©2009 Poultry Science Association, Inc.
Effect of incubation temperatures and chick transportation conditions on bone development and leg health E. O. Oviedo-Rondón,*1 M. J. Wineland,* J. Small,* H. Cutchin,* A. McElroy,† A. Barri,† and S. Martin‡ *Department of Poultry Science, North Carolina State University, Raleigh 27695-7608; †Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306; and ‡Cobb-Vantress Inc., Springdale, AR 72761-1030 Primary Audience: Hatchery Managers, Broiler Managers, Veterinarians, Researchers SUMMARY Bone development can be adversely affected by stressful environmental conditions early in life. One experiment was conducted to evaluate the effects of low temperature during early incubation, high temperature during late incubation, and transportation conditions from hatchery to the farm on the long bone development and leg health of broilers. Bone development was evaluated at hatch before transportation. Gait scores and leg health disorders were recorded at 41 d of age. Although incubation conditions did not affect chick BW, hot temperatures during late incubation reduced the relative weight of femurs and shanks. At 41 d, males had more leg problems than females. Late high temperature and transportation stress increased the incidence of crooked toes and the percentage of chickens with a gait score of 2. Transportation stress, including elevated temperature, caused a greater incidence of twisted legs. We concluded that low early incubation temperature, high late incubation temperature, and transportation stress can increase the incidence of leg problems in commercial broilers. Key words: leg health, incubation, chick transportation, bone, broiler chicken 2009 J. Appl. Poult. Res. 18:671–678 doi:10.3382/japr.2008-00135
DESCRIPTION OF PROBLEM Bone development can be affected by stressful environmental conditions early in life [1, 2], especially by less than optimal incubation temperatures and oxygen concentrations [3, 4]. Prehatch stress impairs embryonic development and increases fluctuating asymmetry in chickens [3–5]. Fluctuating asymmetry between limbs and other bilateral phenotypic traits reflects the
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Corresponding author:
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ability of individuals to cope with stressful conditions during ontogeny [6]. The relative asymmetry (RA) of long bones has been correlated with tibial dyschondroplasia, poorer gait scores, and increased tonic immobility in chickens [6]. Several factors that control endochondral ossification of long bones can be affected by incubation temperatures, mainly during the plateau stage of embryonic development. Incubation temperature has an important impact on the
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672 hormonal axis that controls bone development, which includes thyroid hormones, insulin-like growth factor 1, and growth hormone [7–9]. Increased incubator temperatures resulting in elevated embryonic temperatures and low oxygen concentrations can affect bone development by altering bone weight and length, changing chondrocyte cell density in the tibia proximal epiphyses, and altering the expression of important proteins for ossification, such as collagen type X and transforming growth factor β [3, 4]. Hatcher temperatures greater than 37°C and oxygen concentrations less than 21% should be avoided to ensure optimal bone development at hatching. Very little is known about the effects of suboptimal conditions hours after hatch in either the chick holding room or during transportation. In early reports, newly hatched chicks were unresponsive to stress [10]. However, current commercial experiences [11–13] indicate that it is important to avoid high temperatures and maintain proper ventilation during transportation of chicks to reduce first-week mortality and obtain better performance. The optimal conditions for transportation of chicks remains unknown. In addition, very little is known about the effects of transportation on broiler health. The objective of this study was to evaluate the effects of embryonic incubation temperatures and posthatch transportation stress on long bone development at hatch and on the leg health of broilers at 41 d of age.
MATERIALS AND METHODS This study was conducted under the Animal Care and Use guidelines established by the North Carolina State University and Virginia Polytechnic Institute and State University Animal Care and Use Committees. A total of 5,200 broiler hatching eggs from a Cobb 500 breeder flock [14] of 51 wk of age were incubated in Natureform machines [15] to achieve a low (L) eggshell temperature of 36.7°C or a standard (S) eggshell temperature of 37.5°C during the first week of incubation. During the third week of incubation, the eggs were incubated to achieve the S eggshell temperature (37°C) or a high (H) eggshell temperature of 39°C. All eggs were incubated at S (37°C) from d 8 to 17, with com-
binations of the other temperatures occurring on d 1 to 7 and d 18 to 21 to generate 4 incubation treatments: LS, LH, SS, and SH. At hatch, a subsample of 15 chickens per treatment was removed to obtain BW and residual yolk weights. Postmortem, both legs were dissected and the femur, tibia, and shank weights, lengths, and thicknesses were recorded. The RA of each leg section was calculated [6]. After hatch, chicks were equally separated into 2 transportation groups: a control group (T1) and a stressed group (T2). The transportation stress consisted of a reduced ventilation rate, which resulted in an elevated temperature (40°C) compared with the control temperature (34°C), and most likely reduced oxygen concentrations (not measured). Chickens were exposed to the transportation conditions for 4 h. After transportation, 46 chicks (23 male and 23 female) per treatment were assigned to 4 × 8 ft floor pens (0.7 ft2/chick) with clean pine shavings, nipple drinkers, and hanging feeders. The commercial lighting program and ventilation were monitored continuously from the day of hatch to d 42. Each treatment was replicated with 7 pens for the 42-d trial. All birds were provided with feed and water ad libitum throughout the grow-out period. At 41 d of age, the legs of each broiler were inspected for crooked toes, valgus and varus deformities of the intertarsal joint, hock burns, footpad dermatitis, and gait scores. Walking ability was divided into 6 categories of gait scores, ranging from completely normal (score 0) to immobile (score 5) according to the Kestin method of gait scoring [16]. Percentages of incidence per pen were calculated. All percentage data were transformed to arcsine square root n + 1. Bone data at hatch were analyzed as a 2 × 2 factorial design with early incubation (L vs. S) and late incubation (S vs. H) as main effects. The incidence of leg problems and the gait scores at 41 d of age were analyzed as a 2 × 2 × 2 factorial design that included transportation conditions (T1 vs. T2) as an additional main effect (Table 1). All data were analyzed using the GLM procedures of SAS [17]. Treatment means were separated using the LSM procedure of SAS [17], with a level of significance of P ≤ 0.05 unless otherwise stated.
