Effect of environmental conditions during transport on chick weight loss and mortality M. Yerpes,1 P. Llonch, and X. Manteca Animal Nutrition and Welfare Service, Department of Animal and Food Science, Facultat de Veterinaria, Universitat Autonoma de Barcelona, Bellaterra E-08193, Barcelona, Spain ABSTRACT The present study had 2 objectives: the (May to November), number of stops, type of stop first was to analyze the possible impact of transport on during journey (farm stops and driver stops), time to weight loss and mortality during transport, and first- start the journey, as well as other intrinsic factors of week mortality. The second was to monitor the envi- chicks (gender, breed [Ross and Cobb], breeder flock ronmental condition (i.e., temperature, humidity, and age [wk] and egg storage day). Because the database so on) variability during transport with an effect on included random factors, longitudinal data, and day-old chicks. Probe equipment was installed in a repeated measures, a multivariate model was used to truck of a poultry company from Spain, including a analyze the data. The results showed that chick weight total of 66 journeys made in commercial conditions loss was positively associated with journey duration between May and November 2017. Animal-based and RH. No effect of environmental variables was found measures collected included BW (before and after on mortality during transport. However, chick mor- transport), mortality during transport, mortality dur- tality during the first week of life was related with the ing the first week of life, which were contrasted against percentage of day-old chicks loaded per journey and a series of environmental variables including air tem- chick gender. In conclusion, owing to the environ- perature, RH, and carbon dioxide (CO2) atmospheric mental heterogeneity during transport and the effect of concentration for every journey, number of day-old the environment on chick weight during transport and chicks (%) per journey, transport duration (h), zones mortality at first week of life, there is an urgent need to inside the loading area (zone 1, near to the cabin; zone refine the air-conditioning and ventilation systems of 2, in the central point; and zone 3, close to the back day-old chick transport toward a greater environ- doors), height (1, top; 2, medium; and 3, bottom), mo mental homogeneity. Key words: transport, broiler, day-old chick, performance, animal welfare 2021 Poultry Science 100:129–137 https://doi.org/10.1016/j.psj.2020.10.003 INTRODUCTION transportation when they are 1 d of age. Despite efforts to improve the transportation process, they are still The transport of live animals is considered a great transported for extended periods under suboptimal envi- source of stress (Mitchell, 2009), owing to the exposition ronment conditions (Bergoug et al., 2013; Jacobs et al., to a variety of potential stressors involved, such as 2016). Although in recent years there have been eve- ambient temperature, acceleration, vibration, noise, increasing progress in using sensing devices toward space restrictions, and air pollutants (Mitchell and improved poultry welfare (Neethirajan, 2017; Murillo Kettlewell, 1993; Mitchell, 2009). In accordance with et al., 2020; Nazareno et al., 2020), there are still many the 2019 statistics of the Spanish Ministry of Agricul- knowledge gaps, such as the adequate level of carbon di- ture, Fisheries and Food and the European Commission, oxide (CO2) during transport, or the interaction be- 628 million of chicks produced in Spain and 6,700 million tween environmental variables (temperature, relative of chicks produced in Europe most of them undergoes the humidity, or CO2). In addition to these knowledge gaps, chicks are neonatal animals with an immature physiology Ó 2020 The Authors. Published by Elsevier Inc. on behalf of Poultry (Shinder et al., 2007; Yassin et al., 2009), and they are Science Association Inc. This is an open access article under the CC BY- exposed to many challenges during transportation. NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Received March 21, 2020. From hatching to arriving at the farm, they can be Accepted October 6, 2020. deprived from feed or water for more than 72 h, and 1 Corresponding author: martayerpes@gmail.com this would not be in line with the Council Regulation 129 130 YERPES ET AL. (EC) No 1/2005. Hatching can range few hours within was equipped with thermal isolation of expanded poly- the same flock (up to 48 h), which may result in some urethane and had an internal and external structure chicks being deprived of feed