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Journal of Animal Science - Animal Production

Transportation of market-weight pigs: I. Effect of season, truck type, and location within truck on behavior with a two-hour transport1

 

This article in JAS

  1. Vol. 91 No. 6, p. 2863-2871
     
    Received: Oct 18, 2012
    Accepted: Jan 12, 2013
    Published: November 25, 2014


    3 Corresponding author(s): storrey@uoguelph.ca
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doi:10.2527/jas.2012-6005
  1. S. Torrey 32,
  2. R. Bergeron,
  3. T. Widowski,
  4. N. Lewis44,
  5. T. Crowe§,
  6. J. A. Correa#55,
  7. J. Brown||,
  8. H. W. Gonyou§|| and
  9. L. Faucitano*
  1. Agriculture and Agri-Food Canada, Sherbrooke, Quebec J1M 1Z3, Canada
    University of Guelph, Guelph, Ontario N1G 2W1, Canada
    University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
    University of Saskatchewan, Saskatoon, Saskatchewan S7N 5A2, Canada
    Université Laval, Québec, Québec G1V 0A6, Canada
    Prairie Swine Centre, Saskatoon, Saskatchewan S7H 5N9, Canada

Abstract

There is evidence that season and truck/trailer design play important roles in pig welfare during transportation although little is known about their interaction and effect on pig behavior. This experiment was designed to examine the influence of season and truck/trailer design on the behavior during loading, transit, unloading, and lairage of market-weight pigs transported to slaughter. A total of 3,756 pigs were transported on either a 3-deck pot-belly trailer (PB; n = 181 pigs/wk in 8 experimental compartments) or a double-decker hydraulic truck (DD; n = 85 pigs/wk in 4 compartments) for 2 h to a commercial abattoir in summer and winter (6 wk in each season). Density on both vehicles was 0.40 m2/pig. Accounting for the number of pigs, loading took longer (P = 0.033) onto the DD than the PB, but season did not (P = 0.571) influence loading time. Pigs loaded onto the PB moved backward more (P = 0.003) frequently than those loaded onto the DD. The frequency of tapping by handler was the lone handling intervention affected by truck type, with more (P = 0.014) tapping needed to move pigs on and off DD than PB. During loading, pigs made more (P < 0.001) slips and falls, overlaps, 180° turns, underlaps, and vocalizations in winter compared with summer. On truck, more (P < 0.001) pigs were standing on the DD at the farm and in transit than on the PB whereas more (P = 0.012) pigs were lying in transit in summer than in winter. Pigs took longer to unload (P < 0.001) from the PB than the DD, but no difference between vehicles (P = 0.473) in latency to rest in lairage was found. Pigs slipped and fell more (P < 0.001) during unloading, took longer (P < 0.001) to unload, and had a shorter (P = 0.006) latency to rest in lairage in winter than summer. Vehicle design, in particular the presence of ramps, influenced pig behavior before, during, and after transportation, regardless of the season. Season affected loading and unloading behavior, especially in terms of slips and falls on the ramp, and differences in truck/trailer designs were also partly to blame for unloading times and lairage behavior. Ramps and changes in direction during unloading appear to slow down the handling process.



INTRODUCTION

Mortality during the transportation of pigs to slaughter ranges from 0.02 to 0.25% (Barton-Gade et al., 2007; Haley et al., 2008b; Fitzgerald et al., 2009). Another 0.04 to 0.60% of pigs are nonambulatory on arrival at the plant (Barton-Gade et al., 2007; Averós et al., 2008; Fitzgerald et al., 2009). These losses represent both an animal welfare issue and significant financial loss to the industry.

Factors influencing stress response of pigs to transport include genetics (Fàbrega et al., 2002; Vanelli Weschenfelder et al., 2010), temperature and humidity (Haley et al., 2008a; Ritter et al., 2008), truck variables (Ritter et al., 2007; Fitzgerald et al., 2009), and trip duration (Barton-Gade et al., 2007). Correlations between ambient temperatures and mortality rates during transport are reported in a number of studies (Averós et al., 2008; Haley et al., 2008a). Barton-Gade et al. (2007) found that temperature, relative humidity, and wind speed explained 42% of the mortality in Danish pigs transported to slaughter.

