For years every article on ventilation has carried the warning “but avoiding draughts at stock level”. Is this true and if so is there any experimental work to prove it? Some thoughts would be –
- Outwintered stock are exposed to the most draughts yet it is generally agreed they are the most healthy.
- Given the choice, in cold weather cattle will not stand in a draughts. This is clearly seen in outwintered stock in how they seek shelter which will vary depending on the direction of the wind.
- When housed in groups cattle will lie down in the section of the pen providing the best environment for them. In addition if there are draughts at animal level the majority will be sheltered by the bodies of their colleagues – the same system as used by emperor penguins, incubating eggs in the middle of the Antarctic winter.
- The exceptions to group housing would be individually penned, bucket reared calves who have the additional problem of a relatively high critical temperature. However even in this situation each calf can be given a choice of environment by roofing over the back half of the pen. This is the approach of calf hutches which form draughts by having a completely open door, yet are famed for the high levels of health they maintain.
- Outdoors young calves achieve a similar effect by either lying down wind, alongside their mothers or by lying together in groups.
- Is it possible to have air movement over the heads of stock with no draughts lower down at stock level? The answer is almost certainly no due to the vortex effect.
- Vortexes cause a continuous swirl of contaminated air round the stock ie draughts. To avoid this effective shelterbelts of trees are designed to allow a proportion of the wind to go straight through the wood ie are designed to have draughts.
- In the unlikely event we could provide stock with a draught free area it is likely to be detrimental to the health of stock by reducing the rate at which the bedding would dry out. Providing a clean, dry lie for stock is perhaps the most critical factor influencing their welfare, health and profitability.
Basil Lowman, SAC Consulting Beef Specialist
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