Egg Quality Traits and Shell Microbial Contaminations in Two Commercial Layer Strains Affected by Flock Age and Storage Period

In Egyptian governorates, the poor storage conditions of market-egg at room temperature especially in summer leads to higher economic losses for producers. Therefore, it is very important to evaluate the egg quality characteristics as well as factors affecting them up to arrive to the consumer in the best condition. The park yard system of the egg production sustains the small families’ economics and generates sustainable income (Colin et al., 2004)

There are many factors affecting egg quality, include the bird age (Menezes, 2012 and Ojedapo, 2013), egg size (Butcher and Miles, 2013), genetics (Rayan et al., 2013), environmental factors such as ambient temperature (Leandro et al., 2005 and Hasan and Okur, 2009), relative humidity (Menezes et al., 2009) and storage period (Samli et al., 2005). The genotype is one of the most important factors, which influencing egg weight and other egg characteristics. Many studies have shown heavier eggs in brown hens than in white ones (Vits et al., 2005). Also, Halaj and Grofík (1994) showed that egg shape index in the white hens Shaver Starcross 288 was higher than in the brown Moravia SSL. Contrary, Leyendecker et al., (2001b) reported that yolk weight and Haugh Units significantly higher in white egg chickens (Lohmann LSL) than that of the brown. Similarly, Tumová et al. (1993) found that the yolk weight and percentage significantly higher in Hisex Brown in brown eggs than in white eggs. Also, Ledvinka et al., (2000) indicated that eggshell weight and thickness had a higher in brown hens as compared with lines of White Leghorn.

The age of hens is another factors influencing egg weight. Johnston and Gous 2007 and Ojedapo, 2013) showed that the egg weight increased with the hens’ age. In contrast, Zemková et al. (2007) demonstrated that the egg weight was not affected by age. Also, Van den Brand et al., (2004) found that the age of hens increased yolk weight; albumen weight (Suk and Park 2001) and yolk proportion, but decreased albumen percentage (Rizzi and Chiericato 2005). The age of hens influenced the eggshell quality (Campo et al. 2007), which deteriorated with advancing age of hens. While, Van den Brand et al. (2004) found no significant effect on eggshell thickness and the shape index.

Referring to the storage period, many studies showed that the egg quality negatively affect and significantly reduce the Haugh unit. The findings of Jones and Musgroove (2005) showed a decrease in albumin height and weight of eggs with increase storage period. Also, the results of Samli et al., (2005) indicated that egg weight, albumen height, Haugh unit and yolk indices decreased significantly (P<0.001) with the advance of the storage period. While, Scott and Silversides (2000) found that the egg weight did not change in the first 10 days of the storage. Also, carbon dioxide level in the albumen is inversely related to albumen pH and is influenced by storage time. The findings of Reijrink et al., (2010) indicated that carbon dioxide level is high when an egg is laid and decreases with time causing the pH of the albumen to increase (Reijrink et al., 2010).

The objective of this study was to evaluate the egg quality traits and eggshell contaminations in two commercial layer strains at 48 and 63 weeks of age, at different storage periods 7, 14, 21 and 28 days under room temperature.

 

This study was conducted at Animal & Poultry Production Department, Faculty of Agriculture, Sohag University. A total of 400 eggs were collected from both of Hy-Line W- 36 and Hy-line brown at 48 and 63 weeks of age. All hens 25000 were raised in Tagaried Commercial Poultry Farm and housed in battery cages with 5 hens per cage (330 cm² per hen). All hens were fed ad libitum on a commercial ration containing 16% crude protein with 2724 kcal/ kg ME according to NRC (1994). The fresh tab water was available all the time. All hens were daily exposed to 16L: 8D with light intensity of 30 lux. Fresh eggs were collected and measured within 2 h of being laid. Each of 20 sampled eggs was stored in room temperature (32°C) for 5 periods as 7, 14, 21 or 28 days with relative humidity of 55-60% for all treatments.

Each egg was weighed using a 0.0g sensitive digital scale. Egg length and width (cm) of the egg were measured with electronic digital Vernier caliper sensitive. Shape index (%) is estimated by using this equation: = (egg width/egg length) × 100 (Anderson et al., 2004). Specific gravity of the eggs was measured by using saline solutions varied from 1.060 to 1.100 in increments of 0.005. The surface area (cm²) of each egg was calculated using the formula 3.9782W^0.7056 according Carter (1975), where W is the egg weight in grams. Shell weight per unit surface area (SWUSA) expressed as mg/cm² and egg volume was calculated using formula (0.7608 × EW ×1.0474) according to Carter (1975). Shell weight (shell membrane inclusive) was obtained by weighing on the electronic scale. Eggshells were first dried for 72 hours at room temperature and then the thickness was measured using 0.01-mm precision micrometer. Shell percentage (%) formula = [shell weight (g)/egg weight (g)] ×100.