Truck designs can vary widely, from small single-deck trucks to large 3-deck punch-hole trailers (often referred to as “pot-belly” trailers). Pot-belly trailers are quite common in North America, as they are often dual purpose (transporting either pigs or cattle) and hold a large number of animals. However, these vehicles incorporate both external and internal ramps and a fixed upper deck, factors that have been associated with increased mortality rates in Europe (Riches et al., 1996; Barton-Gade et al., 2007). To date, few studies have examined the effect of season and truck design on pig welfare, especially under extreme weather conditions as found in Canada. Therefore, the objective of this study was to assess the welfare of market-weight pigs through their behavior during transport on different trucks in 2 seasons.


MATERIALS AND METHODS

All procedures in this study were conducted in a manner consistent with and respectful of the provisions of the Comité Institutionnel de Protection des Animaux at the Agriculture and Agri-Food Canada research station in Lennoxville, Quebec. This study was approved by an Institutional Animal Care Committee in accordance with the Canadian Council on Animal Care.

Animals and Treatments

A total of 3,756 crossbred pigs (BW of 118.4 ± 0.4 kg) of the same genetics (Topigs International, Helvoirt, the Netherlands) and from the same commercial farm were used in a factorial experiment. Pigs were transported 2 h in the summer [June to July, 2007; average temperature = 20.7°C (13.5 to 25.6°C) at loading] and winter [February to March, 2008; average temperature = –8.7°C (–11.4 to –3.7°C) at loading] seasons over 6 wk in each season from the commercial growing–finishing unit to a slaughter plant located in the Montreal area using 2 types of vehicles, a pot-belly trailer (PB) and a compact double-decked truck (DD), both specifically designed to transport pigs. The PB was a 16.2-m tri-axle naturally ventilated trailer and it transported 228 pigs on 3 decks distributed in 10 compartments (Fig. 1a). Pigs were selected from several finishing pens and mixed on the truck. The order of loading from each finishing pen was changed every week to control for the distance traveled between the finishing pen and the truck. Pigs were loaded through an external ramp (length: 245 m; slope: 12°) and had to climb an internal ramp (slope: 19°) to go up to the upper deck (4 compartments) or to descend an internal ramp (slope: 22°) to go down to 2 belly compartments. In the middle deck (4 compartments), pigs only used the external ramp to enter the compartments. Compartments 2 and 7 were filled but not used in this experiment. The DD was a 11.0-m naturally ventilated double-deck truck with 4 compartments and a capacity of 85 pigs (Fig. 1b). There was 1 external ramp (length: 170 cm; slope: 10°) to enter the vehicle but no internal ramps because pigs were loaded onto the upper deck (2 compartments) using a hydraulic deck. The stocking density on both vehicles was 0.40 m2/pig (287 kg/m2), and both vehicles were bedded with wood shavings. The side panels were open 100% in the summer and 20% in the winter.

Figure 1.
Figure 1.

Location of compartments in a) pot-belly trailer, and b) double-deck truck. Internal truck ramps are indicated by solid line in compartments 8 and 10, and the door is in the rear of the truck/trailer.

 

Pigs were fed 10 mg/kg of ractopamine hydrochloride (Elanco, Toronto, Canada) daily during the final 2 wk of the finishing period. Feed was withheld 15 to 16 h before loading. Pigs were loaded with the use of paddles and boards at 0400 h in the summer and 0200 h in the winter in groups of 5 to 7 pigs. The PB was always loaded and unloaded before DD. Truck compartments were loaded in this order: 1, 4, 3, 9, 10, 5, 6, and 8 in the PB and 1, 4, 5, and 8 in the DD. Pigs were transported for 2 h to a commercial abattoir and unloaded in this order: 8, 3, 4, 1, 6, 5, 10, and 9 in the PB and 8, 5, 4, and 1 in the DD. Pigs were kept in lairage without mixing truck compartments at 0.51 m2/pig for 1.5 to 2 h. Water was provided during lairage through nipple drinkers. Pigs were handled at loading, unloading, and in lairage using paddles only. Pigs were driven to the CO2 stunner using automatic pushing gates and stunned by CO2 (Jumbo 6 model; Butina, Copenhagen, Denmark) before exsanguination.