and water for longer than coated with aluminum. The trailer had 2 back doors others within the same flock (Jacobs et al., 2016). Feed with nonhermetic enclosure. The inner door was a sail- and water deprivation have been proven to negatively cloth sliding curtain, and the outer door was a lifting affect performance (Decuypere et al., 2001). Despite platform. The sliding curtain was kept closed during chicks being believed to sustain themselves without journeys and only open when chicks were unloaded. feed or water for 72 h after hatching by using reserves The trailer load was distributed in 5 rows of trolleys in their yolk sac (EFSA, 2011), modern genetic lines along the truck with a 10-cm space between them with high growth and metabolic rates may deplete their (Figure 1). The load capacity was 750 boxes with 100 energy reserves more quickly (EFSA, 2011). In addition, chicks per box approximately, which makes an average the transportation process could exacerbate the deple- number of 150,000 chicks per journey. Inside the tion of reserves and dehydration, through excessive ther- container, 2 probes were part of the truck’s equipment moregulatory demands and stress, thus possibly and were located on the roof to record the environmental affecting chicks’ BW and mortality rates (Bergoug temperature. The temperature of the trailer was auto- et al., 2013; EFSA, 2012; Jacobs et al., 2016, 2017). In matically controlled at 27 C 6 2 using fans for ventila- fact, chick mortality during first week of life can reflect tion. The air inlets were distributed along the sides of the stress of transportation process (Bayliss and the container roof, and the air exits (ventilation) were Hinton, 1990; Yassin et al., 2009). located in the central area of the roof in the form of a Given the impact of transport, the general aim of this grid with filter. study was to assess the conditions during transport that may affect broiler chick’s welfare and performance in Day-Old Chick Boxes Spain. To respond to this objective, 2 phases were car- ried out: 1) to analyze the possible impact of transport Chicks were transported in fully perforated plastic on weight loss and mortality during transport; and boxes (60 ! 40 ! 15 cm) following regular procedures first-week mortality and 2) to monitor the environ- in commercial transports (Council Regulation, EC 1/ mental conditions (i.e., temperature, humidity, and so 2005). Every day-old chick trolly carried 28 boxes on) variability during transport with an effect on day- distributed in 2 columns of 14 boxes (Figure 2). old chicks. Data Collection MATERIALS AND METHODS Phase I In the first 10 journeys the loss of weight and This study was conducted in cooperation with a the mortality during transport and first-week mortality broiler hatchery from Spain. Sixty-six journeys were were monitored. For every journey, 27 boxes of day-old monitored from May to November 2017. The study chicks were monitored using 27 Ta and RH probes. was divided into 2 phases, phase I was carried out during The distribution of the Ta and RH probes was different 10 journeys that were used to investigate the association in every journey because the day-old chicks’ boxes were between the environmental conditions inside the randomly selected. The probes were installed in the day- container (air temperature, RH, and CO2 levels) and old chick trolleys considering 3 height points (Figure 2), chick weight loss during transport, mortality during and the height of the probes remained constant in all the transport, and first-week mortality. In 56 journeys for journeys. phase II, the environmental variables found to affect The CO2 probe was located at the central point of the chick’s growth and/or survival during phase I were container at the bottom height (Figure 1). The 27 boxes monitored. Data on the environmental conditions inside were randomly selected in the hatchery before every the truck were monitored using a digital probe equip- journey, and after loading the chicks, they were weighed ment (model TRUCK RHT; Sinergia G6) always with (scale model NVL20000 Navigator XL; OHAUS) and the same truck and driver. The equipment consisted of the number of chicks recorded. On arrival at the farm, 1 data logger, 27 probes for temperature (Ta) ( C) and the boxes were weighed once again, and the number of RH (%) and 1 CO2 probe (ppm). Sensors recorded pa- dead chicks was recorded. In addition to temperature, rameters in 45-s intervals and sent the information to RH, and CO2, the environmental variables considered the data logger via digital radio, so the data logger was were time to start the journey, journey duration (h), used as a receiver for the probe readings. Then, the number and type of stops during journey (farm stops data logger sends the information to a Web portal and driver stops), number of chicks (%) per journey, thanks to a remote connection via 3G/4G, allowing ac- and mo. Animal-based response variables recorded dur- cess to data in real-time. ing the study were weight loss and number of dead chicks during transport and dead chicks during the first week of Truck life. The company provided data on the following breeding The trailer used to transport chicks was and husbandry variables for each flock: flock ID, breed 13 ! 