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Relationship Between Shell Porosity, Shell Thickness, Egg Weight Loss, and Embryonic Development in Japanese Quail Eggs1
Relationship Between Shell Porosity, Shell Thickness, Egg Weight Loss, and Embryonic Development in Japanese Quail Eggs1 F.N.K. SOLIMAN,2 R. E. RIZK,3 and J. BRAKE4-5
and Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-7608 ABSTRACT Japanese quail eggs that hatched (H) or pipped (PIP) exhibited less weight loss through 15 d of incubation than did eggs that died late (LD), whereas eggs containing early dead (ED) embryos exhibited the greatest weight loss. The pore concentration at the large end of each egg was greatest in H eggs when compared with all other types. The pore concentration at the equator was greatest in H eggs and least in the eggs of the ED embryos. All other egg types lay statistically between these two types with regard to equator porosity. The small end pore concentration was similar in H, INF, and LD eggs and in the LD, PIP, and ED eggs. The least number was exhibited by the ED eggs and most by the H eggs. The thinnest shells at the small end were exhibited by H eggs, whereas thicker small end shells were exhibited by ED, LD, and PIP egg types. No differences were observed at the large end or equator. The data suggest that ED eggs exhibit excessive weight loss even though shell porosity was lower and shell thickness was similar to other egg types. This suggests that some functional component of the egg such as the shell membrane or albumen may contribute to this excessive weight loss. A similar statement can be made for LD eggs, which experienced greater weight loss through 15 d than did PIP or H eggs. (Key words: Japanese quail, weight loss, porosity, shell thickness, embryo mortality) 1994 Poultry Science 73:1607-1611
properties of the eggshell. Egg weight loss has been used to estimate vital gas The success of embryonic development exchange (Paganelli et at, 1978; Rahn et ah, in various types of poultry has been 1979) and has been correlated with the related to the functional and structural rate of embryonic metabolism and development (Rahn and Ar, 1980; Burton and Tullett, 1983). Vital gas diffusion occurs through thousands of microscopic Received for publication March 21, 1994. pores, which are the only means of Accepted for publication June 2, 1994. 1 The use of trade names in this publication does not communication between the external enimply endorsement by the North Carolina Agricul- vironment and the chorioallantoic memtural Research Service of the products mentioned, nor brane. The length of the pores and, criticism of similar products not mentioned. therefore, the diffusive pathway, is equal 2 Alexandria University. to shell thickness. Thicker shells produce 3 Animal Production Research Institute. greater resistance to gaseous diffusion 4 North Carolina State University. 5 To whom correspondence should be addressed. (Rahn et ah, 1979). INTRODUCTION
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Downloaded from http://ps.oxfordjournals.org/ at H.E.C. Bibliotheque Myriam & J. Robert Ouimet on June 14, 2015
Faculty of Agriculture, Alexandria University, Alexandria, Egypt, Animal Production Research Institute, Agricultural Research Center, Dokki, Egypt
1608
SOLIMAN ET AL.
MATERIALS AND METHODS The study was conducted at the Poultry Research Center, Faculty of Agriculture, Alexandria University, Egypt. A total of 1955 Japanese quail eggs was obtained from birds housed as two females and one male per cage. The eggs were incubated in forced draft incubators at 10 m above sea level. The dry bulb and wet bulb temperatures were 37.5 and 30 C, respectively. The eggs were weighed at 0, 5,10,15, and 18 d of incubation. Dry chick weights from hatched (H) eggs were obtained at 18 d. Percentage egg weight loss was calculated on an individual egg basis for each incubation interval. At 18 d of incubation, all unhatched eggs were opened and examined macroscopically for evidence of stage of embryonic development. Egg types were classified as infertile (INF), early dead