Haugh units were calculated using the egg weight and albumen height as follows: Hu = 100 log (H-1.7EW^0.37+7.57). Albumen height was measured at 1 cm from the yolk, using a 0.1-mm precision micrometer. Yolk was separated manually, weighed and expressed as percentage of egg weight. Yolk colour was determined on the Roche colour fan. Air cell deep (distance between eggshell and membrane, mm) was measured with same micrometer.

Eggshell samples were collected immediately after each storage period. The microbial populations in egg shell were enumerated by adding 10 g of sample to 90 ml of sterile phosphate buffer saline (PBS) and mixing the solution for five minutes under room temperature. Serial dilutions of the liquid phase in sterile PBS were plated on the surface of MacConkey agar, blood agar, nutrient agar and potato dextrose agar, serial dilutions plates were incubated for 24 hr. to 4 days at 37ºC. Colony-farming units per grams were calculated.

The experimental design was 2 × 2 × 5 factorial arrangement comprising of 2 strains of layer chickens (Hy-Line W-36 and Hy-line brown), 2 ages (48 and 63 weeks in lay) and 5 storage periods (0, 7, 14, 21 and 28 days) using the General Linear Model (GLM) procedure of (SAS 1998) by applying the following model.

 

Y_ijk = μ + S_i + A_j + G_k + SA_ij + SG_ik + AG_jk + SAG_ijk + e_ijk

 

Where: Y_ijk = the observation of the i^th strain (S), the j^th flock age (A) and G^th storage periods. SA_ij is the interaction between strain and breeder’s age, SG_ik is the interaction between strain and storage period, AG_ik is the interaction between breeder’s age and storage period and SAG_ijk is the interaction between strain, breeder’s age and storage period. e_ijk= Random error component was assumed to be normally distributed. Significant differences between treatment means were determined by using Duncan's new multiple ranges test (Duncan, 1955).

 

As shown in Table (1), the effect of strain was highly significant (P<0.05, 0.001 and 0.0001) for all external egg quality traits except for USSA. It was observed that Hy-line brown layers produced significantly (P<0.05) heavier egg weight, volume and egg surface area as compared to Hy-Line W-36. This improvement in egg weight and volume could be attributed to responsible for the bigger eggs laid, as body weight is directly correlated with egg size. These results are in agreement with those of Alewi et al., (2012), who noticed that the weight of eggs was influenced by the type of breed. In current study the brown eggs were heavier than the white eggs, likely because the hens weighed more. Several investigators have compared the eggs of white and brown egg-laying strains (Curtis et al., 1985, 1986; Washburn, 1990). Generally, brown egg layers are believed to be heavier than white egg layers, and that they lay larger eggs with better albumen quality but thinner shells. These differences between white and brown egg layers are not due to a direct relationship with shell color but, rather, due to differences in the genetic origins of the hens. These findings showed that shape index in white eggs is lower (74.55) than that (76.14) of the brown eggs. These results are in agreement with findings of Alsobayel and Albadry, (2011) who found that white shelled eggs has SI value of 74.48 which was close to the ideal shape (74) reported by North and Bell (1990), while brown shelled eggs had higher SI (77.73) which means that they have a rounder shape and are more frequently liable to break when moved through marketing channels.

Eggshell weight and thickness were highly significantly affect (P<0.0001) by strain of layers, while shell proportion and shape index in Hy-line brown layer significantly (P<0.001) increases compared to Hy-Line W-36 strain. These findings are in agreement with Ledvinka et al., (2000), who indicated that the brown hens had a higher shell weight in comparison with lines of White Leghorn. Also, Rayan et al., (2013) indicated that the brown eggs had significantly higher shell percentage compared to the white ones. From our results, could be seen that the egg specific gravity, shell thickness, percent egg shell and shape index increased significantly in Hy-line brown as compared to Hy-Line W-36 strain of layers, an indication of genetic effects on these external egg parameters. The our findings are in agreement with those of Singh et al., (2009), who reported that different strains of laying hens vary significantly in egg shell quality. Alsobayel and Albadry, (2011) found that that white shell eggs had significantly higher weight, surface area and lower shape index and blood spot incidence. Scott and Silversides, (2000) concluded that the main effect of strain was significant for all measures except albumen pH. Eggs from brown hens were heavier than those from white hens