Loading Behavior

During loading, behavior was recorded by direct observation as pigs were moved through a start pen and up a loading ramp onto the truck. Behavior patterns were recorded using a handheld Psion Workabout (Mississauga, ON, Canada) computer. One trained technician observed the pigs and recorded all occurrences of pig behavior (Table 1). A second trained technician recorded the time it took to move the pigs through the start pen and up the ramp. A third trained technician recorded the frequency of any necessary interventions from the handler, including speaking, whistling, other vocal sound, rattle noise (from a paddle), tapping with a paddle, and pushing with a board.


View Full Table | Close Full ViewTable 1.

Ethogram of pig behavior

 
Behavior Description
Balk Pig stops walking for more than 2 s
Turn around As it is being driven in 1 direction, pig turns around to go in opposite direction
Back up Pig walks at least 2 steps in reverse
Backward After turning around, pig walks in reverse for at least 2 steps
Vocalization Pig vocalizes
Underlap Pig lifts the 2 rear legs of another pig with its head
Overlap Pig mounts the back of another pig with its 2 front legs
Slip/fall Leg of the pig splits away from the other legs (slip) or at least 2 legs buckle under (fall)

Behavior on the Truck

Behavior was recorded on each vehicle using still image digital cameras (Pentax Optio W30 7.1 megapixel; Mississauga, ON, Canada) located in the 8 experimental compartments of the PB and in all 4 compartments of the DD, and images were recorded at 1-min intervals. The percentage of pigs within the field of view standing, sitting, or lying was recorded from these images as the truck was waiting at the farm once the truck was fully loaded (approximately 5 min before departure) and on arrival at the abattoir. During transit, the percentage of pigs standing, sitting, or lying was recorded from these images at 5-min intervals. On occasions where the camera view was occluded during an observation, the previous image was observed.

Unloading Behavior

Pigs were unloaded by compartment at the abattoir and driven into lairage pens segregated by truck compartment. Two trained observers noted the behavior of pigs by direct observation. The number of slips/falls and overlaps per compartment were counted, and the time taken to unload each compartment was noted (Table 1).

Lairage Behavior

A video recording system was used to record behavior at 10 frames/s (Panasonic WV-CP240 cameras, Panasonic AG 6730 VCR, and Panasonic AG IA670 encoder/reader module; Mississauga, ON, Canada; Sprite Dedicated Micro multiplexer; Mississauga, ON, Canada). Cameras were installed over each of the pens. Scan sampling was used to determine the number of pigs lying at each minute for the first hour of lairage after all pens had been filled (Lehner, 1996). In addition, the latency for 75% of the pigs in a pen to rest was determined.

Statistical Analyses

Data were analyzed using the mixed model procedure (SAS Inst. Inc., Cary, NC). The experimental unit was the group loaded or unloaded for loading and unloading variables, respectively, the truck/trailer compartment for variables measured on the truck/trailer, and the lairage pen for lairage variables. Data were compared in a model with main effects of truck type and season and their 2-way interaction and the random effect of week nested in truck type and season. The effects of different compartments within each truck type were analyzed in a model with main effects of compartment and season and their 2-way interaction and random effects of week within season and week within season and compartment. Data were weighted for the number of pigs in each compartment, and Tukey-Kramer adjustment was used to compare treatment means. When data did not meet the requirements for ANOVA, they were square-root transformed (untransformed least square means and SE are reported).


RESULTS AND DISCUSSION

Few experiments examining transportation study behavior of pigs from loading through to lairage. Combined with the physiological (Tamminga et al., 2008), environmental (Brown et al., 2011), and meat quality data (Correa et al., 2013) collected in these trials, the present study provides a better understanding of the effect of transportation on pig welfare.

Loading Behavior

Pigs loading onto the DD (11.17 ± 0.61 s/pig) took longer (P = 0.033) to load than those loaded into the PB (9.97 ± 0.51 s/pig). This could be the direct result of the DD being loaded second and the handlers being fatigued after loading the larger PB. In contrast, Brown et al. (2005) found that pigs were more difficult to handle when loaded using a ramp rather than a module forklift. However, the longer loading time onto the DD did not translate into greater mortalities (Correa, 2013). This result disagrees with Ritter et al. (2006), who found that on-truck waiting time at the farm was positively related to mortality, and Averós et al. (2008), who found faster loading times to be positively related to mortality.

