The effect of simulated cold weather transport on core body temperature and behavior of broilers

The effect of simulated cold weather transport on core body temperature and behavior of broilers i

M. L. Strawford,*^ J. M. Watts,* T. G. Crowe,* H. L. Classen,t and P. J. Shaiidi

*Department of Chemical and Biological Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9, Canada; fAnimal and Poultry Science, University of Saskatchewan, 51 Campus Drive, Saskatoon SK, S7N 5A8, Canada; and fFood and Bioproduct Sciences, University of Saskatchewan, I 51 Campus Drive, Saskatoon SK, S7N 5A8, Canada ABSTRACT During the winter in Western Canada, broilers are routinely transported in ambient temperatures ranging from 0°C to —40°C, yet there is little research in this area. This study examined the physiology and behavior of broilers undergoing simulated transport at typical Western Canadian winter temperatures. Croups of 15 broilers aged 32 to 33 d were exposed to an air stream regulated to —5, —10, or — 15°C. Birds were placed into a typical transport drawer. Following baseline observations, the drawer was placed into a test chamber where cold air was drawn past the birds for 3 li. Three replications were conducted at each temperature. The birds adjusted their position within the drawer based upon the temperature distribution within the drawer. In comparison to the baseline period, exposing the birds to a cold air stream caused them to avoid the front plane (P = 0.003) which was the coldest area within the drawer. The birds did not adjust their

usage of the middle (P = 0.308) and rear (P = 0.640) planes, because these were the warmer areas within the drawer. The total amount of space the birds occupied within the drawer did not decrease when exposed to the test chamber (P = 0.669). The core body temperature (CBT) did not vary and was within the known normal range during the normal (P = 0,528), pre-chamber (P = 0.060), and post-chamber (P = 0.285) periods. The CBT of the birds significantly decreased during the inchamber period (P < 0.001) and then increased during the lairage period (P < 0.001). The shrink loss (P = 0.981) and amount of time to resume feed consumption (P = 0.357) were not affected by exposing the birds to temperatures of —5°C and colder. Exposing birds to temperatures of —5°C and colder had a negative effect on the CBT of the birds. However, the birds demonstrated behaviors which mitigated the negative effect that cold exposure could have on their CBT.

Key vi^ords: thermorégulation, shrinkage, space usage, welfare . •

• • •' •

2011 Poultry Science 90:2415 2424 doi:10.3382/ps.2011-01427

INTRODUCTION Thermal stress has been identified as a major problem for broilers during transport (Mitchell et al., 1992). Temperatures inside poultry transport vehicles have been intensively studied and related to physiological signs of poor welfare (Freeman et a l , 1984; Hunter et al., 1999; Nijdam et al., 2005), deaths during transit (Nijdam et a l , 2004; Vecerek et al., 2006) or lairage (Nijdam et al., 2004), and changes in meat quality (Dadgar et al., 2010, 2011). With the exception of the work by Dadgar et al. (2010), most other studies have been done in Europe, where extremely cold ambient

©2011 Poultry Science Association Inc. Received February 15, 2011, Accepted June 11, 2011, 'Corresponding author: megan,strawford®usask,ca

temperatures are of less concern. The welfare of tliose birds was jeopardized by inadequate ventilation inside the trailers leading to hyperthermia. In Canada and the northern United States, during the winter months, poultry transport occurs at temperatvu'es as low as or below — 40°C (Environment Canada, 2000) in passively ventilated and unheated trailers. In some of the first work examining broiler transport in these colder conditions, Knezacek et al. (2010) showed that a range of microclimatic conditions develops inside a 16-m semi-trailer during transport. For example, temperatures within the middle of the trailer ranged from 8.9°C to 28.1°C, when the ambient temperature was - 2 7 . r C . Another study conducted by Hui et al. (2003) showed that during transport at an ambient temperature of —20.7°C, conditions inside a 16-m semi-trailer could range from — 14°C to greater than 26°C. Therefore, while in transit, some birds may suffer heat stress, whereas other birds on the same trailer may experience

2415

2416

STRAWFORD ET AL.

