Poultry Science 2008 Elibol 1913 8

1913

2008 Poultry Science 87:19131918doi:10.3382/ps.2008-00014

Key words: egg weight, incubator position, hatchability, chick quality, broiler hatching egg

ABSTRACT Two experiments, which included 3 incu-bators, were carried out to investigate the effects of egg weight and position relative to incubator (setter) fan on embryonic mortality, second quality chicks, and fertile hatchability of broiler eggs. Three egg weight groups termed small (~62.4 g), average (~65.4 g), and large (~68.9 g) were set in either the incubator trolley most distant from the fan (FAR) or in the incubator trolley nearest the fan (NEAR) as would be the case during single-stage operation in this type of incubator. Fertile hatchability decreased in the large egg weight group due to increased percentage late embryonic mortality in experiment 1, and both percentage early and late em-bryonic mortality in experiment 2. Percentage late em-bryonic mortality and second quality chicks increased

and percentage fertile hatchability decreased for eggs in the FAR position in experiment 1 only. A significant interaction of incubator position egg weight group for late embryonic mortality, second quality chicks, and fertile hatchability was found in experiment 1, but only late embryonic mortality was so affected in experi-ment 2. Experiment 2 was conducted so that eggshell temperatures could be measured. Large eggs in the FAR position at transfer time (E 18) exhibited signifi-cantly higher eggshell temperatures than did the other groups probably because air velocity or air distribution was modified in the FAR position of the incubator and large eggs were most negatively influenced in the trol-ley in this position.

Effect of Egg Weight and Position Relative to Incubator Fan on Broiler Hatchability and Chick Quality1

O. Elibol* and J. Brake2

*Department of Animal Science, Faculty of Agriculture, University of Ankara, Ankara 06110, Turkey; and Department of Poultry Science, North Carolina State University, Raleigh 27695-7608

INTRODUCTIONLong-term genetic selection has resulted in an enor-

mous increase in the growth rate of broilers and evi-dently embryonic metabolism as Hulet and Meijerhof (2001) reported that heat production of eggs from modern broilers was substantially higher than that reported in 1960. Furthermore, previous studies have shown that large eggs did not hatch as well as small eggs (Landauer, 1967; Ogunshile and Sparks, 1995; French, 1997). Although there could be maternal ef-fects and fertility could differ between large and small eggs, French (1997) found that as egg mass increased thermal conductance did not increase proportionally, so larger eggs would be expected to have greater difficulty losing embryonic metabolic heat as well as greater dif-ficulty gaining heat during the initiation of incubation

(Lourens et al., 2005). When large and small eggs were incubated under similar conditions, large eggs exhib-ited higher temperatures during later incubation (Mei-jerhof and van Beek, 1993; Meijerhof, 2002). French (1994) found turkey hatchability to progressively de-crease with increasing egg size at high air temperature (38.5C) but that large eggs exhibited improved hatch-ability when incubated at a reduced air temperature (36.5C) during the second half of incubation mainly due to a decrease in late embryo mortality. Lourens et al. (2006) also observed that a higher heat production required a lower air temperature for large eggs from E 15 onward, which suggested that embryonic growth in large eggs increased at an increasing rate from E 15 onward. Adjusting incubator temperature avoided the adverse effects of high egg temperature during the last week of incubation on embryo development (Lourens et al., 2005).

Measurement of air temperature around eggs within incubators has shown that, depending on the design of the incubator, air temperatures can differ between 0.4 and 3.0C from the setpoint temperature (Kaltofen, 1969; Mauldin and Buhr, 1995; French, 1997). French (2001) concluded from his review of previous work that

Received January 9, 2008.Accepted May 19, 2008.1 The use of trade names in this publication does not imply en-

dorsement of the products mentioned nor criticism of similar prod-ucts not mentioned.

2 Corresponding author: [email protected]

2008 Poultry Science Association Inc.

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there was a strong correlation between the estimated total metabolic heat production of the eggs within the incubator and the air temperature around the eggs. The total metabolic heat production of eggs was depen-dent on the stage of embryo development, size of the eggs, and fertility of the eggs (number of live embryos) so that when either egg mass or fertility was increased during the latter stage of incubation so did the air tem-perature within the incubator (French, 2002).