No effect of season (P = 0.571) or an interaction between truck type and season (P = 0.252) on loading time were found. Season, however, affected most behavior during loading (Table 2). The frequency of slips and falls, 180° turns, and vocalizations was greater (P < 0.001) in winter whereas the frequency of overlaps and underlaps was greater (P < 0.001) in the summer. Pigs loaded onto the PB moved backward more (P = 0.003) frequently than those loaded onto the DD; otherwise, pig behavior was not (P ≥ 0.11) affected by truck type (Table 2). Pigs loaded onto the PB during the summer were observed to back up less often than pigs transported in either DD or PB in the winter (truck × season, P = 0.039). Moreover, less balking was observed among pigs transported in the PB compared with the DD in summer, and the opposite situation occurred during winter transportation (truck × season, P = 0.011; Table 2).


View Full Table | Close Full ViewTable 2.

Frequencies of behaviors of pigs and interventions of the handler during loading onto a double-deck truck (DD) or pot-belly trailer (PB) during summer or winter

 
Summer
Winter
P-value
Item DD (n = 85)1 PB (n = 165)1 DD (n = 84)1 PB (n = 168)1 SE Truck Season Truck × season
Pig behavior
    Slip/fall 0.03 0.03 0.18 0.15 0.01 0.115 <0.001 0.068
    Overlap 0.10 0.09 0.05 0.05 0.01 0.510 <0.001 0.970
    180° turn 0.10 0.09 0.22 0.23 0.02 0.883 <0.001 0.669
    Back up 0.33 0.25 0.43 0.45 0.03 0.620 <0.001 0.039
    Backward 0.03 0.06 0.02 0.04 0.01 0.003 0.148 0.410
    Underlap 0.07 0.09 0.04 0.05 0.01 0.178 0.001 0.979
    Vocalize 0.20 0.26 0.38 0.36 0.03 0.115 <0.001 0.473
    Balk 0.76 0.60 0.17 0.20 0.03 0.107 <0.001 0.011
Intervention of handler
    Speaking 0.85 0.61 0.32 0.37 0.05 0.566 <0.001 0.012
    Whistling 0.07 0.09 0.002 0.005 0.01 0.195 <0.001 0.263
    Other vocal 0.47 0.38 0.003 0.04 0.03 0.929 <0.001 0.237
    Rattling 0.46 0.46 1.15 1.22 0.05 0.293 <0.001 0.392
    Pushing 0.30 0.25 0.15 0.19 0.04 0.616 <0.001 0.472
    Tapping 5.36 4.05 2.25 1.85 0.09 0.014 <0.001 0.602
1Number of groups loaded and observed. Values differ by season due to missing data.

The frequency of whistling, other vocal commands, pushing, and tapping were greater (P < 0.001) in summer than winter whereas rattling was more (P < 0.001) frequent in winter (Table 2). The frequency of tapping was the lone handling intervention affected by truck type, with more (P = 0.014) tapping needed to move pigs on and off DD than PB. Furthermore, handlers spoke the most to pigs being loaded onto the DD in summer and the least to those on the DD in winter (truck × season, P = 0.012; Table 2). Because of personnel changes, the animal handler during loading was not the same for the 2 seasons; therefore, the differences between pig behavior and manipulation may be the result of different handling techniques. Alternatively, because the exterior door was open during loading, these differences may reflect differences in temperature or light, factors considered to influence pig handling (Hemsworth, 2000). Dalla Costa et al. (2007) also found that pigs were more difficult to handle in winter and needed more coercion to load, which led to more handling bruises, and agrees with the finding that more skin damage occurred in pigs in winter (Correa et al., 2013).