embryos that died before 6 d (ED), late dead embryos that died between 6 d and pipping (LD), and embryos that died after external pipping (PIP). Egg contents were removed from a representative portion of the unhatched and hatched eggshells leaving the shell membranes intact. Methylene blue (.5 g of 89% dye/L of 70% ethanol) was pipetted into the shell and allowed to diffuse through the shell to visualize the pores externally (Board and Halls, 1973). Pores were counted under 2.5x power magnification and expressed as number per .25 cm2. Four areas within each of the three eggshell regions, large end (LE), equator (EQ), and small end (SE), were counted and averaged (Peebles and Brake, 1985). Shell thickness with membrane intact (STWM) was measured in three areas of each region with a micrometer capable of .01 mm accuracy and averaged. Data were subjected to analysis of variance using the General Linear models (GLM) procedure of SAS® software (SAS Institute, 1989). The error term was based upon variation among eggs. Differences among means were partitioned using Duncan's multiple range procedure (Duncan, 1955). Statements of statistical significance were based upon P < .05. RESULTS AND DISCUSSION Percentage egg weight loss during various incubation intervals are shown in Table 1. Initial egg weight did not vary among the various egg types. The ED egg
TABLE 1. Egg weight loss during various incubation intervals of Japanese quail eggs in relation to embryonic mortality
Egg type Infertile Hatched Early dead Late dead Pipped X SD
Initial egg weight
n 686 750 116 323 80 1,955
(g) 10.92 10.92 10.73 10.86 10.90 10.86 .03
Days of incubation 0 to 5
5 to 10
10 to 15
0 to 15
15 to 18
0 to 18
2.19d 23.31M 2.84= 2.68= 8.49b 7.90 .69
15.29d 34.63M 18.47= 16.19<* 19.61b 20.83 .73
- (%) 3.63b= 3.34=d 4.30" 3.80b 3.20d 3.66 .04
5.15b 4.33< 6.06» 5.40" 4.68= 5.12 .06
4.30b 3.65= 5.27a 4.31b 3.24<» 4.15 .05
13.10b 11.32= 15.63^ 13.51b 11.12' 12.94 .12
"-^Means in the same column with no common superscript differ significantly (P < .05). J Values based on weight of recently hatched chicks relative to initial egg weight.
Downloaded from http://ps.oxfordjournals.org/ at H.E.C. Bibliotheque Myriam & J. Robert Ouimet on June 14, 2015
Increased eggshell permeability has been associated with increased early and late embryonic mortality in quail (Peebles and Marks, 1991). Low pore numbers have been associated with increased embryonic mortality in chickens (Peebles and Brake, 1985). Similarly, increased shell thickness (pore length) has been found to be associated with early embryonic mortality in chickens (Peebles and Brake, 1985). The purpose of this study was to more clearly define the relationships between egg weight loss, eggshell porosity, eggshell thickness, and embryonic mortality in Japanese quail.
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EGGSHELL CHARACTERISTICS AND QUAIL EMBRYOLOGY TABLE 2. Correlation coefficients between initial Japanese quail egg weight, egg weight at 5, 10, and 15 d of incubation, and percentage egg weight loss to 15 and 18 d of incubation in relation to embryonic mortality Egg weiight
Percentage weight loss
Egg type
5 d
10 d
15 d
0 to 15 d
0 to 18 d
Hatched Early dead Late dead Pipped
.975" .977" .984" .988"
.957" .893" .932" .967**
.932" .817" .874" .889"
.384** .155 .176** .018
.557" .152 .270" .555"
During the 15- to 18-d period, which type exhibited the greatest weight loss during the incubation intervals of 0 to 5 d, includes internal and external pipping and 5 to 10 d, 10 to 15 d, and 0 to 15 d. hatching, the greatest weight loss was Conversely, both the H and PIP egg types exhibited by H eggs followed by PIP eggs exhibited the lowest weight losses during (Table 1). The ED eggs exhibited greater the same incubation intervals. The LD and weight loss than INF eggs with LD eggs INF egg types were generally intermediate intermediate. Thus, embryos that progduring these incubation intervals. These ressed the most lost the most weight results agree with the data of El-Turky et (water) during the final phase of developal. (1981) and Peebles and Marks (1991), ment. Embryos that died before this time who found that ED eggs exhibited a did not exhibit this increase in weight loss, higher rate of water loss through 14 d of which suggests that the increased weight incubation. This suggests that early deaths loss observed was due to increased emare a result of excessive weight loss in bryonic respiration (water production) as Japanese quail eggs. Vick et al. (1993) the embryo approached and passed plareported early deaths to be due to low teau metabolism. A deficiency of water weight loss of eggs from young broiler loss would prevent an influx of oxygen breeder flocks with thick eggshells and and thus asphyxiate the embryo. albumen but the opposite was true for Overall weight loss during 18 d of older flocks, which exhibited thin egg- incubation increased in the following shells and albumen (Brake et al, 1993). The ascending order; LD and INF, ED, PIP, absence of major differences in shell and H (Table 1). For H and PIP eggs, this thickness