2003 Poultry Science Association, Inc. Elevated Egg Holding-Room Temperature of 74 F (23 C) Does Not Depress Hatchability or Chick Quality D. V. Bourassa,* R. J. Buhr,1 and J. L. Wilson* *Poultry Science Department, The University of Georgia, Athens, Georgia 30602; and Poultry Processing and Meat Quality Research Unit, Richard B. Russell Agricultural Research Center, USDA, ARS, P.O. Box 5677, Athens, Georgia 30604-5677 Primary Audience: Breeder Managers, Hatching Egg Producers, Hatchery Managers, Researchers SUMMARY A series of experiments was conducted to determine the effect of holding broiler hatching eggs on the farm at 74 F (23 C) for 1 to 4 d prior to transport to the hatchery. After collection on each of 4 consecutive d, hatching eggs were distributed into two groups that were held at 66 or 74 F (19 to 23 C) and approximately 70% RH. On Day 5, all eggs were transported 10 miles to simulate transportation from the farm to the hatchery. Eggs were then placed into the hatchery egg cooler at 66 F (19 C), held overnight, and set the following morning after being allowed to warm at room temperature for 4 h. After 21 d of incubation, normal hatched chicks were counted, abnormal chicks were noted, and the hatch residue was opened and recorded. Additional eggs for each temperature group were set and opened after 48 h of incubation to determine if embryo somite count (an indication of embryonic development rate) was influenced by the egg holding temperatures. Somite counts after 48 h of incubation were the same for both temperature groups at 20.6 somites. Hatchability of fertile eggs differed between temperature groups by less than 0.1% [90.1% at 66 F (19 C) and 90.2% at 74 F (23 C)]. Elevating the farm holding-room temperature by 8 F (4 C) for broiler breeder eggs would conserve energy on the farm and reduce the potential for egg sweating during transport to the hatchery. Key words: broiler hatching egg, egg holding-room temperature, hatchability, somites 2003 J. Appl. Poult. Res. 12:1 6 DESCRIPTION OF PROBLEM To arrest further embryonic development and permit accumulation of large numbers of eggs for a synchronized hatch, broiler breeder hatching eggs are placed in coolers soon after collection. Farm egg coolers are typically set between 64 and 68 F (18 and 20 C), and eggs are held for 1 to 4 d prior to transport to the hatchery [1, 2]. Lower storage temperatures are recommended should the length of egg storage increase. For example, for eggs held less than 4 d, the egg room temperature should be 68 to 77 F (20 to 25 C). For eggs stored from 4 to 7 d, the temperature should be held at 61 to 63 F (16 to 17 C), and for eggs stored for more than 1 To whom correspondence should be addressed: jbuhr@saa.ars.usda.gov.
