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ANIMAL PRODUCTION |
* Department of Animal Sciences, University of Illinois, Urbana 61801;
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The Maschhoffs Inc., Carlyle, IL 62231; and
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Elanco Animal Health, Greenfield, IN 46140
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Abstract |
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 Top Abstract INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Key Words: floor space • nonambulatory • pig • transport • welfare
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INTRODUCTION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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, 2004). Transport losses may be influenced by numerous factors including genetics, carcass muscling, health status, structural soundness, BW, nutrition, handling, facility design, and conditions during transport to the plant. Few, if any, of these factors have been examined under typical commercial conditions in the United States.
Floor space (stocking density) during transport affects pig behavior, welfare, and meat quality (reviewed by Warriss, 1998). Floor space during transport also affects body temperature, heart rate, and respiration rate of market-weight pigs (von Mickwitz, 1982). Survey evidence suggests that overcrowding pigs during transport is associated with greater mortality rates (Robertson, 1987; Guardia et al., 1996; Riches et al., 1996). In practice, floor space available for the pig during transport is determined by the number of animals placed on each load. Currently, the National Institute for Animal Agriculture (2004) recommends floor space allowances of 0.40 to 0.45 m2/pig for pigs weighing between 114 to 136 kg (equivalent to approximately 0.35 and 0.33 m2/100 kg of BW, respectively). The objective of this study was to investigate effects of 2 floor spaces (0.39 and 0.48 m2/pig) during transport, which represent the range currently being used in commercial practice in the United States, on the incidence of dead and nonambulatory pigs and to evaluate relationships between transport conditions and losses. Differences in floor space were achieved by varying the number of pigs loaded onto the trailer, which confounds effects of floor space and number of pigs per compartment. However, this is the approach that will be used to change floor space during transport under practical conditions, which was the objective of this study.
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MATERIALS AND METHODS |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Two floor space treatments (0.39 and 0.48 m2/pig) were compared in a split-plot design that utilized 74 trailer loads of finishing pigs. The main plot was the deck of trailer; the subplot was transport floor space; and the trailer load of pigs was the block. Therefore, floor space treatments were compared within each of 2 decks of each trailer load of pigs. The protocol for this project was approved by the University of Illinois Institutional Animal Care and Use Committee.
Animals, Farms, and Pig Handling
The pigs used in this study were market-weight (mean BW 129.0 ± 0.63 kg) barrows and gilts that were the progeny of PIC 337 sires mated to C22 dams (PIC USA, Franklin, KY).
Two farms within the same production system were used. One of the farms had 4 and the other had 2 wean-to-finish buildings. Pigs were raised in mixed-sex pens of 25 to 30 pigs and were fed the same diets during the grow-finish period. Loads from the first farm were taken when the 4 buildings were emptied in April (number of loads = 18) and in late October through early November (n = 24). Loads from the second farm were taken when the 2 buildings were emptied in July (n = 14) and January (n = 18).
The approach to emptying the buildings that was used by this production system was to send the heaviest pigs (approximately 25% of the pigs) from each pen of 25 to 30 pigs to the packing plant at wk 20 postweaning. The remaining pigs were then marketed 3 to 4 wk later. The loads used in this study were taken after the heaviest 25% of the pigs had been removed.
A total of 12,511 pigs were transported. Pigs were loaded by personnel from the University of Illinois, with assistance from farm employees and with the same university personnel being involved for all loads. In summary, groups of 4 to 6 pigs were removed from the pen and were moved down the center aisle of the building and onto the trailer using sorting boards and, if necessary, electric goads. The width of the center aisle in the buildings at the first farm was 56 cm for 2 barns and 81 cm for the other 2 barns, whereas the width of the center aisles for the 2 buildings at the other farm was 81 cm. The angle of the covered ramps used to load pigs onto the trucks at both farms was 10° or less. Groups from 3 or 4 pens were mixed in each compartment on the trailer. The incidence of pigs that became nonambulatory at the farm during loading was recorded. However, only the pigs that became nonambulatory at the farm after loading were transported.