suggests that poor albumen clearly reflected the advanced stage of quality, which permits excessive weight embryonic development compared with loss, or some other physical attribute of the LD egg type. The high weight loss of the egg, may be involved in early deaths the ED eggs is difficult to explain but may, in Japanese quail eggs. in part, be the result of unregulated water From inspection of Table 1, weight loss loss due to some functional difference seemed to be greatest from 5 to 10 d and such as poor albumen quality or other 15 to 18 d of incubation. In contrast, physical attribute of the egg. Although turkey egg weight loss has been character- embryonic death may alter tne rate of gas ized as highest during the first 7 d exchange and weight loss (Tyler and (Christensen and McCorkle, 1982), where- Simkiss, 1959; Kayar et al, 1981), the as the chicken egg seems to have its consistent differences in weight loss belowest weight loss during the middle tween egg types found in this study and period of incubation compared with that of Peebles and Marks (1991) suggests higher weight losses at the beginning and that differences in rate of water loss may end of incubation (Brake et al, 1993; Vick be causally related to embryonic mortality. et al, 1993). This suggests that Japanese The correlation coefficients between iniquail eggs exhibit a slightly different tial egg weight and egg weight at 5, 10, pattern of weight loss than do chicken or and 15 d of incubation are shown in Table turkey eggs. A direct comparison under 2. Highly significant correlation coeffithe same conditions is needed to clarify cients were evident at all times but the this point. magnitude of the coefficient decreased
Downloaded from http://ps.oxfordjournals.org/ at H.E.C. Bibliotheque Myriam & J. Robert Ouimet on June 14, 2015
" P <, .01.
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SOLIMAN ET AL. TABLE 3. Eggshell pore concentration in different eggshell regions of Japanese quail eggs exhibiting different stages of embryonic development
Egg type
Large end
Equator
Small end 2
(n/.25 cm ) 104 103 76 88 54 425
7.57b 8.56a 7.01 b 7.02b 7.43b 7.52 .08
6.61 ab 6.93* 5.72c 6.24abc 5.98bc 6.30 .08
7.23b 7.91a 6.00c 6.76b 6.87b 6.95 .08
7.14 7.80 6.24 6.67 6.76 6.92 .22
"-"Means in the same column with no common superscript differ significantly (P < .05).
with day of incubation reflecting increasing egg to egg variability. Percentage weight loss was significantly correlated with initial egg weight for H and LD egg types from 0 to 15 d and for H, LD, and PIP egg types from 0 to 18 d of incubation. This probably reflects a less variable weight loss in those egg types that permitted further development than that observed in the ED egg type. This may be due to physical attributes of the egg contributed by the dam or active participation by the embryo. Eggshell pore concentration of various egg types is shown in Table 3. Porosity at the LE was greater in the H egg type than for all other egg types. Peebles and Brake (1985) found the same for broiler hatching eggs. Greater porosity over the air space has been determined to be beneficial to development because the diffusion in this region could theoretically account for 80% of respiratory exchange (Romijn, 1950). A
deficiency in this area has been linked to late embryonic mortality in turkeys (Christensen, 1983). Similarly, H eggs exhibited greater porosity at the EQ than LD, PIP, or INF eggs. The ED eggs exhibited fewer pores at the EQ than all other types. Visschedijk (1968) suggested that EQ pores could compensate for lack of LE pores, but this did not occur in the other egg types in this study. Differences in observed porosity in the SE region may be related to the eggshell thinning observed in this region due to calcium mobilization, which may have made some small pores more passable to the dye used. Eggshell thickness of various egg types is shown in Table 4. No differences were found in the LE or EQ regions. At the SE, the thinnest shells were found in the H eggs. The PIP, LD, and ED egg types exhibited the thickest shells at the SE and INF eggs were intermediate. The SE data
TABLE 4. Eggshell with membrane thickness in different eggshell regions of Japanese quail eggs exhibiting different stages of embryonic development Egg type
n
Large end
Equator
, Infertile Hatched Early dead Late dead Pipped X
SD :
104 103 76 88 54 425
.22 .23 .23 .22 .23 .22 .09
.23 .23 .23 .23 .24 .23 .09
Small end
X
.24bc .24c .25 ab .25" .26a .25 .12
.23 .23 .24 .23 .24 .23 .06
,,
Means in the same column with no common superscript differ significantly (P < .05).