2 7 d, the temperature should be lowered to 50 to 54 F (10 to 12 C) [3]. Farm egg cooler temperatures between 64 and 68 F (18 and 20 C) are below the temperature that will arrest further embryonic development, known as physiological zero [commonly accepted to be 68 to 70 F (20 to 21 C)] and will also accommodate additions of warm eggs to the egg-holding cooler several times daily [4, 5]. A slightly higher temperature of 76 F has been reported for physiological zero when determined as the temperature that hatching eggs must be warmed above to reinitiate development [6]. Hatching eggs are ordinarily transported to the hatchery twice weekly. Increasing the egg holding temperature by a few degrees for 3 to 4 d may not have detrimental effects on hatchability and chick quality while decreasing the potential for egg sweating as well as lowering energy consumption on the farm. Egg sweating occurs when a cool egg is moved into a warm room, because moisture from the air will condense onto the cooler eggshell surface. Trucks that transport eggs from the farm to the hatchery may not be refrigerated. Environmental temperature and relative humidity could then be a factor as to whether or not the eggs sweat. If eggs are held at warmer temperatures, then sweating would be less likely to occur during transport. If an egg is moved from an egg cooler set at 68 F (20 C) and placed into a transport vehicle at 74 F (23 C), the egg will sweat if the RH is 76% or higher. On the other hand, if an egg is held at 74 F (23 C) and transported at 74 F (23 C) then sweating is not likely to occur unless the RH is 100%. It has been shown that recontamination of hatching eggs occurs during transport from the farm to the hatchery, and egg sweating may play an important role [7]. Sweating may be detrimental because as condensation collects on the egg, dust and bacteria may accumulate more easily, therefore giving rise to the heightened possibility of contamination [8]. Bacterial contamination of the albumen and yolk was demonstrated when eggs were permitted to sweat for 1, 2, or 5 h during 12 d of storage, whereas the contents of control unsweated eggs remained free from contamination [9]. Sweating may also be a potential source of cross-contamination of eggs from different farms during transport or within the hatchery. JAPR: Research Report Finally, a warmer temperature for egg holding at the breeder farm may have a beneficial effect on hatchability. After oviposition the blastoderm has initiated differentiation into the three embryonic germinal layers: ectoderm, mesoderm, and endoderm. An embryo that has developed these three layers is described as entering the gastrulation stage of development. Embryos that are in an early gastrulation stage do not hatch as well as those that are in more advanced stages of gastrulation [10]. If these early gastrulation embryos can continue to develop by holding the eggs at a higher temperature on the farm for 3 or 4 d, hatchability of these eggs may be improved. MATERIALS AND METHODS Hatching eggs were collected from a university broiler breeder flock at 29, 37, 43, and 47 wk of age (Trials 1 through 4, respectively) once per day in the afternoon. Hens were housed in an environmental-type building partitioned into floor pens that were two-thirds elevated slats and one-third litter. Hens were provided a typical corn-soybean meal breeder layer diet in mash form (2,860 kcal ME/kg and 16% CP). Each day, eggs from each egg flat that were cracked, dirty, or misshapen were discarded, and the remaining eggs were evenly distributed into four 88-egg racks and labeled duplicate racks A and B(n= 88 eggs/rack). Two racks (one A and one B) were held in a cooler at 74 ± 2 F (23 ± 1 C) for the experimental groups. The other two racks were held at 66 ± 2 F (19 ± 1 C) and served as the control groups. To monitor air temperature in both egg coolers, data loggers were used to record temperature and RH every minute, directly above the eggs [11]. We used a total of 5,632 broiler breeder eggs (704/treatment per trial) in the four trials of this experiment. For each trial, eggs were collected for 4 consecutive d between 1400 and 1600 h. On Day 5, the eggs were loaded into an unrefrigerated vehicle and driven 10 miles to simulate transportation from the farm to the hatchery. All eggs were then held at 66 F (19 C) overnight, and on Day 6 they were allowed to warm at room temperature for 4 h and then set in an incubator [12] operating at 99.5 F (23 C) and 55% RH, with turning every hour. One rack from each of the two treatment groups was placed on each
