by Carrie Bargren, DVM
The leaves on the trees have fallen, the crops are (mostly) in and the temperatures are dropping. It must be fall! But before the first hard frost settles, there are a number of items to get done. One of those should be ensuring that the calves are prepared for winter weather. The following are a few categories of calf care and management that should be modified for the winter to ensure the calves not only survive, but thrive.
Milk Volume In cold weather, calves must use energy to stay warm, and therefore they require more calories. A calf less than three weeks old begins directing its energy for warmth at ambient temperatures of 59°F or less, and a 30 day calf uses energy for warmth at 50°F or less. In warmer weather, all energy is directed toward weight gain, growth and a healthy immune system, but the colder the temperature, the more energy the calf must divert from those uses and redirect to creating heat. Fortunately, simply increasing the volume of milk fed can provide sufficient calories through all but extreme cold. Feeding 4 quarts twice daily, or 2 gallons total per day, will maintain weight gain and growth even at 0°F. A scouring calf will require an additional 1 to 2 feedings of oral electrolytes to stay hydrated until their scours resolve.
Calf Jackets All calves on milk should be in calf jackets as soon as the temperature drops below the thresholds noted above: 59°F for a calf less than three weeks old, and 50°F for a calf 30 days old through weaning. Jackets help calves regulate their body temperatures so they can conserve energy. Jackets serve as supplements to increased feed volumes, not replacements.
Bedding When the temperature drops below the threshold, a calf should have additional bedding so she can nest. A deeply bedded pen should have enough bedding that a calf’s legs are generally not visible when she is lying down. The extra bedding creates insulation, and a calf can raise her surrounding temperature by seven degrees while nesting, possibly even more when combined with a calf jacket.
Deeper bedding also reduces the chance for infection as urine and feces fall down through the bedding and away from the calf. The warmth created also supports the immune system: increased nesting ability is correlated with a decrease in the prevalence of respiratory disease.
However, wet bedding loses heat three times faster than dry, so it must be changed regularly, if not more frequently, in the winter. Leaving soiled bedding in with the calves and only
adding new bedding on top creates an environment that encourages disease both directly through contact with the dirty bedding and indirectly by increasing the humidity in the pen, which allows aerosolized infectious particles to linger.
Ventilation In the winter, naturally ventilated barns rely on heat created by the animals to circulate air. Their body heat rises and is funneled out of the ridge which creates negative pressure in the barn and pulls fresh air in through the eaves. For lactating cows, this method works well due to the large amount of heat they produce, but calves can hardly create enough heat to keep themselves warm, much less keep air circulating.
Without good air circulation, calf barns can actually be colder inside than outside in the winter. They cool off overnight, but when the air warms up on a sunny day, it never makes it inside the barn due to the lack of circulating air. Positive pressure tube systems work well to supplement naturally ventilated barns and maintain more consistent temperatures inside.
All the air in a barn should be exchanged every 15 minutes in the winter. This maintains good air quality by removing airborne bacteria, dust and humidity without creating drafts. Positive pressure tube systems are designed to direct fresh air over the calf pens without creating a draft, allowing calves to conserve body heat. Proper ventilation will also remove infectious particles that are aerosolized by a sick calf, keeping them away from healthy calves. In warmer weather, the air should be exchanged more frequently both because new air is needed and because the airflow cools cows: figure at least 15 times per hour and up to 60 times an hour on hot days.
If there are heaters in the calf barn, make sure they have been tuned and are ready to work hard this winter.
Many of the same ventilation principles apply to cow barns. There should be completely new, fresh air in the barn every 15 minutes. Any moisture that accumulates on the rafters, ceiling or walls indicates poor ventilation and increases the risk of respiratory disease in the herd. A properly ventilated barn, no matter the design, should be dry.
Cold weather is hard on everyone, but especially calves who have little body fat and an immature immune system. Think about your winter calf protocols, modify them and write them down so everyone knows what should happen. With a plan in place, when the frigid weather hits, both you and the calves will be prepared.
RVVC is pleased to announce the wedding of Dr. Erin Harris to Steven Murphy on August 27th, 2016 in West Bend, WI, and the wedding of Dr. Nessa Moellers to Luke Stika on November 5th, 2016 in Spillville, IA. Join us in congratulating them the next time you’re at the Reedsburg location or pass them on the road.