Downloaded from http://ps.oxfordjournals.org/ at H.E.C. Bibliotheque Myriam & J. Robert Ouimet on June 14, 2015
Infertile Hatched Early dead Late dead Pipped 5c SD
EGGSHELL CHARACTERISTICS AND QUAIL EMBRYOLOGY
REFERENCES Board, R. G., and N. A. Halls, 1973. The cuticle: a barrier to liquid and particle penetration of the shell of the hen's egg. Br. Poult. Sci. 14:69-79. Brake, J., T. J. Walsh, and S. V. Vick, 1993. Hatchability of broiler eggs as influenced by storage and internal quality. Zootech. Int. January:30, 32-37, 40-41. Burton, F. G., and S. G. Tullett, 1983. A comparison of the effect of eggshell porosity on the respiration and growth of domestic fowl, duck
and turkey embryos. Comp. Biochem. Physiol. 75A:167-174. Christensen, V. L., 1983. Distribution of pores on hatching and non-hatching turkey eggs. Poultry Sci. 62:1312-1316. Christensen, V. L., and F. M. McCorkle, 1982. Turkey egg weight losses and embryonic mortality during incubation. Poultry Sci. 61:1209-1213. Coleman, J. R., S. M. Dewitt, P. Batt, and A. R. Terepka, 1970. Electron probe analysis of calcium distribution during active transport in chick chorioallantoic membrane. Exp. Cell. Res. 63:216-220. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. El-Turky, A. I., Y. M. Kader, N. Z. Mohanna, L. Goher, and I. F. Sayed, 1981. Certain factors affecting rate of weight loss in incubated eggs. Agric. Res. Rev. (Cairo) 59:29-43. Kayar, S. R., G. K. Synder, G. F. Birchard, and C. P. Black, 1981. Oxygen permeability of the shell and membranes of chicken eggs during development. Respir. Physiol. 46:209-221. Paganelli, C. V., R. A. Ackerman, and H. Rahn, 1978. The avian egg: In vivo conductances to oxygen, carbon dioxide, and water vapor in late development. Pages 212-218 in: Respiratory Function in Birds, Adult and Embryonic. J. Piiper, ed. Springer-Verlag, Berlin, Germany. Peebles, E. D., and J. Brake, 1985. Relationship of eggshell porosity to stage of embryonic development in broiler breeders. Poultry Sci. 64: 2388-2391. Peebles, E. D., and J. Brake, 1986. The role of the cuticle in water vapor conductance by the eggshell of broiler breeders. Poultry Sci. 65: 1034-1039. Peebles, E. D., and H. L. Marks, 1991. Effect of selection for growth and selection diet on eggshell quality and embryonic development in Japanese quail. Poultry Sci. 70:1474-1480. Rahn, H., and A. Ar, 1980. Gas exchange of the avian egg: time, structure and function. Am. Zool. 20: 477-484. Rahn, H., A. Ar, and C. V. Paganelli, 1979. How bird eggs breathe. Sci. Am. 240:46-55. Romijn, C, 1950. Foetal respiration in the hen. Gas diffusion through the eggshell. Poultry Sci. 29: 42-51. SAS Institute, 1989. SAS® User's Guide, Statistics. Version 5. SAS Institute Inc., Cary, NC. Tyler, C, and K. Simkiss, 1959. Studies on eggshells. XII. Some changes in the shell during incubation. J. Sci. Food Agric. 10:611-615. Vick, S. V., J. Brake, and T. J. Walsh, 1993. Effect of incubation humidity and flock age on hatchability of broiler hatching eggs. Poultry Sci. 72: 251-258. Visschedijk, A.H.J., 1968. The air space and embryonic respiration. 1. The pattern of gaseous exchange in the fertile egg during the closing stages of incubation. Br. Poult. Sci. 9:173-194.
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are consistent with the removal of calcium from the eggshell for bone formation during the final stages of embryonic development in H eggs. This is consistent with the fact that the chorioallantoic membrane, which mobilizes calcium from the shell (Coleman et al, 1970), would be most active in the region it remained in contact with the longest. Optimum hatchability has been reported to depend upon a proper relationship between pore concentration and pore length (shell thickness), which provides the proper water (weight) loss for optimum growth (Burton and Tullett, 1983; Christensen, 1983). This is consistent with the data of H, PIP, LD, and ED egg types, for which higher porosity and thinner shells were associated with successful incubation, some of which must be associated with late stage mobilization of eggshell calcium. However, weight loss did not follow the same trend. There was paradoxically higher weight loss prior to 15 d in ED and LD egg types than in H eggs. This suggests that high weight loss was the cause and not the result of embryonic mortality. This is supported by the INF eggs data, which were generally intermediate between H eggs and other types. This suggests either some dysfunction in pore structure and size or an as yet undefined role of albumen quality, cuticle, or shell membrane function, assuming that storage and incubation are equal. This is similar to previous results with eggs from older broiler breeder flocks, which are known to have poor albumen quality and a thinner cuticle (Peebles and Brake, 1986; Vick et al, 1993).