BOURASSA ET AL.: EGG HOLDING TEMPERATURE AND HATCH 3 TABLE 1. Infertility and hatchability of eggs set, hatchability of fertile eggs, and abnormalities of embryos and chicks from eggs held at 66 and 74 F (19 and 23 C) for 1 to 4 d prior to setting A Infertility of Hatch of eggs Hatch of Embryo & chick Holding eggs set set fertile eggs abnormalities C temperature Trials B (%) (%) (%) (%) 66 F (19 C) 1, 2, 3, 4 8.0 79.2 86.4 27.1 1, 3, 4 8.6 82.1 90.1 38.8 74 F (23 C) 1, 2, 3, 4 7.6 79.9 86.5 20.3 1, 3, 4 7.8 83.1 90.2 27.4 Probability P 1, 2, 3, 4 0.8370 0.6641 0.9503 0.1549 1, 3, 4 0.6530 0.5394 0.9368 0.1884 A n = 704 eggs set per trial for each egg holding temperatures. B In Trial 2 a lack of turning from Days 11 to 14 of incubation resulted in decreased hatchability. C Percentage of late dead embryos and cull chicks. level of the setter buggy, and treatment groups were alternated from the front and back of the incubator. At 11 d of incubation, eggs were candled, and all nonviable eggs were removed and broken out to determine infertile, positive development, and early dead embryos. At transfer (18 d), the eggs were candled again to determine middle dead, and viable eggs were moved into one hatcher. When the chicks hatched at 21 d, normal chicks were counted, abnormal chicks were noted, and the entire remainder was broken out and recorded. Typical abnormalities entailed anterior and posterior duplications, brain hernias, spinabifida, or malpositions. Recorded abnormalities for hatched chicks were poor umbilical closure, weak legs, and head anomalies. FIGURE 1. Hatchability of eggs set and hatchability of fertile eggs with increasing flock age. Somite Counts In addition to the previous stated procedures, 120 extra eggs were collected and held for both temperature groups following the same procedures described. After 48 h of incubation, these eggs were placed into a refrigerator at 35 F(2 C) to rapidly arrest development and then were opened for somite count determination over the following 3 d. Somites were counted to determine whether eggs held at the higher temperature showed a corresponding accelerated development compared to the control. Each egg was opened into a bowl half filled with water, and the embryo was stained with neutral red [13]. The vitelline membrane over the embryo was removed, and additional stain was applied. Individual somites from the auditory pit to the last complete somite were counted under a dissection microscope and recorded. Forty-eight hours of incubation was chosen because there are adequate number of somites to count at this age. Statistical Analysis Hatchability of eggs set, hatchability of fertile eggs, and somite counts were analyzed with the general linear model procedure of SAS software [14], and the percentage of fertile eggs and percentage of abnormalities for embryos and chicks were analyzed by the chi-squared test procedure. The experimental unit was a rack of 88 eggs, with two racks per treatment per day. Sources of variation in the model included the following main effects: egg holding temperature
4 66 or 74 F (19 or 23 C), day of egg collection (1 through 4), trials (1 through 4), and duplicate egg racks (A or B). There was no significance attributed to the day of egg collection or duplicate egg racks (A and B) within or between trials; therefore the data were combined and reanalyzed by holding temperature treatment and trial. There was a significant effect in Trial 2 on hatchability due to the accidental absence of turning during incubation on Days 11 through 14 (turner remained off following candling). Therefore, the results were analyzed and are presented including and excluding Trial 2. For all analyses, significance was determined at P < 0.05. RESULTS AND DISCUSSION The results of these four trials demonstrated that broiler hatching eggs can be safely held at 74 F (19 C) on the farm (8 For4 C higher than is commonly recommended) for 1 to 4 d prior to transport to the hatchery and maintain high hatchability and chick quality. There were no significant