The effectiveness of heat transfer from eggs to the surrounding incubator air and uniformity of egg tem-perature has been demonstrated to be mainly deter-mined by the rate of air flow over the eggs as well as difference between egg and air temperatures (Sother-land et al., 1987; Owen, 1991; French, 1997). French (2001) found variations of up to 1.2C within an incu-bator and that reducing this air temperature variation required a uniform air flow throughout the incubator.

Preliminary observations of distinct differences in fertile hatchability and chick quality between eggs placed in trolleys that were positioned close to and most distant from the incubator fan in a commercial hatchery created an interest in characterization of the details of this practical problem. The most obvious fac-tor to examine in detail was egg weight (size). There-fore, the present study was conducted to evaluate effect of egg weight and position (location) within an incuba-tor (setter) during incubation on embryonic mortality, second quality chicks, and apparent hatchability of fer-tile broiler eggs.

MATERIALS AND METHODSBroiler hatching eggs were produced from 2 multi-

house commercial flocks of Ross 308 feather-sexable strain females mated to Ross 344 males. Males and fe-males had been grown sex-separate in light-controlled facilities on an 8-h photoperiod and photostimulated at 21 wk of age. The feeding and BW programs were as generally described by Ross (1998). Experimental eggs were collected 4 times daily and stored for 2 d at 18C and 75% RH before setting. All remaining space in the incubator was filled with eggs from the same flock that had been stored from 2 to 5 d before setting.

In experiment 1, hatching eggs were obtained from a flock at 51 wk of age. A large number of eggs were weighed individually and divided into 3 egg weight groups termed small, average, and large. Mean egg weights were 62.5 0.12, 65.6 0.13, and 69.0 0.17 g for the 3 groups, respectively. Each egg weight group was randomly divided into 2 groups that were set in either the wheeled incubator trolley most distant from the fan (FAR) or in the trolley nearest the fan (NEAR) as would be the case for single-stage operation (Figure 1). In experiment 1, two setters were used as machine replicates. An incubation tray of 150 eggs constituted an experimental replicate. There were a total of 60 trays and all egg weight-position combinations were

represented by 10 trays each (5 trays per incubator) for a total of 9,000 eggs.

Experiment 2 was conducted as experiment 1 except that the eggs came from a second multihouse flock at 58 wk of age and mean egg weight was 62.4 0.16, 65.3 0.14, and 68.8 0.18 g for the small, average, and large groups, respectively. In experiment 2, only one setter was used and there were a total of 30 trays, thus, each egg weight-position combination was represented by 5 replicate trays each for a total of 4,500 eggs. Eggshell temperature was measured at E 18 of experiment 2 from 10 fertile eggs in each egg weight-position combi-nation group in the middle of both the NEAR and FAR dollies using an infrared ear thermometer (Braun Ear Thermometer Type 6013, The Gillette Company, Bos-ton, MA) by placing the sensor tip of the instrument, previously allowed to equilibrate with incubator tem-perature for 15 min, in direct contact with the equator of the egg (Leksrisompong et al., 2007). The middle dol-lies, which were full of eggs, were removed from the in-cubators immediately before the eggshell temperature measurements to make access to the eggs possible. The eggs in the FAR trolley were measured first.

The machines used were a Petersime Model 576 set-ter and a Model 192 hatcher. The setter air tempera-ture set points were 37.4 0.2C dry bulb and 28.9 0.2C wet bulb. The hatcher air temperature set points were 37.2 0.2C dry bulb and 30 0.2C wet bulb. In-cubators were monitored remotely by computer 6 times daily for proper operation. All experimental groups were placed in a single hatcher at the time of trans-fer on E 18 in both experiments, but relative positions within the machines were maintained. The general air flow and temperature patterns of this type of machine have been described (Van Brecht et al., 2003).