During the July replicate only, all pigs showing physical signs of stress (i.e., open-mouth breathing, skin discoloration, or both) during the loading process were identified by the investigator and marked with a unique color corresponding to the deck of the trailer onto which they were loaded. These animals were monitored on arrival at the plant.
Trailer Design, Floor Space Treatments, and Transportation
Two designs of a standard commercial swine trailer were used. The trailers had 2 decks and were constructed of aluminum with holes in all of the trailer sides for ventilation. The designs were similar except that the dimensions of the compartments (Table 1) and the angle of the internal loading ramp (trailer design 1 = 21° and trailer design 2 = 24°) differed. To account for this difference in compartment sizes, floor space treatments were compared within 2 approximately similarly sized compartments located in the same general area of the trailer on the top and bottom decks (i.e., for trailer design 1, the second and third compartments from the front of the trailer were used; for trailer design 2, the first and third compartments were used). Therefore, the effects of floor space on transport losses at the plant were evaluated on 296 test compartments with 5,409 pigs. The number of trailer loads of pigs transported in trailer designs 1 and 2 were 35 and 39, respectively. Loads were transported on 4 d in replicates 1 (April) and 2 (July) and on 6 and 5 d in replicates 3 (October/November) and 4 (January), respectively. The average number of loads per day was 2.9, with a range of 1 to 7 loads (Table 2).
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). The remaining trailer compartments were stocked at a floor space of approximately 0.45 m2/pig, which was the standard used by this system. After the completion of loading, pigs were transported approximately 3 h (~240 km) to a commercial packing plant. For the loads transported in July, pigs were sprayed with a water mist via a water sprinkling system installed within the trailer for approximately 5 min immediately on arrival at the plant. For the loads transported in January only, some of the air vents were covered (approximately 75%) and sawdust bedding was provided at a depth of approximately 2.54 cm to minimize cold stress.
The timing of all events (loading, waiting period at the farm before transport, transport, waiting period at the plant before unloading, unloading, and total time from loading to unloading) was recorded. A temperature and relative humidity sensor (HOBO H8 Loggers, Onset Computer Corporation, Bourne, MA) was placed between the 2 test compartments on each deck of each trailer to continuously log (1-min intervals) information in the trailers from the beginning of loading to the end of unloading. This information was used to calculate the average temperature and relative humidity for each event during transportation (i.e., loading, waiting at the farm, journey, waiting at the plant, and unloading). Additionally, average BW of pigs on each load (based on the total weight of the load recorded at the plant) and the number of the loads transported within each day of the study were recorded.
Identification of Dead and Nonambulatory Pigs
Drivers unloaded trailers according to the standard procedures for this production system (using a sorting board and, if necessary, an electric goad). Upon completion of unloading, the number of dead pigs was recorded by compartment. Packing plant employees identified nonambulatory pigs in the holding pens and as pigs were moved from the holding pen to the weigh scale. Nonambulatory pigs were defined as pigs that were unable to stand, walk, or keep up with the rest of the group due to injury or fatigue (Anderson et al., 2002; Ellis et al., 2003). Total losses were defined as the sum of dead and nonambulatory pigs at the plant. Nonambulatory pigs at the plant were classified as nonambulatory, injured; or nonambulatory, noninjured (for 65 of the loads only).
Statistical Analysis
Data for transport losses (dead; total nonambulatory; nonambulatory, injured; nonambulatory, noninjured; and total losses) were not normally distributed and, thus, did not meet the assumptions for ANOVA. Therefore, these data were subjected to a 
2 rank-based transformation using the RANK procedure of SAS (SAS Inst. Inc., Cary, NC). Transformed data were analyzed as a split-plot design with hierarchical nesting using the MIXED procedure of SAS; the main plot was trailer deck, the subplot was transport floor space, and the trailer load of pigs was the block. The model included fixed effects of trailer design, trailer deck, transport floor space, farm, replicate nested within farm, and all possible interactions. The model also included the random effects of loading day nested within replicate and farm, load nested within trailer design, replicate, and farm, and the load x trailer deck interaction. The experimental unit for the transport floor space treatments was the trailer compartment. The load x trailer deck interaction was used as the error term to test the effects of trailer deck, and the residual error was used to test the effect of transport floor space.
