Pig production is a major industry in Canada (Dorjee et al., 2013) and its success over the years relied heavily on the availability of highly improved breeding stock. Breeding stock production is typically located in areas where disease pressure is low and biosecurity perimeters are wide. However, being able to take advantage of these biosecurity benefits also requires that breeding stock would need to be transported to pig dense regions. While in transit, the potential exists where breeding stock may be exposed to airborne disease contamination.
Therefore it’s important to limit the infection of these animals during transport and consequently close the biosecurity gap by which potential infection can be introduced to commercial herds. In addition, the livestock transport industry is also facing growing pressure to provide more people-friendly and welfare-friendly vehicles (i.e., capable of providing stable, acceptable environmental conditions, reduced incidence of fatigued animals) in response to growing public awareness of animal welfare issues. Therefore, we need to re-visit the design of livestock trailers currently used in the industry and address these issues by incorporating new design features that improve worker safety and animal welfare.
This project was carried out in four phases: survey of relevant stakeholders in livestock transport, computer simulation of various trailer design configurations to select the best design option, design and assembly of a new prototype trailer, and testing and evaluation of trailer performance.
A questionnaire which gathered inputs on the current observed strengths and deficiencies of commercial swine transport trailers was distributed to a number of stakeholders involved in pig transportation. Responses gathered from the survey were summarized and formed the basis for the initial design of the new trailer, including desired features and preferences in new trailer design.
To create a baseline case for latter comparisons with the new trailer design, computer simulations were done on a conventional straight deck trailer (two decks and five compartments in the upper deck and six in the bottom deck). Six trailer design options based on alternative locations and different number of air inlets and air outlets (which are the main drivers of air movement in mechanical ventilation systems) were evaluated in summer and winter conditions.
Top designs were selected based on (1) ventilation effectiveness, and (2) the capability to meet the environmental requirement of pigs during transport. Heat removal effectiveness (HRE) was used to evaluate the ventilation effectiveness of each design option. The best design configuration for the air- filtered trailer from simulations was implemented in the construction of the prototype trailer.
The final design featured a trailer with two separate compartments: a front compartment that houses generator set, a bank of six air filters, ventilation controller, supplemental heater, and two axial fans; and a livestock compartment with solid aluminum walls, two decks with a hinged upper deck floor and a roof that can be lifted open, and a hydraulic loading platform.
Based on this design, the prototype trailer showed overall reduction of 96.9% in concentration of aerosolized model virus (bacteriophage Phi X174) inside the animal compartment relative to upstream of the filter (MERV-8 pre-filter and MERV-16 main filter). In addition, monitoring of two trips showed the mechanical ventilation system was able to maintain the desired thermal conditions within the animal compartment. A supplemental heating unit helped to ensure the temperature (animal compartment) did not go lower than 10°C during the trips under winter conditions. Events during the trip such as slowing down or full stops affected environmental conditions inside the trailer, although the desired conditions were quickly restored once the trip resumed. More information on this project can be found online at prairieswinecetnre.com •
— By Bernardo Predicala
Prairie Swine Centre