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and Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27695-7608 ABSTRACT Japanese quail eggs that hatched (H) or pipped (PIP) exhibited less weight loss through 15 d of incubation than did eggs that died late (LD), whereas eggs containing early dead (ED) embryos exhibited the greatest weight loss. The pore concentration at the large end of each egg was greatest in H eggs when compared with all other types. The pore concentration at the equator was greatest in H eggs and least in the eggs of the ED embryos. All other egg types lay statistically between these two types with regard to equator porosity. The small end pore concentration was similar in H, INF, and LD eggs and in the LD, PIP, and ED eggs. The least number was exhibited by the ED eggs and most by the H eggs. The thinnest shells at the small end were exhibited by H eggs, whereas thicker small end shells were exhibited by ED, LD, and PIP egg types. No differences were observed at the large end or equator. The data suggest that ED eggs exhibit excessive weight loss even though shell porosity was lower and shell thickness was similar to other egg types. This suggests that some functional component of the egg such as the shell membrane or albumen may contribute to this excessive weight loss. A similar statement can be made for LD eggs, which experienced greater weight loss through 15 d than did PIP or H eggs. (Key words: Japanese quail, weight loss, porosity, shell thickness, embryo mortality) 1994 Poultry Science 73:1607-1611
properties of the eggshell. Egg weight loss has been used to estimate vital gas The success of embryonic development exchange (Paganelli et at, 1978; Rahn et ah, in various types of poultry has been 1979) and has been correlated with the related to the functional and structural rate of embryonic metabolism and development (Rahn and Ar, 1980; Burton and Tullett, 1983). Vital gas diffusion occurs through thousands of microscopic Received for publication March 21, 1994. pores, which are the only means of Accepted for publication June 2, 1994. 1 The use of trade names in this publication does not communication between the external enimply endorsement by the North Carolina Agricul- vironment and the chorioallantoic memtural Research Service of the products mentioned, nor brane. The length of the pores and, criticism of similar products not mentioned. therefore, the diffusive pathway, is equal 2 Alexandria University. to shell thickness. Thicker shells produce 3 Animal Production Research Institute. greater resistance to gaseous diffusion 4 North Carolina State University. 5 To whom correspondence should be addressed. (Rahn et ah, 1979). INTRODUCTION
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Downloaded from http://ps.oxfordjournals.org/ at H.E.C. Bibliotheque Myriam & J. Robert Ouimet on June 14, 2015
Faculty of Agriculture, Alexandria University, Alexandria, Egypt, Animal Production Research Institute, Agricultural Research Center, Dokki, Egypt
1608
SOLIMAN ET AL.
MATERIALS AND METHODS The study was conducted at the Poultry Research Center, Faculty of Agriculture, Alexandria University, Egypt. A total of 1955 Japanese quail eggs was obtained from birds housed as two females and one male per cage. The eggs were incubated in forced draft incubators at 10 m above sea level. The dry bulb and wet bulb temperatures were 37.5 and 30 C, respectively. The eggs were weighed at 0, 5,10,15, and 18 d of incubation. Dry chick weights from hatched (H) eggs were obtained at 18 d. Percentage egg weight loss was calculated on an individual egg basis for each incubation interval. At 18 d of incubation, all unhatched eggs were opened and examined macroscopically for evidence of stage of embryonic development. Egg types were classified as infertile (INF), early dead
embryos that died before 6 d (ED), late dead embryos that died between 6 d and pipping (LD), and embryos that died after external pipping (PIP). Egg contents were removed from a representative portion of the unhatched and hatched eggshells leaving the shell membranes intact. Methylene blue (.5 g of 89% dye/L of 70% ethanol) was pipetted into the shell and allowed to diffuse through the shell to visualize the pores externally (Board and Halls, 1973). Pores were counted under 2.5x power magnification and expressed as number per .25 cm2. Four areas within each of the three eggshell regions, large end (LE), equator (EQ), and small end (SE), were counted and averaged (Peebles and Brake, 1985). Shell thickness with membrane intact (STWM) was measured in three areas of each region with a micrometer capable of .01 mm accuracy and averaged. Data were subjected to analysis of variance using the General Linear models (GLM) procedure of SAS® software (SAS Institute, 1989). The error term was based upon variation among eggs. Differences among means were partitioned using Duncan's multiple range procedure (Duncan, 1955). Statements of statistical significance were based upon P < .05. RESULTS AND DISCUSSION Percentage egg weight loss during various incubation intervals are shown in Table 1. Initial egg weight did not vary among the various egg types. The ED egg
TABLE 1. Egg weight loss during various incubation intervals of Japanese quail eggs in relation to embryonic mortality
Egg type Infertile Hatched Early dead Late dead Pipped X SD
