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Determination of embryonic temperature profiles and eggshell water vapor conductance constants in incubating Ross × Ross 708 broiler hatching eggs using temperature transponders1,2
Determination of embryonic temperature profiles and eggshell water vapor conductance constants in incubating Ross × Ross 708 broiler hatching eggs using temperature transponders1,2 R. Pulikanti,* E. D. Peebles,*3 W. Zhai,* and P. D. Gerard† *Department of Poultry Science, Mississippi State University, Mississippi State, 39762; and †Department of Mathematical Sciences, Clemson University, Clemson, SC 29634 ABSTRACT The comprehensive profiles of the internal and external temperatures of embryonated Ross × Ross 708 broiler hatching eggs during incubation were determined using temperature transponders, and eggshell water vapor conductance (GH2O), specific GH2O (gH2O; GH2O adjusted to a 100 g set egg weight basis), and GH2O constants (KH2O) were calculated. On each of 8 replicate tray levels of an incubator, 2 nonembryonated and 4 embryonated eggs were each implanted with a transponder on d 10.5 of incubation for the determination of internal (air cell) temperatures of nonembryonated (Tnem) and embryonated (Temb) eggs, respectively. In addition, 2 water-filled vials, each containing a transponder, were used on each tray level for the determination of the external microenvironment temperatures (Text) of the embryonated and nonembryonated eggs. Between 10.5 and 18 d of incubation, incubator data logger temperatures were determined every 5 min; and incubator dry bulb temperature, Text, Tnem, Temb, and the difference between Temb and Tnem (∆T) were
determined every 12 h. Over the days of incubation, regression coefficients for Temb and ∆T were positive, whereas the regression coefficient for Tnem was negative. There was a significant day of incubation × type of temperature measurement (Text, Tnem, and Temb) interaction for temperature. Between 13 and 18 d of incubation, mean values of Temb readings that were recorded every 12 h were consistently higher than those of Text and Tnem, indicating the importance of air cell transponder implantation for the efficient estimation of broiler embryo temperature. Furthermore, mean values of the percentage of daily incubational egg weight loss, GH2O, gH2O, and KH2O of the embryonated eggs were 0.54 ± 0.019%, 14.4 ± 0.56 mg of H2O/d per Torr, 25.0 ± 0.96 mg of H2O/d per Torr per 100 g, and 5.20 ± 0.205, respectively. The results suggest that transponders may be implanted in the air cells of broiler hatching eggs to detect incubational variations in Temb and to subsequently calculate GH2O, gH2O, and KH2O.
Key words: broiler, conductance, egg, temperature, transponder 2012 Poultry Science 91:55–61 doi:10.3382/ps.2011-01759
INTRODUCTION
stimuli on embryonic life and the monitoring of those parameters for maximal productivity are of importance to the broiler industry (Bamelis et al., 2005). Among various external factors, incubation temperature is considered to be a major factor that influences embryo temperature (French, 1997), heat production (Janke et al., 2002), and development (Decuypere and Bruggeman, 2007). Incubation temperature also has a major influence on the hatchability and posthatch performance of chickens (Wilson, 1991). Lourens et al. (2005) noted specific relationships between broiler embryo temperature and development and subsequent hatchability and posthatch performance. It has been reported that the optimal incubation temperature for chicken eggs is 37 to 38°C (Wilson, 1991; Decuypere and Bruggeman, 2007; De Smit et al., 2008). French (1997) suggested that embryonic temperature is a function of incubator temperature, heat
The embryonic stage currently occupies a greater proportion of the entire life of the commercial broiler than ever before. Therefore, the embryo’s physiological responses to its incubational environment have an increased effect on subsequent posthatch performance and processing yield. A thorough and in-depth understanding of the potential influences of various external ©2012 Poultry Science Association Inc. Received July 26, 2011. Accepted September 28, 2011. 1 This is Journal article number J-11994 from the Mississippi Agricultural and Forestry Experiment Station supported by MIS-322210. 2 Use of trade names in this publication does not imply endorsement by Mississippi Agricultural and Forestry Experiment Station of these products nor similar ones not mentioned. 3 Corresponding author: [email protected]
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exchange between the embryo and its external microenvironment, and the metabolic heat production of the growing avian embryo. French (1997) further suggested that because the avian embryo is largely poikilothermic during early incubation, its temperature is largely influenced by the incubator temperature, and that during the later stages of incubation, as the embryo produces larger amounts of metabolic heat, its temperature rises above the incubator temperature. Previously, Lourens et al. (2005) and Joseph et al. (2006) used eggshell temperature as a means to estimate embryonic temperature. Lourens et al. (2005) also graphically reported variations in broiler eggshell temperatures between 1 and 18 d of incubation. However, Eren Ozcan et al. (2010) and Lourens et al. (2011) suggested limitations associated with the measurement of eggshell temperature for the estimation of embryonic temperature, given that eggshell temperature can be influenced by the thermal conductivity of the eggshell and the velocity of air flow around the egg. In other studies, internal egg content temperatures (Turner, 1990; Janke et al., 2004; Renema et al., 2006) were used as standard expressions of embryonic temperature. Janke et al. (2004) suggested that embryonic heat production and body temperature may be estimated based on internal egg temperature. Although these techniques allowed for the determination of an egg’s internal environmental temperature proximal to the embryo, they were limited in application because of their relative invasiveness to the growing embryo (Turner, 1990; Janke et al., 2004) and because of the potential for increased embryonic mortality (Janke et al., 2004). Pulikanti et al. (2011a,b) suggested that transponders may be safely implanted into the air cells of incubating eggs for the determination of internal egg temperature. Pulikanti et al. (2011b) successfully recorded the internal (air cell; Temb) and external microenvironment (water vial; Text) temperatures of embryonated Ross × Ross 308 broiler hatching eggs between 10.5 and 18.5 d of incubation. These researchers subsequently used the Temb and Text values along with incubator RH and atmospheric pressure values for the calculation of the water vapor pressure gradient across the eggshell (∆PH2O; Torr), eggshell water vapor conductance (GH2O; mg of H2O/d per Torr), and specific GH2O (gH2O; GH2O adjusted to a 100 g set egg weight basis; mg of H2O/d per Torr per 100 g). However, Pulikanti et al. (2011b) did not use implanted nonembryonated eggs as external temperature controls, and they did not determine the GH2O constants (KH2O) of embryonated eggs. Moreover, they did not provide detailed comparative profiles of Temb, Text, and incubator dry bulb (Tinc) and data logger (Tlog) temperatures during the second half of incubation. Therefore, the current experiment was conducted using Ross × Ross 708 broiler hatching eggs to compare the mean values and semicircadian variations of Temb, Text, Tinc, and Tlog and the internal (air cell) temperatures of nonembryonated eggs (Tnem) between 10.5 and 18 d of incubation. Further-
more, calculations of ∆PH2O, GH2O, and gH2O values of embryonated and nonembryonated eggs, and KH2O values of embryonated eggs were performed.
MATERIALS AND METHODS General In total, 720 broiler hatching eggs were collected from a young (30 wk of age) Ross × Ross 708 breeder flock. The eggs were held under standard storage conditions for 3 d before set. Eggs having malformed shells, or that were contaminated, misshapen, cracked, or not within ± 10% of the mean weight of all eggs collected, were discarded from the experiment. On d 0 of incubation, eggs were randomly labeled and weighed to record their set egg weight. At least 60 eggs were set on each of 8 replicate tray levels of a Jamesway model 500 single stage incubator (Jamesway Incubator Company Inc., Cambridge, ON, Canada). The eggs were incubated for 18 d under standard commercial conditions at 37.5°C dry bulb and 28.8°C wet bulb temperatures. On d 10.5 of incubation, the eggs were weighed and candled, and those containing slanted air cells were discarded. Subsequently, on each tray level, 4 embryonated eggs were randomly selected and the air cells of those eggs were implanted with a transponder (implantable programmable temperature transponder; IPTT-300; Bio Medic Data Systems Inc., Seaford, DE) for the determination of Temb. Transponders were implanted in the air cells of 2 nonembryonated eggs and these were positioned within 5 cm from each implanted egg on each tray level for the determination of Tnem. Furthermore, 2 sealed water-filled plastic vials (10-mL capacity), each containing a transponder, were positioned within 5 cm from each implanted embryonated and nonembryonated egg for the determination of Text (Pulikanti et al., 2011b). The materials and procedures used for transponder implantation and temperature data recording in this experiment were similar to those described previously by Pulikanti et al. (2011a,b).