differences in hatchability in the four trials for eggs collected on Days 1 to 4, and therefore the data have been presented combined for day of egg collection for each trial. Hatchabilities of fertile eggs were 92.9, 75.3, 87.1, and 90.7% for Trials 1 to 4, respectively (Figure 1). A lack of turning in the setter from Days 11 to 14 of incubation in Trail 2 most likely resulted in the corresponding reduction in hatchability [15]. However, there were no significant differences in hatchability between the two egg holding temperature groups. Figure 1 shows the hatchability of fertile eggs as the flock age increased over the four trials. For each trial, the values for the control and treatment groups overlapped and responded in the same pattern over time. The results are presented in Table 1, with and without Trial 2, because of the depressed hatchability in this trial compared to the other three trials. With Trial 2 included, the hatchability of fertile eggs was 86.4% for eggs held at 66 F (19 C) compared to 86.5% for eggs held at 74 F (23 C). The average hatchability of fertile eggs with Trial 2 excluded was 90.1% for eggs held at 66 F (19 C) compared to 90.2% for eggs held at 74 F (23 C). The percentages of infertile eggs set did not differ among egg holding temperature groups JAPR: Research Report FIGURE 2. Percentage infertile of eggs set and abnormalities of embryos and hatched chicks with increasing flock age. and were 1.6, 6.5, 8.9, and 14.1% for Trials 1 through 4, respectively (Figure 2). This trend of the breeder flock from 29 to 47 wk of age could be attributed to the nature of the study for which the eggs were collected (rooster mating behavior). The addition of spike roosters had not occurred. It is important to note that detected infertility did not differ between the two egg holding temperature groups (Figure 2), therefore large numbers of very early dead embryos or blastoderms that failed to reinitiate development were not incorrectly classified as infertile. This distinction is important when reviewing the impact of egg holding temperature and storage length from the literature. Typically as egg storage length increases, there are associated increases in apparent infertility [16]. The increased infertility from 29 to 47 wk of age in this study resulted in corresponding reductions in hatchability of eggs set as the four trials progressed, but there were no differences between egg holding temperature groups (Figure 1). Hatchabilities of eggs set decreased as flock age increased for Trials 1 to 4 from 91.4, 70.4, 79.0, and 77.5% (Figure 1). The incidence of embryonic and chick abnormalities also did not significantly differ between the two egg holding treatment groups or among the four trials (Figure 2). Combining embryo and chick abnormalities and when expressed as a percentage of total number of dead embryos and cull chicks, there were numerically fewer abnormalities from the eggs held at 74 F (23 C; 20.3%) than those held at 66 F (19 C;
BOURASSA ET AL.: EGG HOLDING TEMPERATURE AND HATCH 5 27.1%; Table 1). Therefore, the increased holding temperature of 8 F (4 C) did not induce elevated levels of embryo or chick abnormalities. Somite counts after 48 h of incubation were also similar for the two egg holding temperature groups at 20.6 somites per egg. The number of somites after 48 h of incubation for eggs held at 66 F (19 C) was 20.3 somites and for eggs held at 74 F (23 C) was 20.9 somites. A maximum somite count of 25 and a minimum of 16 were counted for the 60 embryos in each egg holding temperature group. Elevation of egg holding temperature by 8 F for 1 to 4 d was not sufficient to result in significant acceleration of somite formation after 48 h of incubation. However, when eggs from Single Comb White Leghorn hens were left in the nest for 6 to 7 h and then stored at 56.8 F (13.8 C) for 4 d, preincubation embryonic development was advanced by 1.22 Eyal-Giladi and Kochav stages [17]. Similarly, when the eggs from broiler breeder hens were allowed to remain in the nest for 6.5 h compared to those collected after 1.5 h, advance- ment in embryonic development of 1.29 Eyal- Giladi and Kochav stages was reported [18]. This postlay development was attributed to the elevated environmental temperatures [from 80 to 86 F (27 to 30 C)] or possible partial