Relationships between transport conditions and losses were evaluated using Pearson correlations with the CORR procedure of SAS.
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RESULTS AND DISCUSSION |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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On average, times for loading, waiting at the farm, and total journey time were 45, 5, and 193 min, respectively (Table 2). Waiting times at the plant before unloading averaged 47 min but varied greatly by replicate (41.9, 9.2, 89.6, and 53.9 ± 5.8 min for the January, April, July, and October/November replicates, respectively). Throughout this study, pigs were loaded between 1900 and 0800, with majority of pigs being loaded between the hours of 0100 and 0800. It is likely that longer waiting times at the plant in July were due to more loads from other producers arriving at the plant during the same time as loads from this study. This would result in longer waiting periods before unloading. Unloading times averaged 21 min, including time to remove dead animals from the trailer. The average total time from the beginning of loading to the end of unloading was 310 min with a range from 230 to 546 min (Table 2).
As expected, average temperatures inside the trailer varied considerably across replicates (mean temperatures: 2.6, 10.9, 24.0, and 14.5 ± 1.02°C for the January, April, July, and October/November replicates, respectively). In general, temperatures inside the trailer increased when the trailer was not moving (i.e., during waiting at the farm, waiting at the plant, and unloading). Temperatures increased during loading and continued to increase and peaked during the wait at the farm (Table 2). Once the journey began, temperatures dropped by approximately 3°C. Upon arrival at plant, temperatures increased until the trailer was unloaded. Previous studies have also reported temperature inside the trailer increased during loading (Christensen and Barton-Gade, 1996; Chevillon, 2000; Hamilton et al., 2003) and when the trailer was not moving (Guise, 1991; Christensen and Barton-Gade, 1996; Hamilton et al., 2003) but decreased during transport (Chevillon, 2000).
Overall, average relative humidity in the trailer was 74.2% (Table 2). Relative humidity was lowest during loading (69.2%) and greatest after loading during the wait at the farm (81.3%). Relative humidity dropped to an average of 74.7% during the journey and remained relatively constant until pigs were unloaded.
Relationships Between Pig Responses at the Farm and the Plant
In the first replicate of this study, which was carried out in April, the incidence of nonambulatory pigs identified at the farm was very similar to the incidence of nonambulatory pigs identified at the plant (farm = 0.60% vs. plant = 0.73%). This suggested a possible relationship between the incidence of nonambulatory pigs at the farm and the incidence of nonambulatory pigs at the plant. Therefore, in the second replicate, which was carried out in July, pigs showing signs of stress during loading at the farm were marked and closely monitored on arrival at the plant. A total of 155 (6.61%) of the 2,346 pigs loaded were classified as exhibiting physical signs of stress (i.e., open-mouth breathing, skin discoloration, or both) after loading, and these were monitored at the plant. Three of these pigs were classified on the truck at the farm as nonambulatory, noninjured; 1 of these died on the truck, and 1 was nonambulatory, and the other was normal at the plant. Of the 152 pigs that showed physical signs of stress (i.e., open-mouth breathing, skin discoloration, or both) at the farm but remained ambulatory, only 1 was classified as nonambulatory, noninjured at the plant, and the remainder were considered normal. Overall 152 (98%) of the 155 pigs exhibiting signs of stress at the farm were considered normal at the plant.
Over the entire study, there were 32 (0.26%) nonambulatory pigs identified on the truck at the farm (Table 3), and 25 of these were followed from the farm to the plant, and 18 (72%) were normal at the plant, 3 (12%) were dead on arrival, and 4 (16%) were nonambulatory, noninjured at the plant.
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). However, recent research has demonstrated that blood acid-base measures of aggressively handled pigs return to prehandling baseline levels by 2 h posthandling (Bertol et al., 2002), and this suggests that these pigs can recover from handling stress if allowed to rest. Current National Pork Board recommendations suggest that pigs that become non-ambulatory at the farm should be allowed to recover at the farm (NPB, 2004). Collectively, our data from monitoring pigs exhibiting signs of stress and nonambulatory pigs at the farm through the plant suggest the majority of pigs recovered during the journey of approximately 3 h to the plant; however, a significant percentage of nonambulatory pigs (28%) did not. This has important implications for handling and recovery of nonambulatory, noninjured pigs. Additional research is necessary to more precisely establish the time necessary for nonambulatory, noninjured pigs to fully recover.