Hatch Monitor On d 18.5 of incubation, each implanted embryonated egg was candled, and the eggs that contained live embryos were placed in individual hatching baskets and subsequently transferred to their corresponding tray levels in a Jamesway model 500 single stage hatcher unit (Jamesway Incubator Company Inc.). The eggs in the hatcher were maintained at approximately 36.1°C dry bulb and 27.6°C wet bulb temperatures and were individually monitored for hatch every 12 h through d 21.5 of incubation.
Embryo Survivability Survivability of the embryos was determined by candling eggs on d 18.5 of incubation and was further con-
BROILER EMBRYO TEMPERATURE PROFILES
firmed based on hatch success through d 21.5 of incubation (Pulikanti et al., 2011b). All of the egg parameters for embryonated eggs described below were determined on implanted eggs that contained live embryos through hatch (d 21.5 of incubation).
Data Collection Between 0 and 18 d of incubation, Tinc, incubator wet bulb temperature readings, and atmospheric pressure values were recorded every 12 h. Moreover, between 0 and 18 d of incubation, Tlog readings were recorded every 5 min using wireless data loggers (La Crosse Technology, La Crescent, MN). Furthermore, between 10.5 and 18 d of incubation, temperature readings were recorded every 12 h from transponders contained within water vials, nonembryonated eggs, and embryonated eggs for the determination of Text, Tnem, and Temb, respectively. Between 10.5 and 18 d of incubation, a total of approximately 16 Tinc (sixteen 12-h periods); 6,912 Tlog (sixteen 12-h periods × 12 h × twelve 5-min readings per h × 3 data loggers); 256 Text and Tnem (16 twelve-h periods × 16 water vials or nonembryonated eggs); and 416 (sixteen 12-h periods × 26 embryonated eggs) Temb readings were recorded. For the determination of Temb, 26 rather than 32 implanted embryonated eggs (4 per each of 8 tray levels) were used, and this was due to the elimination of eggs that contained embryos that failed to hatch by d 21.5 of incubation or because of technical errors in the temperature determination process. Subsequently, differences between embryonated and nonembryonated egg internal (air cell) temperatures (∆T) were calculated every 12 h by subtracting the mean value of Tnem readings (n = 16) from the mean value of Temb readings (n = 16; ∆T = Temb – Tnem).
Eggshell Water Vapor Conductance Average daily incubational weight (moisture) loss (EWL; mg) values of embryonated and nonembryonated eggs between 10.5 and 18 d of incubation were determined for the subsequent calculation of the respective percentage of EWL values. The 10.5 to 18 d mean values of Text and Temb along with the incubator RH and atmospheric pressure values were used for the calculation of ∆PH2O. Subsequently, GH2O [GH2O = EWL (mg)/ΔPH2O (Torr)] and gH2O {gH2O = [GH2O/ set egg weight (g)] × 100} of embryonated and nonembryonated eggs were calculated using the procedures and equations described by Ar et al. (1974) and Ar and Rahn (1978) and modified by Pulikanti et al. (2011b). Based on the hatch monitor data between 18.5 and 21.5 d of incubation, incubation length (in days) of individual embryonated eggs were determined. Furthermore, the GH2O constants (KH2O) of the embryonated eggs were calculated by using the formula {KH2O = [GH2O × incubation length (d)/set egg weight (g)]} as described by Ar et al. (1974) and Ar and Rahn (1978).
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Statistical Analysis For the analyses of Text, Tnem, Temb, and ∆T, each tray level was considered as a replicate unit. All data were analyzed using version 9.1 SAS Institute (2003). The REG procedure was used for regression analyses of Tinc, Tlog, Text, Tnem, Temb, and ∆T over the days of incubation, and the MEANS procedure was used to determine CV values for these parameters. A repeated measures analysis was employed using the MIXED model that accounted for the variability among the trays to examine the influence of the days of incubation, type of temperature measurement (Text, Tnem, and Temb), and the interaction of the days of incubation and the type of temperature measurement on the temperature. The MIXED procedure was also used for a one-way ANOVA in set egg weight, percentage of EWL, ∆PH2O, GH2O, and gH2O between nonembryonated and embryonated eggs. Least squares means were compared in the event of significant global effects (Steel and Torrie, 1980). Furthermore, global effects, regression trends, and differences among least squares means were considered significant at P ≤ 0.05.
RESULTS AND DISCUSSION An approximate 90.6% (29 out of 32 total) embryo survivability was observed in the implanted embryonated eggs. The mean values of the percentage of EWL in nonembryonated and embryonated implanted eggs for the 10.5 to 18 d incubational period were 0.54 ± 0.03 and 0.54 ± 0.02%, respectively (Table 1). The mean percentage of EWL of implanted embryonated Ross × Ross 708 eggs in this experiment was in close comparison to that (0.55 ± 0.015%) reported by Pulikanti et al. (2011b) in embryonated Ross × Ross 308 broiler hatching eggs. The mean values of Tinc, Tlog, Text, Tnem, Temb, and ∆T for the 10.5 to 18 d incubational period in the current study were 37.5 ± 0.02, 37.4 ± 0.02, 37.6 ± 0.04, 37.6 ± 0.03, 38.1 ± 0.05, and 0.14 ± 0.032°C, respectively (Table 2). The 10.5 to 18 d mean value of Temb were numerically higher (approximately 0.6°C) than those for all other temperature measurements, including Tinc, Tlog, Text, and Tnem (Table 2), suggesting that the transponders inserted in the air cells of the embryonated eggs provided a closer estimate of the embryo temperature. The 10.5 to 18 d mean values of Text and Tnem were similar to each other, but those were numerically higher than the 10.5 to 18 d mean values of Tinc and Tlog (Table 2). This indicates that the external microenvironmental temperatures of the incubating embryonated eggs may be effectively determined by the use of transponders that are contained within water vials or that are inserted in the air cells of nonembryonated eggs located within 5 cm of the embryonated eggs. However, the higher CV of Text compared with that of Tnem indicates that the transponders present in the water vials were more sensitive to minute fluctuations in the external microenvironmental temperatures of the
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Pulikanti et al. Table 1. Mean values, incubation length in days, and conductance constants (KH2O) of embryonated Ross × Ross 708 broiler hatching eggs between 10.5 and 18 d of incubation Item1
Nonembryonated egg2
Set egg weight (g) ∆PH2O EWL (%) GH2O gH2O Incubation length (d) KH2O
55.6 20.2 0.54 14.0 25.2
± 0.74b ± 0.20 ± 0.026 ± 0.69 ± 1.29 — —
Embryonated egg3 57.6 20.2 0.54 14.4 25.0 20.8 5.20
± ± ± ± ± ± ±
0.46a 0.22 0.019 0.56 0.96 0.07 0.205
a,bMeans
within a row with no common superscript differ significantly (P ≤ 0.05). (Torr) = water vapor pressure gradient across the eggshell, EWL = average daily percentage of incubational egg weight loss, GH2O (mg of H2O/d per Torr) = eggshell water vapor conductance, and gH2O (mg of H2O/d per Torr per 100 g) = specific GH2O (GH2O adjusted to a 100-g set egg weight basis) of nonembryonated and embryonated Ross × Ross 708 broiler hatching eggs. 2A total of 16 nonembryonated eggs (2 nonembryonated eggs on each of 8 incubator tray levels) were used for the calculation of the mean values. 3A total of 26 embryonated eggs were used for the calculation of the mean values. 1∆P H2O
embryonated eggs. Such temperature fluctuations in the immediate vicinity of an incubating embryonated egg may be attributable to changes in the level of metabolic heat that are produced from the actively metabolizing and rapidly growing broiler embryo during the latter half of incubation. More importantly, a significant interaction (P ≤ 0.001) of days of incubation × type of temperature measurement (Text, Tnem, and Temb) was observed for temperature. The values of Text, Tnem, and Temb that were observed every 12 h are provided in Table 3. Beginning on d 13 of incubation, Temb consistently remained significantly higher than Text and Tnem. These observations further support the importance of air cell transponder implantation for a more accurate estimation of broiler embryo temperature during incubation. Although Tinc (CV = 0.18) and Tlog (CV = 0.17) showed similar levels of variation between 10.5 and 18 d of incubation (Table 2; Figure 1), the 12-h mean values of Tlog in that time interval were calculated using temperature readings that were taken every 5 min from 3 data loggers that covered the entire area inside the incubator. Conversely, Tinc was determined every 12 h Table 2. Mean values of temperature readings from incubator dry bulb thermometer (Tinc) and data loggers (Tlog); and transponders present in water vials (Text) and nonembryonated (Tnem) and embryonated egg air cells (Temb), between 10.5 and 18 d of incubation1 Item2
Mean (°C)
SEM
N3
Tinc Tlog Text Tnem Temb
37.5 37.4 37.6 37.6 38.1
0.02 0.02 0.04 0.03 0.05
16 6,912 256 256 416
1T inc = temperature reading from incubator dry bulb thermometer; Tlog = temperature reading from data loggers; Text = transponder reading from water vials; Tnem = transponder reading from nonembryonated eggs; and Temb = transponder reading from embryonated eggs. 2T , T , T inc ext nem, and Temb were recorded every 12 h. The Tlog was recorded every 5 min. 3Represents the total number of readings used in the calculation of the mean and SEM for each parameter.