3 ! 2.5 m long, wide and high, respectively. It (Ross or Cobb), egg storage (d), breeder flock age DAY-OLD CHICK TRANSPORT 131 Figure 1. Air view of the truck, highlighting the center and lateral rows. The colored squares represent the boxes with temperature and RH probes. The red cross indicates the position of the CO2 probe. (wk), chick gender, and farm (house reference). The age allowed the monitorization of potential differences be- of the breeders was categorized as per the Cobb guide tween zones and positions (comparing the central row (2008): 33 wk (young breeders), 34–50 wk (adult with the 2 sides of the container) in the container breeders), and 51 wk (old breeders). (Figure 1). This setup allowed controling 3 of 5 trolleys Phase II In Phase II, the following 56 journeys were that were distributed horizontally at 3 different height used to monitor the environmental profile inside the points (top, medium, and bottom), following the same container. Probes of Ta and RH were distributed in 3 distribution as in the first 10 journeys (Figure 2). zones among the container: zone 1, near to the cabin; zone 2, in the central point; and zone 3, close to the back doors (Figure 3). This probes’ distribution Statistical Analysis Statistical analysis was carried out using the statisti- cal software SAS v9.4 (SAS Institute Inc., Cary, NC), for Windows. The significance level was set at P , 0.05. The experimental unit was each journey. Data on Ta, RH, and CO2 were normally distributed, based on the graphical evaluation of the residuals (histo- gram and Q–Q plot). To respond the 2 objectives of the study, the statistical analysis was carried out in 2 parts, following the steps described in the following. In phase I, a bivariate linear regression analysis was carried out between fixed effects and response variables, and a correlation study between continuous variables was assessed using Pearson correlation coefficient. Because the database included random factors, longitu- dinal data, and repeated measures, a multivariate model was used. The fixed effects considered in phase I analysis were Ta ( C), RH (%), CO2 (ppm), percentage of day-old chicks loaded per journey (%), transport duration (h), height (1, top; 2, medium; and 3, bottom), mo (May to November), number of stops, type of stop during journey (farm stops and driver stops), time to start the journey, chick gender, breed (Ross and Cobb), breeder flock age (wk), and egg storage (d). The response variables were weight loss (%) and mortality (%) during transport and at first week of life. In phase II, a bivariate linear regression analysis was carried out between fixed effects and response variables, and a correlation study between air temperature and RH was assessed using Pearson correlation coefficient. A multivariate model was used, and the fixed effects considered were the environmental variables including number of day-old chicks (%) per journey, transport Figure 2. Lateral view of day-old chick trolley inside the truck. Dis- tribution of the temperature and RH probes inside the day-old chick trol- duration (h), zones inside the loading area (zone 1, ley. The colored squares were the boxes with temperature and RH near to the cabin; zone 2, in the central point; and probes. zone 3, close to the back doors), position inside load 132 YERPES ET AL. Figure 3. Lateral view of the truck. Distribution of the temperature and RH probes inside the container. The colored squares were the boxes with temperature and RH probes. area (0, central row; 1, lateral rows), height (1, top; 2, analysis of this variable could not be carried out owing middle; and 3, bottom), mo (May to October), number to the low incidence of mortality during transport. and type of stops during journey, and start time of the Chicks mean mortality during the first week of life was journey. The response variables were temperature ( C) 2.02% (SD 5 1.21). The correlation between chick mor- and