Average BW and Overall Transport Losses
The average live pig weight was recorded for each load and was 129 kg; however, this ranged from 113.0 to 140.8 kg for individual loads (Table 3).
The overall percentage of nonambulatory pigs at the plant was 0.85% (Table 3) for the 12,511 pigs transported. During the first 9 loads of the study, investigators observed that pigs became nonambulatory due to fatigue (nonambulatory, noninjured) or injury (nonambulatory, injured). Therefore, for the remaining 65 trailer loads of the study, nonambulatory pigs (0.79%) were classified as nonambulatory, injured (0.24%) or nonambulatory, noninjured (0.55%). The ratio of noninjured pigs to injured pigs was approximately 2:1 (Table 3). The number of transport deaths was 0.23%, which is similar to the national average for the United States (Ellis et al., 2003). The total losses in this study were 1.08%, and this is similar to results from a number of field studies (Ellis et al., 2003; 2004).
In this study, total number of animals lost during transport (dead and nonambulatory) was 135 on 74 loads. Interestingly, pattern of losses across loads was very sporadic as illustrated in Figure 1, where information on total losses by day of the study is presented. Furthermore, 60% of transport losses occurred on just 28% of loads (i.e., loads with 3 or more losses), whereas 51% of loads had 1 loss or less and accounted for only 17.8% of total losses (Table 4). Ellis et al. (2003) also reported a sporadic incidence of transport losses with 60% of transport losses being on just 20% of the loads. It is unclear why this variation in transport losses occurs; however, factors potentially associated with the incidence of losses on different loads of pigs on different days are environmental conditions, loading distances at the farm, people involved (handling crews and drivers), and waiting times at the plant.
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In the current study, we examined effects of stocking pigs at 0.39 and 0.48 m2/pig during transport on transport losses at the plant. Based on the average pig weights recorded for each load, these floor space treatments correspond to 0.30 and 0.37 m2/100 kg, respectively. The current recommendations of the National Institute for Animal Agriculture (2004) approximate to 0.33 to 0.35 m2/100 kg of BW. Weights were only available for the total load of pigs and not for individual compartments of animals. This latter data could only have been collected by weighing the pigs before loading, and this was not done to avoid any effect of previous handling of the pigs for weighing before loading on the animal response to the transportation process.
Increasing floor space during transport from 0.39 to 0.48 m2/pig did not affect the incidence of nonambulatory, injured pigs at the plant but reduced the percentage of total losses at the plant (0.88 vs. 0.36 ± 0.16%, respectively; P < 0.05) with reductions in total nonambulatory pigs (0.62 vs. 0.27 ± 0.13%, respectively; P < 0.05) and nonambulatory, noninjured pigs (0.52 vs. 0.15 ± 0.11%, respectively; P < 0.01). Also, there was a tendency for pigs transported at 0.39 m2/pig to have a greater percentage of dead pigs (0.27 vs. 0.08 ± 0.08%, respectively; P = 0.06; Table 5) than pigs transported at 0.48 m2/pig. These findings agree with commercial surveys that have suggested overcrowding pigs during transport is associated with increased mortality rates during transport (Robertson, 1987; Guardia et al., 1996; Riches et al., 1996).
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Trailer Deck
The deck of the trailer onto which the pigs were loaded and transported had no effect on transport losses (Table 5). Climbing loading ramps has been shown to be a significant stressor to pigs (van Putten and Elshof, 1978), and therefore, greater losses for pigs transported on the top deck that have to climb an internal ramp on the truck might be expected. It would appear that in the current study, any extra stress associated with climbing the internal ramp did not result in an increase in transport losses for pigs on the top deck.