These results showed that eggs from Hy-Line W-36 having significantly (P<0.05, 0.01 and 0.001) heavier yolk weight, yolk height and better Haugh unit and albumen height than eggs from the Hy-line brown. There were significantly dramatic changes in Haugh unit (53.18 to 48.07%), albumen height (4.04 to 3.55 mm) and yolk height from 10.10 to 9.31 mm in Hy-Line W-36 and Hy-line brown. These results are in conformity with those observed by Leyendecker et al., (2001b), who found significantly higher value for Haugh units in white layers than in brown hens. Also, Scott and Silversides, (2000) concluded that the main effect of strain was significant for all measures except albumen pH. Eggs from brown hens had more shell and albumen but less yolk. This difference between strains was reflected in the percentages of the components. The albumen pH of eggs from the two strains was nearly identical, but the albumen height of eggs from white hens was greater. Similar results were also found by Rayan et al., (2013), who found that Haugh units and yolk weights of the white eggs were significantly heavier than those of brown ones. Also, our findings showed a reduction in yolk colour in eggs produced from Hy-Line W-36 implies that the carotenoids and the xanthophyll's, which constitute the pigmentation were undergoing deterioration. The yolk weights of the white eggs were significantly heavier than those of brown ones. This result is in agreement with the findings of Leyendecker et al., (2001b) who stated that yolk weight for white egg were significantly higher (Lohmann LSL) in comparison with the brown Lohmann Tradition.

Data presented in Table (2) showed that egg weight, egg volume and surface area increased with increasing of the hen's age. This may be attributed to the increasing egg size with the hen's age. These results are in agreement with those of Johnston and Gous (2007), who reported that the egg weight increased with the hens’ age. In contrary, Zemková et al., (2007), showed that the egg weight was insignificantly affected by layer age. The present results revealed that there was a significant increase in egg shell weight, while egg shape index was decreased with advanced of layers age. The increase in eggshells of older layers could be attributed to their production of heavier eggs than those of young. Similar result was noticed by Suk and Park (2001) who observed that the eggshell weight was heavier in older hens than those of young. The decrease in shape index with increasing age could be attributed to the directly proportional to egg width and inversely to egg length, which means that with increasing age, the rate of eggs becomes longer is faster as compared rate of being wider. These results are in agreement with Rayan et al., (2013), who showed that egg shape index was decreased with advanced of layers age.

The age of the hens had an influence on albumen height, with higher values (P<0.0001) in eggs from younger hens (3.93 mm) at 48 weeks, compared with (3.67 mm) at 63 weeks of age. These results are in agreement with the findings of Carvalho et al., (2003) who found that the albumen height is negatively affected as the age of the laying hen's increases. Haugh units and albumin height were also decreased significantly (P<0.001) with increasing hen age. The decrease in Haugh unit of eggs could be attributed to physical and chemical reactions that occur, leading to protein degradation. These results are in agreement with the results of Silversides et al., (2001), who reported that the Haugh unit of eggs obtained from hens at 26 weeks of age was 88.48, while it decreased to reach 77.40 at 65 weeks of age.

The lowest (P≤0.0001) yolk weight 17.92g was at 48 weeks of age compared with 18.44g at the age 63 weeks of age. These results are in agreement with those of Tumová and Ledvinka (2009), who confirmed that the yolk weight significantly increased with the hens’ age. Similar results were also found by Suk and Park (2001), who reported that the yolk weight increased with increase in age of the hens. Also, Singh et al., (2009), found that the yolk weight increasing with advancing layer age.

There was no effect of age on eggshell thickness and eggshell ratio. These findings are in harmony with Van den Brand et al., (2004) stated that no effect of flock age on eggshell thickness, while the shape index of the eggs decreased with age.

Therefore, the internal and external characteristics of egg changes significantly with age, while egg shell quality deteriorates, egg weight, yolk weight and albumen weight increase as the age increase in chickens (Hurnik et al., 1997).The relationship between weight, length and width of eggs has been reported by (Daviloo, 2000) who also noted the proportion of yolk, albumen and shell that contribute to the egg weight increase with the hen’s age, reaching a plateau by the end of the laying cycle. Suk and Park (2001) observed that the albumen weight increased with the increase in age of birds. Ojedapo (2013) found that the age has a significant effect on the egg quality traits and weight in various season of the year, specifically late dry and early wet season. It was revealed that egg weight, shell weight, yolk weight, albumen weight increased with age at the experimental season while shell thickness and other parameters measured decreased with age.

The effect of storage period on the external egg quality traits were found to be significant (P<0.05) for all traits except shell weight and shape index as in Table 1. Statistical analysis showed that the egg weight, volume, surface area and USSA were significantly decreased with the length of storage eggs, while specifies gravity, shell thickness and proportion were significantly increased with the length of storage eggs. These decreases in egg weight and volume with storage could be attributed to less moisture loss from the eggs. These results are in agreements with the findings of Tabidi (2011), who found the loss in egg weight, could be attributed to loss of humidity from inside the egg due to evaporation effects. Also, Hasan and Okur (2009), who noticed a decrease in weight within 10 days of storage at 29ºC. Also, Siyar et al., (2007) reported significant (P<0.001) egg weight decrease of 0.36 and 0.57g respectively, within 7 and 14 d of storage. Inversely, there were no significant differences (P<0.05) in shell weight and shape index with the length of storage eggs.