cold stress, depending on where they are located within the vehicle. Very little is known about how cold exposure affects broiler welfare during transport. According to Hunter et al. (1999), broilers may be transported safely at —4°C, provided they are kept dry and the trailer is adequately ventilated, whereas wet birds may show signs of hypothermia in ambient temperatures as high as -f8°C. Dadgar et al. (2010) examined the meat quality of broilers from commercial loads exposed to ambient temperatures ranging from 11°C to —27°C. When the exposure temperature was below 0°C, there were negative effects on meat quality such as higher ultimate pH, a* value, and water binding capacity, and decreased L*, which lead to a higher incidence of the dark, firm, dry quality defect. Further work by Dadgar et al. (2011) found that the effect of temperature on meat quality during simulated cold weather transport is age dependent, with meat quality being negatively affected at temperatures below — 8°C and — 14°C for 5- and 6-wk-old broilers, respectively. However, in both studies by Dadgar and others, birds were restricted in their movements and unable to make physical contact with each other. In commercial situations, broilers are able to withstand cold temperatures, to an extent, by manipulating the temperature within the drawer through their behavior. According to Delezie et al. (2007), transporting broilers at lower loading densities allowed the birds to regulate their body temperature behaviorally because of the increased space within the drawer. This increased space within the drawers would allow the birds to move around, huddle, or space themselves out depending on ambient temperature. However, too much space can be detrimental because there is an increased risk for injury (Delezie et al, 2007). The objectives of this study were to examine the thermoregulatory responses of birds in drawers under cold conditions typical of those they might experience during transport in winter months in Western Canada.

MATERIALS AND METHODS

Birds Over 2 d, a total of 66 male and 69 female Ross 308 broilers, aged 32 to 33 d, were observed. The birds were exposed to 3 temperature treatments: —5°C, —10°C, or — 15°C; there were 3 replicates per temperature treatment. There were 15 birds per replicate and the sex ratio was either 7 males and 8 females or 8 males and 7 females in a drawer. The University Committee of Animal Care and Supply of the University of Saskatchewan reviewed and approved the protocols for this study to ensure adherence to the Canadian Council on Animal Care guidelines (CCAC, 1993). One to two days before entering the chamber, the birds were sorted into 9 groups of 15. Each group was lioused in a 1.68-111 by 1.98-m pen that had straw bedding, one hanging feeder (44 cm in diameter) and 6 nip-

ple drinkers. Following sorting, the birds were each fitted with 2 metal wing bands and painted with colored livestock markers to facilitate individual identification, and were administered an internal temperature logging device (DS1922L iButton, Maxim Integrated Products, Sunnyvale, CA).

Data Collection Seven hours before entering the test chamber, the feed was removed from the pen. Each replicate was divided into 4 periods, the pre-chamber, in-chamber, lairage, and post-chamber periods. The pre-chamber period began 2 h before entering the test chamber. The birds were weighed, and then loaded into a single commercial transport drawer (Ariglia Autoflow, Wortliain Ling, Norfolk, UK) with a wire mesh cover (Figure 1). The drawer provided a total of 0.8625 m'^ of space, which resulted in a loading density of 31.3 kg/m^, which is well below the recoiiiiiieiided density of 63 kg/ m^ put forth by the Canadian Recommended Codes of Practice (CARC. 2003). Once the birds were loaded into the drawer, they no longer had access to water. The drawer was moved to the pre-chamber observation area and the birds were allowed to acclimate to the drawer for 1 h before data collection began. After the 1-h acclimation period, the behavior of the birds in the drawer was video recorded for 1 h. Upon the completion of the pre-chamber observations, the birds were loaded into the test chamber, which had been pre-cooled to the required temperature. The birds remained in the test chamber for 3 h for the in-chamber period. The test chamber (Figure 2) was a sealed, insulated box, measuring 124.5 cm long, 78.5 cm wide, and 64 cm high, which can house 2 Aiiglia Autoflow drawers. However, in the current experiiiieiit, birds were only housed in the top drawer and the bottom row was left empty. The test chamber was equipped with a fan that drew in cold air from outside the building and pulled air through the chamber at a flow rate of 0.36 in"^/s. In the event that the outdoor temperature was much colder than the desired set temperature, there was the option to mix the cold outdoor air with air from within the room. The outdoor and indoor air passed through a microprocessor-controlled preheating system that warmed the air to the desired temperature (within ±1°C of the set point) before it reached the birds. After the air passed over the birds, it was exhausted outside the building. There were 4 LED lights located in each corner of the chamber to provide 2 lx of lighting to facilitate video recording the birds. After being removed from the test chamber, the birds were moved into the post-chamber observation area for the lairage period. To simulate what typically occurs following transport, the birds were left in the drawer for 2 h. After the lairage period, the birds were weighed and released into a pen with access to feed and water and

SIMULATED COLD WEATHER TRANSPORT OF BROILERS

I

2417

Direction of Air Flow Front Plane

75 cm

14

II 11

15

12

ii 5

b 8

•

2

Middle Plane Rear Plane

115 cm Figure 1. An overhead view of the drawer showing the dimensions and the 15 cells and 3 planes within the drawer that were used for the space usage observations. The small circles indicate the locations of the miniature data loggers within the drawer. The crate was 28 cm tall.

their behavior was video recorded for 1 h for the postchamber period. Upon completion of the behavior observations, the birds were killed by cervical dislocation to recover the internal temperature loggers.

