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Effective ventilation brings pig health benefits in chilling times. During extremes of weather pig farmers tend to become more aware of the specific ventilation needs of the pigs in their care. In particular, as winter turns to spring and back to winter in the same day, respiratory stress can be a problem particularly when there is a vast daily fluctuation in ambient temperature. The change to all-in/all-out production imposes greater
demands on the competence of the ventilation system because of the wider
weight range between the entry and exit weights of pigs in the same
building. When lightweight pigs first enter the building, ensuring that
excessive air movement does not chill the pigs is important and this
is often brought about by running the pig environment at the minimum
ventilation rate or simply depending on air leakage to achieve it. As pig farmers become more aware of their responsibilities
within the food chain and increasingly commit themselves to producing
wholesome pork from healthy pigs, making the time to develop a better
understanding of cold weather objectives should be a cost-effective
investment. The minimum ventilation rate has to cater for the
least number of pigs at their lightest weight and their lowest feed
intake. Heat loss from the building, heat generated from the pigs and
ancillary equipment in addition to any supplementary heat must also
be taken into account. During intervals of cold weather, especially
when body weights and stocking density are low, air flow is reduced
to a level which:
It's all about removing contaminants from the pig environment by diluting the contaminants within the air space occupied by the pigs. In practice, the criteria for minimum ventilation rate are the acceptability of carbon dioxide and humidity content within the room. As pigs grow they eat more and respiration volume increases and a by-product of this metabolism is the generation of carbon dioxide gas and water vapour. Since these are relatively easily measured they are used as the standard for setting the minimum ventilation rate. However, the reality is that the key factor could be concentration of noxious gases in the slurry. Unlike carbon dioxide, the output of these noxious gases might not necessarily increase as the pigs grow. Hence depending on carbon dioxide and water vapour to determine the minimum ventilation rate could result in over ventilation. The balance of scientific opinion, however, is that a minimum ventilation rate of 0.3 per cent carbon dioxide is a good practical compromise. If the CO2 level is allowed to creep up to 0.5 per
cent or above, pig keepers become very much aware of a 'heavy' atmosphere
and complain of headaches, it doesn't do the pigs any good either and
they respond by reducing their feed intake and so growth rates plummet. Recognising that ambient temperatures are much lower in winter and wind speeds higher are the first steps in developing a strategy for coping with challenges to the pig environment. Recording minimum and maximum room temperature everyday and adjusting ventilation rates accordingly is a more cost-effective approach than having to be rescued by expensive medication.
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