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Evaluation of Temperature Conditions in Trucks during Transport of Market Pigs to Slaughter

7 December 2011, at 12:00am

Pigs are exposed to variable temperatures during transport, according to a report by Drs Harold Gonyou and Jen Brown and others at the Prairie Swine Centre (PSC) in Canada, following studies over four seasons.

Jen Brown PhD

Previous research at PSC has shown there is significant variation in conditions (temperature and humidity) among different compartments in trucks transporting market pigs.

This study examined conditions in truck compartments in greater depth by measuring temperature and humidity variation during transport of market pigs throughout the year. Pigs were transported from a commercial farm in Saskatchewan to a packing plant on a weekly basis, involving approximately 7.5 hours of travel. This report describes the variable conditions observed during transport in different seasons, with pigs transported in the ‘belly’, upper-front and middle-front compartments encountering the least favourable conditions.

Harold Gonyou PhD

Background

Transportation of pigs to slaughter involves economic losses due to deaths, ‘suspect’ animals on arrival at the processing plant and reduced meat quality, and raises concerns regarding the welfare of pigs. Death losses in market pigs during transport in Canada range from 0.05 to 0.17 per cent, accounting for approximately 16,000 pigs per year, with an additional 0.10 to 0.20 per cent of animals becoming non-ambulatory during transport. These losses are seasonal, with higher losses reported in summer, and vary among compartments within a truck.

Previous research at PSC has demonstrated significant variation in temperature and humidity conditions between different compartments on trailers. In this study, which began in January 2010 and was completed in March 2011, PSC examined temperature and humidity conditions on a commercial tri-axle trailer to examine how conditions vary in compartments during different seasons of the year.


Figure 1. Placement of data loggers in the trailer (compartment 3)

Experimental Approach

Animals used in this study were market pigs weighing approximately 115kg. The animals included a mixture of males (barrows) and females, and were assembled from multiple pens. All animals were from a single commercial farm in Saskatchewan. The trials were conducted on a weekly basis, beginning on 8 January 2010 and completed on 7 March 2011. The pigs were generally loaded early in the morning (approximately 04:00 am) and travelled for approximately 7.5 hours, arriving at the packing plant approximately at 12 noon.

A single tri-axle livestock trailer was used for the study. Compartments in the upper deck were numbered from 1, at the front, to 4, at the back. The middle deck was numbered from 5, at the front, to 8, at the back. Compartments in the pot-belly were numbered 9, at the front, and 10, at the back. Pigs were loaded in eight of the 10 compartments. Compartments 6 and 7 were not used due to availability of pigs and load limitations. Loading density was approximately 0.41 square metres per pig (0.36 square metres per 100 kg).

Temperature and relative humidity within the compartments were monitored using data logging devices (iButtons). The devices were programmed to record data at five-minute intervals. Five data loggers were mounted in each compartment, with all loggers placed 130cm above the floor to standardise the measures between compartments. The devices were suspended from the ceiling on strips of hard plastic (Figure 1); one was mounted in the centre of each compartment and the remaining four were placed 15cm from the centre of each wall. Two data loggers were also mounted on the truck side mirrors outside the trailer to monitor ambient conditions.

To compare seasonal variation in transport conditions, four seasons were identified based on ambient temperatures at the time of departure (approximately 5:00 a.m.). Season 1 included trips where the ambient temperature was below minus 10°C (extreme cold), Season 2 included ambient temperatures from 0°C to -10°C (moderate cold), Season 3 included ambient temperatures from 0°C to 10°C (mild, above zero), and Season 4 included ambient temperatures above 10°C (extreme, above zero). Temperatures were determined for each compartment at the time the truck left the farm (departure), and as the truck was travelling to the packing plant. The number of truck loads per each season and the average ambient temperatures (outdoors) at the time of departure from farm, during travelling, and on arrival at the packing plant are presented in Table 1.


Table 1. Average and range of ambient temperatures (outdoors) encountered at the time of departure from the farm, during transport, and on arrival at the packing plant

Results

The average temperature within each compartment of the truck at the time of departure is presented in Table 2. In all four seasons, temperatures at departure were lowest in the ‘belly’ compared to other compartments, and highest in the middle-front and upper-front compartments.

During transport, compartments in the middle-front (compartment 5) and upper-front deck (compartments 1 and 2) had higher temperatures than the others in all four seasons (Table 2 and Figure 2). These compartments had relatively poor ventilation, as the front of the trailer was solid. Compartment 5 is also immediately above the truck drive wheels and transmission, which will be dissipating heat. Furthermore, previous research indicates that cool air enters at the back of the truck during transport, becoming warmer as it moves towards the front of the truck. Together these factors may have contributed to higher temperatures in the front compartments.

In extreme cold conditions (Season 1), compartments in the ‘belly’ had the lowest temperatures, and a similar trend was found in Season 2 (Table 2 and Figure 2). These compartments had higher ceiling heights as the compartments immediately above them were not used. Thus, extreme cold conditions in the ‘belly’ compartments was likely due to cool air entering from the back of the truck and the absence of pigs above them to warm the ceilings.


Figure 2. Truck temperatures during transportation in four seasons



Table 2. Average temperatures within truck compartments at the time of departure from the farm and during transport to the packing plant.

The Bottom Line

Pigs are exposed to variable temperatures during transport, with pigs transported in ‘belly’ compartments encountering lower than average temperatures, and those in upper-front and middle-front compartments encountering elevated temperatures. The effects of different boarding and insulation treatments on transport conditions during winter were examined but further analysis is needed to determine their effectiveness.

The results of these studies will provide important information for improving conditions during transport, and for the direction of future research.

December 2011