At the time of removing the chicks from the hatch-ers, all unhatched eggs were opened and examined macroscopically by a single experienced individual to determine percentage fertility and percentage embry-onic mortality [early (E 0 to 6), middle (E 7 to 17), late (E 18 to 21 plus pipped)]. Determination of fertility at hatching has a small margin of error, which determi-nation at any other time will also experience, but such small errors should be randomly distributed and not significantly affect the current results, based upon the experience of the authors. Percentage fertile hatchabil-ity was calculated as the number of first quality chicks hatched per 100 fertile eggs set. Percentage second quality chicks was calculated as the number that were not able to stand properly or chicks that showed visible signs of poor incubation conditions, such as improper-ly healed navels, per 100 fertile eggs. Eggs that were cracked were excluded from the analysis. The inci-dence of contaminated eggs was less than 1% (data not shown). The results were analyzed by ANOVA with the GLM procedure of SAS (SAS Institute Inc., 1990). The data of experiment 1 were initially analyzed as a 2 3 factorial with incubator as a block whereas egg weight

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group and incubator trolley position were the main effects in a randomized complete block design. There were no effects found due to incubator, so the data from the 2 incubators were combined and data of both exper-iments 1 and 2 were analyzed as a completely random-ized 2 3 factorial with egg weight group and incuba-tor position as the main effects. Between-tray variation (residual) was the source of the error term.

RESULTS AND DISCUSSIONFertile hatchability, percentage second quality

chicks, and percentage embryonic mortality as affected by egg weight and position relative to incubator fan in experiment 1 are shown in Table 1. Fertility averaged 94.1% and did not differ due to treatment (data not shown). Fertile hatchability decreased in the large egg weight group primarily due to an increased percentage late dead. Further, percentage late dead decreased as egg weight decreased across all 3 egg weight classes. Fertile hatchability was higher from the eggs in the NEAR position as compared with the FAR position largely due to significantly lower percentage late em-bryonic mortality and percentage second quality chicks. There were significant interactions of egg weight group position for percentage fertile hatchability, percent-age second quality chicks, and percentage late dead embryos.

Fertile hatchability, percentage second quality chicks, and percentage embryonic mortality as affected

by egg weight and position relative to incubator fan in experiment 2 are shown in Table 2. Fertility aver-aged 80.6% in this older flock but did not differ due to treatment (data not shown). Fertile hatchability was decreased significantly in the large egg weight group due to increased percentage early and late embryonic mortality. Fertile hatchability was only affected nu-merically by incubator position in experiment 2. There was also a significant interaction of incubator position egg weight for percentage late dead as in experiment 1. It was thought that the higher early deads in the large egg weight group was due to a slower initial rise in egg temperature (Lourens et al., 2005).

Hatchability of fertile eggs decreased with increas-ing egg weight as percentage late embryonic mortal-ity increased, as expected within a single batch of eggs from one maternal source, in both experiments (Tables 1 and 2). This result was consistent with previous re-ports (Landauer, 1967; Ogunshile and Sparks, 1995; French, 1997). An explanation for increased late em-bryonic mortality due to increasing egg size was that larger eggs would be expected to have greater difficulty initially achieving adequate embryonic temperature and then losing embryonic metabolic heat during later incubation (Lourens et al., 2005). The higher heat pro-duction and increased difficulty of heat dissipation in large eggs has been found to result in higher embryo temperatures in large eggs (Meijerhof and van Beek, 1993; Meijerhof, 2002). A 70-g egg has a 27% larger embryo but 8% less surface area for gaseous exchange

Figure 1. Design of the experiment showing the NEAR and FAR trolley relative to fan position and air flow. Within the trolley at each posi-tion, eggs were placed in the 3 egg weight groups (large, average, and small) to complete a 2 3 design.

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relative to a 55-g egg (Peebles and Brake, 1987) and evidently for heat gain or dissipation as well because thermal conductance does not change proportionally to egg mass (French, 1997).

The eggshell temperature data of experiment 2 in Table 3 suggested an interaction between increasing egg weight and incubator location with respect to in-creasing egg temperature at E 18. This would some-what explain the position egg weight interaction for percentage late deads in experiment 2. Given the con-

sistency of these particular incubators (Van Brecht et al., 2003), the significantly higher late dead embryos found in experiment 1, and the effects of increased fer-tility on egg temperature (French, 2002), it would be highly probable that the effects on egg temperature with respect to position and egg weight also occurred in experiment 1. Difference in air velocity was a prob-able explanation because it has been found to play an important role in heat transfer from eggs to their en-vironment. With greater air velocity, more heat will