Exposure Temperature Each transport drawer was fitted with 16 miniature data loggers (DS1923 iButton, Maxim Integrated Products) positioned around the periphery of the drawer and hung from the wire mesh above the birds (see Fig-

ure 1 for the position of the data loggers within the drawer). The data loggers recorded the temperature throughout the drawer at intervals of 1 min for the duration of the experiment. These measurements were stored within the devices and downloaded into Excel using OneWireViewer (Maxim Integrated Products) after the experiment was completed. The temperature levels recorded on the sensors were used to calculate the temperatm-e values iu 15 different locations within the drawer using 3-D mapping software (Tecplot, Tecplot Inc., Bellevue, WA). The values generated by the

Top View of Heater

Insulated Extension for Cam era

Chici
Drawer

Figure 2. Schematic diagram of the test chamber system, illustrating the air intake and exhaust, heater, fan, camera, and the location of the drawer within the system.

2418

STRAWFORD ET AL.

mapping software were used to calculate the average exposure temperature by plane for each data collection period within each set point temperature. In addition to the data loggers, there was a thermocouple (Type-T, Omega Engineering Inc., Stamford, CT) that sensed the temperature of the air before it contacted the birds at the same location as the sensor that controlled the microprocessor-controlled preheating system (25 cm in front of the drawer of birds). For the average incoming air temperature calculation, the first 30 min of temperatures were omitted, because the temperature can be quite variable during this time while the system stabilizes. The average incoming air temperature was calculated for each replicate and a mean temperature was calculated for each exposure temperature. Space Usage. To determine the space used by the birds during the pre-chamber and in-chamber periods, the positions of the birds were recorded using color camcorders. The locations of individual birds within the drawer were recorded every 10 min. To facilitate data collection, the drawer was divided into 15 cells, which were based on the location of the temperature sensors (Figure 1). The locations of birds were recorded by noting the cell number which best described the bird location. Each cell within the drawer was mutually exclusive. If a bird occupied 2 or more cells when the observation was made, the cell in which the bird occupied the most space was the recorded location. If the bird was not visible, it was recorded as being under other birds, as they tended to burrow beneath other birds in the drawer. For the data analysis, the drawer was divided into 3 planes. Each plane was composed of a row of cells running parallel to each other, and perpendicnlar to the direction of airflow. For example, the front plane was composed of cells 1, 4, 7, 10, and 13 (Figure 1). For every 10-min period, the fraction of birds present in the front, middle, and rear planes and the proportion of birds that were burrowed under others were calculated as Percentage of birds present = 100 x (number of birds in the respective area/15 birds), and the fraction of available space occupied by birds was calculated using Proportion of space usage = 100 x (number of cells occupied by birds/15 cells). BW. The BW of the birds were recorded 2 h before entering the chamber (pre-chainber BW), and again at the completion of the lairage behavior observations (post-chamber BW^) to allow for shrinkage to be calculated. The shrink (in kilograms) was calculated by subtracting the post-chamber BW from the pre-chamber

BW. The shrinkage percentage of the birds was calculated using the following equation: Shrinkage (%) = 100 x [(pre-chamber BW — post-chamber BW) -f pre-chamber BW]. Core Body Temperature. The core body temperature (CBT) was recorded by the internal temperature logging device. This sensor was lubricated, inserted into the mouth, and massaged down the alimentary tract into the proventriculus. The sensor remained in the pruventriculus for the duration of the experiment. Every bird within the drawer was outfitted with a logger which was programmed to record the bird's internal temperature at 1-niin intervals. Three hours before entering the test chamber, the core body temperature of the birds was recorded for 30 niin and was used to calculate the baseline CBT. During this time, the birds were still in their home pen and had not been subjected to handling or other interference. For the pre-chamber, in-chamber, lairage and post-chamber periods, the initial and final CBT was calculated for each period using the readings from the first 10 niin and last 10 niin of each respective period. Feeding Behavior. During the post-chamber observation, the time (expressed in seconds) taken by each bird to interact with the feeder following release from the drawer was recorded. Three birds did not approach the feeder during the 1-h observation period (1 bird from each exposure temperature). Those birds were excluded from the data analysis because we were unable to determine when they actually resumed eating.

Statisticai Anaiysis The experimental design was a completely randomized design. The experimental unit was the drawer of 15 birds. For each replicate (3 rephcates per exposure temperature), the means were calculated for the prechamber BW, post-chamber BW, shrinkage (in kilograms and %), initial and final CBT (for each period of time) and latency to eat, and these were analyzed using the Mixed procedure in SAS (SAS Institute Inc., Cary, NC). Temperature was in the main plot. For the BW and average CBT data, gender was in the sub-plot. Average CBT had a second sub-plot, wliich was time. Before conducting the analysis, the data were tested for normality, and only the latency to eat data were skewed and underwent log-transformation. The least squared means and standard error are presented in the tables and graphs. Differences between exposure temperature, sex, and any interactions were separated by the PDIFF procedure of SAS. To determine the change in CBT over time during the in-chamber period, a regression analysis was conducted using the GLM procedure in SAS. Bcîcause of technical difficulties with the recordings obtained from

SIMULATED COLD WEATHER TRANSPORT OF BROILERS the video cameras, only one in-chamber space usage recording for the — 15°C exposure temperature and 2 recordings for the —5°C and — 10°C exposure temperatures were analyzed. The lack of replication resulted in the space usage data undergoing a chi-squared analysis using the PROC FREQ in SAS.