with the use of a single incubator dry bulb thermometer that was located at the top right-hand corner of the incubator. Therefore, Tlog was considered to be a more reliable indicator of overall incubation temperature (temperature of the air circulating inside the incubator) when compared with Tinc. Nevertheless, when comparing the use of Tinc or Tlog with Text or Tnem, this study further suggests that a single factory-installed dry bulb thermometer as a standard component in commercial incubators, or the use of data loggers that are widely dispersed within an incubator, may not be sufficient in providing an accurate estimation of the external microenvironmental temperature of an incubating egg. The mean values of Text and Temb over the 10.5 to 18 d incubational period for the Ross × Ross 708 eggs
Table 3. Mean values of temperature readings that were recorded within 12-h periods from transponders present in water vials (Text) and nonembryonated (Tnem) and embryonated egg air cells (Temb) as influenced by days of incubation × type of temperature measurement interaction between 10.5 and 18 d of incubation1 Days of incubation 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0
Text
Tnem
Temb
37.40b
37.73a
37.75a 37.84 37.93a 37.91a 38.04a 38.05a 38.00a 38.08a 38.25a 38.16a 38.26a 38.19a 38.26a 38.15a 38.35a 38.19a
37.71 37.64b 37.54b 37.94ab 37.36b 37.55b 37.66b 37.30c 37.65b 37.71b 37.36c 37.70b 37.58b 37.63b 37.53b
37.80 37.93a 37.65b 37.76b 37.60b 37.59b 37.49b 37.64b 37.56b 37.63b 37.74b 37.66b 37.44b 37.51b 37.49b
a–cMeans within a row with no common superscript differ significantly (P ≤ 0.001). 1A total of approximately 16 T ext and Tnem, and 26 Temb readings recorded within each 12-h time period between 10.5 and 18 d of incubation were used in the calculation of mean values. For all temperature measurements, pooled SEM = 0.104.
BROILER EMBRYO TEMPERATURE PROFILES
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Figure 1. Semicircadian variable patterns in the temperature readings of incubator dry bulb thermometer (diamonds) and data loggers (black squares) and transponder readings located in water vials (black circles) and nonembryonated (black triangle) and embryonated egg air cells (black squares with white crosses) between 10.5 and 18 d of incubation. For each type of temperature measurement, each of the 16 values (sixteen 12-h periods between 10.5 and 18 d of incubation) represents the mean value of the corresponding temperature readings that were recorded within that 12-h time period.
reported in this study (Table 2) were in close comparison to those reported for Ross × Ross 308 eggs by Pulikanti et al. (2011b). The mean values of Text and Temb for the 10.5 to 18.5 d incubational period, as reported by Pulikanti et al. (2011b), were 37.1 ± 0.03 and 37.8 ± 0.09°C, respectively. Close comparisons of the mean values of the percentage of EWL, Text, and Temb observed in the current experiment with those reported by Pulikanti et al. (2011b) indicate that the eggs in these 2 experiments were subjected to similar incubational conditions, which would have caused similar physiological growth responses in the embryos. Between 10.5 and 18 d of incubation, significant positive regression trends were observed for Temb and ∆T; whereas a significant negative regression trend was observed for Tnem (Table 4; Figures 1 and 2). The variations in Tinc, Tlog, Text, Tnem, and Temb every 12 h between 10.5 and 18 d of incubation are presented in graphical form in Figure 1. The physiological basis for the significant negative regression of Tnem over days of incubation is unclear. Nonetheless, the regression values (Table 4) and the associated graphs (Figures 1 and 2) of the different types of temperature measurements indicated that Temb showed a significant progressive increase between 10.5 and 18 d of incubation, which resulted in a significant difference between Temb and Tnem. Similarly, the internal egg and eggshell temperatures for turkey eggs reported by French (1997) showed progressive increases during the second half of incubation. However, the eggshell temperatures in that experiment were observed to remain consistently lower and more variable than the corresponding internal egg temperatures. This could be attributed to the fact that eggshell temperatures are more susceptible to variations in the thermal conductivity of the eggshell and the air flow around the egg (Eren Ozcan et al., 2010; Lourens et al., 2011). In the current study, Tinc, Tlog, and Tnem
displayed minimal variations (CV = 0.18, 0.17, and 0.23, respectively), whereas Text showed the greatest variation (CV = 0.42; Table 4). Although the mean values of Text and Tnem were similar to each other, the variable pattern of Text over a relatively broad range of temperatures would indicate that Text was more sensitive than were Tinc, Tlog, and Tnem to minute fluctuations in the temperatures of the microenvironment surrounding the incubating embryonated egg. The higher sensitivity of the transponders present in the water vials to variations in external microenvironment egg temperatures may be attributable to the smaller size and higher surface area-to-volume ratio of the water vials compared with that of the nonembryonated eggs. Nevertheless, the cyclical pattern of variations in Text within a range that extended between Temb and other external temperature measurements suggests that Text was influenced by embryo heat production and incubator temperature. The progressive increases in Temb between 10.5 and 18 d of incubation is an effect that results from the continued increase in embryo metabolism (Janke et al., 2002) and the fact that embryonic tissue continues to occupy a greater proportion of the egg’s interior (Romanoff, 1960; Parkhurst and Mountney, 1988). Subsequently, metabolic heat production by the embryo increases during the later part of incubation (Sturkie, 1965; Janke et al., 2002). According to De Smit et al. (2008), during the first half of incubation (d 1–10.5), chicken embryos undergo tissue differentiation and organ formation, during which time they require energy from an external source, and therefore, continuously absorb heat from the air circulating inside the incubator. De Smit et al. (2008) also suggested that during the second half of incubation (d 10.5–21), the embryos undergo rapid growth and development and actively metabolize available nutrients in the egg for this purpose.
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Figure 2. Semicircadian variable patterns between 10.5 and 18 d of incubation for differences in the mean embryonated and nonembryonated egg air cell transponder temperature readings. Each of the 16 mean values for the differences represents the difference between the mean embryonated and nonembryonated egg readings recorded in that 12-h time period.