Initial egg weight
n 686 750 116 323 80 1,955
(g) 10.92 10.92 10.73 10.86 10.90 10.86 .03
Days of incubation 0 to 5
5 to 10
10 to 15
0 to 15
15 to 18
0 to 18
2.19d 23.31M 2.84= 2.68= 8.49b 7.90 .69
15.29d 34.63M 18.47= 16.19<* 19.61b 20.83 .73
- (%) 3.63b= 3.34=d 4.30" 3.80b 3.20d 3.66 .04
5.15b 4.33< 6.06» 5.40" 4.68= 5.12 .06
4.30b 3.65= 5.27a 4.31b 3.24<» 4.15 .05
13.10b 11.32= 15.63^ 13.51b 11.12' 12.94 .12
"-^Means in the same column with no common superscript differ significantly (P < .05). J Values based on weight of recently hatched chicks relative to initial egg weight.
Downloaded from http://ps.oxfordjournals.org/ at H.E.C. Bibliotheque Myriam & J. Robert Ouimet on June 14, 2015
Increased eggshell permeability has been associated with increased early and late embryonic mortality in quail (Peebles and Marks, 1991). Low pore numbers have been associated with increased embryonic mortality in chickens (Peebles and Brake, 1985). Similarly, increased shell thickness (pore length) has been found to be associated with early embryonic mortality in chickens (Peebles and Brake, 1985). The purpose of this study was to more clearly define the relationships between egg weight loss, eggshell porosity, eggshell thickness, and embryonic mortality in Japanese quail.
1609
EGGSHELL CHARACTERISTICS AND QUAIL EMBRYOLOGY TABLE 2. Correlation coefficients between initial Japanese quail egg weight, egg weight at 5, 10, and 15 d of incubation, and percentage egg weight loss to 15 and 18 d of incubation in relation to embryonic mortality Egg weiight
Percentage weight loss
Egg type
5 d
10 d
15 d
0 to 15 d
0 to 18 d
Hatched Early dead Late dead Pipped
.975" .977" .984" .988"
.957" .893" .932" .967**
.932" .817" .874" .889"
.384** .155 .176** .018
.557" .152 .270" .555"
During the 15- to 18-d period, which type exhibited the greatest weight loss during the incubation intervals of 0 to 5 d, includes internal and external pipping and 5 to 10 d, 10 to 15 d, and 0 to 15 d. hatching, the greatest weight loss was Conversely, both the H and PIP egg types exhibited by H eggs followed by PIP eggs exhibited the lowest weight losses during (Table 1). The ED eggs exhibited greater the same incubation intervals. The LD and weight loss than INF eggs with LD eggs INF egg types were generally intermediate intermediate. Thus, embryos that progduring these incubation intervals. These ressed the most lost the most weight results agree with the data of El-Turky et (water) during the final phase of developal. (1981) and Peebles and Marks (1991), ment. Embryos that died before this time who found that ED eggs exhibited a did not exhibit this increase in weight loss, higher rate of water loss through 14 d of which suggests that the increased weight incubation. This suggests that early deaths loss observed was due to increased emare a result of excessive weight loss in bryonic respiration (water production) as Japanese quail eggs. Vick et al. (1993) the embryo approached and passed plareported early deaths to be due to low teau metabolism. A deficiency of water weight loss of eggs from young broiler loss would prevent an influx of oxygen breeder flocks with thick eggshells and and thus asphyxiate the embryo. albumen but the opposite was true for Overall weight loss during 18 d of older flocks, which exhibited thin egg- incubation increased in the following shells and albumen (Brake et al, 1993). The ascending order; LD and INF, ED, PIP, absence of major differences in shell and H (Table 1). For H and PIP eggs, this thickness suggests that poor albumen clearly reflected the advanced stage of quality, which permits excessive weight embryonic development compared with loss, or some other physical attribute of the LD egg type. The high weight loss of the egg, may be involved in early deaths the ED eggs is difficult to explain but may, in Japanese quail eggs. in part, be the result of unregulated water From inspection of Table 1, weight loss loss due to some functional difference seemed to be greatest from 5 to 10 d and such as poor albumen quality or other 15 to 18 d of incubation. In contrast, physical attribute of the egg. Although turkey egg weight loss has been character- embryonic death may alter tne rate of gas ized as highest during the first 7 d exchange and weight loss (Tyler and (Christensen and McCorkle, 1982), where- Simkiss, 1959; Kayar et al, 1981), the as the chicken egg seems to have its consistent differences in weight loss belowest weight loss during the middle tween egg types found in this study and period of incubation compared with that of Peebles and Marks (1991) suggests higher weight losses at the beginning and that differences in rate of water loss may end of incubation (Brake et al, 1993; Vick be causally related to embryonic mortality. et al, 1993). This suggests that Japanese The correlation coefficients between iniquail eggs exhibit a slightly different tial egg weight and egg weight at 5, 10, pattern of weight loss than do chicken or and 15 d of incubation are shown in Table turkey eggs. A direct comparison under 2. Highly significant correlation coeffithe same conditions is needed to clarify cients were evident at all times but the this point. magnitude of the coefficient decreased
Downloaded from http://ps.oxfordjournals.org/ at H.E.C. Bibliotheque Myriam & J. Robert Ouimet on June 14, 2015
" P <, .01.
