Remember energy needs during final trimester

For most spring calving beef herds, energy needs in winter become more important as the cow fights harsh weather conditions and approaches -- or is in -- her final trimester before calving. During that time, she is preparing herself for both birth and lactation, in addition to rapid calf growth and development.

Diets lacking sufficient amounts of energy during that time can result in loss of cow body condition score regardless of environmental conditions. That can lead to lighter calves at calving and weaning, decreased milk production from the cow, longer post-partum interval, delayed rebreeding for the cow and can negatively impact a calf’s lifetime performance. Wind, wet weather and poor housing conditions can magnify the issue as well.

By understanding the importance of adequate energy and clean hair coats have on cows during the latter portion of winter, beef producers can prepare a plan to deliver appropriate amounts of energy to help cows and their future calves.

A major factor in determining increased energy needs for cows during extreme weather conditions is being aware of what is called the thermoneutral zone. The thermoneutral zone is the temperature range where cattle do not need to expend additional energy to maintain their core body temperature. When temperatures decrease to less than the thermoneutral zone, cattle will need to use additional energy to maintain their core body temperature; the area is called the lower critical temperature. Hair coat, wind and moisture conditions impact the lower critical temperature.

Cows adapted to cold climates will grow a heavy winter coat. Heavy winter coats work by trapping air to create insulation and allow the lower critical temperature to decrease if the cow’s body condition score is sufficient. Cows with heavy winter coats will have a lower critical temperature of around 18 degrees Fahrenheit under normal coat conditions -- minimal wind, clean, dry coats. Under those normal conditions, a rule of thumb is to increase energy in the ration by one percent for every degree less than the lower critical temperature. It is important to remember that during the final trimester, the cow’s rumen capacity is reduced due to the calf’s rapid growth. That reduces the cows’ voluntary feed intake and emphasizes the need for producers to test forages to be sure nutrient-dense high-quality feedstuffs are being delivered to meet cow needs.