Consequently, embryos tend to lose excess metabolic heat to the surrounding atmosphere inside the incubator. The relative advantage of using the transponders for determination of internal egg (air cell) temperatures was clearly evident from their efficient and closer reflection of the progressive increases in the corresponding embryonic temperatures during the later part of incubation. Furthermore, the transponders used in the current experiment were capable of detecting the minute temperature differences that existed between Temb and Tinc at each 12-h time period between 10.5 and 18 d of incubation. These findings support the suggestions by Lourens et al. (2005), that embryo temperature can be noticeably different from the incubator temperature at certain periods during incubation. For the 10.5 to 18-d incubational period in the present study, mean values of GH2O and gH2O in embryonated eggs were 14.4 ± 0.56 mg of H2O/d per Torr and 25.0 ± 0.96 mg of H2O/d per Torr per 100 g, respectively; whereas, those of nonembryonated eggs were 14.0 ± 0.69 mg of H2O/d per Torr and 25.2 ± 1.29 mg of H2O/d per Torr per 100 g, respectively (Table 1). The close comparison of the mean values of GH2O and gH2O between nonembryonated and embryonated eggs in the current experiment support the potential use of nonembryonated eggs of known shell properties (calibrated eggs) for an indirect estimation of the conductance parameters of embryonated eggs, as suggested by
previous researchers (Tullett, 1982; Visschedijk et al., 1985). The mean GH2O value of Ross × Ross 308 broiler hatching eggs reported by Pulikanti et al. (2011b) was 13.9 ± 0.47 mg of H2O/d per Torr; whereas the mean GH2O values reported by Ar et al. (1974) and Ar and Rahn (1978) for Gallus gallus (domestic chicken) eggs were 14.4 ± 2.38 and 14.4 (SEM not reported) mg of H2O/d per Torr, respectively. The mean gH2O value reported by Pulikanti et al. (2011b) in Ross × Ross 308 broiler hatching eggs was 24.5 ± 0.75 mg of H2O/d per Torr per 100 g, whereas the mean gH2O values of Gallus gallus eggs reported by Ar et al. (1974) and Ar and Rahn (1978) were 26.5 ± 3.36 and 26.7 mg of H2O/d per Torr per 100 g, respectively. As gH2O is calculated by accounting for variations in egg weight, it is used as a more standardized expression of eggshell conductance when compared with GH2O. It was not possible to statistically compare the gH2O values of different strains or species among the different experiments. However, the gH2O values of Ross × Ross 708 broiler hatching eggs reported in the current experiment and of Ross × Ross 308 eggs in a similar experiment by Pulikanti et al. (2011b) were closely comparable to each other. Nevertheless, the gH2O values of Ross × Ross 308 and 708 eggs were not as comparable to the mean gH2O value of Gallus gallus eggs reported by Ar et al. (1974) and Ar and Rahn (1978). This difference may be attributable to differences in breed or strain and in the methodolo-
Table 4. Regression values (adjusted R2, slope, Y-intercept, CV, and P-value) from temperature and transponder readings over 10.5 to 18 d of incubation1,2 Item Adjusted R2 Slope Y-intercept CV P-value
Tinc
Tlog
Text
Tnem
Temb
∆T
0.07 −0.01 37.6 0.18 ≤0.160
−0.03 0.01 37.3 0.17 ≤0.460
−0.07 −0.001 37.6 0.42 ≤0.946
0.38 −0.03 38.1 0.23 ≤0.006
0.77 0.06 37.2 0.22 ≤0.001
0.86 0.10 −0.93 20.6 ≤0.001
1T inc = temperature reading from incubator dry bulb thermometer; Tlog = temperature reading from data loggers; Text = transponder reading from water vials; Tnem = transponder reading from nonembryonated eggs; Temb = transponder reading from embryonated eggs; and ∆T = differences between 12 h mean values of Temb and Tnem. 2T log was recorded every 5 min, whereas Tinc, Text, Tnem, and Temb were recorded and ∆T was calculated every 12 h. For ∆T and each type of temperature measurement (Tinc, Tlog, Text, Tnem, and Temb), 16 mean values (sixteen 12-h periods between 10.5 and 18 d of incubation) were used for regression analysis.
BROILER EMBRYO TEMPERATURE PROFILES
gies used in the different experiments, including differences in the devices used for the determination of embryo temperature. The mean values of incubation length and KH2O in embryonated Ross × Ross 708 broiler hatching eggs were 20.8 ± 0.07 d and 5.20 ± 0.205, respectively (Table 1). Although, it was not possible to statistically examine differences in the respective KH2O values reported in the current experiment with those reported by Ar et al. (1974) and Ar and Rahn (1978), the mean value of KH2O reported in the current experiment was numerically different from the KH2O value (5.61) of Gallus gallus eggs reported by Ar et al. (1974) and Ar and Rahn (1978). The potential differences in KH2O values between the eggs of different species, breeds, or strains could be attributed to the associated differences in their eggshell porosities (Washburn, 1990). In conclusion, transponders implanted in the air cells of embryonated broiler hatching eggs were shown to be efficient in detecting incubational variations in the embryonic temperature between 10.5 and 18 d of incubation and for the subsequent calculation of GH2O, gH2O, and KH2O. The progressive increases in Temb and ∆T values between 10.5 and 18 d of incubation reflected an increase in metabolic heat production by the growing broiler embryo during the latter half of incubation. Transponders placed in water vials or that are inserted into nonembryonated egg air cells may be more reliable indicators of the external microenvironmental temperatures of incubating embryonated eggs than are incubator dry bulb thermometer or data logger temperature readings. Transponders in water-filled vials may also be more reliable than transponders implanted in the air cells of nonembryonated eggs due to their higher sensitivity to minute temperature fluctuations in the immediate vicinity of a rapidly growing and actively metabolizing broiler embryo. It can also be inferred that nonembryonated eggs may be used as calibrated eggs for the indirect determination of GH2O and gH2O of embryonated eggs, whereas the determination of KH2O necessitates the use of embryonated eggs.
ACKNOWLEDGMENTS We express our appreciation for the expert technical assistance of S. K. Womack of the Mississippi State University Poultry Science Department.
REFERENCES Ar, A., C. V. Paganelli, R. B. Reeves, D. G. Greene, and H. Rahn. 1974. The avian egg: Water vapor conductance, shell thickness, and functional pore area. Condor 76:153–158. Ar, A., and H. Rahn. 1978. Interdependence of gas conductance, incubational length, and weight of the avian egg. Pages 227–236 in Respiratory function in Birds, Adult and Embryonic. J. Piiper, ed. Springer, Berlin, Germany. Bamelis, F., B. Kemps, K. Mertens, B. De Ketelaere, E. Decuypere, and J. DeBaerdemaeker. 2005. An automatic monitoring of
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the hatching process based on the noise of the hatching chicks. Poult. Sci. 84:1101–1107. Decuypere, E., and V. Bruggeman. 2007. The endocrine interface of environmental and egg factors affecting chick quality. Poult. Sci. 86:1037–1042. De Smit, L., V. Bruggeman, M. Debonne, J. K. Tona, B. Kamers, N. Everaert, A. Witters, O. Onagbesan, L. Arckens, J. De Baerdemaeker, and E. Decuypere. 2008. The effect of nonventilation during early incubation on the embryonic development of chicks of two commercial broiler strains differing in ascites susceptibility. Poult. Sci. 87:551–560. Eren Ozcan, S., S. Andriessens, and D. Berckmans. 2010. Computational study of the heat transfer of an avian egg in a tray. Poult. Sci. 89:776–784. French, N. A. 1997. Modeling incubation temperature: The effects of incubator design, embryonic development, and egg size. Poult. Sci. 76:124–133. Janke, O., B. Tzschentke, and M. Boerjan. 2004. Comparative investigations of heat production and body temperature in embryos of modern chicken breeds. Avian Poult. Biol. Rev. 15:191–196. Janke, O., B. Tzschentke, J. Höchel, and M. Nichelmann. 2002. Metabolic responses of chicken and muscovy duck embryos to high incubation temperatures. Comp. Biochem. Physiol., Part A Mol. Integr. Physiol. 131:741–750. Joseph, N. S., A. Lourens, and E. T. Moran Jr. 2006. The effects of suboptimal eggshell temperature during incubation on broiler chick quality, live performance, and further-processing yield. Poult. Sci. 85:932–938. Lourens, A., R. Meijerhof, B. Kemp, and H. Van den Brand. 2011. Energy partitioning during incubation and consequences for embryo temperature: A theoretical approach. Poult. Sci. 90:516– 523. Lourens, A., H. van den Brand, R. Meijerhof, and B. Kemp. 2005. Effect of eggshell temperature during incubation on embryo development, hatchability, and posthatch development. Poult. Sci. 84:914–920. Parkhurst, C. R., and G. J. Mountney. 1988. Poultry meat and egg production. Van Nostrand Reinhold Co., New York, NY. Pulikanti, R., E. D. Peebles, and P. D. Gerard. 2011a. Physiological responses of broiler embryos to in ovo implantation of temperature transponders. Poult. Sci. 90:308–313. Pulikanti, R., E. D. Peebles, and P. D. Gerard. 2011b. Use of implantable temperature transponders for the determination of air cell temperature, eggshell water vapor conductance, and their functional relationships in embryonated broiler hatching eggs. Poult. Sci. 90:1191–1196. Renema, R. A., J. J. R. Feddes, K. L. Schmid, M. A. Ford, and A. R. Kolk. 2006. Internal egg temperature in response to preincubation warming in broiler breeder and turkey eggs. J. Appl. Poult. Res. 15:1–8. Romanoff, A. L. 1960. The Avian Embryo. The Macmillan Co., New York, NY. SAS Institute. 2003. SAS Proprietary Software Release 9.1. SAS Inst. Inc., Cary, NC. Steel, R. G. D., and J. H. Torrie. 1980. Principles and Procedures of Statistics: A Biometrical Approach. 2nd ed. McGraw-Hill Inc., New York, NY. Sturkie, P. D. 1965. Avian Physiology. Comstock Pub. Assoc., New York, NY. Tullett, S. G. 1982. A further study of changes in eggshell porosity with flock age in turkeys. Turkeys 29:25–26. Turner, J. S. 1990. The thermal energetics of an incubated chicken egg. J. Therm. Biol. 15:211–216. Visschedijk, A. H. J., H. Tazawa, and J. Piiper. 1985. Variability of shell conductance and gas exchange of chicken eggs. Respir. Physiol. 59:339–45. Washburn, K. W. 1990. Genetic variation in egg composition. Pages 781–804 in Poultry Breeding and Genetics. R. D. Crawford, ed. Elsevier, Amsterdam, the Netherlands. Wilson, H. R. 1991. Physiological requirements of the developing embryo: Temperature and turning. Pages 145–156 in Avian Incubation. S. G. Tullet, ed. Butterworth-Heinemann Ltd, Oxford, UK.
