We’re not the only ones who feel the cold of winter – calves do too. We can protect ourselves by wearing more layers and turning up the heat, but when it comes to calves, it’s up to farmers to adapt the housing and feeding regimes for their livestock to the cold winter conditions.
When temperatures plummet, calves exposed to the cold are more susceptible to respiratory tract infections (pneumonia), and if they’re not fed adequately, they won’t grow as quickly because they’re using their energy to keep warm instead.
The thermoneutral zone is the temperature range where calves don’t need any additional energy to maintain their body temperature. From birth until four weeks of age, this range is between 10°C and 25°C (50 – 77°F), and from four weeks to weaning, it increases to 0°C to 25°C (32 – 77°F). This means that if temperatures are outside of these ranges, calves need extra nutrition to keep warm and healthy.
Signs your calves might be suffering from cold stress:
- They’re shivering, breathing rapidly, or have raised hair.
- Their hooves or muzzles are excessively cold and losing colour – the body could be diverting blood from the extremities.
- They’re showing a decrease in body temperature. 39°C (102.2°F) is normal; cold stress begins at 38°C (100.4°C).
Practical tips for helping your calves weather the winter properly:
- A good rule of thumb is to increase the amount of milk replacer by two per cent for every degree the temperature falls below 5°C. When the outside temperature is 5°C, 4 litres/day at a concentration of 125g/l is starvation for a calf.
- Introduce changes to a calf’s feeding program gradually and carefully. If you’re feeding more milk, provide it as an extra meal or two instead of increasing the size of the meals you’re already feeding.
- Feed milk at a warm temperature (38.5°C); otherwise, the calf uses its own energy stores to warm the milk to body temperature.
- Click here for recommendations on how much milk replacer to feed, based on calf age and environmental temperature.
- Ensure calves have enough bedding to keep them dry and warm. During the fall, winter and spring months, ensure you are bedding with straw, which will help to reduce a calf’s heat loss. Straw should be at least 8 cm (three inches) deep, and dry.
- To determine if a calf has enough straw, do the “kneel test”: kneel on the bedding for 20 seconds and if your knees get wet, change the bedding or add to it.
- Dry off newborn calves and use heat lamps to keep them warm. Wet hair cannot insulate the calf, and as the water evaporates, it takes heat with it and is extremely energy‐costly in young calves. Follow other good winter management practices such as blanketing, providing enough straw for nesting, and making sure calves have free access to warm water.