Ventilation is key when winter housing cattle
Tuesday November 24 2009
The constant downpours of last week will have forced almost all cattle into sheds. Despite of the difficulties of paying for new sheds erected under the Farm Waste Management Scheme I'm sure many farmers were glad to have them as land became flooded.
Weanlings, dry suckler cows and autumn calving cows with calves that were clearing off the last of the grass had to be housed, although doing so when cattle were wet was not ideal. This means that sheds are now full to capacity.
The weather is often very wet and mild in the months of November and December resulting in high humidity in the house. The weeks immediately after housing is the time when ventilation is most severely tested. Ventilation plays a vital role in maintaining good animal performance and disease control.
Signs of poor ventilation are excessive condensation on the roof and other surfaces, mould growth on timbers, bad odour resulting from ammonia in the airspace, wet coats on cattle and dirty hides. Efficient ventilation should get rid of excess moisture, respiratory disease organisms, dust and waste gases.
Obviously, when the air outside is saturated with moisture it is difficult to keep a good atmosphere in the shed. As air warms it can carry more moisture, so the greater the temperature difference between the inside and outside, the better the air movement and exchange of moisture. Currently we have relatively warm weather and good temperatures even at night and this makes ventilation difficult in calm conditions.
Newer houses have much better ventilation than older houses so, if you have a choice, put the weanlings and younger cattle in the newest house. In older houses where there could be inadequate ventilation remedial action can be taken.
For a start, keep doors open provided this does not create a strong draught. After that, make sure there are no blockages in the existing inlet and outlets. If there is space boarding you could remove every second board or, better still, turn a metre length of space boarding into a door with hinges that can be opened in calm conditions and closed when it is windy.
If there is a cap on the roof apex it is likely to be too low, so it could be raised or removed to help the escape of stale air. Advice on methods of upgrading the ventilation efficiency of cattle houses can be got from your Teagasc adviser.
The Department of Agriculture specification outlines the ventilation standards for new houses. This specifies that "outlet ventilation shall be provided along the full length of the roof apex: 450mm (18") wide for a house of 15m wide; 600mm for a house of up to 24m wide; and 750mm for larger houses".
The inlet area should be twice the outlet area, which is achieved by having the same open area at both eaves as is provided at the apex, either as an open space or the equivalent open space provided through vented sheeting or space boarding. Cattle houses are ventilated by natural means and this operates in two ways: (i) by the effect of wind; (ii) by the stack effect on a calm day.
In Ireland wind ventilation is most common. To avoid downdraughts a strong incoming wind needs the same space at the other side of the house to escape. The stack effect works on the fact that warm air produced by the heat from the stock rises and some escapes through the roof apex and is replaced by cool air drawn in at the eaves.
When cattle are fed to appetite, they produce far more heat than is required to maintain body temperature so this waste heat has to be eliminated from the body and from the house environment. If animals are too warm they will sweat to get rid of excess heat. Chipping a strip of hair along the back bone improves heat dissipation from the body.
Keep a close watch on cattle, especially weanlings, which have been recently housed. Note individual animals that do not come forward to feed or are slow to feed and also look for discharges from the nose and eyes. Check the temperature -- it should be about 38°C. If it is above this by more than 1°C you could have a case of pneumonia, and this is likely to require a vet's attention.
- Liam Fitzgerald
Irish Independent