determined every 12 h. Over the days of incubation, regression coefficients for Temb and ∆T were positive, whereas the regression coefficient for Tnem was negative. There was a significant day of incubation × type of temperature measurement (Text, Tnem, and Temb) interaction for temperature. Between 13 and 18 d of incubation, mean values of Temb readings that were recorded every 12 h were consistently higher than those of Text and Tnem, indicating the importance of air cell transponder implantation for the efficient estimation of broiler embryo temperature. Furthermore, mean values of the percentage of daily incubational egg weight loss, GH2O, gH2O, and KH2O of the embryonated eggs were 0.54 ± 0.019%, 14.4 ± 0.56 mg of H2O/d per Torr, 25.0 ± 0.96 mg of H2O/d per Torr per 100 g, and 5.20 ± 0.205, respectively. The results suggest that transponders may be implanted in the air cells of broiler hatching eggs to detect incubational variations in Temb and to subsequently calculate GH2O, gH2O, and KH2O.
Key words: broiler, conductance, egg, temperature, transponder 2012 Poultry Science 91:55–61 doi:10.3382/ps.2011-01759
INTRODUCTION
stimuli on embryonic life and the monitoring of those parameters for maximal productivity are of importance to the broiler industry (Bamelis et al., 2005). Among various external factors, incubation temperature is considered to be a major factor that influences embryo temperature (French, 1997), heat production (Janke et al., 2002), and development (Decuypere and Bruggeman, 2007). Incubation temperature also has a major influence on the hatchability and posthatch performance of chickens (Wilson, 1991). Lourens et al. (2005) noted specific relationships between broiler embryo temperature and development and subsequent hatchability and posthatch performance. It has been reported that the optimal incubation temperature for chicken eggs is 37 to 38°C (Wilson, 1991; Decuypere and Bruggeman, 2007; De Smit et al., 2008). French (1997) suggested that embryonic temperature is a function of incubator temperature, heat
The embryonic stage currently occupies a greater proportion of the entire life of the commercial broiler than ever before. Therefore, the embryo’s physiological responses to its incubational environment have an increased effect on subsequent posthatch performance and processing yield. A thorough and in-depth understanding of the potential influences of various external ©2012 Poultry Science Association Inc. Received July 26, 2011. Accepted September 28, 2011. 1 This is Journal article number J-11994 from the Mississippi Agricultural and Forestry Experiment Station supported by MIS-322210. 2 Use of trade names in this publication does not imply endorsement by Mississippi Agricultural and Forestry Experiment Station of these products nor similar ones not mentioned. 3 Corresponding author: [email protected]
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exchange between the embryo and its external microenvironment, and the metabolic heat production of the growing avian embryo. French (1997) further suggested that because the avian embryo is largely poikilothermic during early incubation, its temperature is largely influenced by the incubator temperature, and that during the later stages of incubation, as the embryo produces larger amounts of metabolic heat, its temperature rises above the incubator temperature. Previously, Lourens et al. (2005) and Joseph et al. (2006) used eggshell temperature as a means to estimate embryonic temperature. Lourens et al. (2005) also graphically reported variations in broiler eggshell temperatures between 1 and 18 d of incubation. However, Eren Ozcan et al. (2010) and Lourens et al. (2011) suggested limitations associated with the measurement of eggshell temperature for the estimation of embryonic temperature, given that eggshell temperature can be influenced by the thermal conductivity of the eggshell and the velocity of air flow around the egg. In other studies, internal egg content temperatures (Turner, 1990; Janke et al., 2004; Renema et al., 2006) were used as standard expressions of embryonic temperature. Janke et al. (2004) suggested that embryonic heat production and body temperature may be estimated based on internal egg temperature. Although these techniques allowed for the determination of an egg’s internal environmental temperature proximal to the embryo, they were limited in application because of their relative invasiveness to the growing embryo (Turner, 1990; Janke et al., 2004) and because of the potential for increased embryonic mortality (Janke et al., 2004). Pulikanti et al. (2011a,b) suggested that transponders may be safely implanted into the air cells of incubating eggs for the determination of internal egg temperature. Pulikanti et al. (2011b) successfully recorded the internal (air cell; Temb) and external microenvironment (water vial; Text) temperatures of embryonated Ross × Ross 308 broiler hatching eggs between 10.5 and 18.5 d of incubation. These researchers subsequently used the Temb and Text values along with incubator RH and atmospheric pressure values for the calculation of the water vapor pressure gradient across the eggshell (∆PH2O; Torr), eggshell water vapor conductance (GH2O; mg of H2O/d per Torr), and specific GH2O (gH2O; GH2O adjusted to a 100 g set egg weight basis; mg of H2O/d per Torr per 100 g). However, Pulikanti et al. (2011b) did not use implanted nonembryonated eggs as external temperature controls, and they did not determine the GH2O constants (KH2O) of embryonated eggs. Moreover, they did not provide detailed comparative profiles of Temb, Text, and incubator dry bulb (Tinc) and data logger (Tlog) temperatures during the second half of incubation. Therefore, the current experiment was conducted using Ross × Ross 708 broiler hatching eggs to compare the mean values and semicircadian variations of Temb, Text, Tinc, and Tlog and the internal (air cell) temperatures of nonembryonated eggs (Tnem) between 10.5 and 18 d of incubation. Further-
more, calculations of ∆PH2O, GH2O, and gH2O values of embryonated and nonembryonated eggs, and KH2O values of embryonated eggs were performed.
MATERIALS AND METHODS General In total, 720 broiler hatching eggs were collected from a young (30 wk of age) Ross × Ross 708 breeder flock. The eggs were held under standard storage conditions for 3 d before set. Eggs having malformed shells, or that were contaminated, misshapen, cracked, or not within ± 10% of the mean weight of all eggs collected, were discarded from the experiment. On d 0 of incubation, eggs were randomly labeled and weighed to record their set egg weight. At least 60 eggs were set on each of 8 replicate tray levels of a Jamesway model 500 single stage incubator (Jamesway Incubator Company Inc., Cambridge, ON, Canada). The eggs were incubated for 18 d under standard commercial conditions at 37.5°C dry bulb and 28.8°C wet bulb temperatures. On d 10.5 of incubation, the eggs were weighed and candled, and those containing slanted air cells were discarded. Subsequently, on each tray level, 4 embryonated eggs were randomly selected and the air cells of those eggs were implanted with a transponder (implantable programmable temperature transponder; IPTT-300; Bio Medic Data Systems Inc., Seaford, DE) for the determination of Temb. Transponders were implanted in the air cells of 2 nonembryonated eggs and these were positioned within 5 cm from each implanted egg on each tray level for the determination of Tnem. Furthermore, 2 sealed water-filled plastic vials (10-mL capacity), each containing a transponder, were positioned within 5 cm from each implanted embryonated and nonembryonated egg for the determination of Text (Pulikanti et al., 2011b). The materials and procedures used for transponder implantation and temperature data recording in this experiment were similar to those described previously by Pulikanti et al. (2011a,b).
Hatch Monitor On d 18.5 of incubation, each implanted embryonated egg was candled, and the eggs that contained live embryos were placed in individual hatching baskets and subsequently transferred to their corresponding tray levels in a Jamesway model 500 single stage hatcher unit (Jamesway Incubator Company Inc.). The eggs in the hatcher were maintained at approximately 36.1°C dry bulb and 27.6°C wet bulb temperatures and were individually monitored for hatch every 12 h through d 21.5 of incubation.
Embryo Survivability Survivability of the embryos was determined by candling eggs on d 18.5 of incubation and was further con-
BROILER EMBRYO TEMPERATURE PROFILES
firmed based on hatch success through d 21.5 of incubation (Pulikanti et al., 2011b). All of the egg parameters for embryonated eggs described below were determined on implanted eggs that contained live embryos through hatch (d 21.5 of incubation).