Table 1. The effect of egg weight and position relative to incubator fan on fertile hatchability of first quality chicks, second quality chicks, and embryonic mortality in experiment 1

Variable

Position relative to fan

Egg weight1Position,

mean SELarge Average Small

(%)Fertile hatchability2 NEAR 91.00 1.033 88.90 1.033 90.56 1.033 90.15 0.60a

FAR 81.69 1.033 87.68 1.033 88.31 1.033 85.89 0.60bMean 86.34 0.73b 88.29 0.73a 89.44 0.73a

Second quality chicks2 NEAR 1.15 0.533 1.91 0.533 1.55 0.533 1.53 0.29bFAR 4.58 0.533 2.36 0.533 2.51 0.533 3.15 0.29aMean 2.86 0.36 2.13 0.36 2.03 0.36

Early dead NEAR 3.93 0.54 4.24 0.54 4.52 0.54 4.23 0.31FAR 5.37 0.54 5.10 0.54 4.35 0.54 4.94 0.31Mean 4.65 0.38 4.67 0.38 4.43 0.38

Mid dead NEAR 0.22 0.15 0.14 0.15 0.49 0.15 0.28 0.08FAR 0.57 0.15 0.43 0.15 0.28 0.15 0.43 0.08Mean 0.40 0.10 0.29 0.10 0.38 0.10

Late dead NEAR 3.00 0.523 3.96 0.523 2.25 0.523 3.07 0.30bFAR 6.87 0.523 3.79 0.523 3.57 0.523 4.74 0.30aMean 4.94 0.37a 3.87 0.37b 2.91 0.37c

a,bMain effect means SE for egg weight and position effects that possess different superscripts differ significantly (P < 0.05). There were 10 replicate trays of 150 eggs each used for each interaction mean divided equally among 2 similar incubators.

1Mean egg weights from 51-wk-old flock were 62.5, 65.6, and 69.0 g for the small, average, and large groups, respectively.2Calculated based upon the number of first quality or second quality chicks hatched per 100 fertile eggs set.3There was a significant (P 0.05) interaction of egg weight and position effects as shown by the respective interaction means.

Table 2. The effect of egg weight and position relative to incubator fan on fertile hatchability of first quality chicks, second quality chicks, and embryonic mortality in experiment 2

Variable


Egg weight1Position,

mean SELarge Average Small

(%)Fertile hatchability2 NEAR 81.73 1.45 86.06 1.45 87.09 1.45 84.96 0.84

FAR 78.82 1.45 84.54 1.45 86.43 1.45 83.26 0.84Mean 80.27 1.02b 85.30 1.02a 86.76 1.02a

Second quality chicks2 NEAR 1.04 0.32 0.51 0.32 0.94 0.32 0.83 0.18FAR 1.50 0.32 0.99 0.32 0.80 0.32 1.10 0.18Mean 1.27 0.22 0.75 0.22 0.87 0.22

Early dead NEAR 9.54 1.00 6.70 1.00 5.81 1.00 7.35 0.57FAR 10.41 1.00 7.32 1.00 7.66 1.00 8.46 0.57Mean 9.98 0.70a 7.01 0.70b 6.74 0.70b

Mid dead NEAR 1.26 0.21 0.99 0.21 0.32 0.21 0.86 0.12FAR 0.83 0.21 0.17 0.21 0.78 0.21 0.59 0.12Mean 1.05 0.15 0.58 0.15 0.55 0.15

Late dead NEAR 5.93 0.753 5.21 0.753 4.88 0.753 5.34 0.43FAR 8.10 0.753 5.98 0.753 3.21 0.753 5.76 0.43Mean 7.01 0.52a 5.59 0.52b 4.05 0.52b

a,bMain effect means SE for egg weight and position effects that possess different superscripts differ significantly (P < 0.05). There were 5 replicate trays of 150 eggs each used for each interaction mean set in a single incubator.

1Mean egg weights from 58-wk-old flock were 62.4, 65.3, and 68.8 g for the small, average, and large groups, respectively.2Calculated based upon the number of first quality or second quality chicks hatched per 100 fertile eggs set.3There was a significant (P 0.05) interaction of egg weight and position effects as shown by the respective interaction means.




