Strategies for rearing calves at low temperatures

Body temperature regulation in calves develops with the age. Newborns are less equipped to deal with a cold environment than older calves. Therefore, the adaptation of the young dairy calf to a cold environment is mainly dependent upon the availability of adequate housing, management and nutrition.

The thermoneutral zone is the range of temperature within which the animal uses no additional energy (above that of normal metabolism) to maintain its body temperature. If environmental temperatures fall below the thermoneutral zone (also called below the lower critical temperature), a calf will use energy which could have been partitioned for growth, to keep warm. If we want our calves to grow optimally, we need to try and avoid this from happening.

The thermoneutral zone is not only governed by temperature, but also wind speed, bedding quality and moisture. For example:

• Wet newborn calves are at a greater risk of reaching the lower critical temperature during cold temperatures.
• Bedding material can act as an insulator, reducing heat loss via conduction when calves are lying down.
• Draughty conditions at calf level can reduce environmental temperatures and increase the risk of reaching the lower critical temperature.

Nonetheless, there are a number of strategies to ensure calves stay warm enough during colder months. Sufficiently deep enough bedding allows the calf to nest and trap a boundary layer of warm air around itself. Deep nests allow for colder and better-ventilated spaces, since the animal will have part of the body protected (Nordlund, 2008). Bedding depth can be assessed by looking at calves when they are lying down – ideally it should be deep enough that the legs of the majority of calves are not visible.

Draughts can be avoided by ensuring housing incorporates solid side panels approximately 1.2 m in height at the calf level. Calf jackets may also be of use – but are of most benefit for calves between one and four weeks of age and sick individuals, and they require excellent hygiene to prevent the spread of infection (particularly those associated with diarrhoea).

Increasing the plane of nutrition is one of the easiest methods of optimising the growth of calves in cold conditions. The (metabolisable) energy requirements for maintenance of a calf under thermoneutral conditions (15-20C) are approximately 1.75 Mcal/d for a 45kg calf (Drackley, 2008). For each 5°C drop below 15°C, feed calves (less than three weeks of age) extra energy by providing an extra 50g of milk replacer or 0.33L of whole milk per day (AHDB, 2019).

Our team of vets are always more than happy to consider the energy content of your milk feeding regimes, if they can be improved as well as any other factors about calf health and housing. So please don’t hesitate to get in touch if you’d like to discuss this topic further!

References:

AHDB, 2019. Calf Management Booklet. Accessed at: https://media.ahdb.org.uk/media/Default/Imported%20Publication%20Docs/CalfManagement_180619_WEB.pdf

Drackley JK. Calf nutrition from birth to breeding. The Veterinary Clinics of North America. Food Animal Practice. 2008 Mar; 24(1):55-86. DOI: 10.1016/j.cvfa.2008.01.001.

Nordlund KV. Practical considerations for ventilating calf barns in winter. Vet Clin North Am Food Anim Pract. 2008; 24(1):41–54. doi:10.1016/j.cvfa.2007.10.006