Relationships Between Transport Conditions and Transport Losses
As expected, causes of losses were correlated (Table 6). Nonambulatory pigs at the farm were positively correlated to total nonambulatory pigs (r = 0.35; P < 0.01) and total losses (r = 0.35; P < 0.01) at the plant. This is not unexpected given that, based on the monitoring of pigs from the farm to the plant in this study, a proportion (28%) of nonambulatory pigs at the farm did not recover during the journey. Percentages of dead and nonambulatory, noninjured pigs on arrival were positively correlated (r = 0.28; P < 0.05), suggesting there may be some common predisposing factors in these 2 conditions. The percentage of nonambulatory, injured pigs was not correlated to any of the other losses (Table 6).
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). Waiting time at farm, unloading time at the plant, and total time were positively correlated with plant nonambulatory, noninjured pigs (r = 0.24, 0.41, and 0.27, respectively; P < 0.05); total transport time (including stops), unloading time, and total time from loading to unloading were positively correlated with transport deaths (r = 0.29, 0.52, and 0.40; respectively; P 
0.01); and waiting time at the plant, unloading time, and total time were positively correlated with total plant losses (r = 0.24, 0.51, and 0.36; P < 0.05). Only unloading time at plant was correlated with total nonambulatory pigs at the plant (r = 0.32; P = 0.01), whereas event times were not correlated to nonambulatory pigs at the farm or nonambulatory, injured pigs at the plant. As mentioned above, unloading time was positively correlated to percentage of total nonambulatory pigs, nonambulatory, noninjured pigs, transport deaths, and total losses. However, these may not be direct relationships; unloading time included the time to unload dead and nonambulatory pigs from the trailer.
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). However, several authors have reported transport deaths are greatest in summer months and lowest in winter months (Allen et al., 1974; Smith and Allen, 1976). The relationship between ambient temperature and transport deaths has been described as hyperbolic or curvilinear (Smith and Allen, 1976; Warriss and Brown, 1994), where losses are very low when temperature is below 10°C but increase dramatically when temperature is above 15 to 18°C. In the current study, losses were greatest for the replicate in January (1.47%) compared with 1.06%, 1.01%, and 0.80% for the replicates carried out in July, October/ November, and April, respectively. Hamilton (unpublished data) analyzed data relating to 2,199 loads from 1 yr within the same production system and also reported that total losses were greatest in winter. Additional research is necessary to establish seasonal variation in transport losses and relationships between conditions during transport and transport losses.
The only relationship observed between relative humidity in the trailer and losses was between levels during loading and percentage of nonambulatory pigs at the farm (Table 7; r = 0.46; P < 0.001). However, this may not be a direct relationship because high relative humidity during loading was generally associated with rain, which led to slippery conditions on the loading ramps. Previous studies have reported no relationship between relative humidity and deaths during transport (Allen et al., 1974; Smith and Allen, 1976; Robertson, 1987).
Nonambulatory pigs at the farm were positively correlated with load number within the day (r = 0.25; P < 0.05; Table 7). This could be associated with increased fatigue of loading crew members at the farm, potentially resulting in aggressive handling of pigs.
Additionally, average BW of the load was not correlated to losses at the plant (Table 7). Trailers were loaded on the basis of floor area per pig and not per unit of BW. Consequently, as BW increased, pigs had less floor space when expressed on a weight per floor area basis. It should be noted that we recorded the average BW of the load and not of the weight of each compartment.
In summary, results of this study show that approximately 1% of all pigs transported were dead or nonambulatory at the plant and that the incidence was very sporadic among loads. Floor space on the trailer had a substantial effect on transport losses, and providing a greater level of floor space (0.48 compared with 0.39 m2/pig) reduced transport losses and consequently improved welfare of pigs during transportation. In addition, transport times and conditions on the trailer may affect losses at the plant. Additional research is necessary to establish the minimum floor space on the trailer that results in the minimum transport losses.
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Footnotes |
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3 Current address: Premium Standard Farms, Highway 65 North, Princeton, MO 64673.
2 Corresponding author: mellis7{at}uiuc.edu
Received for publication October 6, 2005. Accepted for publication March 9, 2006.
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LITERATURE CITED |
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TopAbstractINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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