Low (L) eggshell temperature of 36.7°C from d 1 to 7 of incubation Low (L) eggshell temperature of 36.7°C from d 1 to 7 of incubation Low (L) eggshell temperature of 36.7°C from d 1 to 7 of incubation Low (L) eggshell temperature of 36.7°C from d 1 to 7 of incubation Standard (S) eggshell temperature of 37.5°C from d 1 to 7 of incubation Standard (S) eggshell temperature of 37.5°C from d 1 to 7 of incubation Standard (S) eggshell temperature of 37.5°C from d 1 to 7 of incubation Standard (S) eggshell temperature of 37.5°C from d 1 to 7 of incubation
LST1
Standard (S) eggshell temperature of 37°C from d 18 to 21 of incubation Standard (S) eggshell temperature of 37°C from d 18 to 21 of incubation High (H) eggshell temperature of 39°C from d 18 to 21 of incubation High (H) eggshell temperature of 39°C from d 18 to 21 of incubation Standard (S) eggshell temperature of 37°C from d 18 to 21 of incubation Standard (S) eggshell temperature of 37°C from d 18 to 21 of incubation High (H) eggshell temperature of 39°C from d 18 to 21 of incubation High (H) eggshell temperature of 39°C from d 18 to 21 of incubation
Late incubation
All eggs were incubated at a standard temperature (37°C) from d 8 to 17.
1
SHT2
SHT1
SST2
SST1
LHT2
LHT1
LST2
Early incubation
Treatment
Control (T1) transport, with a ventilation temperature of 34°C Stressed (T2) transport, with a reduced ventilation rate resulting in an elevated temperature of 40°C Control (T1) transport, with a ventilation temperature of 34°C Stressed (T2) transport, with a reduced ventilation rate resulting in an elevated temperature of 40°C Control (T1) transport, with a ventilation temperature of 34°C Stressed (T2) transport, with a reduced ventilation rate resulting in an elevated temperature of 40°C Control (T1) transport, with a ventilation temperature of 34°C Stressed (T2) transport, with a reduced ventilation rate resulting in an elevated temperature of 40°C
Chick transport
Table 1. Treatments assigned to fertile eggs during early and late incubation1 and to hatching chicks during transportation from the hatchery to the farm
Oviedo-Rondón et al.: INCUBATION TEMPERATURES 673
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Table 2. Effect of early and late incubation temperatures on BW (g), residual yolk (%), relative weights1 (%), and relative asymmetry2 (RA) of bones at day of hatch BW of 0-d sample (g)
Item Treatment3 LH LS Mean SH SS Mean Late incubation treatment mean4 High temperature Standard temperature SEM
Femur
Shank
%
RA
%
RA
%
49.8 48.4 49.1 48.9 48.0 48.5
9.01 8.23 8.62a 7.92 7.56 7.74b
0.94 0.99 0.97 0.98 0.99 0.98
6.12 6.56 6.34 6.72 5.85 6.28
1.66b 1.78a 1.72 1.77ab 1.76ab 1.76
8.22 9.26 8.74a 5.94 4.59 5.26b
5.87 6.09 5.98 5.81 5.94 5.87
4.30 3.32 3.81a 2.12 1.67 1.89b
49.3 48.2 0.6
8.46 7.89 0.25
0.96b 0.99a 0.16
6.42 6.21 0.75
1.71 1.77 0.31
7.08 6.93 0.93
5.84b 6.01a 0.75
3.21 2.50 0.38
0.079 0.066 0.002
0.010 0.909 0.368
0.659 0.013 0.505
