Vehicle Design Impact on the Transportation of Hogs

Death losses during transportation in Canada may be low (0.10%), but the total loss amounts to approximately 16,000 pigs per year. In addition, other pigs arrive at the processing plant as 'suspect' animals due to fatigue, and may need to be euthanized at the plant. We know that the rate of loss is higher during the summer months, and it differs with farm of origin, and transporters. It is generally acknowledged that some compartments on trucks are worse than others in terms of death losses, but there is no universal agreement on which compartments these or and the magnitude of the differences.

Besides the loss of pigs, there may also be an economic loss due to poor meat quality arising from stressful handling and transportation, and this could be more substantial than the death losses. Little is known about the quality of meat coming from different compartments in a vehicle, nor about differences in environmental conditions among compartments.

We have organized a collaborative project with researchers at several universities and research stations to study the effect of handling and transport on the physiological and behavioural responses of pigs, and on meat quality. Our collaborators include Drs. Trever Crowe (Saskatchewan), Nora Lewis (Manitoba), Renee Bergeron, Tina Widowski, Cate Dewey (Guelph), Stephanie Torrey and Luigi Faucitano (AAFC, Lennoxville). Currently, two graduate students, Jorge Andres Correa and Emily Tamminga, are working on the project under the supervision of Drs. Faucitano and Widowski, respectively.

The initial phase of the project involved collecting information under standard transportation conditions in both Quebec and western Canada, in both summer and winter. We have followed 36 truck loads of pigs. Our data include the behaviour of pigs during loading, on the truck, at unloading and in lairage, the thermal conditions within each compartment of the truck at each stage of the process, the core body temperature of pigs from barn to lairage, the heart rate of pigs from the barn to unloading or to lairage (in Quebec), certain blood parameters indicative of stress, and meat quality up to 24 hr after slaughter.

During the project we modified and validated new methods for monitoring heart rate and core body temperature. Heart rate was recorded using Polar heart rate monitors, similar to those used by athletes, held in place with saddle cinches. The monitors were programmed and placed on the pigs several hours before loading at the farm. We were able to collect recordings for up to 11 hrs of handling and transport. We placed heart rate monitors on approximately 15% of the pigs, with at least two animals equipped within each compartment.

We measured core body temperature by bolusing the pigs with temperature loggers and recovered these from the digestive tracts after slaughter. These loggers have previously been used in poultry transport work at the University of Saskatchewan. The loggers are about 1.2 cm in diameter and can be programmed to record temperature for several days. Again, these were administered to the same 15% of the pigs that were equipped with heart rate monitors several hours before loading. We collected the grey offal from these pigs at the plant and searched the stomach, caecum and intestines for the temperature loggers. The majority of the loggers were found in the stomach, others in the caecum, and a few in the intestines. We recovered approximately 85% of the devices.

To date, our analysis has been limited to the summer trials in Quebec. The pigs were market weight (approx. 120 kg), and had been fed Paylean during the final three weeks of the growth period. Loading density on the vehicles was 0.41 m2/pig, equivalent to a k value of 0.017 m2/kg0.667. Pigs were loaded using paddles and herding boards only. No electric prods were used at the farm, on the truck, or at the plant. We used both a three-deck pot-belly trailer with internal ramps (six loads of 228 pigs) and a double-deck trailer without ramps (top deck lifted by hydraulics; six loads of 85 pigs). The pot-belly trailer was specifically designed to transport pigs. The ramp to the upper deck had a less severe slope than a typical dual-purpose (cattle and pigs) pot-belly, and the front compartment of the middle deck was reached without first climbing up to the top deck, as is the case in many dual-purpose trailers. Pigs were loaded early in the morning and transported for two hours to the plant where they were promptly unload. After two hours of lairage, which included sprinkling, the pigs were slaughtered.

