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What is the Thermo-Neutral Zone?

calf jacket

Not familiar with Thermo-Neutral zone? The TNZ of a calf is the range of temperature in which the animal uses no additional energy to maintain its body temperature.

Calves are the future of your herd and taking care of them at a young age will decrease costs throughout the animal’s lifetime, allowing for more profitability in your operation.

How Cold is Too Cold? Calves have a zone in which they are comfortable, not too warm or too cold. This Thermo-Neutral zone is the range of temperature in which a calf uses no additional energy to maintain its body temperature. Any temperature higher or lower will mean that the calf is burning reserve energy to maintain core body temperature, all of this at the expense of growth.

calf

In new born calves and up to four weeks of age this is between 10C and 25C. Calves at one month it is between 0C and 23C.

In winter, waterproof calf jackets can help decrease cold weather stress on your animals. The Canadian Journal of Veterinary research (1989; 53:275-278) reported a 52% increase of overall animal insulation on calves that wore calf jackets.

A calf requires 2% more energy for every 1 degree C below the thermo-neutral zone, therefore at freezing point (0C) a calf requires 20% more milk/feed just for maintenance.

Dairy breed calves do not have enough body fat to maintain their own body temperature in cold weather. Feed is often limited by number of feeds per day and the amount given per feed. Keeping the calf warm therefore is the most cost effective way of maximising the feed given.

Calf Jackets

With the use of calf jackets you can make significant savings on feed, medication and bedding costs, by focusing the calves energy on growth rather than keeping warm. In turn this can reduce the risk of pneumonia and scours from chills and draughts.


Don’t forget that a calf’s coat should be dry and clean as it is its barrier to the environment and insulation. Newborn calves should have ample time to dry before being moved in a hutch and these have to be located in dry areas.Calf scour is the most common cause of death in calves. It accounts for nearly 30% of deaths in calves less than one month old. Pneumonia is the most common cause of death in cattle of all ages over one month old. The use of calf jackets from birth can have a significant impact on the health of your animals for the duration of their lives.

AniMak have two models of calf jackets available: canvas calf jacket and a waterproof calf jacket. 

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Information taken from Penn State College of Agricultural Sciences.