RH (%). In addition, the following interactions tality at first week of life and the continuous variables were considered in the multivariate model of phase II: was weak and not significant for any of them height*position, height*zone, position*zone. (Table 1). The percentage of day-old chicks loaded per Finally, for the 2 phases, each journey was considered journey (%) and chick gender had effect on chick mortal- a random factor, and the variables were manually ity during the first week of life (P 5 0.0082 and removed one by one from the model following a step- P 5 0.0087, respectively). The higher the percentage of wise manner using a significance level of 0.05 as refer- chicks loaded in the truck, the higher the mortality ence. The P-values of multiple comparisons were (estimate 5 0.305 6 0.114) was observed. As for chick adjusted with the Tukey correction. The results will be gender, male chicks (estimate 5 0.607 6 0.052) had presented using SD and the abbreviation 6 for SE. the highest mortality rate, followed by mixed chicks (estimate 5 0.541 6 0.099), and females (estimate 5 0.498 6 0.049) had the lowest mortality RESULTS Phase I Table 1. Results for Pearson correlation coefficients and P-values Weight Loss During Transport During transport, the for the dependent variables (chick weight loss during transport, mean weight loss of the chicks was 2.96% (SD 5 1.22). mortality at first week of life, and RH) and continuous variables considered in the study. The correlation between chick weight loss and the continuous variables was weak for most variables; it Pearson Correlation Coefficients seemed that the CO2 level have a negative correlation Prob . jrj under H0: Rho 5 0 with chick weight loss but it was not significant. Another Weight loss variable that had a positive correlation with chick Effect Corr. P-value weight loss was journey duration; in this case, the corre- Temperature 20.09999 0.1375 lation was significant (Table 1). The variables showing HR 0.12800 0.0569 an effect over weight loss during transport were journey CO2 20.8773 0.2443 Time to start the journey 20.1479 0.0228 duration (P 5 0.0006) and RH (P 5 0.0188) (Table 2). Journey duration 0.46479 ,0.0001 The estimated effect of journey duration and RH level Percentage of chicks loaded per journey 20.02285 0.7487 over weight loss was - 0.2407 (60.06889) and - 0.07745 Breeder flock age (wk) 20.00474 0.9421 Egg storage (d) 20.07276 0.2928 (60.03269), respectively. The environmental Ta, CO2, Mortality at first week of life the percentage of day-old chicks loaded per journey, Temperature 0.00646 0.9132 height inside the trolley, mo, number of stops, type of HR 20.09725 0.1001 stop during journey, time to start the journey, and the CO2 0.14695 0.0342 Time to start the journey 0.05456 0.1258 breeding variables did not show a significant effect on Journey duration 0.03309 0.5753 weight loss during transport (Table 2). Percentage of chicks loaded per journey 0.13148 0.0251 Chick Mortality During Transport and at First Week Breeder flock age (wk) 0.3254 0.0568 Egg storage (d) 0.2156 0.0687 of Life Mean chick mortality during transport was RH 0.055% (SD 5 0.043), which is equivalent to 15 dead Temperature 20.5532 0.0001 chicks of 27,031 chicks monitored. The statistical DAY-OLD CHICK TRANSPORT 133 Table 2. Results from the multivariate model used to analyzed the effect of the independent variables under study over the chick weight loss during transport (10 journeys, May to November, 2017, Spain). Type III tests of fixed effects Effect Num DF Den DF F value Pr . F Month 5 111 0.37 0.8674 Height inside the trolley 2 111 0.71 0.4955 Time to start the journey 1 111 0.37 0.5417 Journey duration 1 111 7.28 0.0006 Number of stops during journey 2 111 2.06 0.1327 Percentage of DOC per journey 1 111 0.65 0.4226 Chick gender 1 111 0.52 0.4711 Temperature 1 111 0.22 0.6390 RH 1 111 2.95 0.0188 CO2 1 111 2.89 0.0921 rate. The environment variables, journey duration, significant differences were found between zone 2 (in height inside the trolley, mo, number of stops, type of the central point) vs. 3 (close to the back doors). The dif- stop during journey, and time to start the journey and ferences in RH between zones inside the container varied the other breeding variables did not have a significant ef- more than 2%, being zone 3 (close to the back doors) the fect on first-week mortality (Table 3). most heterogeneous. The interaction height*position was significant (P , 0.0001), which means that the RH at certain height inside the trolley was different Phase II depending on the position (row) inside the