RESULTS AND DISCUSSION For each plane within the drawer, the average temperatures during the pre-chamber, chamber, and lairage periods are shown in Table 1. The average temperature within the pen during the post-chamber period and the temperature of the air before it reached the birds in the chamber are also shown in Table 1. Although the heating system in the test chamber was able to control the temperature of air entering the chamber, the temperatures recorded by the data loggers were, on average, 4°C, 9°C, and 6°C warmer than the set point for the front, middle, and rear planes, respectively. It is evident that the increased temperatures were the result of heat produced by the birds. The distribution of the birds within the drawer while they were in the chamber was related to the temperature variation within the drawer (Figures 3a-3d). During the pre-chamber period, there was a relatively uniform distribution of the birds and temperatures throughout the drawer. During the last 10 min of the in-chamber period, there was a noticeable change in space use within the drawer. The birds decreased their use of the front plane (Figure 3a; P — 0.003), but did not significantly alter their occupancy rates in the middle (Figure 3b; P = 0.309) or the rear (Fignre 3c; P ^ 0.540) planes. During the in-chamber period, the front plane was, on average, 5°C colder than the middle plane and the rear plane was only, on average, 2.5°C colder than

2419

the middle plane. Thus, the shift in locations of the birds was in response to the temperature profile within the drawer. The adjustment of bird location within the drawer may have also contributed to the wide variation in temperatures among the planes because of varying bird density throughout the drawer. The increase in the portion of birds that burrowed beneath others (Figure 3d) within the drawer at the end of the chamber exposure period was not statistically significant (P = 0.338), nor was the 0.10-m^ decline in the total amount of space used (Figure 4) during the in-chamber period statistically significant {P = 0.669). When birds are cold, regardless of species, they will attempt to reduce their heat transfer to the environment. They reduce their surface area by hiding the more vulnerable parts of their body (the head and feet), ruffling their feathers to increase the insulative capabilities, and huddling if in a gi'oup (Dawson and Whittow, 2000). In the present stndy, the broilers performed additional adaptive responses. They moved away from the cold incoming air stream in the front plane and congregated in the middle and rear planes. The reduced total space usage, even thougli it was not statistically significant, suggests that the birds were huddling to reduce the amount of heat lost to the environment. The burrowing behavior suggests that the broilers were attempting to further reduce their heat loss by sheltering themselves from the incoming cold air stream. The pre-chamber and post-chamber BW and shrink loss are summarized in Table 2. There was not a difference in the BW of the birds at the beginning of the experiment {P = 0.312), and exposure temperature did not affect the post-chamber BW (P = 0.357) or shrink when measured in kilograms {P = 0.745) or percentage {P = 0.981). In this experiment, the average shrink rate was 5%, which is comparable to previously pnblished

Table 1. Mean temperature conditions presented to birds during the pre-chamber, in-chamber, lairage, and post-chamber periods (least squares means with SD in parentheses beside each mean and SE at end of each row) Exposure temperature -10°C Pre-cbamber temperature' (°C) Front plane Middle plane Rear plane In-chamber temperature^ (°C) Incoming air^ Fi-ont plane Middle plane Rear plane Lairage temperature' (°C) Fi'ont plane Middle plane Rear plane Post-chamber temperature"* (°C)

23.02 (0.47) 24.69 (1.13) 23.24 (0.86)

21.03 (1.32) 23..33 (1.66) 22.15 (1.04)

-4.17 -1.45 3.68 0.56

(0.41) (1.91) (5.15) (2.28)

-9.31 -7.10 -2.60 -4.52

(0.07) (1.72) (4.81) (2.24)

20.88 22.63 21.04 21.47

(1.14) (1.88) (1.11) 0.67)

20.64 21.98 20.54 20.57

(1.31) (1.58) (1.31) (1.46)

-1.5T

S1-:

22.55 (0.62) 24.53 (0.98) 23.21 (0.66)

0.34 0.43 0.27

-13.38 (1.54) -10.17(1.95) -4.48 (5.36) -6.99 (3.79)

0.89 0.05 1.38 0.98

19.45 20.99 19.54 19.73

(1.41) (2.18) (1.44) (1.42)

0.36 0.56 0.37 0.42

'There were 48 total observations per temperature: 15 were made in tlie front and reax plane.s, and 18 were recorded in the middle plane. ^There were 3 observations for each exposure temperature. •^Tliere were not any planes during the post-chamber period; these means represent the average temperature recorded in the pen during this period. There were a total of 12 observations, 4 in each of the 3 replications.