incubation of the eggs by the hens during the 6.5-h period. The pre-egg collection advancement in development from Single Comb White Leghorns, however, was not sufficient to alter hatchability (95.9%) [17]. In the present report, embryos were not evaluated prior to setting, and, therefore, it is not known if after 1 to 4 d of holding eggs at 74 F (23 C) there would have been a detectable advancement in development. Future research will attempt to quantify the actual energy savings that result by elevating the breeder farm egg cooler temperature 8 F to 74 F (23 C). The role that egg sweating plays in eggshell surface contamination during transport from the farm to the hatchery will also be evaluated. Variability in breeders strains, age of breeders, and the season of the year may all impact the quantitative benefits related to hatchability in response to elevated holding temperatures. CONCLUSIONS AND APPLICATIONS 1. Holding broiler hatching eggs in the farm egg cooler for 1 to 4 d at 74 F (23 C) vs. 66 F (19 C) did not alter hatchability or incidence of embryo or chick abnormalities. 2. It may be possible to save refrigeration energy costs by increasing farm egg cooler temperatures by 8 F (4 C) and still maintain high hatchability. 3. Holding broiler hatching eggs on the farm for 1 to 4dat74 F (23 C) vs. 66 F (19 C) did not advance embryo somite counts after 48 h of incubation or apparently alter incubation length. 4. Increasing on-farm broiler hatching egg holding temperature to 74 F (23 C) may prevent egg sweating during transport and thereby decrease the incidence of surface bacterial contamination. REFERENCES AND NOTES 1. Peterson Farms www.petersonfarms.com 2. Cobb 500 Breeder Management Guide. Cobb-Vantress, Inc., 1998. 3. Meijerhof, R. 1992. Pre-incubation holding of hatching eggs. World s Poult. Sci. J. 48:57 68. 4. Edwards, C. L. 1902. The physiological zero and the index of development for the egg of the domestic fowl. Am. J. Physiol. 6:351 397. 5. Proudfoot, R. G., and H. W. Hulan. 1982. Care of hatching eggs. Publication 1573/E, Agriculture Canada, Ottawa, ON, Canada. 6. Funk, E. M., and H. V. Biellier. 1944. The minimum temperature for embryonic development in the domestic fowl (Gallus domesticus). Poult. Sci. 23:538 540. 7. Berrang, M. E., J. F. Frank, R. J. Buhr, J. S. Bailey, N. A. Cox, and J. M. Mauldin. 1997. Microbiology of sanitized broiler hatching eggs through the egg production period. J. Appl. Poult. Res. 6:298 305. 8. Forsythe, R. H., J. C. Ayres, and J. L. Radlo. 1953. Factors affecting the microbiological population of shell eggs. Food Technol. 7:49 56. 9. Fromm, D., and P. H. Margolf. 1958. The influence of sweating and washing on weight loss, bacteria contamination and interior physical quality of 12-day old shell eggs. Poult. Sci. 37:1273 1279. 10. Hays, F. A., and C. Nicolaides. 1934. Variability in development of fresh-laid hen eggs. Poult. Sci. 13:74 90. 11. Sensitech Hatware. 1997. Ryan HAT Version 1.9. Sensitech, Redmond, WA.
6 JAPR: Research Report 12. NatureForm, NMC 2000, Jacksonville, FL. 13. Neutral Red. For 100 ml of solution, mix 0.85 g NaCl, 0.042 g KCl, 0.025 g CaCl, and 100 ml distilled water. Add 0.068 g Neutral Red (Sigma # N6634). Mix. Jackie Pisenti, University of California-Davis, jmpisenti@ucdavis.edu. 14. SAS Institute. 1994. SAS/STAT Guide for Personal Computers. Version 7 Edition. SAS Institute Inc., Cary, NC. 15. Wilson, H. R. 1991. Physiological requirements of the developing embryo: Temperature and turning. Pages 145 156 in Avian Incubation. S. G. Tullett, ed. Butterworth-Heinemann, Northants, England. 16. Landauer, W. 1967. The hatchability of chicken eggs as influenced by environment and heredity. Monograph 1 (rev.). Storrs Agricultural Experiment Station, University of Connecticut, Storrs, CT. 17. Fasenko, G. M., F. E. Robinson, J. G. Armstrong, J. S. Church, R. T. Hardin, and J. N. Petitte. 1991. Variability in preincubation embryo development in domestic fowl. 1. Effects of nest holding time and method of egg storage. Poult. Sci. 70:1876 1881. 18. Fasenko, G. M., J. L. Wilson, F. E. Robinson, and R. T. Hardin. 1999. Effects of length of egg nest holding time and high environmental temperatures on prestorage embryonic development, survival, and hatchability of broiler breeders. J. Appl. Poult. Res. 8:488 492.