container, Microclimate Profile The container was at 29.38 C reaching differences of more than 5% within the same (SD 5 0.97) temperature and 47.97% (SD 5 4.43) hu- height inside the trolley among positions inside the midity. Table 4 shows the descriptive analysis of the container (Figure 4). These patterns could be related average Ta and RH in the container, as per zone, position to the association between air Ta and RH (Table 4), inside the container, and height inside the trolley. which means that when air temperature was high, RH RH The results showed that the RH was different was low and vice versa. The association between Ta and among heights inside the trolley (upper, middle, and bot- RH makes that variations in Ta among locations inside tom), positions (central and lateral rows), and zones the container impacted the RH. (zone 1, near to the cabin; zone 2, in the central point; No differences in RH levels were detected as per and zone 3, close to the back doors) inside the container journey duration (h), type of truck stop during journey, (all P , 0.05). Related to height inside the trolley, upper and percentage of day-old chicks per journey (%). How- height had a higher RH (estimate 5 49.22% 6 0.628) ever, differences were detected between mo for the RH than middle (estimate 5 46.80% 6 0.627) and bottom levels (P 5 0.0265), being August and September the (estimate 5 47.95% 6 0.628) height. In the case of posi- mo with the highest RH levels (mean 5 49.40 tions inside the container, the central row showed a SD 5 3.47 and 50.51 SD 5 4.95; respectively) compared lower RH (estimate 5 47.41% 6 0.615)than lateral with May, June, and July (mean 5 46.16 SD 5 3.49, rows (estimate 5 48.57% 6 0.615). Regarding zones in- 46.82 SD 5 4.55, and 45.92 SD 5 4.08; respectively). side the container, zone 1(near to the cabin) showed a Air temperature The results showed that the tempera- lower RH (estimate 5 46.50% 6 0.638) than zones 2 ture was different among heights inside the trolley (up- (in the central point) (estimate 5 48.56% 6 0.625; per, middle, and bottom), positions (central and lateral P , 0.001) and 3 (close to the back doors) rows), and zones (zone 1, near to the cabin; zone 2, in (estimate 5 48.90% 6 0.624; P , 0.001), whereas no the central point; and zone 3, close to the back doors) Table 3. Results from the multivariate model used to analyzed the effect of the independent variables under study over the chick mortality during the first week of life (10 journeys, May to November, 2017, Spain). Type III tests of fixed effects Effect Num DF Den DF F value Pr . F Month 4 123 0.59 0.6719 Chick gender 2 123 1.87 0.1578 Number of stops during journey 2 123 1.35 0.2626 Time to start the journey 1 123 0.71 0.4016 Percentage of DOC per journey 1 123 0.68 0.4098 Journey duration 1 123 0.02 0.8913 Temperature 1 123 1.40 0.2395 RH 1 123 0.78 0.3787 CO2 1 123 0.39 0.5330 Type of stops during journey 1 123 1.68 0.1974 134 YERPES ET AL. Table 4. Descriptive analysis of the average air temperature and (estimate 5 29.97 C 6 0.145) than upper RH inside the container of the truck by zones (1, near cabin; 2, (estimate 5 28.66 C 6 0.146) and bottom center container load; and 3, back doors), position (central row, (estimate 5 29.72 C 6 0.146) heights, the difference be- lateral rows), and height (1, upper; 2, middle; and 3- bottom). tween mean temperatures varied on average 1.06 C. Variables Mean SD Min. Max. P-value With regard to positions inside the container, there  Air temperature ( C) were differences between central row and lateral rows, Height the central row was the one that showed a higher Ta Upper 28.80 0.971 25.88 31.04 ,0.0001 (estimate 5 29.84 C 6 0.133), whereas the lateral Middle 29.92 1.122 27.55 32.67 Bottom 29.41 1.019 26.50 31.38 rows showed lower air Ta  Zones (estimate 5 29.06 C 6 0.133). In the case of zones inside Near cabin 30.19 1.186 25.43 33.11 ,0.0001 the container, there were different temperatures between Center 28.80 1.434 25.62 31.00 Back doors 29.01 1.458 25.37 31.97 zone 1 (near to the cabin) vs. 2 (in the central point) and Positions 1 (near to the cabin) vs. 3 (close to the back doors) (all Lateral rows 29.07 0.948 26.66 31.24 ,0.0001 P , 0.001). Zone 1 (near to the cabin) showed the high- Central row 29.96 1.320 26.53 32.71 RH (%) est mean temperature (estimate 5 30.35 C 6 0.154) Height compared with zones 2 (in the central point) Upper 48.82 4.643 40.91 59.08 ,0.0001 (estimate 5 28.95 C 6 0.143) and 3 (close to the back Middle 46.81 4.589 38.95 58.12 Bottom 48.29 4.307 40.50 57.63 doors) (estimate 5 29.05 C 6 0.143); the mean air tem- Zones