Calf rearing is now being recognised by farmers as a task that requires meticulous attention to detail in order to maximise the liveweight gain from calves and for target weights to be met throughout the animal’s lifetime. Calf rearing is also a time-consuming task, with farmers looking to reduce the time to feed and bed calves to focus on other matters on the farm, or simply reduce their working hours.
It’s no surprise that more farmers are conscious of how they are designing their calf houses regarding both these points.
Ventilation is critical in every animal house, but especially so in a calf house. The difficulty in creating adequate ventilation is preventing draughts.
The best way to assess ventilation is to crouch down to a calf’s height. If there is a smell of ammonia, there is inadequate ventilation in the shed. Similarly, if you can feel a cool breeze at this height, calves can as well, and will use up energy to keep themselves warm as opposed to putting it in to growth.
Natural ventilation using the ‘stack effect’ of calves’ body heat, causing the warm, stale air to rise and exit through an adequately covered outlet and replaced with cool, clean air from the sides of the building, is one of the most effective ways of creating ventilation. For this to work, a roof pitch of 15-22° is recommended to funnel the air out of an appropriately covered ridge outlet.
A typical air inlet of 0.08m² per calf is required on normal sites and 0.05m² per calf for exposed sites. Air outlet size at the ridge should be half of the overall inlet size. Calf sheds positioned at right angles to the prevailing wind work best. Air inlets should be less than 3m from floor height.
Bedding and drainage
Many farmers have used different bedding materials to bed calves, whether for labour or cost benefits. However, a deep straw bed has a superior nesting score in comparison to other bedding materials, with calves in well-bedded pens comfortable at temperatures as low as 8°C, despite preferring an ambient temperature of 15-20°C.
Calves will require 15-20kg (a small square bale) of straw per week, with a good rule of thumb being one 4x4 round bale for each calf brought through to weaning.
Calves spend up to 80% of their time lying down, so maintaining a clean, dry bed under them is essential to prevent them unnecessarily using energy reserves to keep themselves warm.
To minimise bedding requirements, floors should be adequately sloped to a 75x75mm effluent channel. A 1:20 slope towards the effluent channel is recommended by the Department of Agriculture. Ample access for a tractor or telehandler to mechanically clean out calf pens will likely result in more frequent cleaning out, so appropriate doorways of greater than 3m wide should be fitted.
The Department recommends 2-2.5m² per calf. Individual pens used in the first few days must be a minimum of 1m x 1.5m, with a length of 1.7m recommended.
The correct feeder and drinking space must be provided to encourage feed and water intake and to discourage bullying. For bucket feeding, calves require 350mm of feed space each.
What can I do if my calf house is poorly ventilated?
What can I do if there are draughts in my calf house?