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be removed from the eggshell during late incubation or accumulated by the egg during early incubation. At low air velocity, egg temperature has been found to in-crease. Egg temperature increased with increasing egg weight in the study of Meijerhof and Lourens (1999). This could explain the position egg weight interac-tions for percentage late deads as well as percentage fertile hatchability and second quality chicks because the more evident effects in experiment 1 were consis-tent with greater fertility (embryo heat) in the presence of similar egg mass. There have also been problems re-ported with chick quality from large eggs in the pres-ence of a lower air flow in an incubator, which could be consistent with the data of experiment 1. This means that problems with embryo temperature may not only be reflected in a reduced fertile hatchability but may also influence chick quality and posthatch growth and performance. Data from a recent study by Hulet et al. (2007) found that chicks hatched from eggs with a high eggshell temperature during the last 3 d of incubation exhibited a lower BW at 44 d of age than chicks hatched from eggs with lower eggshell temperature.

The present data support the suggestion of Meijer-hof (2002) that the design of incubators should focus primarily on providing a uniform embryo temperature for all eggs within an incubator with a maximum dif-ference in embryo temperature of 0.3C between indi-vidual eggs in the incubator as a goal. The results of the present research can extend the conclusion of Mei-jerhof (2002) to include more consistent temperatures for larger eggs in areas of lower air flow to improve heat gain or dissipation, fertile hatchability, and chick quality and decreasing late dead embryos. However, in practice this may be quite difficult because different air temperatures have been shown to be required to main-tain eggshell temperatures constant at 37.8C in small and large egg weight classes to obtain no significant differences in embryonic mortality and fertile hatch-ability (Lourens et al., 2006). One solution that has been explored would be to use these single-stage in-cubators on a multistage basis, placing the freshly set eggs in the hot locations in the incubator and using the cool locations for the eggs that were near the end of the incubation process. Improved fertile hatchability re-

sulted with larger old flock eggs but not smaller young flock eggs in such an experiment (Elibol and Trkolu, 2001), suggesting a discrete egg size threshold, consis-tent with the present and previous reports.

REFERENCES

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French, N. A. 2002. The critical importance of incubation temperature. Pages 1720 in Practical Aspects of Com-mercial Incubation. D. C. Deeming, ed. Ratite Conference Books, Lincolnshire, UK.

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Hulet, R. M., and R. Meijerhof. 2001. Real time incubation temperature control and heat production of broiler eggs. Poult. Sci. 80(Suppl. 1):128. (Abstr.)

Kaltofen, K. S. 1969. The effect of air movements on hatch-ability and weight loss of chicken eggs during artificial in-cubation. Pages 177190 in The Fertility and Hatchability of the Hens Egg. T. C. Carter and B. M. Freeman, ed. Oliver and Boyd, Edinburgh, UK.

Landauer, W. 1967. The hatchability of chicken eggs as in-fluenced by environment and heredity. Monograph 1 (Re-vised), Univ. Conn. Agric. Exp. Stn., Storrs, CT.

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Lourens, A., H. van den Brand, R. Meijerhof, and B. Kemp. 2005. Effect of eggshell temperature during incubation on embryo development, hatchability and post-hatch devel-opment. Poult. Sci. 84:914920.

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Table 3. Effect of egg weight and egg position relative to incubator fan on eggshell temperature at transfer (C) on E 18 in experiment 21

Egg weight


NEAR FAR

Large 38.7 0.1b 39.4 0.1aAverage 38.8 0.1b 38.8 0.1bSmall 38.6 0.1b 38.8 0.1b

a,bMeans SE that possess different superscripts differ signifi-cantly (P < 0.05).

1There were 10 fertile eggs from each of 5 trays in each cell mea-sured.

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SAS Institute Inc. 1990. SAS Users Guide: Statistics. Ver-sion 6 ed. SAS Institute Inc., Cary, NC.

Sotherland, P. R., J. R. Spotila, and C. V. Paganelli. 1987. Avian eggs: Barriers to the exchange of heat and mass. J. Exp. Zool. Suppl. 1:8186.

Van Brecht, A., J. M. Aerts, P. Degraeve, and D. Berckmans. 2003. Quantification and control of the spatiotemporal gradients of air speed and air temperature in an incuba-tor. Poult. Sci. 82:16771687.




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