perature differences detected between zones inside the Near cabin 47.24 4.621 38.27 60.63 0.0028 container varied more than 1 C, being zone 3 (close to Center 48.75 5.596 39.73 61.37 Back doors 49.06 5.645 38.61 63.85 the back doors) the most heterogeneous. The interac- Positions tions height*position and position*zone were statisti- Lateral rows 48.38 4.307 40.10 57.47 ,0.0001 cally significant (P , 0.0001 and P 5 0.0170; Central row 47.20 4.900 38.86 60.31 respectively). Figure 5 shows the temperatures esti- mate values as per the significant interactions. The inside the container (all P , 0.0001). Related to height interaction position*zone (Figure 4A) showed that air inside the trolley, there were differences between the up- temperature in a certain position (row) inside the per vs. middle height and upper and bottom height (all container was different depending on the zone inside the P , 0.001); middle height had the higher Ta container, this difference could vary by more than 1 C. Figure 4. Estimate RH values and SE during day-old chicks transport. Interaction between height and position (back-door view). DAY-OLD CHICK TRANSPORT 135 maintained over time, lasting up to day 21 after birth. Jacobs et al. (2016) suggested that any weight reduction after transport is probably because of delayed feed intake, as in their study, the negative effect of transport on the chicks’ weight did not persist until slaughter age. The same result was confirmed by other authors (Batal and Parsons, 2002; Bergoug et al., 2013). In fact, Bai~ ao et al. (1998) suggested that the negative effect observed on chick weight and subsequent impact at early ages may be more related to a longer interval between hatching and housing than to transport itself. Likely because of this reason, in their study, the weight and feed efficiency at the end of the growth period did not change. In the case of RH, this environmental variable impacts the capacity for heat exchange (sensible and latent) of broiler chicks (Lin et al., 2005; Schimidt et al., 2009). The loss of evaporative heat increases with temperature but decreases with humidity. When the RH is higher than 60%, heat dissipation is reduced, which harms the reduction of body temperature (Kettlewell et al., 2000; Nazareno et al., 2016). In line also with our results, Figure 5. Estimates of the mean temperature values and SE during when chicks are exposed to a heat challenge with high day-old chicks transport. (A) Interaction between zone and position (air view). (B) Interaction between height and position (back-door view). RH, the efficacy of the thermoregulation system may be compromised, and chicks will need to use other path- In addition, the differences detected in this interaction ways to lose heat, accelerating metabolism. When this for upper and bottom height inside the trolley depending occurs, part of the energy that should be used to gain on position inside the container were significant weight will be dedicated to thermoregulatory process, (P 5 0.0005 and P , 0.0001; respectively). However, the reducing performance (Abreu et al., 2017). Lin et al. differences between positions inside the container at (2005) suggested that broiler chicks are sensitive to middle height inside the trolley were not significant changes in humidity, even when temperatures are ther- (P 5 0.1348). The height*position interaction moneutral, and observed the influence of RH on cloacal (Figure 4B) showed that the air temperature gradient by and peripheral temperatures. They showed that when heights inside the trolley were more pronounced in the temperature and RH are high, the evaporative and non- central position (row) than in the lateral positions (rows) evaporative heat loss decrease and chicks activate alter- inside the container. Moreover, the differences detected native physiological pathways to redistribute heat in this interaction for zones 1 (near to the cabin), 2 (in within the body to adapt to the environment. This, the central point), and 3 (close to the back doors) inside may explain why the higher environmental humidity in the container depending on position inside the container high temperatures results in greater weight loss in were significant (P 5 0.0263, P , 0.0001 and chicks. P 5 0.0005; respectively). Chick Mortality During Transport and at First Wk of Finally, no differences in air temperature were Life The impact of mortality for the performance and the detected depending on journey duration (h), type of welfare of any animal production system are unquestion- stop, percentage of day-old chicks load per journey able. As per