1610
SOLIMAN ET AL. TABLE 3. Eggshell pore concentration in different eggshell regions of Japanese quail eggs exhibiting different stages of embryonic development
Egg type
Large end
Equator
Small end 2
(n/.25 cm ) 104 103 76 88 54 425
7.57b 8.56a 7.01 b 7.02b 7.43b 7.52 .08
6.61 ab 6.93* 5.72c 6.24abc 5.98bc 6.30 .08
7.23b 7.91a 6.00c 6.76b 6.87b 6.95 .08
7.14 7.80 6.24 6.67 6.76 6.92 .22
"-"Means in the same column with no common superscript differ significantly (P < .05).
with day of incubation reflecting increasing egg to egg variability. Percentage weight loss was significantly correlated with initial egg weight for H and LD egg types from 0 to 15 d and for H, LD, and PIP egg types from 0 to 18 d of incubation. This probably reflects a less variable weight loss in those egg types that permitted further development than that observed in the ED egg type. This may be due to physical attributes of the egg contributed by the dam or active participation by the embryo. Eggshell pore concentration of various egg types is shown in Table 3. Porosity at the LE was greater in the H egg type than for all other egg types. Peebles and Brake (1985) found the same for broiler hatching eggs. Greater porosity over the air space has been determined to be beneficial to development because the diffusion in this region could theoretically account for 80% of respiratory exchange (Romijn, 1950). A
deficiency in this area has been linked to late embryonic mortality in turkeys (Christensen, 1983). Similarly, H eggs exhibited greater porosity at the EQ than LD, PIP, or INF eggs. The ED eggs exhibited fewer pores at the EQ than all other types. Visschedijk (1968) suggested that EQ pores could compensate for lack of LE pores, but this did not occur in the other egg types in this study. Differences in observed porosity in the SE region may be related to the eggshell thinning observed in this region due to calcium mobilization, which may have made some small pores more passable to the dye used. Eggshell thickness of various egg types is shown in Table 4. No differences were found in the LE or EQ regions. At the SE, the thinnest shells were found in the H eggs. The PIP, LD, and ED egg types exhibited the thickest shells at the SE and INF eggs were intermediate. The SE data
TABLE 4. Eggshell with membrane thickness in different eggshell regions of Japanese quail eggs exhibiting different stages of embryonic development Egg type
n
Large end
Equator
, Infertile Hatched Early dead Late dead Pipped X
SD :
104 103 76 88 54 425
.22 .23 .23 .22 .23 .22 .09
.23 .23 .23 .23 .24 .23 .09
Small end
X
.24bc .24c .25 ab .25" .26a .25 .12
.23 .23 .24 .23 .24 .23 .06
,,
Means in the same column with no common superscript differ significantly (P < .05).
