Maintaining Heifer Performance in Cold Stress
Published on Thu, 10/27/2016 - 3:22pm
By Pat Hoffman
We're all feeling the immense chill right now, especially as we're out working with animals. We place particular focus on young calves as changes in feeding and management are required to help calves not only survive, but also grow to their potential despite the temperature outside.
What we might now focus on as much are the effects of winter weather on older heifers.
The effects of winter are more profound on calves, but that does not mean older heifers are immune to cold conditions. Because older dairy heifers are frequently reared in a wide array of environmental conditions, it challenges our ability to universally define the exact energy requirements of a dairy heifer in the winter. However, most heifers - regardless of age or size - will require more energy in the diet during winter. Calculating exactly how much extra dietary energy to keep heifers growing on pace in the winter is a little bit of science and a lot of experience and art.
So let’s start with a little science.
As a heifer grows, she gains body mass and rumen capacity. As a result, she is more adept at handling cold. But extraneous winter or housing conditions can have an additional effect on heifers’ maintenance energy needs.
For example, at the same winter temperature, a heifer lying on wet bedding requires more energy than a heifer lying on dry bedding. Likewise, a heifer with a dirty hair coat has less insulation than a heifer with a clean, dry, long hair coat.
Do our heifers frequently stand or lie in the winter sun? Do the cold winter night winds blow on them? Are they walking on lumpy, icy, jagged walking surfaces or standing in a cold rain? Can they get to water or has it become an ice sculpture? All these winter conditions can occur and require more maintenance energy by the heifer.
What does this mean management-wise?
With younger lighter heifers (less than 600 pounds), we should provide a good environment and perfect resting areas before relying on feeding more energy to overcome winter conditions. For these heifers, walk the pens and ask, “Do we need more feed energy or should we improve the bedding?”
For all heifers, walking pens, noting environmental conditions and proactively discussing those notes with your nutritionist can pay dividends. The walkthrough checklist should include bodyweight, resting surfaces, coat conditions, crowding, lot conditions, walking surfaces, body condition, etc.
Generally, for dairy heifers, you should reduce dietary NDF 2 to 3 percentage units in the winter. For tougher winter conditions (wind, frozen or wet bedding, or frozen, uneven walking surfaces), reduce dietary NDF 3 to 4 percentage units, but always monitor heifer growth and body condition frequently.
Reducing dietary NDF in winter heifer diets accomplishes two things. First, the diet will have more caloric density and, second, heifers will eat more feed. In general, for every 2-percentage-unit reduction in dietary NDF, heifers will eat 1 pound more of dry matter.
Finally, remember winter to a heifer is where she lives, not where we live.
In freestall or other confinement barns, winter may end in March. That’s because heifers are fully protected from precipitation, wind and internal barn temperatures may rise to above 50 degrees F. Thus, don’t continue winter diets too long or over-conditioning may occur. Winter may end much later for heifers with outside exposure due to cold winds, icy rains and muddy lots.
About the author: Pat Hoffman is a Vita Plus dairy technical support specialist. He received professor emeritus status after completing a 35-year career with the UW-Madison Department of Dairy Science. Based at the Marshfield ag research Station, Hoffman's UW-Extension services included application of dairy research and the development of dairy outreach education programs. His research focused on development of dairy replacement heifers. Hoffman earned his bachelor's degree from UW-Platteville and his master's in dairy science from UW-Madison. He is a member of the American Dairy Science Association and previously served as president of the Midwest Branch.