By Aerica Bjurstrom
January and February bring some of the coldest days of the year, and March can bring some of the snowiest, making winter a challenging time to manage herd health and nutrition.
Cattle experience cold stress at different temperatures, depending on conditions and coat length. The lower critical temperature is an animal’s ability to withstand cold conditions. According to Penn State University Extension, the LCT is the temperature at which maintenance requirements increase to the point where animal performance is negatively affected.
You may think LCT only impacts animals in winter; however, an animal with a wet summer coat at 60 degrees F can experience cold stress. Typically, summer cold stress is short-lived, and animals recover quickly with sunshine and a warm breeze. Winter temperatures prove to be more challenging to manage, as cold snaps can last for days and sometimes weeks.
Early-season subfreezing temperatures and long cold snaps can be the hardest on animals. Cows need to adapt to winter temperatures by transitioning from fall hair coats to winter coats. The heavy winter hair coat has a layer of insulation in it that traps air in between the hairs. A wet, saturated coat loses its insulation ability, causing the animal to suffer cold stress at a much higher temperature than it would if the hair coat were dry.
Research from Kansas State University shows the LCT of a cow with full winter coat is about 20 degrees. Research from North Dakota State University states that a cold-adapted cow in good body condition can have an LCT as low as minus 6 degrees if conditions are dry and still. It goes without saying that cold, windy and rainy conditions are stressful on cows. Minimizing exposure to unfavorable conditions will help cows be more productive and efficient.
Dry bedding
Windbreaks and dry bedding are essential in winter months. Beef cattle are quite adept at managing during the winter months without cover, if need be. If you do provide a shed or barn for loafing, make sure it is well-ventilated. Heavy condensation in barns or sheds can almost be as bad as rain, since moisture will accumulate on cattle and penetrate the dry insulation layer of their coat.
Reducing contact with muddy yards and wet manure is also an important management practice. An animal with manure or mud caked into its coat cannot combat cold, wind or moisture, therefore requiring higher dry matter intake.
Keeping cows in good body condition over winter helps them in several ways. The ideal body condition score of a late-term pregnant beef cow is 5 to 7. Research has shown that cows with ideal BCS maintain weight better, produce higher-quality colostrum and breed back faster than cows with lower BCS. A typical pregnant beef cow eats about 2.5% of her body weight in ideal conditions. A cold-stressed cow can require 1% or more dry matter intake for maintenance.
Winter calving
Once a beef cow calves, she will need increased energy to maintain BCS. There is a difference in beef cow milk production, depending on breed and genetics, but a typical beef cow will produce about 1.5 gallons of milk per day. Be sure to keep a close eye on BCS of fresh cows in cold temperatures. Those cows must maintain BCS while also feeding a growing calf.
Don’t forget about calves in the cold weather. A newborn calf can deplete its body fat stores within hours of birth if it is not up and nursing. Quality colostrum at first nursing is essential, and the sooner the calf nurses, the better.
Newborn calves are born with a body temperature of about 103 degrees. Body temperature quickly decreases after birth, which is why it is essential for the cow to lick the calf clean and allow the coat to dry. The longer the calf is cold-stressed, the less likely it will survive. If a calf’s mouth gets cold before it nurses, it may not be able to suckle. The first feeding of colostrum heavily impacts the calf’s ability to survive.
High-risk calves — twins, difficult births and those born from malnourished cows — require special attention. These calves are often weaker and may require help to dry off or nurse. Calves under extreme cold stress may require a calf blanket for a short time to help them adjust to their environment. Always provide plenty of dry bedding for cows and calves. Once calves are on the ground, you will need to provide additional bedding to make sure the little ones don’t need to compete with their mother for a warm, dry place to rest.
A successful calving season starts with a good foundation. Keep cows happy and healthy, and healthy calves will be your reward for good management.
Bjurstrom is the Extension ag agent in Kewaunee County, Wis.This column is provided by the University of Wisconsin-Extension’s Wisconsin Beef Information Center.