Behavior on the Truck

Although few studies examined on-truck behavior, results of the present study are in line with previous reports for market-weight pigs traveling for shorter durations (Kim et al., 2004; Barton-Gade, 2008). Truck type affected pig behavior on the trucks, at the farm, in transit, and at the abattoir before unloading. At the farm and in transit, more pigs were standing (P < 0.001) and fewer were sitting (P < 0.001) and lying (at the farm: P < 0.001; in transit: P = 0.013) on the DD than on the PB (Table 3); however, this may have more to do with loading order than truck type as the DD was always loaded second. As such, more time elapsed between loading and departure on the PB, allowing pigs to habituate to their environment before leaving the farm.


View Full Table | Close Full ViewTable 3.

On-truck behavior (% of observations) in winter and summer during transport on the double-deck truck (DD) or pot-belly trailer (PB)

 
Truck
Season
P-value
Item DD (n = 43)1 PB (n = 71)1 Summer (n = 72)1 Winter (n = 42)1 SE Truck (T) Season T × season
Farm
    Standing 71.4 12.9 47.2 37.1 5.4 <0.001 0.186 0.688
    Sitting 24.1 63.1 41.2 46.0 4.2 <0.001 0.415 0.930
    Lying 3.9 23.1 9.7 17.3 3.6 <0.001 0.133 0.233
Transit
    Standing 56.1 36.6 42.6 50.0 3.5 <0.0001 0.138 0.407
    Sitting 38.1 50.3 44.0 44.5 1.5 <0.0001 0.821 0.101
    Lying 4.5 11.0 11.0 4.5 1.8 0.013 0.012 0.365
Arrival
    Standing 41.6 30.7 35.7 36.5 4.4 0.084 0.899 0.008
    Sitting 51.0 54.7 51.1 54.6 3.0 0.377 0.403 0.020
    Lying 4.3 16.2 16.4 4.1 3.7 0.025 0.022 0.006
1Number of compartments observed. Values differ by season due to missing data.

Although season did not influence on-truck behavior during the wait at the farm, location within the 2 trucks did affect behavior. At the time the DD left the farm, more (P = 0.008) pigs were standing on the lower deck (79.3 ± 5.6 and 85.2 ± 5.6% for compartments 5 and 8, respectively) than the upper deck (60.1 ± 5.6 and 62.0 ± 5.6% for compartments 1 and 4, respectively; results not presented). Furthermore, the percentage of pigs sitting was less (P = 0.013) in compartments 5 (19.3 ± 4.8%) and 8 (14.3 ± 4.8%) compared with the upper deck compartments (36.2 ± 4.8 and 29.4 ± 5.0% for compartments 1 and 4, respectively); however, there were no (P = 0.152) differences between compartments 5 and 4. These results are likely due to the order of loading because pigs in compartments 1 and 4 were the first to be loaded, allowing them more time to settle down by the time the truck left the farm.

In contrast to the DD, there were no (P > 0.05) differences among compartments in any of the postures on the PB at the time the truck left the farm. However, an interaction occurred (P = 0.021) between season and compartment for the percentage of pigs standing. In the summer, the percentage of pigs standing was greater in compartment 3 (45 ± 8.6%) than compartments 8 (21.7 ± 8.6%) and 9 (19.3 ± 8.6%) and in compartment 4 (43.3 ± 8.6%) compared with compartment 9 whereas in winter, the proportion was greater in compartment 10 (41.7 ± 10.4%) compared with compartments 3 (13.5 ± 10.4%), 4 (7.0 ± 9.4%), and 1 (0.2 ± 9.4%; results not presented). The least proportion of pigs standing in compartments 3, 4, and 1 in winter may be explained by the order of loading because these were the first to be loaded. However, it is difficult to explain why pigs from compartments 3 and 4 stood the most at the farm in the summer, despite the fact that they were among the first to be loaded.

During transport, most pigs split their time between standing and sitting, which agrees with previous reports that few pigs lie down during short-duration trips (Guise et al., 1997; Kim et al., 2004; Peeters et al., 2008). More (P < 0.001) pigs were sitting and lying on the PB compared with the DD (Table 3). This may also be a carryover effect of the longer latency to leave the farm after loading. Both trucks traveled the same route for the same duration of time, so road type and driver speed was unlikely to have influenced behavior as has been reported in other studies (Peeters et al., 2008; Spence and Cockram, 2011).