2420

STRAWFORD ET AL, DPre-Chamber p Pre-Chamber

• Last 10 min In Chamber

Last 10 min In Chamber

ÍT 0.8 E ^

0.7

3

0.6

g. 0.5

1 0.4 -5°C

-lO'C

-15°C

•-

0.3 -5C

60

Figure 4. The total amount of space the birds occu])ied during the pre-chamber and at the end of in-chamber periods (P = O.GöÜ), There were 2 observations for the -t'5°C and -10°C exposure temperatuies and 1 observation for the -15°C expasure temperature.

SO

20 10

c

10°C

-15*C

-10'C

-15*C

.10°C

-is-c

50

40 30 20 S

-lOX -IS^C Exposure Temperature

10

Q.

I in

-5°C

Exposure Temperature

Figure 3. The percentage of birds occupying the (a) front (P = 0,009), (b) middle ( P = 0,308), and (c) rear {P= 0,640) planes or (d) burrowed below other birds within drawer (P — 0,338) when exposed to —5, —10, or — 15°C during the pre-chamber and in-chamber periods. There were 2 observations for the -5°C and —10°C exposure temperatures and 1 observation for the -15°C exposure temperature.

studies with a similar duration of feed withdrawal (Moran and Bilgih, 1995; Nijdam et al., 2005; Aviagen, 2009).

Table 3 summarizes the CBT of the birds throughout the experiment. The CBT did not differ among the treatments and remained relatively constant during the baseline period (P = 0.528), pre-chamber (P = 0.060), and post-chamber (P = 0.285) periods. During these periods, the mean CBT of the broilers was within the normal CBT range, which is 41.5 ± 1.0°C (Dawsoii and Whittow, 2000). The CBT did differ during the in-chamber (P < 0.001) and lairage (P < 0.001) periods (Table 3). During the in-chamber period, the CBT of the birds at the start of the period was higher than at the end for all 3 exposure temperatures. In addition, upon completion of the in-chamber period, birds exposed to -10°C had a lower CBT than birds exposed to — 5°C. During the lairage period, the CBT of the birds at the start of the period was lower than when the period ended. The mean CBT recorded during the last 10 min of lairage returned to the normal CBT range. Similar to what waa seen during the in-chamber period, at the start of the lairage period, the CBT of the birds exposed to — 10°C was lower than those exposed to —5°C. During all of the observation periods, the maximum CBT recorded never exceeded the upper level of the normal CBT range (42.5°C) outlined by Dawson and Whittow (2000). Research by Khalil et al. (2004) monitored the body temperature of laying hens and found that the body temperature dropped as low as 39.4°C when the lights were out and the bird was resting. According to Richards (1977), when the rectal temperatures of broilers fell below 39.3°C, the birds were considered to be hypothermie. In the current experiment, the CBT of 11% (-5°C), 55% (-10°C), and 44% (15°C) of the birds fell below 39.3°C and could have been considered hypothermie. These data demonstrate that exposing broilers to —5°C did not put the welfare of the majority of the birds within the drawer at risk. However, at exposure temperatures of —10° and —15°, the CBT of half the birds was considered hypothermie. Sturkie (1946) found that when the CBT of laying hens

SIMULATED COLD WEATHER TRANSPORT OF BROILERS

2421

Table 2. The effect of exposing broilers to - 5 , -10, or -15°C on BW and shrink loss Exposure temperature 1 Item Pre-chamber BW (^kg) Post-chamber BW^ (kg) Shrinkage (kg) Shrinkage (%)

-IO°C

-15°C

SE

P-valiic

1.72 1.64 0.080 4.8

1.85 1.76 0.088 4.8

0.06 0.07 0.010 0.7

0.312 0.357 0.744 (1,981

1.73 1.64 0.090 ,'•).()

^There were 3 observations made for each variable. total feed withdrawal time was 12 h.

reached 28°C, the hens could not survive beyond 42 h. None of the birds in the current experiment had a body temperature that fell into that range, but that does not mean that their welfare was not compromised. Further research is necessary to determine when a decrease in the CBT begins to have a negative effect on the welfare of broilers. During the lairage period, the birds were kept at approximately 20°C. Past research found that following exposure to temperatures of 0°C and colder, when broilers are housed at room temperature during a 2-h lairage period, the majority of birds are capable of increasing their CBT, but their final CBT was still below the CBT measured at the start of the experiment (Dadgar et al., 2011). In a commercial situation, when the lairage sheds reach capacity, the birds are occasionally left outdoors on the truck, exposed further to the weather elements. Had these birds experienced something similar, the authors suspect that the recovery seen in the current experiment and noted by Dadgar et al. (2011) would not have been possible.