Data Collection Between 0 and 18 d of incubation, Tinc, incubator wet bulb temperature readings, and atmospheric pressure values were recorded every 12 h. Moreover, between 0 and 18 d of incubation, Tlog readings were recorded every 5 min using wireless data loggers (La Crosse Technology, La Crescent, MN). Furthermore, between 10.5 and 18 d of incubation, temperature readings were recorded every 12 h from transponders contained within water vials, nonembryonated eggs, and embryonated eggs for the determination of Text, Tnem, and Temb, respectively. Between 10.5 and 18 d of incubation, a total of approximately 16 Tinc (sixteen 12-h periods); 6,912 Tlog (sixteen 12-h periods × 12 h × twelve 5-min readings per h × 3 data loggers); 256 Text and Tnem (16 twelve-h periods × 16 water vials or nonembryonated eggs); and 416 (sixteen 12-h periods × 26 embryonated eggs) Temb readings were recorded. For the determination of Temb, 26 rather than 32 implanted embryonated eggs (4 per each of 8 tray levels) were used, and this was due to the elimination of eggs that contained embryos that failed to hatch by d 21.5 of incubation or because of technical errors in the temperature determination process. Subsequently, differences between embryonated and nonembryonated egg internal (air cell) temperatures (∆T) were calculated every 12 h by subtracting the mean value of Tnem readings (n = 16) from the mean value of Temb readings (n = 16; ∆T = Temb – Tnem).
Eggshell Water Vapor Conductance Average daily incubational weight (moisture) loss (EWL; mg) values of embryonated and nonembryonated eggs between 10.5 and 18 d of incubation were determined for the subsequent calculation of the respective percentage of EWL values. The 10.5 to 18 d mean values of Text and Temb along with the incubator RH and atmospheric pressure values were used for the calculation of ∆PH2O. Subsequently, GH2O [GH2O = EWL (mg)/ΔPH2O (Torr)] and gH2O {gH2O = [GH2O/ set egg weight (g)] × 100} of embryonated and nonembryonated eggs were calculated using the procedures and equations described by Ar et al. (1974) and Ar and Rahn (1978) and modified by Pulikanti et al. (2011b). Based on the hatch monitor data between 18.5 and 21.5 d of incubation, incubation length (in days) of individual embryonated eggs were determined. Furthermore, the GH2O constants (KH2O) of the embryonated eggs were calculated by using the formula {KH2O = [GH2O × incubation length (d)/set egg weight (g)]} as described by Ar et al. (1974) and Ar and Rahn (1978).
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Statistical Analysis For the analyses of Text, Tnem, Temb, and ∆T, each tray level was considered as a replicate unit. All data were analyzed using version 9.1 SAS Institute (2003). The REG procedure was used for regression analyses of Tinc, Tlog, Text, Tnem, Temb, and ∆T over the days of incubation, and the MEANS procedure was used to determine CV values for these parameters. A repeated measures analysis was employed using the MIXED model that accounted for the variability among the trays to examine the influence of the days of incubation, type of temperature measurement (Text, Tnem, and Temb), and the interaction of the days of incubation and the type of temperature measurement on the temperature. The MIXED procedure was also used for a one-way ANOVA in set egg weight, percentage of EWL, ∆PH2O, GH2O, and gH2O between nonembryonated and embryonated eggs. Least squares means were compared in the event of significant global effects (Steel and Torrie, 1980). Furthermore, global effects, regression trends, and differences among least squares means were considered significant at P ≤ 0.05.
RESULTS AND DISCUSSION An approximate 90.6% (29 out of 32 total) embryo survivability was observed in the implanted embryonated eggs. The mean values of the percentage of EWL in nonembryonated and embryonated implanted eggs for the 10.5 to 18 d incubational period were 0.54 ± 0.03 and 0.54 ± 0.02%, respectively (Table 1). The mean percentage of EWL of implanted embryonated Ross × Ross 708 eggs in this experiment was in close comparison to that (0.55 ± 0.015%) reported by Pulikanti et al. (2011b) in embryonated Ross × Ross 308 broiler hatching eggs. The mean values of Tinc, Tlog, Text, Tnem, Temb, and ∆T for the 10.5 to 18 d incubational period in the current study were 37.5 ± 0.02, 37.4 ± 0.02, 37.6 ± 0.04, 37.6 ± 0.03, 38.1 ± 0.05, and 0.14 ± 0.032°C, respectively (Table 2). The 10.5 to 18 d mean value of Temb were numerically higher (approximately 0.6°C) than those for all other temperature measurements, including Tinc, Tlog, Text, and Tnem (Table 2), suggesting that the transponders inserted in the air cells of the embryonated eggs provided a closer estimate of the embryo temperature. The 10.5 to 18 d mean values of Text and Tnem were similar to each other, but those were numerically higher than the 10.5 to 18 d mean values of Tinc and Tlog (Table 2). This indicates that the external microenvironmental temperatures of the incubating embryonated eggs may be effectively determined by the use of transponders that are contained within water vials or that are inserted in the air cells of nonembryonated eggs located within 5 cm of the embryonated eggs. However, the higher CV of Text compared with that of Tnem indicates that the transponders present in the water vials were more sensitive to minute fluctuations in the external microenvironmental temperatures of the
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Pulikanti et al. Table 1. Mean values, incubation length in days, and conductance constants (KH2O) of embryonated Ross × Ross 708 broiler hatching eggs between 10.5 and 18 d of incubation Item1
Nonembryonated egg2
Set egg weight (g) ∆PH2O EWL (%) GH2O gH2O Incubation length (d) KH2O
55.6 20.2 0.54 14.0 25.2
± 0.74b ± 0.20 ± 0.026 ± 0.69 ± 1.29 — —
Embryonated egg3 57.6 20.2 0.54 14.4 25.0 20.8 5.20
± ± ± ± ± ± ±
0.46a 0.22 0.019 0.56 0.96 0.07 0.205
a,bMeans
within a row with no common superscript differ significantly (P ≤ 0.05). (Torr) = water vapor pressure gradient across the eggshell, EWL = average daily percentage of incubational egg weight loss, GH2O (mg of H2O/d per Torr) = eggshell water vapor conductance, and gH2O (mg of H2O/d per Torr per 100 g) = specific GH2O (GH2O adjusted to a 100-g set egg weight basis) of nonembryonated and embryonated Ross × Ross 708 broiler hatching eggs. 2A total of 16 nonembryonated eggs (2 nonembryonated eggs on each of 8 incubator tray levels) were used for the calculation of the mean values. 3A total of 26 embryonated eggs were used for the calculation of the mean values. 1∆P H2O
embryonated eggs. Such temperature fluctuations in the immediate vicinity of an incubating embryonated egg may be attributable to changes in the level of metabolic heat that are produced from the actively metabolizing and rapidly growing broiler embryo during the latter half of incubation. More importantly, a significant interaction (P ≤ 0.001) of days of incubation × type of temperature measurement (Text, Tnem, and Temb) was observed for temperature. The values of Text, Tnem, and Temb that were observed every 12 h are provided in Table 3. Beginning on d 13 of incubation, Temb consistently remained significantly higher than Text and Tnem. These observations further support the importance of air cell transponder implantation for a more accurate estimation of broiler embryo temperature during incubation. Although Tinc (CV = 0.18) and Tlog (CV = 0.17) showed similar levels of variation between 10.5 and 18 d of incubation (Table 2; Figure 1), the 12-h mean values of Tlog in that time interval were calculated using temperature readings that were taken every 5 min from 3 data loggers that covered the entire area inside the incubator. Conversely, Tinc was determined every 12 h Table 2. Mean values of temperature readings from incubator dry bulb thermometer (Tinc) and data loggers (Tlog); and transponders present in water vials (Text) and nonembryonated (Tnem) and embryonated egg air cells (Temb), between 10.5 and 18 d of incubation1 Item2
Mean (°C)
SEM
N3
Tinc Tlog Text Tnem Temb
37.5 37.4 37.6 37.6 38.1
0.02 0.02 0.04 0.03 0.05
16 6,912 256 256 416
1T inc = temperature reading from incubator dry bulb thermometer; Tlog = temperature reading from data loggers; Text = transponder reading from water vials; Tnem = transponder reading from nonembryonated eggs; and Temb = transponder reading from embryonated eggs. 2T , T , T inc ext nem, and Temb were recorded every 12 h. The Tlog was recorded every 5 min. 3Represents the total number of readings used in the calculation of the mean and SEM for each parameter.