A greater (P = 0.012) percentage of pigs lying during transport was observed in the summer than winter (Table 3), which is consistent with the findings of Peeters et al. (2008) that fewer pigs were standing on-truck in higher temperatures. On the DD, there were no (P > 0.05) differences between compartments in the percentage of pigs standing and sitting during transport, but the compartment effect was significant on the PB (Table 4). More (P < 0.001) pigs were standing in the front (compartment 5), mid top (compartment 3), and rear middle (compartment 8) than in compartments 4, 6, 9, and 10, and the least percentage (P < 0.001) of pigs standing was observed in compartment 4. In addition, the percentage of pigs sitting was greatest (P < 0.001) for compartments 4, 6, and 10 and least for compartments 3, 5, and 8. Although vibration on the 2 trucks was not measured in the present study, it is quite possible that this differed between and within the trucks (Tarrant and Grandin, 2000), which may have influenced pig behavior. Pigs find vibration to be aversive (Stephens et al., 1985; Warriss, 1998) and will sometimes experience motion sickness during transport (Randall and Bradshaw, 1998), but the welfare implications of adopting different postures in transit are unclear.


View Full Table | Close Full ViewTable 4.

Behavior of pigs (% of observations) by compartment during transport in summer (June, July) or winter (February, March) on the pot-belly trailer

 
Season
Compartment (Comp)
P-value
Item Summer Winter 1 3 4 5 6 8 9 10 SE Season Comp Season × Comp
Farm
    Standing 30.92 20.14 12.85 29.60 25.17 36.17 24.18 22.24 20.81 33.20 6.77 0.152 0.146 0.021
    Sitting 55.56 57.72 62.52 56.89 53.38 52.42 61.02 62.28 51.68 52.95 6.44 0.681 0.748 0.562
    Lying 13.21 22.86 23.67 12.34 16.89 10.58 13.75 27.32 26.25 13.46 6.03 0.041 0.243 0.088
Transit
    Standing 39.40 43.93 41.59ab 51.68a 28.43c 50.92a 31.79bc 50.09a 39.25b 35.58bc 4.31 0.225 <0.001 0.072
    Sitting 51.88 50.61 50.52ab 43.60b 62.44a 42.75b 61.79a 45.10b 47.75ab 56.00a 3.45 0.698 <0.001 0.051
    Lying 9.54 5.17 7.68 4.34 8.93 6.00 6.39 4.43 12.76 8.31 2.42 0.117 0.100 0.909
Arrival
    Standing 25.00 43.96 25.70 50.09 12.42 41.57 20.72 34.59 32.97 57.73 10.98 0.062 0.004 0.012
    Sitting 57.94 47.77 61.61 46.59 64.23 43.75 61.04 49.93 55.62 40.04 10.26 0.250 0.127 0.007
    Lying 16.35 8.31 12.70 3.14 21.31 14.10 18.37 15.47 11.41 2.15 7.69 0.226 0.232 0.103
    Unloadin time, sec/pig 2.92 3.20 3.28ab 3.28ab 3.82a 2.38c 3.01b 2.84b 2.80bc 3.11b 0.25 0.111 0.005 0.072
a−cWithin a row, means lacking a common superscripted letter differ (P < 0.05).

Interactions (P < 0.05) occurred between truck type and season on all behavior on arrival at the abattoir (Table 3). Most pigs were standing on the DD in summer and the least on the PB in summer (49.62 ± 6.32% vs. 21.85 ± 5.10% of observations; truck × season, P = 0.008). A reverse situation was observed for sitting behavior on the truck on arrival at the abattoir, with the most pigs sitting in the PB during summer and the least on the DD in summer (57.94 ± 3.05% vs. 44.21 ± 4.32% of observations; truck × season, P = 0.020). Furthermore, pigs on the PB in summer were observed lying more often (29.70 ± 3.98% of observations) compared with pigs on the PB in winter or pigs on the DD, regardless of season, who were observed lying for less than 6% of the time (truck × season; P = 0.006). This increased lying behavior on the PB in the summer cannot be associated solely with warmer temperatures in the summer because average temperatures were similar in DD and PB in summer (25.2 to 26.4°C vs. 25.5 to 26.5°C) and winter (0.2 to 4.2°C vs. 0.9 to 9.9°C).