our results, no effect of transportation was (%), and mo. found on mortality during transport, which confirms the findings of other studies (Bergoug et al., 2013; Jacobs et al., 2016). Ritz et al. (2005) emphasized the difficulty DISCUSSION in associating mortality during transport with thermal Phase I stress or any other transport variable or even with any effect during all the growth period. However, we found Weight Loss During Transport Weight of chicks is a that transportation was indeed associated with mortality crucial variable when considering performance of chicks, during the first week of life and more precisely with the as it will influence their capacity to grow. However, percentage of day-old chicks transported per journey. weight loss might also indicate welfare problems as it Similarly, Chou et al. (2004) found an association between can be a consequence of stress during transport mortality during the first week of life and transportation (Mitchell 2009; Jacobs et al., 2016). As per our results, distance. However, this association is still controversial as weight loss during transport is associated with journey other authors did not find any relationship between the duration and RH, and these results coincide partially same variables (Bergoug et al., 2013; Jacobs et al., 2016). with those from Jacobs et al. (2016) and Bergoug et al. This difference could be because of the fact that Chou (2013). The latter explained that a negative correlation et al. (2004) focused on journey duration without between weight loss and journey duration was considering other fixed effects related to transport such as 136 YERPES ET AL. environment conditions during transport or the percent- may have offered a more realistic overview of what is age of chicks transported per journey. happening inside the truck than the integrated probes. Regarding the percentage of day-old chicks loaded per The variability detected in RH and temperature inside journey, according to Nazareno et al. (2016), there are 2 the container was in line with other studies. However, environments inside the truck (the container environ- there is a lot of variation between authors as regards ment and the environment inside transport boxes), the thermal and RH range inside the container. with the highest averages for air Ta and RH inside the Meijerhof (1997) and Weeks and Nicol (2000) sug- chick boxes. Considering the existence of these 2 envi- gested a temperature range between 24 C and 26 C, ronments that can thwart environmental stability, in without alluding to RH, whereas Marques (1994) rec- addition to the quantity of chicks load per journey, the ommended temperatures between 22 and 31 C and a greater percentage of chicks per journey the higher the RH of 50%. Finally, Nazareno et al. (2016) found that divergence between those environments, likely the temperature and RH means were 28.5 C (23.3 C– increasing temperature inside the transport boxes. These 32.2 C) and 40.5% (31.4%–54.1%), respectively. This could lead to thermal heat stress for the chicks, making it was the study that had the most similar results to our more difficult for them to dissipate heat (Ernst et al., study. 1984; Yalçin et al., 1997). It is well established that There are several possible reasons for this environ- heat stress may facilitate dehydration and increase rate mental variability. First, as mentioned earlier, it could mortality in early life (Bergoug et al., 2013; Piestun be the influence of air circulation added to an inefficient et al., 2017). ventilation system, causing a wide range of temperature In addition to transport variables, we also found that and RH (12 C and 40%) (Nazareno et al., 2015a), with the first-week mortality differs as per chick gender. Our particularly conflictive hot spots. Quinn and Baker results are in accordance with those from Leitner et al. (1997) suggested that the distribution of dead chicks in (1988), who detected significant differences for mortality the truck does not follow a random distribution but re- between males and females during the first 8 wk of life. flects the variation in ventilation and areas with critical They hypothesized that males are more susceptible to environmental conditions. The second reason could be pathogens and therefore have a higher mortality. How- heat metabolic production (Yalçin et al., 2001), as it ever, infectious diseases were not monitored in the pre- could exacerbate the existing thermal gradient between sent study, and therefore, we cannot confirm the zones, positions, and heights inside the container. In hypothesis of Leitner et