The CBT of the birds changed throughout the exposure to the test chamber when exposed to —5°C (Figure 5a), -10°C (Figure 5b), and -15°C (Figure 5c). During the initial exposure to the chamber, the decline in the CBT was quite rapid. Near the end of the chamber exposure period, the decline in the CBT began to slow down. This suggests that the birds tend to be most affected during the beginning of the journey. The slower rate of decrease in CBT during the latter part of the chamber exposure may also be attributed to the birds' behavioral and physiological responses (hiding head and feet, huddling, ptiloerection, vasoconstriction, shivering, and increased metabolic rate). Despite the birds' early response to the stimuli, there can be a delay between the reactions to the stimuli and when the birds experience benefits from those responses. In previous work conducted by this research group, the effect that exposure temperatures of -|-20°C, — 15°C, — 12°C, and —8°C had on individual birds was investigated (Leer et al., 2008). To do this, each bird was housed in its own separate partitioned area within the

Table 3. The core body temperatnre of the broilers during the baseline, pre-chamber, in-chamber, lairiige, and post-chamber periods (the range appears in parentheses below the mean) Exposure temperature^ Core body temperature (°C) Baseline Pre-chamber Initial Final In-chamber Initial Final Lairage Initial Final Post-chamber Initial Final

-5°C

-lOT

-1.5T

SE

41.04 (40.44-41.03)

-11.18 (40.61-41.18)

41.15 (40.29-41.21)

0.09

0.528

41.16 (40.32-41.14) 41.10 (40.16-41.14)

41.20 (40.18-41.21) 41.03 (40.18-41.17)

41.34 (40.61-41.34) 41.27 (40.2a-41.60)

0.10

0.060

41.22=^ (40.16-41.46) 40.14*' (37.62-40.68)

41.33" (40.43-41.60) 39.49'"' (36.83-40.61)

0.26

<0.001

(40.27-41.23) 39.08<= (35.19-39.62)

40.19'' (37.98-40.68) 41.01" (39.60-41.17)

39.16<^ (34.44-39.61) 40.82*'' (38.68-41.11)

39.48'''^ (36.19-40.56) 41.18" (40.12-41.50)

0.24

<0.001

41.30 (39.65-41.41) 41.12 (.38.66-41.18)

41.28 (39.33-41.40) 40.95 (.38.82-41.22)

0.14

0.285

(40.62-41.67) 41.41 (40.07-41.64)

41.23»

élM

lacking a common superscript (within each observation period) differ {P < 0.05). were 3 observations made for each time period within each observation period.

F-value

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STRAWFORD ET AL.

(-15°C exposure), 38.8°C (-12°C exposure), 39.4°C (-8°C exposure), and 40.6°C (+20°C exposure). When 41 .s the change in CBT at similar exposure temperatures is compared between studies, the CBT does not drop as drastically in the current study. AUowiug the birds to move resulted in the mitigated decline in the CBT. By moving away from the cold incoming air, huddling in the warmer areas within the drawer, and burrowing beneath other birds within the drawer, the birds appeared to liave minimized the amount of heat they lost to the environment. The stocking rate of 15 birds per drawer used in this 80 100 120 140 160 180 study is not representative of commercial levels (18 to 24 birds per drawer is typical). It is possible that under commercial stocking densities bird CBT could undergo a more drastic response at any particular expiosure temperature. At higher densities, there may not be enough space within the drawer to allow the birds to adjust y = 5E-05x^ - 0.0226X + 41.43 their location within the drawer. Therefore, a bird may R= = 0.9935 be trapped in an area with cold incoming air and the reduced space to move may deny them the opportunity to move to a warmer location within the group of birds in the drawer, unlike the situation in the current experiment. There was no difference in the amount of time it took the birds to resume eating after the lairage pe20 40 60 80 100 120 140 160 180 riod (Table 4; P = 0.357). The authors hypothesized that the amount of time that birds took to resume feed intake would indicate how exposure to simulated cold weather transport affected the birds' physiological state and well-being. If exposure to the chamber was energetically demanding on the birds, they may adjust their priorities from feed consumption to performing behaviors associated with trying to conserve heat to maintain their body temperature. Overall, regardless of exposure temperature, the birds resiuned feed intake quite quickly. However, they had 2 h to warm up following chamber exposnre and their CBT had returned to baseline levels. Returuing the CBT to baseline levels would have required additional energy expenditure, therefore 0 20 40 60 80 100 120 140 160 180 Time (min) further increasing the motivation to eat. In future experiments, it may be advisable to ascertain bird time Figure 5. The change in core body temperature (CBT) over time during the iu-chamber period when exposed to (a) — 5°C, (b) — lO'C, or to eating immediately following exposure to the test (c) — 15°C. There were 3 observations for each exposure temperature. chamber, to determine if the birds have a stronger motivation to perform thermoregulatory behaviors or eat. Sex affected the BW and the CBT of the birds (Table 5). Male birds weighed more than females at start (P drawer, which deprived the birds of the opportunity to < 0.001) and end {P < 0.001) of the experiment. Males manipulate their thermal environment and to interact lost more weight than females {P = 0.027), but this did with other birds in the drawer. Upon completion of the not result in a difference in the percent shrink loss (P 3-h exposure periods, the CBT of the birds was 37.7°C Table 4. The amount of time it took the birds to approach the feeder after exposure to the test chamlK •r Ex[)osur<' temperature Item Latency to eat' (s)

