As colder months approach, cattle producers in many parts of the country prepare to manage their herds’ nutritional needs with available forages that are dormant and lower quality. In addition, herds that calve in late winter or early spring must consider the risk of moderately to extremely cold temperatures. 

Because calves are born wet, have thin skin and very little body fat, they lose body heat rapidly and can quickly become severely cold-stressed.

Severe cold stress in newborn calves occurs when the body temperature drops below 94˚F. At this temperature, the calf becomes depressed, unable to rise, unwilling to suckle and will temporarily lose the ability to shiver. 

During periods of cold or wet weather, newborn calves (less than 1 to 2 days of age) should be checked every few hours with a thermometer, and any calf with a below-normal temperature, even if it appears OK, should be warmed so body temperature can rise above 100˚F. 

The good news is if the calf can be warmed up and its body temperature can begin to rise, the shivering response will return and their core temperature will slowly increase. 

Prevention of cold stress involves management to ensure calves can be born with no or minimal assistance, so both the calf and dam can stand shortly after calving to begin suckling. Calving difficulties are minimized by proper heifer development, proper bull selection for calving ease, and proper nutrition so that heifers and cows calve in a body condition score (BCS) of 5 to 6 on a 9-point scale. 

Winter concerns for bulls

While it is true that bulls, because they are never pregnant or lactating, have lower nutritional requirements than cows of the same age, it is important bulls not lose excessive weight during the winter and that they are protected from the negative effects of cold weather. 

Semen evaluation of bulls stressed due to cold temperatures or weight loss will reveal decreased motility and a greater number of abnormal sperm cells. If the bulls do not have adequate time to recover before the start of the breeding season, a hard winter can result in poor breeding success in a spring breeding season. 

Another winter concern for bulls is the risk for frostbite of the scrotum — particularly in situations of very low wind chill or a combination of mud and cold. If a bull’s scrotum is in contact with cold ground, it is possible for the skin to be severely damaged. The underlying testicular tissue will be damaged as well.

Cow and heifer condition

For most of the United States and Canada, the base ingredient in winter rations is usually standing dormant forage or hay. Heifers, first-calf heifers and thin cows that need to gain body condition often need more energy than can be supplied by dormant forage or hay alone. Therefore, many situations require heifers and cows be fed supplemental protein, energy or both, depending on the nutrient makeup of the base forage.

Understanding the interaction between starch, fiber and protein in the cows’ rumen allows us to determine the most appropriate supplement. 

By planning for winter now, ranchers can avoid being caught off-guard by extreme events and can manage the typical weather and forage conditions. 
Editor’s note: Robert L. Larson is a professor of production medicine and executive director of Veterinary Medicine Continuing Education at Kansas State University in Manhattan, Kan.