By Tina Kohlman
The thermal neutral zone (comfort zone) for newborn calves is 50-78°F while one-month-old calves' thermal neutral zone is 32-78°F. Once the temperature reaches below the lower critical temperature of 32°F for our one-month-old calves or 50°F for our newborn calves, the energy they consume is now used for maintenance making less available for growth and immune function.
Is it really that bad? See if from the calf's perceptive. If a 100-pound calf has only 1.5 pounds of fat reserves at birth, this fat reserve can easily be depleted within 18 hours under certain conditions. For every 1°F drop below the lower critical temperature, maintenance requirements increase 1%. If increased energy is not provided, calves have the potential to become sick and/or die.
Based on a NAHMS USDA study, only 33% of dairy producers change calf-feeding practices in cold weather. Failure to minimize the effects of cold stress on calves, results in depressed immune function, increased risk of sickness, poor response to treatment, decreased growth performance and possible death.
Keep them dry
A calf can stand a good deal of cold weather if it is dry and protected from drafts. To minimize cold stress one area of focus is the calf's environment. This environment includes the calf's resting space, feeding area, and walking surface. As temperatures begin to drop in fall, the following are ways to minimize cold stress:
* A dry, clean place to lie with plenty of bedding. Based on University of Wisconsin-Madison research, calves tend to lay down nearly 50% of the time during the day and 100% of the time at night. Wet bedding causes the calf's hair coat to "clump" and lose insulation value. Ideal bedding provides a good base to soak up liquid, provide a "buffer" from the cold ground, provide insulation and allow the calf to nestle. Dairy Calf & Heifer Association (DHCA) Gold Standards recommend 6" to 12" or 20-25 pounds of bedding per calf to provide a good base. To maintain the base, two to three pounds of bedding per day should be added to the pen or hutch. It is the amount of bedding used that is more important than the specific material used.
* Plenty of fresh air with minimal draft. UW-School of Veterinary Medicine research shows as temperatures fall, pneumonia incidences rise. Pneumonia can be attributed by cold stress and calves not meeting their energy need to support their immune systems. Also, pneumonia can be attributed by the air quality as we close up barns during the winter. DCHA Gold Standard II indicates indoor ventilation should be 50 CFM during mild weather and 15 CFM during cold weather to provide good air quality while minimizing cold air drafts.
* Provide calf blankets to help keep calves warm. North Dakota State University research shows calves wearing calf blankets during cold weather had 1.4 pounds daily gain from birth to 4 weeks of age as compared to 1.2 pounds of gain by calves with no blanket. Blankets should fit properly and allow room for growth. Blankets should be dry. Monitor blanket usage to minimize sweating or over heating which would affect the insulation value of the calf's hair coat.
* Minimum frost or condensation during very cold weather to minimize bacterial growth in pens and calving environment.
As you plan for this winter's calf management program, don't forget about the calf's environment and focus on comfort and cleanliness to help your calf thrive the winter season!
Kohlman is the Fond du Lac County Extension dairy and livestock agent.