The temperature within the truck compartments reached its highest level during either the wait at the farm after loading and before departure (averaging between 24 and 30 C), or at the plant after arrival prior to unloading (averaging between 26 and 30 C). During the actual transport the temperatures in all compartments averaged between 24 and 27 C. In the pot-belly trailer, the hottest compartment while waiting at the farm was the front of the middle level. After the vehicles arrived at the processing plant, the temperatures in the upper level of compartments increased by 3 degrees within a few minutes.

Core body temperatures for pigs were highest when the truck was waiting to leave the farm. Because the pot-belly trailer was always loaded first, core temperatures during the on-farm waiting period were higher in the pot-belly (40.62 C) than the double-deck (40.15 C) pigs. The highest core temperatures were found in pigs on the upper deck of the pot-belly while still at the farm. Core temperatures dropped somewhat during transport (40.18 C), and fell below pre-loading temperatures (to 39.82 C) once they were sprinkled with water in lairage. It is not clear if the higher core body temperatures in pigs on the top deck are due to the greater exertion required to climb to that deck, or to the high environmental temperatures encountered there during the long stationary period.

Pigs were unloaded by compartment at the abattoir and driven into lairage pens segregated by truck compartment. Behaviour during unloading (slips and falls), time to unload each compartment (adjusted for number of pigs per compartment), latency to rest (75% of pen lying) and total time lying during the first hour of lairage were observed. Accounting for the number of pigs, unloading from the pot-belly took longer than from the double-deck ( 2.9±0.1 vs 2.1±0.2 sec/pig), but there was no difference in the number of slips and falls during unloading. During lairage, there was no difference between trucks in the time taken for 75% of the pigs to lie down, approximately 35 min for both vehicles, but pigs from the doubledeck tended to spend more time lying than pigs from the pot-belly trailer (51 vs 45% of time lying).

Although trailer design did not influence latency to rest, pigs from the pot-belly took longer to unload and spent less time lying in lairage. The higher activity in the lairage pen tended to result in higher levels of CPK and lactate, indicators of physical stress, at slaughter. Further analyses will determine the effect of location within the truck on behaviour.

On arrival at the plant, the number of dead-on-arrival (DOA), downers (NANI) and pigs with rectal prolapse was noted. A higher incidence of DOA (0.44 vs 0.20 %) and NANI (0.51 vs 0.20 %), and pigs showing rectal prolapse on arrival (0.29 vs 0.20 %) was observed in the pot-belly trailer. However, insufficient animals were involved in the study to determine differences among compartments for these low-incidence parameters.

The quality of the longissimus dorsi muscle was classified as pale, soft and exudative (PSE); moderate PSE, red, firm and non-exudative (RFN or normal); pale, firm and non-exudative (PFN); red, soft and exudative (RSE); moderate DFD and dark, firm and dry (DFD); based on muscle pH, light reflectance (colour), and drip loss measured at 24 h post-mortem. Meat quality was good overall, with most loins falling into the RFN class. Meat quality did not differ between the two vehicles, but within the pot-belly trailer, the incidence of DFD pork, indicative of chronic stress, was seen in the loins of pigs from the upper and lower decks (19%).

The summer Quebec trials involved the hottest conditions we encountered in the study. Although we have yet to conduct conclusive correlation analyses, high temperatures within the compartment, high core body temperatures, and poorer meat quality were all most common in the upper deck of the pot-belly vehicle. Factors that affect meat quality may differ in summer and winter, and between the short hauls in Quebec (2 hr) and longer hauls in western Canada (8 hr). Our analysis of the data continues, and we will shortly begin the second phase of the study to find ways of alleviating the stressors we observed.

Acknowledgements:  Project funding is being provided by Ontario Pork, Maple Leaf Pork, Natural Sciences and Engineering Research Council, and Agriculture and Agri-Food Canada. Program funding is provided by Alberta Pork, Sask Pork, Manitoba Pork and the Agriculture Development Fund of Saskatchewan. A collaborative project at Agriculture and Agri-Food Canada, Lennoxville was funded by the Swine Producers Board of Quebec, the Animal Compassion Foundation, and F. Menard Inc.