• ( '

275

-lO'C 6S

^There were 3 observations made for each exposure temperature.

- i : ,'V :l

SE

P-value

IIS

o,:i.57

2423

SIMULATED COLD WEATHER TRANSPORT OF BROILERS Table 5. The effect that sex had on BW, shrink, and core body temperature during the normal, prechamber, in-chamber, lairage, and post-chamber periods Male

Variiil)!«'

BW and shrink Pre-chamber BW (kg) Post-chamber BW^ (kg) Shrink (kg) Shrink (%) Core body temperature ("C) Normal Pre-chamber In-chamber Lairage Post-chanibiT

Female

1.89» 1.80" 0.093« 5.0 41.09 41.13 40.24'' 40.08'^ 41.16''

1.64'' 1.56'' 0.079'' 4.8 41.16 41.24 40.59"* 40.53" 41.38"

SE

P-vnluc

0.04 0.04 0.006 0.4

<0.001 <0.001 0.027 0.406

0.06 0.07 0.13 0.13 0.07

0.360 0.212 0.015 0.006 0.010

differ (P < 0.05). total feed withdrawal time was 12 h.

= 0.406). The GBT did not differ between sexes during the normal (P = 0.360) and pre-chamber (P = 0.212) periods. The GBT of the females was higher during the in-chamber (P = 0.008), lairage (P = 0.006), and postchamber (P = 0.010) periods. One might have expected the males to be better able to maintain their GBT during cold exposure, because they were significantly larger than the females. Typically, as the size of the birds increases, so does their abihty to thermoregulate because they have more energy reserves to maintain their GBT (Blem, 2000). However, Dawson and Whittow (2000) stated that the ability of a bird to cope with ambient temperature is dependent on the degree of feather coverage. Ross 308 males have noticeably reduced feather coverage when compared with that of the females because of sex-linked late feathering; this may have resulted in the males being more susceptible to the cold temperatures despite being larger. During transportation, birds undergo a multitude of Stressors such as catching, handling, and loading into the drawer, feed and water withdrawal, the motion during transport (acceleration, deceleration, and vibration), noise, social disruption, and thermal extremes. The stress during loading was minimized in this study compared with standard on-farm practices. The birds were handled one at a time and were not carried over long distances by the legs. Rather, they were resting on their breast and were gently placed into the drawer one at a time. Social disruption was minimized, the amount of mixing the birds underwent was minimal, and the birds were allowed to adjust to their new social group for at least 10 h before they were loaded into the drawers. Also, the stress caused by movement, noise, and vibration was minimal compared with typical conditions on a truck. Normally, birds at the bottom of a stack are subject to soiling with wet feces from birds in the drawer(s) above. Past research has shown that birds are better able to withstand the effects of low temperatures during transport if they remain dry (Hunter et al. 1999). Therefore, had the birds been wet during this experiment, they may have had a more negative response to exposure to the cold temperatures. It is unlikely birds will undergo ideal conditions in the com-

mercial setting as seen in this experiment, and these additional Stressors could potentially exacerbate the negative responses of the birds. The results from this study suggest that exposing birds to temperatures at or below — 5°G affects the behavior and physiology of broilers, but the GBT response was not as drastic as reported by Dadgar et al. (2011). The birds in this study were able to cope with and recover from the conditions to which they were exposed. Other typical transport Stressors were eliminated or minimized to isolate the effect of low temperatures. The density used in this experiment is not one that would typically be employed in the commercial setting, and further research is necessary to understand the behavioral and physiological responses of broilers exposed to cold conditions at those higher densities. il

ACKNOWLEDGMENTS

!

The authors acknowledge the help of the staff of the University of Saskatchewan's Poultry Research Gentre for their assistance during the planning and execution of this study. Funding for this project was provideci by NSERG, AAFG, Alberta Ghicken Producers, Alberta Farm Animal Gare, Ganadian Poultry Research Gouncil. Poultry Industry Gouncil, Saskatchewan Ghicken Industry Development Fund, Lilydale Inc., and Ghicken Farmers of Saskatchewan.

