There are some “added extras” in caring for calves over winter – just like getting a vehicle ready for the colder months, according to Cargill’s calf and heifer specialist Bianca Theeruth.
“As temperatures fall, calves need extra energy for maintenance. We need to feed more to avoid this energy being diverted from their growth requirements.”
The temperature range – or thermoneutral zone – for calves is typically between 10° and 25°. Within this, the calf will generally maintain its body temperature and requires no additional energy to keep warm.
“However, this temperature range varies with the age of the animal. In winter, we are particularly concerned about the lower end; the lower critical temperature,” she explained.
“For calves under three weeks old, the lower critical temperature is between 10° and 15°. Below this, the calf will use its energy reserves to maintain a core body temperature of 38-39° – diverting it away from growth.”
She continued: “For calves more than three weeks old, the lower critical temperature is between 5° and 10°. This is due to its more advanced rumen development that generates heat, its higher energy starter feed intake and more internal fat stores.”
The graph below shows the extra energy requirements above maintenance (7.87MJ/day) for calves up to three weeks old and for calves more than three weeks old as temperatures fall.
If this extra energy isn’t supplied calves burn body fat reserves and then muscle tissue. This causes weight loss and depresses the immune system.
Extra energy requirements of young calves as temperature falls
“As a rule of thumb, for every degree the temperature drops below the calf’s lower critical temperature, the energy required for maintenance increases by 1%.
“It is important that farmers recognise this and adapt the calves’ diets so that they don’t run short of energy for growth. Nutrition is first line of defence against the cold,” Bianca explained.
In the first three weeks, when starter feed intakes are minimal, the extra energy must come from increasing milk or milk replacer.
- Increase calf milk replacer by 100g/calf/day and split between feeds. No more than 900g/day of calf milk replacer should be fed;
- Feed a high 20% fat milk replacer;
- Increase the volume of liquid – from 5L to 6L/calf/day – across two feeds;
- A third feed could also be introduced with a maximum of 900g of powder in 6L of mixed milk per calf per day. Split the total concentration and volume into three feeds instead of two. However, care must be taken as this may hinder starter feed intake, which can delay rumen development.
Management and accommodation
Bianca also touched on the importance of good management practises and adequate accommodation.
“Management is equally important as nutrition. Milk should be fed at – or slightly above – body temperature. A texturised, coarse and muesli-type starter feed will also encourage intakes. Calves need fresh, clean water from day one,” she explained.
Calf accommodation is crucial and – in winter – poorly-ventilated and draughty accommodation will create problems. Moving and fresh air is needed as much in winter as in summer.
Dry bedding is one of the most important factors in calf management. A dry, deep straw bed will provide insulation and the calf will create a nest effect. Calf jackets for young or sick calves will help in retaining body heat.
“A few small changes and an increase in the calf’s energy supply, as temperatures fall, will help to avoid pitfalls that can throw the calf off its growth target. Keeping calves warm, well-fed and comfortable will pay dividends,” she concluded. Click here for more information
