As summer draws to a close and you start planning for winter housing the question you need to ask is ‘are my buildings fit for purpose’? That’s fit for the purpose of housing cattle, and fit for the age of cattle intended to be housed.
One of the biggest risk factors for pneumonia is when calves come in for winter housing. Why? Because often calves are meeting the bacteria and viruses which cause pneumonia for the first time (these pathogens survive much longer in enclosed compared to open air), and stress (from weaning and winter housing) increases cortisol levels which reduces immune function; the body is preparing for fight or flight, not fighting off infection. So what we need to ensure is that our buildings are fit for purpose, and suitable for the age of animal to be housed. An ideal shed for older store cattle, is unlikely to be the ideal environment for recently weaned 6 week old dairy bred calves.
There are four key considerations to ensure buildings function properly and the disease risks from winter housing are minimised; ventilation (fresh air), moisture management, wind speed (draughts), and temperature. In today’s blog we will look at ventilation and moisture management in more detail;
Viruses and bacteria do not survive well in fresh air. Ensuring good air quality in cattle buildings reduces infectious burdens and promotes lung defences.
In order to get fresh air into your buildings you need:
- Inlet- somewhere for fresh air to get in
- Oulet-somewhere for stale air to get out
Natural ventilation uses heat generated by cattle inside a building to drive the ‘stack effect’ whereby warm air rises, leaves through the building ‘outlet’, creating a negative pressure which draws fresh air into the building through the inlet. During the winter housing period even on a very still day the heat produced by the housed cattle should be sufficient to drive the stack effect, ensuring a constant movement of fresh air into the building.
The efficiency of natural ventilation is determined by various factors:
a. Area of outlet – roughly 0.04m2 is required for calves, rising to over 0.1m2 for adult cat tle
b. Design of outlet – certain open-ridge designs will enhance the stack effect
c. Area of inlet – minimum 2x outlet area, ideally 4x outlet
d. Pitch of roof – steeper pitches enhance the stack effect
e. Stocking density – small calves in large air spaces may not generate sufficient heat to drive the ‘stack effect’
f. Position of inlet – if close to or adjoining other buildings the ‘cleanliness’ of the incoming air could be reduced, and ventilation efficiency affected
g. Cold buildings – inherently cold buildings (those with lots of exposed concrete, high moisture levels and no organic bedding) will reduce the amount of heat
It’s obvious to see from the above that problems can occur when for example there is no or insufficient outlet for stale air to escape, or insufficient inlet area to allow fresh air to enter the building. Or the building may have plenty of inlets and outlets but may be inappropriate for the age of cattle; young calves housed in large buildings with concrete walls may not produce sufficient heat to drive the stack effect. Or the heat they do produce gets negated by the cold concrete, meaning that the stack effect simply doesn’t work, again leading to a poorly ventilated building.
In some buildings the only way to ensure sufficient ventilation is to insert mechanical ventilation systems (forced ventilation), which drive the removal of stale air and provision of fresh air. Various options are available. Ventilation fans force fresh air into the buildings, where extractor fans remove stale air FROM the building. Expert advice should be sought regarding the most appropriate system, and the correct installation of any such system, to ensure maximum benefit is derived from it throughout the winter housing period.
High levels of moisture in a buildingincreases the survival time of pathogens both in the air and in the bedding. It reduces ambient temperature, and increases the lower critical temperature (the temperature at which a calf starts utilising energy to keep warm) and of course increases requirements for bedding.
Some obvious areas to look at addressing now include repairing leaky downpipes, and broken leaky/overflowing water feeders, and ensuring pens are sloped so they can drain adequately. During the winter housing period, when cattle are inside avoid using excess water to clean feed areas as this raises moisture and humidity levels in the shed.
Winter IS coming, and now is a good time to look at your buildings with a fresh pair of eyes and see what changes need making to help keep your animals healthy throughout the winter housing period. Stay tuned for our next blog on how to control wind speed (draughts) and temperature in your winter housing.
There is more excellent information available on the AHDB beef and lamb website:
For further information please see the product’s SPC or contact your veterinary surgeon or Zoetis UK Limited, Walton Oaks, Dorking Road, Tadworth, Surrey KT20 7NS. http://www.zoetis.co.uk/ Customer Support: 0845 300 8034 Use medicines responsibly (www.noah.co.uk/responsible) Date of Preparation: Aug-16