with the use of a single incubator dry bulb thermometer that was located at the top right-hand corner of the incubator. Therefore, Tlog was considered to be a more reliable indicator of overall incubation temperature (temperature of the air circulating inside the incubator) when compared with Tinc. Nevertheless, when comparing the use of Tinc or Tlog with Text or Tnem, this study further suggests that a single factory-installed dry bulb thermometer as a standard component in commercial incubators, or the use of data loggers that are widely dispersed within an incubator, may not be sufficient in providing an accurate estimation of the external microenvironmental temperature of an incubating egg. The mean values of Text and Temb over the 10.5 to 18 d incubational period for the Ross × Ross 708 eggs
Table 3. Mean values of temperature readings that were recorded within 12-h periods from transponders present in water vials (Text) and nonembryonated (Tnem) and embryonated egg air cells (Temb) as influenced by days of incubation × type of temperature measurement interaction between 10.5 and 18 d of incubation1 Days of incubation 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 16.0 16.5 17.0 17.5 18.0
Text
Tnem
Temb
37.40b
37.73a
37.75a 37.84 37.93a 37.91a 38.04a 38.05a 38.00a 38.08a 38.25a 38.16a 38.26a 38.19a 38.26a 38.15a 38.35a 38.19a
37.71 37.64b 37.54b 37.94ab 37.36b 37.55b 37.66b 37.30c 37.65b 37.71b 37.36c 37.70b 37.58b 37.63b 37.53b
37.80 37.93a 37.65b 37.76b 37.60b 37.59b 37.49b 37.64b 37.56b 37.63b 37.74b 37.66b 37.44b 37.51b 37.49b
a–cMeans within a row with no common superscript differ significantly (P ≤ 0.001). 1A total of approximately 16 T ext and Tnem, and 26 Temb readings recorded within each 12-h time period between 10.5 and 18 d of incubation were used in the calculation of mean values. For all temperature measurements, pooled SEM = 0.104.
BROILER EMBRYO TEMPERATURE PROFILES
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Figure 1. Semicircadian variable patterns in the temperature readings of incubator dry bulb thermometer (diamonds) and data loggers (black squares) and transponder readings located in water vials (black circles) and nonembryonated (black triangle) and embryonated egg air cells (black squares with white crosses) between 10.5 and 18 d of incubation. For each type of temperature measurement, each of the 16 values (sixteen 12-h periods between 10.5 and 18 d of incubation) represents the mean value of the corresponding temperature readings that were recorded within that 12-h time period.
reported in this study (Table 2) were in close comparison to those reported for Ross × Ross 308 eggs by Pulikanti et al. (2011b). The mean values of Text and Temb for the 10.5 to 18.5 d incubational period, as reported by Pulikanti et al. (2011b), were 37.1 ± 0.03 and 37.8 ± 0.09°C, respectively. Close comparisons of the mean values of the percentage of EWL, Text, and Temb observed in the current experiment with those reported by Pulikanti et al. (2011b) indicate that the eggs in these 2 experiments were subjected to similar incubational conditions, which would have caused similar physiological growth responses in the embryos. Between 10.5 and 18 d of incubation, significant positive regression trends were observed for Temb and ∆T; whereas a significant negative regression trend was observed for Tnem (Table 4; Figures 1 and 2). The variations in Tinc, Tlog, Text, Tnem, and Temb every 12 h between 10.5 and 18 d of incubation are presented in graphical form in Figure 1. The physiological basis for the significant negative regression of Tnem over days of incubation is unclear. Nonetheless, the regression values (Table 4) and the associated graphs (Figures 1 and 2) of the different types of temperature measurements indicated that Temb showed a significant progressive increase between 10.5 and 18 d of incubation, which resulted in a significant difference between Temb and Tnem. Similarly, the internal egg and eggshell temperatures for turkey eggs reported by French (1997) showed progressive increases during the second half of incubation. However, the eggshell temperatures in that experiment were observed to remain consistently lower and more variable than the corresponding internal egg temperatures. This could be attributed to the fact that eggshell temperatures are more susceptible to variations in the thermal conductivity of the eggshell and the air flow around the egg (Eren Ozcan et al., 2010; Lourens et al., 2011). In the current study, Tinc, Tlog, and Tnem
displayed minimal variations (CV = 0.18, 0.17, and 0.23, respectively), whereas Text showed the greatest variation (CV = 0.42; Table 4). Although the mean values of Text and Tnem were similar to each other, the variable pattern of Text over a relatively broad range of temperatures would indicate that Text was more sensitive than were Tinc, Tlog, and Tnem to minute fluctuations in the temperatures of the microenvironment surrounding the incubating embryonated egg. The higher sensitivity of the transponders present in the water vials to variations in external microenvironment egg temperatures may be attributable to the smaller size and higher surface area-to-volume ratio of the water vials compared with that of the nonembryonated eggs. Nevertheless, the cyclical pattern of variations in Text within a range that extended between Temb and other external temperature measurements suggests that Text was influenced by embryo heat production and incubator temperature. The progressive increases in Temb between 10.5 and 18 d of incubation is an effect that results from the continued increase in embryo metabolism (Janke et al., 2002) and the fact that embryonic tissue continues to occupy a greater proportion of the egg’s interior (Romanoff, 1960; Parkhurst and Mountney, 1988). Subsequently, metabolic heat production by the embryo increases during the later part of incubation (Sturkie, 1965; Janke et al., 2002). According to De Smit et al. (2008), during the first half of incubation (d 1–10.5), chicken embryos undergo tissue differentiation and organ formation, during which time they require energy from an external source, and therefore, continuously absorb heat from the air circulating inside the incubator. De Smit et al. (2008) also suggested that during the second half of incubation (d 10.5–21), the embryos undergo rapid growth and development and actively metabolize available nutrients in the egg for this purpose.
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Figure 2. Semicircadian variable patterns between 10.5 and 18 d of incubation for differences in the mean embryonated and nonembryonated egg air cell transponder temperature readings. Each of the 16 mean values for the differences represents the difference between the mean embryonated and nonembryonated egg readings recorded in that 12-h time period.
Consequently, embryos tend to lose excess metabolic heat to the surrounding atmosphere inside the incubator. The relative advantage of using the transponders for determination of internal egg (air cell) temperatures was clearly evident from their efficient and closer reflection of the progressive increases in the corresponding embryonic temperatures during the later part of incubation. Furthermore, the transponders used in the current experiment were capable of detecting the minute temperature differences that existed between Temb and Tinc at each 12-h time period between 10.5 and 18 d of incubation. These findings support the suggestions by Lourens et al. (2005), that embryo temperature can be noticeably different from the incubator temperature at certain periods during incubation. For the 10.5 to 18-d incubational period in the present study, mean values of GH2O and gH2O in embryonated eggs were 14.4 ± 0.56 mg of H2O/d per Torr and 25.0 ± 0.96 mg of H2O/d per Torr per 100 g, respectively; whereas, those of nonembryonated eggs were 14.0 ± 0.69 mg of H2O/d per Torr and 25.2 ± 1.29 mg of H2O/d per Torr per 100 g, respectively (Table 1). The close comparison of the mean values of GH2O and gH2O between nonembryonated and embryonated eggs in the current experiment support the potential use of nonembryonated eggs of known shell properties (calibrated eggs) for an indirect estimation of the conductance parameters of embryonated eggs, as suggested by
previous researchers (Tullett, 1982; Visschedijk et al., 1985). The mean GH2O value of Ross × Ross 308 broiler hatching eggs reported by Pulikanti et al. (2011b) was 13.9 ± 0.47 mg of H2O/d per Torr; whereas the mean GH2O values reported by Ar et al. (1974) and Ar and Rahn (1978) for Gallus gallus (domestic chicken) eggs were 14.4 ± 2.38 and 14.4 (SEM not reported) mg of H2O/d per Torr, respectively. The mean gH2O value reported by Pulikanti et al. (2011b) in Ross × Ross 308 broiler hatching eggs was 24.5 ± 0.75 mg of H2O/d per Torr per 100 g, whereas the mean gH2O values of Gallus gallus eggs reported by Ar et al. (1974) and Ar and Rahn (1978) were 26.5 ± 3.36 and 26.7 mg of H2O/d per Torr per 100 g, respectively. As gH2O is calculated by accounting for variations in egg weight, it is used as a more standardized expression of eggshell conductance when compared with GH2O. It was not possible to statistically compare the gH2O values of different strains or species among the different experiments. However, the gH2O values of Ross × Ross 708 broiler hatching eggs reported in the current experiment and of Ross × Ross 308 eggs in a similar experiment by Pulikanti et al. (2011b) were closely comparable to each other. Nevertheless, the gH2O values of Ross × Ross 308 and 708 eggs were not as comparable to the mean gH2O value of Gallus gallus eggs reported by Ar et al. (1974) and Ar and Rahn (1978). This difference may be attributable to differences in breed or strain and in the methodolo-
Table 4. Regression values (adjusted R2, slope, Y-intercept, CV, and P-value) from temperature and transponder readings over 10.5 to 18 d of incubation1,2 Item Adjusted R2 Slope Y-intercept CV P-value
Tinc
Tlog
Text
Tnem
Temb
∆T
0.07 −0.01 37.6 0.18 ≤0.160
−0.03 0.01 37.3 0.17 ≤0.460
−0.07 −0.001 37.6 0.42 ≤0.946
0.38 −0.03 38.1 0.23 ≤0.006
0.77 0.06 37.2 0.22 ≤0.001
0.86 0.10 −0.93 20.6 ≤0.001
1T inc = temperature reading from incubator dry bulb thermometer; Tlog = temperature reading from data loggers; Text = transponder reading from water vials; Tnem = transponder reading from nonembryonated eggs; Temb = transponder reading from embryonated eggs; and ∆T = differences between 12 h mean values of Temb and Tnem. 2T log was recorded every 5 min, whereas Tinc, Text, Tnem, and Temb were recorded and ∆T was calculated every 12 h. For ∆T and each type of temperature measurement (Tinc, Tlog, Text, Tnem, and Temb), 16 mean values (sixteen 12-h periods between 10.5 and 18 d of incubation) were used for regression analysis.
