle in Extreme Cold — Expert Tips from Paul Beck.