al. (1988). addition, the combination of the 2 environmental vari- ables (RH and Ta) could compromise transpiration, Phase II exacerbated by the imposed high number of birds in a transport container and in the day-old chick boxes Taking into account that there were transport-related (Mitchell and Kettlewell, 1998). The third reason is the variables affecting the welfare and productivity of existence of 2 environments, one inside the container broilers, it was considered important to study the perfor- and the other inside the chick box, the latter having mance of environmental variables during transport and the highest averages for temperature and RH the most likely reasons to explain environmental varia- (Nazareno et al., 2016). Therefore, to achieve a comfort- tions inside the trailer. able environment for the transport of day-old chicks, the Microclimate Profile The findings obtained in the truck design and the air-conditioning system efficiency microclimate assessment (Table 1) indicate an environ- should facilitate the homogenization of the environment mental heterogeneity inside the container and coincide throughout the trailer, avoiding significant fluctuations with the studies conducted by Knezacek et al. (2010), of humidity and temperature among the containers. Filho et al. (2014), and Nazareno et al. (2015b). Marques In conclusion, under commercial conditions, transpor- (1994) and Quinn and Baker (1997) attributed this tation of day-old chicks increased weight loss during heterogeneity to low air circulation, caused by problems transport, with journey duration and RH having a nega- in the air-conditioning and ventilation system of trailers, tive impact on chicks’ BW. No effect of transportation as well as to the nonstandardisation of load density in was detected on mortality during transport. However, journeys. mortality during first week of life was affected by the per- RH and air temperature As shown in phase I, the RH centage of chicks loaded per journey. Variations in RH had an effect on weight loss during transport. Humid- and air temperature during transport may have a nega- ity affects the animal depending on the environmental tive effect over welfare and productivity of day-old temperature. For this reason, the importance of the as- chicks. To address these, there is an urgent need to refine sociation between Ta and RH is discussed. It is impor- the air-conditioning and ventilation systems of day-old tant to clarify the temperature difference between the chick transport to achieve a greater environmental ho- integrated probes and the trial probes. In the case of mogeneity in trailer. Improving the control of environ- integrated probes, there were only 2 probes installed mental variables during transport may help to increase at the truck’s roof with roughly 25 cm between the environmental homogeneity inside the truck, which probe and day-old chicks’ trolleys, whereas there were this article demonstrates to have beneficial effects for 27 trial probes located next to the chicks’ boxes. The productivity and the welfare of chicks after transport, localization as well as the number of the trial probes in the poultry farm. DAY-OLD CHICK TRANSPORT 137 ACKNOLEWEDGEMENTS Kettlewell, P. J., R. P. Hoxey, and M. A. Mitchell. 2000. Heat pro- duced by broiler chickens in a commercial transport vehicle. J. Marta Yerpes was supported by Secretaria d’Universi- Agric. Engng. Res. 75:315–326. Knezacek, T. D., A. A. Olkowski, P. J. Kettlewell, M. A. Mitchell, and tats i Recerca del Dep. d’Economia i Coneixement de la H. L. Classen. 2010. Temperature gradients in trailers and changes Generalitat de Catalunya (2015DI065), Spain. The au- in broiler rectal and core body temperature during winter trans- thors thank Carlos Gonzalez and Miren Arbe from portation in Saskatchewan. Can. J. Anim. Sci. 90:321–330A. Poultry Vaccination Services & Equipment of Ceva Leitner, G., E. D. Heller, and A. Friedman. 1988. Sex-related differ- ences in immune response and survival rate of broiler chickens. Vet. Corporate for their assistance with the logistics and Immunol. Immunopathol. 21:249–260. contribution to this research. Carlos Gonzalez contrib- Lin, H., H. F. Zhang, H. C. Jiao, T. Zhao, S. J. Sui, X. H. Gu, uted to the design of the study and coordinated the Z. Y. Zhang, J. Buyse, and E. Decuypere. 2005. Thermoregulation responses of broiler chickens to humidity at different ambient research. Miren Arbe contributed to the interpretation temperatures. I. one week of age. Poult. Sci. 84:1166–1172. of the results. Marques, D. 1994. 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