Vehicle ventilation

Fit fans on your livestock transporter to remove the heat and moisture produced by the pigs while they are being carried on the vehicle, suggests an advisory bulletin produced for a governmental ministry.

April 1, 2008

A controlled movement of air within the container part of the truck can be achieved by a combination of suitably positioned mechanical fans of sufficient capacity and natural apertures. (Illustration courtesy Defra, UK)

Consider the arrangements needed for controlling the climate not only in your pig-houses, but also on the vehicles used to transport the pigs. An advisory document issued to producers in the UK reminds them that ventilation within the vehicle is important to remove the heat and moisture produced by animals during transport. It also advocates active ventilation using mechanical fans as allowing more opportunities to modify conditions around the animals than with passive ventilation especially when the truck is stationary.

Written for the governmental department for rural affairs by ADAS Roslin Welfare Consultants, the document says the preferred method of ventilating livestock vehicles is by a process of controlled mechanical ventilation. Unlike controlled-environment systems such as those found on refrigerated trucks, this provides only a regulated ventilation rate. The temperature of the air entering through the inlet is no different from that externally. As this air passes over the pigs, it collects the heat and moisture that they have produced.

There is little opportunity to control the movement of air within a naturally ventilated vehicle, the British advisers continue. The forward motion of the transporter creates an area of low pressure around the container sides at the front end. This would have the effect of drawing in air through the rear vents when the truck moves forward at speed. The air would then move forward over the pigs and leave through the front vents.

"This effect explains why fresh shavings that have been spread evenly over the floor at the start tend to be blown to the front of an empty vehicle while it drives to the farm for loading," they comment. "Ventilation holes in the front headboard will let air into the container, but this air will be drawn out again by suction through the front vents and will not travel the length of the container." An exception occurs on a truck moving at low speed in a strong cross-wind, in which case the resulting air-flow would be through and across the container.

The document offers a diagram illustrating how a series of suitably positioned mechanical fans at the front of the truck could achieve controlled ventilation, provided that the fans were of a sufficient capacity. But, it warns, simply mounting fans on existing ventilation openings is unlikely to ensure that air flows over all the pigs, because air will always take the path of least resistance.

"It is better to install fans at one end of the vehicle containers and apertures at the other end, with closed sides in between. The direction of air-flow created by the fans should enhance the natural flow of air within the container caused by the vehicle's forward movement. Extraction fans at the front and natural inlet apertures at the rear are probably the most effective arrangement.

"However, in case of mechanical failure, a fan-ventilated vehicle should always have the capability of opening sufficient side apertures to enable emergency natural ventilation."

Gene survey tracks Pacific colonists

Newly published studies using mitochondrial DNA from modern and ancient pigs across East Asia and the Pacific have demonstrated that a single genetic heritage is shared by modern Vietnamese wild boar, modern feral pigs on the islands of Sumatra, Java, and New Guinea, ancient Lapita pigs in Near Oceania and modern and ancient domestic pigs on several Pacific islands. The finding is called significant because it causes archaeologists to reconsider the origins of the first people to colonise the Pacific islands.

Established models of human migration assert that the ancestors of Pacific islanders originated in Taiwan or islands in south-east Asia and passed through the Philippines as they dispersed into the remote Pacific. In direct contradiction to these long-standing ideas, however, the work with pigs has suggested that ancient human colonists may have originated in Vietnam and travelled between numerous islands before first reaching New Guinea and later landing on Hawaii and French Polynesia.

A report in US academic journal Proceedings of the National Academy of Sciences by British scientists from Durham University and the University of Oxford describes their survey of DNA and tooth shape in modern and ancient pigs. The results are said to open a new window into the history of human colonisation of the Pacific, by giving clues to the movement of pigs between the isolated islands. The early colonists presumably took pigs with them as they moved from mainland East Asia through south-east Asian islands and on into Oceania, bringing their domestic plants and animals with them. PIGI