Upon arrival at the abattoir, the percentage of pigs sitting on the DD was greater (P = 0.011) for compartments 4 (58.0 ± 5.4%) and 8 (61.0 ± 5.4%) compared with compartments 1 (43.4 ± 5.0%) and 5 (42.3 ± 4.8%). An interaction (P = 0.005) between season and compartment also occurred within the DD for the percentage of pigs standing (Fig. 2), with a greater (P < 0.030) percentage of pigs standing on the upper deck (compartments 1 and 4) in the summer than in the winter, but the percentage of pigs standing did not differ between seasons for the lower compartments (5 and 8). An interaction between season and compartment also occurred for the percentage of pigs standing (Fig. 3; P = 0.012) and sitting (Fig. 4; P = 0.007) on the PB. This is due to a greater (P < 0.001) percentage of pigs sitting and a lower (P = 0.001) percentage of pigs standing in compartment 10 in the summer than in the winter and a greater (P = 0.003) percentage of pigs standing in compartment 5 in the winter compared with summer. Because temperatures were similar among compartments in both vehicles in both seasons, these interactions are difficult to explain and may be related to factors that were not monitored during the study, such as vibrations and lateral movements.

Figure 2.
Figure 2.

Interactive effect of season (summer: June, July; winter: February, March) and compartment within the double-deck truck (P = 0.005) on the standing behavior of pigs on arrival at the abattoir. a−cBars lacking common letters differ, P < 0.05.

 
Figure 3.
Figure 3.

Interactive effect of season (summer: June, July; winter: February, March) and compartment within the pot-belly trailer (P = 0.012) on the standing behavior of pigs on arrival at the abattoir. a−cBars lacking common letters differ, P < 0.05.

 
Figure 4.
Figure 4.

Interactive effect of season (summer: June, July; winter: February, March) and compartment within the pot-belly trailer (P = 0.007) on the sitting behavior of pigs on arrival at the abattoir. a−cBars lacking common letters differ, P < 0.05.

 

Unloading Behavior

As with loading, unloading from the PB was always done before the DD, but unloading was generally 3 to 4 times quicker than loading. Therefore, it was anticipated that the unloading order would not have as big of an impact on the results as did the loading order. However, pigs transported in the PB took longer (P < 0.001) to unload than pigs transported on the DD (3.06 ± 0.10 vs. 2.51 ± 0.11 s/pig) even though they were unloaded first. On the PB, compartment affected (P = 0.005) unloading duration (Table 4). Pigs in compartment 4 took longer (P < 0.001) to unload than pigs in compartment 5 whereas pigs in the other compartments had intermediate values. Results did not differ between the 3 upper deck compartments (1, 3, and 4), which may be partially explained by the fact that they had to descend a ramp, which has been shown to make unloading more difficult (Brown et al., 2005; Kephart et al., 2010). Within the DD, pigs coming from compartment 4 took longer (P = 0.006) to unload (2.99 ± 0.17 s/pig) than those from compartment 1 (2.12 ± 0.17 s/pig) or 5 (2.28 ± 0.17 s/pig), and pigs from compartment 8 were intermediate (2.66 ± 0.17 s/pig); these differences are difficult to explain because there were no ramps involved.

Pigs took longer (P < 0.001) to unload in winter than summer (3.10 ± 0.11 vs. 2.65 ± 0.10 s/pig) and, during unloading, pigs slipped and fell more (P < 0.001) in winter than in summer (0.34 ± 0.04 vs. 0.04 ± 0.01 slips and falls/pig); however, no effect of truck type (P = 0.12) or an interaction between truck and season (P = 0.57) on the number of slips and falls was found (results not presented). The seasonal differences in unloading time and slips and falls were due to the unloading facility design, where the unloading ramp, albeit wide enough for the pigs to unload simultaneously, had an aluminum base that became slippery when temperatures dropped below freezing (company has rectified this problem). No differences between trucks (P = 0.68) or seasons (P = 0.35) were detected in overlapping behavior during unloading, and compartment effects within the DD or the PB were not significant (P > 0.05) for slips and falls or overlapping (results not presented).

