Change the system? – then at least check the facilities

As producers struggle to find ways of averting the costs associated with endemic diseases a range of operational systems are being employed – including batch farrowing and all-in/all-out stocking of facilities.  All operational changes need to be carefully `thought  through’.

A prime example of this can be illustrated with mechanically ventilated housing - for growers and finishing pigs - in particular.  Many such buildings were designed and erected over twenty years ago and whilst some may have been uprated there are a considerable number still operating with fan capacities similar to those originally installed.

It was usual, until relatively recently, for ventilation capacities to be based on the average weight of pigs in the building.   Pre-2000 this might well have been assumed – in a finisher house for example – to be about 60-65kg with pigs entering at about 30kg and being marketed at 90-95kg, with continuous stocking being practised.

Now – with all-in/all-out stocking being practised and with generally heavier terminal weights it is likely that average weights within the building will only match the 60-65kg assumption made for the original design and operation for a relatively brief period.

What this might well mean is that ventilation rate might be excessive when pigs are first housed – particularly in colder periods – and woefully inadequate towards the point when the house occupants are reaching their extended slaughter weight – again especially during warmer periods. This might call for, not just a change in fan capacities but more sophisticated control so that less air is moved when pigs are first housed and more is moved when they approach their maximum weight.  This differential may require that more than ten times the amount of air needs to be moved for larger pigs than for smaller ones in an all-in/all-out system, which may be outside the capacity of many older houses which were initially designed on a `compromise basis’.

This implied lack of control over ventilation rates, temperature, and humidity levels may offset the targeted advantage from all-in/all-out operation, and a change of use of buildings demands close consideration of environment control capacities to ensure that the full potential of the system is realised.  During cold weather, over-ventilated pigs try to cope by eating more.  In summer, if pigs are under ventilated there is serious risk of suffocation - or health and performance problems at best.  Changing to all-in/all-out involves more than changing the average weight of pigs housed.

May 2006