BROILER EMBRYO TEMPERATURE PROFILES
gies used in the different experiments, including differences in the devices used for the determination of embryo temperature. The mean values of incubation length and KH2O in embryonated Ross × Ross 708 broiler hatching eggs were 20.8 ± 0.07 d and 5.20 ± 0.205, respectively (Table 1). Although, it was not possible to statistically examine differences in the respective KH2O values reported in the current experiment with those reported by Ar et al. (1974) and Ar and Rahn (1978), the mean value of KH2O reported in the current experiment was numerically different from the KH2O value (5.61) of Gallus gallus eggs reported by Ar et al. (1974) and Ar and Rahn (1978). The potential differences in KH2O values between the eggs of different species, breeds, or strains could be attributed to the associated differences in their eggshell porosities (Washburn, 1990). In conclusion, transponders implanted in the air cells of embryonated broiler hatching eggs were shown to be efficient in detecting incubational variations in the embryonic temperature between 10.5 and 18 d of incubation and for the subsequent calculation of GH2O, gH2O, and KH2O. The progressive increases in Temb and ∆T values between 10.5 and 18 d of incubation reflected an increase in metabolic heat production by the growing broiler embryo during the latter half of incubation. Transponders placed in water vials or that are inserted into nonembryonated egg air cells may be more reliable indicators of the external microenvironmental temperatures of incubating embryonated eggs than are incubator dry bulb thermometer or data logger temperature readings. Transponders in water-filled vials may also be more reliable than transponders implanted in the air cells of nonembryonated eggs due to their higher sensitivity to minute temperature fluctuations in the immediate vicinity of a rapidly growing and actively metabolizing broiler embryo. It can also be inferred that nonembryonated eggs may be used as calibrated eggs for the indirect determination of GH2O and gH2O of embryonated eggs, whereas the determination of KH2O necessitates the use of embryonated eggs.
ACKNOWLEDGMENTS We express our appreciation for the expert technical assistance of S. K. Womack of the Mississippi State University Poultry Science Department.
REFERENCES Ar, A., C. V. Paganelli, R. B. Reeves, D. G. Greene, and H. Rahn. 1974. The avian egg: Water vapor conductance, shell thickness, and functional pore area. Condor 76:153–158. Ar, A., and H. Rahn. 1978. Interdependence of gas conductance, incubational length, and weight of the avian egg. Pages 227–236 in Respiratory function in Birds, Adult and Embryonic. J. Piiper, ed. Springer, Berlin, Germany. Bamelis, F., B. Kemps, K. Mertens, B. De Ketelaere, E. Decuypere, and J. DeBaerdemaeker. 2005. An automatic monitoring of
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the hatching process based on the noise of the hatching chicks. Poult. Sci. 84:1101–1107. Decuypere, E., and V. Bruggeman. 2007. The endocrine interface of environmental and egg factors affecting chick quality. Poult. Sci. 86:1037–1042. De Smit, L., V. Bruggeman, M. Debonne, J. K. Tona, B. Kamers, N. Everaert, A. Witters, O. Onagbesan, L. Arckens, J. De Baerdemaeker, and E. Decuypere. 2008. The effect of nonventilation during early incubation on the embryonic development of chicks of two commercial broiler strains differing in ascites susceptibility. Poult. Sci. 87:551–560. Eren Ozcan, S., S. Andriessens, and D. Berckmans. 2010. Computational study of the heat transfer of an avian egg in a tray. Poult. Sci. 89:776–784. French, N. A. 1997. Modeling incubation temperature: The effects of incubator design, embryonic development, and egg size. Poult. Sci. 76:124–133. Janke, O., B. Tzschentke, and M. Boerjan. 2004. Comparative investigations of heat production and body temperature in embryos of modern chicken breeds. Avian Poult. Biol. Rev. 15:191–196. Janke, O., B. Tzschentke, J. Höchel, and M. Nichelmann. 2002. Metabolic responses of chicken and muscovy duck embryos to high incubation temperatures. Comp. Biochem. Physiol., Part A Mol. Integr. Physiol. 131:741–750. Joseph, N. S., A. Lourens, and E. T. Moran Jr. 2006. The effects of suboptimal eggshell temperature during incubation on broiler chick quality, live performance, and further-processing yield. Poult. Sci. 85:932–938. Lourens, A., R. Meijerhof, B. Kemp, and H. Van den Brand. 2011. Energy partitioning during incubation and consequences for embryo temperature: A theoretical approach. Poult. Sci. 90:516– 523. Lourens, A., H. van den Brand, R. Meijerhof, and B. Kemp. 2005. Effect of eggshell temperature during incubation on embryo development, hatchability, and posthatch development. Poult. Sci. 84:914–920. Parkhurst, C. R., and G. J. Mountney. 1988. Poultry meat and egg production. Van Nostrand Reinhold Co., New York, NY. Pulikanti, R., E. D. Peebles, and P. D. Gerard. 2011a. Physiological responses of broiler embryos to in ovo implantation of temperature transponders. Poult. Sci. 90:308–313. Pulikanti, R., E. D. Peebles, and P. D. Gerard. 2011b. Use of implantable temperature transponders for the determination of air cell temperature, eggshell water vapor conductance, and their functional relationships in embryonated broiler hatching eggs. Poult. Sci. 90:1191–1196. Renema, R. A., J. J. R. Feddes, K. L. Schmid, M. A. Ford, and A. R. Kolk. 2006. Internal egg temperature in response to preincubation warming in broiler breeder and turkey eggs. J. Appl. Poult. Res. 15:1–8. Romanoff, A. L. 1960. The Avian Embryo. The Macmillan Co., New York, NY. SAS Institute. 2003. SAS Proprietary Software Release 9.1. SAS Inst. Inc., Cary, NC. Steel, R. G. D., and J. H. Torrie. 1980. Principles and Procedures of Statistics: A Biometrical Approach. 2nd ed. McGraw-Hill Inc., New York, NY. Sturkie, P. D. 1965. Avian Physiology. Comstock Pub. Assoc., New York, NY. Tullett, S. G. 1982. A further study of changes in eggshell porosity with flock age in turkeys. Turkeys 29:25–26. Turner, J. S. 1990. The thermal energetics of an incubated chicken egg. J. Therm. Biol. 15:211–216. Visschedijk, A. H. J., H. Tazawa, and J. Piiper. 1985. Variability of shell conductance and gas exchange of chicken eggs. Respir. Physiol. 59:339–45. Washburn, K. W. 1990. Genetic variation in egg composition. Pages 781–804 in Poultry Breeding and Genetics. R. D. Crawford, ed. Elsevier, Amsterdam, the Netherlands. Wilson, H. R. 1991. Physiological requirements of the developing embryo: Temperature and turning. Pages 145–156 in Avian Incubation. S. G. Tullet, ed. Butterworth-Heinemann Ltd, Oxford, UK.