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Infertile Hatched Early dead Late dead Pipped 5c SD
EGGSHELL CHARACTERISTICS AND QUAIL EMBRYOLOGY
REFERENCES Board, R. G., and N. A. Halls, 1973. The cuticle: a barrier to liquid and particle penetration of the shell of the hen's egg. Br. Poult. Sci. 14:69-79. Brake, J., T. J. Walsh, and S. V. Vick, 1993. Hatchability of broiler eggs as influenced by storage and internal quality. Zootech. Int. January:30, 32-37, 40-41. Burton, F. G., and S. G. Tullett, 1983. A comparison of the effect of eggshell porosity on the respiration and growth of domestic fowl, duck
and turkey embryos. Comp. Biochem. Physiol. 75A:167-174. Christensen, V. L., 1983. Distribution of pores on hatching and non-hatching turkey eggs. Poultry Sci. 62:1312-1316. Christensen, V. L., and F. M. McCorkle, 1982. Turkey egg weight losses and embryonic mortality during incubation. Poultry Sci. 61:1209-1213. Coleman, J. R., S. M. Dewitt, P. Batt, and A. R. Terepka, 1970. Electron probe analysis of calcium distribution during active transport in chick chorioallantoic membrane. Exp. Cell. Res. 63:216-220. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics 11:1-42. El-Turky, A. I., Y. M. Kader, N. Z. Mohanna, L. Goher, and I. F. Sayed, 1981. Certain factors affecting rate of weight loss in incubated eggs. Agric. Res. Rev. (Cairo) 59:29-43. Kayar, S. R., G. K. Synder, G. F. Birchard, and C. P. Black, 1981. Oxygen permeability of the shell and membranes of chicken eggs during development. Respir. Physiol. 46:209-221. Paganelli, C. V., R. A. Ackerman, and H. Rahn, 1978. The avian egg: In vivo conductances to oxygen, carbon dioxide, and water vapor in late development. Pages 212-218 in: Respiratory Function in Birds, Adult and Embryonic. J. Piiper, ed. Springer-Verlag, Berlin, Germany. Peebles, E. D., and J. Brake, 1985. Relationship of eggshell porosity to stage of embryonic development in broiler breeders. Poultry Sci. 64: 2388-2391. Peebles, E. D., and J. Brake, 1986. The role of the cuticle in water vapor conductance by the eggshell of broiler breeders. Poultry Sci. 65: 1034-1039. Peebles, E. D., and H. L. Marks, 1991. Effect of selection for growth and selection diet on eggshell quality and embryonic development in Japanese quail. Poultry Sci. 70:1474-1480. Rahn, H., and A. Ar, 1980. Gas exchange of the avian egg: time, structure and function. Am. Zool. 20: 477-484. Rahn, H., A. Ar, and C. V. Paganelli, 1979. How bird eggs breathe. Sci. Am. 240:46-55. Romijn, C, 1950. Foetal respiration in the hen. Gas diffusion through the eggshell. Poultry Sci. 29: 42-51. SAS Institute, 1989. SAS® User's Guide, Statistics. Version 5. SAS Institute Inc., Cary, NC. Tyler, C, and K. Simkiss, 1959. Studies on eggshells. XII. Some changes in the shell during incubation. J. Sci. Food Agric. 10:611-615. Vick, S. V., J. Brake, and T. J. Walsh, 1993. Effect of incubation humidity and flock age on hatchability of broiler hatching eggs. Poultry Sci. 72: 251-258. Visschedijk, A.H.J., 1968. The air space and embryonic respiration. 1. The pattern of gaseous exchange in the fertile egg during the closing stages of incubation. Br. Poult. Sci. 9:173-194.
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are consistent with the removal of calcium from the eggshell for bone formation during the final stages of embryonic development in H eggs. This is consistent with the fact that the chorioallantoic membrane, which mobilizes calcium from the shell (Coleman et al, 1970), would be most active in the region it remained in contact with the longest. Optimum hatchability has been reported to depend upon a proper relationship between pore concentration and pore length (shell thickness), which provides the proper water (weight) loss for optimum growth (Burton and Tullett, 1983; Christensen, 1983). This is consistent with the data of H, PIP, LD, and ED egg types, for which higher porosity and thinner shells were associated with successful incubation, some of which must be associated with late stage mobilization of eggshell calcium. However, weight loss did not follow the same trend. There was paradoxically higher weight loss prior to 15 d in ED and LD egg types than in H eggs. This suggests that high weight loss was the cause and not the result of embryonic mortality. This is supported by the INF eggs data, which were generally intermediate between H eggs and other types. This suggests either some dysfunction in pore structure and size or an as yet undefined role of albumen quality, cuticle, or shell membrane function, assuming that storage and incubation are equal. This is similar to previous results with eggs from older broiler breeder flocks, which are known to have poor albumen quality and a thinner cuticle (Peebles and Brake, 1986; Vick et al, 1993).
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