5 April 2023

2 minute read

By: Penn State University

North America

Here are some basic rules to evaluate the feed requirements of beef cows during the winter:

• Maintenance energy requirements increase by about 1% for each 1°F below 32°F. The energy for maintenance for beef cows in the last 1/3 of pregnancy is about 11 mega-calories per day. With an air temperature in dry air and no wind of 22°F, there is a 10% greater energy requirement. This 1.1 mega-calories of energy needed is equivalent to about one pound of corn or two pounds of orchard grass hay.
• The rule for accounting for wind chill is to use the wind chill temperature to adjust feed energy using 32°F as the baseline. For example, if the wind chill is 0°F, then the cow requires 32% more energy. This is about 3 pounds of corn or 5-6 pounds of orchard grass hay.
• The most serious condition is when the animal gets wet because the hair and hide lose their insulation capacity. The rule for cattle that are wet is to use 59°F as the starting point and change the feed energy needs by 2% for each degree below 59°F. For example, if the cattle are wet and the wind chill is 9°F, the energy requirement is 100% higher (50° X 2%). This is equivalent to feeding an additional 20 pounds of corn or 40 pounds of orchard grass hay to a cow each day. Obviously, most cows could not consume enough feed to keep them at maintenance under these conditions, so they will start losing body condition. The loss in body condition will be abated by protection from the wind and (or) a drier environment. A windbreak or shelter from the rain is economically feasible under these conditions as well as being good animal husbandry.