REFERENCES Aviagen. 2009. Ross Broiler Management Manual. Aviagen Ltd., Newbridge, UK. Blem, C. R. 2000. Energy balance. Pages 327-341 in Sturkie's Avian Physiology. G. C. Whittow, ed. Academic Press, Toronto, ON, Canada. CARC. 2003. Recommended Code of Practice for the Care and Handling of Farm Animals: Chickens. Tiu'keys and Breeders from Hatchery to Processing Plant. Can. Agric.-Food Res. Council, Ottawa, ON, Canada. CCAC. 1993. Cuide to the Care and Use of Experimental Animals. Vol. 1. E. D. Olfert, B. M. Cross, and A. A. McWilliam, ed. CCAC, Ottawa, ON, Canada. Dadgar, S., E. S. Lee, T. L. V. Leer, N. Burlinguette. H. L. Classen. T. G. Crowe, and P. J. Shand. 2010. Effect of microclimate

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temperature during transportation of broiler chickens on quality of the pecio7ïïfe major muscle. Poult. Sei. 89:1033-1041. Dadgar, S., E. S. Lee, T. L. V. Leer, T. G. Crowe, H. L. Classen, and P. J. Shand. 2011. Effect of acute cold exposure, age, sex and lairage on broiler breast meat quality. Poult. Sei. 90:444 457. Dawson. W. R.. and G. C. Whittow. 2000. Regulation of body temperature. Pages 343 390 in Sturkie's Avian Physiology. G. C. Whittow, ed. Academic Press. Toronto. ON, Canada. Delezie. E., Q. Swennen, J. Buyse. and E. Decuypere. 2007. The effect of feed withdrawal and crating density in transit on metabolism and meat quality of broilers at slaughter weight. Poult. Sei. 86:1414-1423. Environment Canada. 2000. Cftnadian Climate Normals or Average 1971 2000. Accessed Apr. 2011. http://www.chmate.weatheroffice.ge.ca/climate_normals/index_e.html. Freeman, B. M., P. J. Kettlewell, A. C. C. Manning, and P. S. Berry. 1984. Stress of traiLsportation for broilers. Vet. Rec. 114:286287. Hui, K. P. C , T. G. Crowe, H. L. Classen, E. M. Barber, T. D. Knezacek, and M. R. L. Bantle. 2003. Poultry transportation under Canadian prairie conditions. Presented at the annual meeting of the Canadian Society of Animal Science, Saskatoon, SK, Canada. Hunter. R. R.. M. A. Mitchell, and A. .]. Carlisle. 1999. Wetting of broilers dm'ing cold weather transport: A major source of physiological .stress? Br. Poult. Sei. 40:S48-S49. Khalit, A. M., K. Matsui, and K. Takeda. 2004. Diurnal and oviposition-related changes in heart rate, body temperature and locomotor activity of laying hens. Anim. Sei. J. 75:169-174. Knezacek, T. D., Á. A. Olkowski, P. J. Kettlewell, M. A. Mitchell, and H. L. Classen. 2010. Temperature gradients in trailers

and changes in broiler rectal and core body temperature during winter transportation in Saskatchewan. Can. J. Anim. Sei. 90:321-330. Leer, T. L. V., N. A. Burhnguette, S. Dadgar, E. S. Lee, T. D. Knezacek, T. G. Crowe, P. J. Shand. and H. L. Cla.s.sen. 2008. Sinmlation of cold temperature transportation of broiler chickens. Poult. Sei. 87(Suppl. 1):61. (Abstr.) Mitchell, M. A., P. J. Kettlewell, and M. H. Maxwell. 1992. Indicators of pliysiological stress in broiler chickens during road tran.sportation. Anim. Welf. 1:91-103. Moran, E. T., and S. F. Bilgili. 1995. Influence of broiler livehaul on carcass quality and further-processing yields. J. Appl. Poult. Res. 4:13-22. Nijdam, E., E. Delezie, E. Lambooij. M. .1. Nabuurs, E. Decuypere, and J. A. Stegeman. 2005. Feed withdrawal of broilers before transport changes plasma hormone and metabolite concentrations. Poult. Sei. 84:1146-1152. Nijdam. E., P. Arens. E. Lambooij, E. Decuypere, and J. A. Stegeman. 2004. Factors influencing bruises and mortality of broilers during catching, transport and lairage. Poult. Sei. 83:1610 1615. Richards, S. A. 1977. The influence of loss of plumage on temperature regulation in laying hens. .]. Agrie. Sei. 89:393 398. Sturkie, P. D. 1946. Tolerance of adult chickens to hypothermia. Am .1. Physiol. 147:531-536. Vecerek, V., S. Grbalova. E. Voslarova. B. Janackova, and M. Malena. 2006. Effects of travel distance and the season of the year on death rates of broilers transported to poultry processing plants. Poult. Sei. 85:1881-1884.

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