Ventilation in Modern Dairy Buildings
Richard Henning, Dairying Development Advisor, CAFRE
The Farm Nutrient Management Scheme is being utilised on many farms to provide additional slurry capacity and on a number of farms a house is going to be erected for additional or improved dairy cow accommodation. Due attention needs to be given to provide an appropriate environment for the cow in terms of feed and water space, cubicle provision and adequate ventilation. This article will concentrate on the key aspects necessary for providing good ventilation in dairy buildings thus improving the living environment for both the farmer and the dairy herd.
The aim of good ventilation is to provide a constant supply of fresh air to all stock in the house PLUS an outlet for stale air to remove:
- Excess heat – dairy cows are more susceptible to heat stress (even under warm humid days in N. Ireland) than to cold but the layout should not create draughts.
- Moisture – this is important to keep cubicle beds dry
- Pathogens and dust for a healthy disease free environment.
Ventilation can be provided naturally through the siting and design of the house or artificially using fans. With Northern Ireland being exposed to mild southwesterly winds for most of the year and occasional cold northerly/easterly winds, natural ventilation should be possible on most farms.
Heat produced by livestock in a shed causes a natural upward movement of warm stale air. If this air can exit the building at the roof ridge, then fresh air will be drawn in through the side walls (cladding). This is called the stack effect.
The stack effect can be maximised by:
- The correct pitch (slope) of the roof. As a rule of thumb, livestock buildings should have a pitch of between 1 in 4 and 1 in 3. For example, a shed 18m (60’) wide should rise from eaves to ridge by between 2.25m (7’6”) to 3m (10’), with a typical eaves height of 4.2m (14’). The ridge should be 6.45 (21’6”) to 7.2m (24’) above ground level.
- The provision of adequate outlet (open ridge). As a guide the ridge opening should be 5 cm (2”) for every 3 m (10’) of building width. For example the same 18 m (60’) wide shed should have a 30cm (12”) opening. Care is needed in the internal design of houses to avoid open ridges directly above cubicle beds.
- The provision of adequate air inlet. This can take the form of space boarding, “ventilated” cladding or mechanical curtains. Again care needs to be taken in siting new buildings along side existing sheds as this can impair the inflow of fresh air to both sheds.
Many manufacturers now install sidewall curtains but remember, dairy cows do not like draughts and cubicle beds need to be kept dry to control bacterial growth. Ideally if such devices are to be installed then consideration should be given to linking them to integrated weather stations and/or strategically placed thermostats within the building. This will provide a means of control during changeable weather conditions without adding to the time pressures on the farmer with another job to do.
Dairy buildings are an investment which will have an important effect on not only the health and welfare of your cows, but also their profitability. Time spent planning new building projects is time well spent.
If you require further advice on or assistance on improving dairy cow welfare through better accommodation, contact your local dairying development advisor.