One way to help calves thrive through cold conditions is protecting them with calf jackets. And anyone who uses calf jackets has their own practices and preferences for implementing them. Among those “rules of thumb” shared by the experts in the trenches are:

From Minnie Ward at Calf Star:

• When we start wearing hoodies in the fall, calf jackets should go on.

From Marissa Hake, DVM, “Dr. Hake — Calf Vet”:

• If the ground is frozen and the calf is less than 21 days old, it should have a calf jacket.
• DO NOT put a calf jacket on a wet calf. That trapped moisture will chill the calf instead of keeping it warmer. Make sure newborns are fully dry before putting jackets on.
• Wet jackets = BAD. If a jacket gets wet or covered with manure, remove and replace it with a clean, dry jacket.
• After 21 days of age, calves become better at thermoregulation. Weather/health permitting, jackets can be removed at this age.
• If there is a need to leave jackets on for longer than 3 weeks, make sure the straps don’t dig in.

From “Starting Strong” by Vita Plus:

• Follow the “Rule of 90” – when the high and low ambient temperature total 90°F or less,  calves less than 3 weeks old should have a jacket on.
• As spring approaches, remove jackets as daytime temperatures warm up to ensure the calves are not “sweating” under their jackets.

And from Penn State Dairy Extension:

• • Don’t wait until weaning to remove calf jackets. Doing so will add another level of stress to an already stressful time. Removing jackets when calves begin generating more body heat by beginning ruminating — but while they are still on milk – will allow them to adapt to their new environment when the added protection of the jacket is removed.