Lairage Behavior

Compared with other studies (Geverink et al., 1996; Brown et al., 1999; Barton-Gade, 2008), pigs in the present study had much shorter latencies to rest in lairage. Pigs were not commingled from different truck compartments in the lairage pens as is often done at slaughter plants, and this may have resulted in the shorter latencies to rest. Season affected latency to rest in lairage (P = 0.007). Pigs transported in summer rested after 39.71 ± 2.04 min in lairage whereas those transported in winter rested after 31.65 ± 2.08 min in lairage, possibly because pigs transported in summer spent more time drinking (results not presented). Although truck type did not (P = 0.473) affect latency to rest in lairage, a compartment × season interaction (P < 0.001) was found within the PB (Fig. 5). Pigs in compartment 8 had a longer (P < 0.001) latency to rest in the summer than in winter and the shortest latency to rest in winter. This compartment was the first to be unloaded, but it is unclear why the latencies in the 2 seasons would differ in this compartment. A compartment × season interaction (P = 0.035) also occurred within the DD, with pigs in compartments 1 and 5 having longer latencies to rest in summer than winter. The 2 greatest latencies were found on the top level (Fig. 6). Brown et al. (2005) found that, although unloading was generally deemed more difficult with a ramp than a hydraulic lift, heart rates of pigs were the same after unloading in both systems. It may be that a moving floor creates some degree of stress on the pigs as this is a novel experience.

Figure 5.
Figure 5.

Interactive effect of season (summer: June, July; winter: February, March) and compartment within the pot-belly trailer (P < 0.001) on latency to rest in lairage after transportation. a−cBars lacking common letters differ, P < 0.05.

 
Figure 6.
Figure 6.

Interactive effect of season (summer: June, July; winter: February, March) and compartment within the double-deck truck (P = 0.035) on latency to rest in lairage after transportation. a−cBars lacking common letters differ, P < 0.05.

 

Season influenced the lairage behavior of pigs from the 2 trucks differentially. In winter, pigs transported on the PB spent less time lying than pigs on the DD whereas in the summer, they spent more time lying than pigs transported on the DD (truck × season, P = 0.001; Table 5). Pigs from the PB also spent less time standing in the summer than pigs from the DD (truck × season, P = 0.008) and more time sitting in the winter that pigs from the DD (truck × season, P = 0.005). Pigs transported in the PB were unloaded immediately on their arrival at the abattoir whereas pigs transported in the DD waited as the PB was unloaded (approximately 45 min). As a result, pigs from the DD may have been warmer in the summer and spent more time standing during drinking (not measured) as a result.


View Full Table | Close Full ViewTable 5.

Behavior1 during lairage (mean ± SE) in winter (February, March) and summer (June, July) after transport on the double-deck truck (DD) or pot-belly trailer (PB)

 
Season Lying Standing Sitting
Summer
    DD (n = 24)2 41.88 ± 2.79% 33.16 ± 1.85% 24.69 ± 1.64%
    PB (n = 48)2 51.13 ± 1.97% 24.39 ± 1.40% 24.32 ± 1.22%
Winter
    DD (n = 24)2 52.13 ± 2.79% 25.77 ± 1.85% 20.28 ± 1.64%
    PB (n = 48)2 45.29 ± 1.97% 25.03 ± 1.40% 27.56 ± 1.22%
P-value
    Season 0.362 0.025 0.664
    Truck (T) 0.617 0.002 0.011
    Season × T 0.001 0.008 0.005
1Percentages do not sum to 100% because a category of “other behavior” was included in observations (not included in the analyses).
2Number of lairage pens observed.

Many of the differences between the 2 trucks may have been the result of the logistics of this commercial study and not being able to balance for loading and unloading order. However, season, truck/trailer type, and location within truck affected pig behavior. Season affected unloading behavior, especially in terms of slips and falls on the unloading ramp, and differences in truck/trailer designs were also partly to blame for unloading times and lairage behavior. Ramps and changes in direction during unloading appear to affect behavior and slow down the handling process. Because the DD does not have internal ramps and loading and unloading are in a single direction, use of this truck has the potential to reduce interventions and behaviors of handlers that can contribute to injuries and losses.

 

References

Footnotes


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