The albumin and yolk heights were decreased with the length of storage. This could be attributed to destroy of mucin fibers, which gives both of albumen and yolk their gel-like texture to loss their structure and so the albumen and yolk becomes watery (Gavril and Usturoi, 2012 and Tebesi et al., 2012). In contrast, shell weight was not changed by storage period. These results are in agreement with those of Ahn et al., (1999), who found that shell weight dose not change with storage.

Haugh units were significantly decreased with increasing storage period, since it amounted 76.37 in fresh eggs decreased to reach 24.25 in eggs at 28 day. These results are in agreement with the findings of Tona et al., (2004), who reported storage period adversely affected Haugh units. Also, Yolk colour was considerably decreased with increasing storage period. These findings are in agreement with the results obtained by Siyar et al., (2007) and Tebesi et al., (2012), who observed decreased Haugh units in storage eggs compared to fresh whole and yolk only eggs.

External egg quality traits except USSA and shell thickness were not affected by the interaction. Haugh units, air cell deep, albumen height, yolk height and yolk colour were affected by the interaction. These results are in agreement with Lukáš Zita et al., (2009), who found highly significant interactions (Genotype × Age) were also seen in eggshell quality characteristics. Also, they indicated that interaction between genotype and age of hens was found in albumen weight and Haugh units. Similarly, Scott, and Silversides, (2000) found that the interactions between storage time and strain were significant for albumen pH and height. The albumen pH of fresh eggs was lower for eggs from brown than those from white hens (Table 2), but after storage the albumen pH of eggs from both strains of hens was similar. The albumen height of eggs from brown hens was lower at all storage times, but the difference between strains was less for fresh eggs and for those that had been stored for 10day than it was for other periods of storage.

Data presented in Table 3 showed that strain effect was insignificant for all bacterial and fungal eggshell traits, which were statistically similar in both strains.

As in our study, De Reu et al., (2005b), comparing different pilot housing systems, also found no systematic significant difference in bacterial eggshell contaminations with total counts of aerobic and Gram-negative bacteria between the beginning and end of lay. Referring to flock age, these findings showed that E. coli contaminations on the eggshells was significantly higher (P<0.01) in the hens at 63 weeks of age, whereas bacillus subtilis and P. Pluresence were significantly lower (P<0.05) compared to 48 weeks of age. These results are disagreement with Potais et al., (2003a) found no effect of the hen age on bacterial eggshell contaminations. Inversely, Candida albicans was significantly decreased (P<0.0001) with increasing storage period.

The study on the influence of storage period on the bacterial shell contamination showed that a significant (P<.0.05) differences in the bacillus subtilis recovered from the shell of the eggs stored at 28 days compared to fresh eggs. While, E. coli and P. Pluresence bacteria increased insignificantly during the storage period of 28 days. These results are in agreement with the findings of Gentry and Quarles (1972), who reported no marked differences in viable counts after 1 day storage of the freshly laid eggs at 4°C. In contrast, Candida albicans and Aspergillus niger were significantly decreased with increasing storage period, since it decreased from (5.50 and 3.83) in fresh eggs to reach (4.25 and 1.25) at 28 days.

 

1- Egg quality traits in brown hens improved remarkable compared to white, while no significant difference in the shell microbial contaminations in both strains.

2- Increase in the deterioration of egg quality traits and shell microbial contaminations with increasing hen age.

3- The storage period had significantly affects on the egg quality traits and shell microbial contaminations. However, the use of the shorter storage period 7 days could be recommend, since its application had no adverse effect on egg quality traits and increase the shell microbial contaminations at room temperature (32°C).

 

Alsobayel, A.A., and M.A. Albadry, (2011). Effect of storage period and strain of layer on internal and external quality characteristics of eggs marketed in Riyadh area. Journal of the Saudi Society of Agricultural Sciences (2011) 10, 41–45.

Scott, T. A. and F. G. Silversides, (2000). The Effect of Storage and Strain of Hen on Egg Quality. Poultry Science 79:1725–1729

Ojedapo, L.O., (2013). Effect of age and season on egg quality traits of brown layer strain reared in derived savanna zone of Nigeria.Transnational Journal of Science and Technology July 2013 edition vol.3, No.7 ISSN 1857-8047.

Reijrink I. A. M.; van Duijvendijk L. A. G.; Meijerhof R.; Kemp, B. and van den Brand H. (2010). Influence of air composition during egg storage on egg characteristics, embryonic development, hatchability, and chick quality. Poult. Sci. 89:1992–2000.

Ahn, D. U., J. L. Sell, C. Jo, M. Chamruspollert and M. Jeffrey. (1999). Effects of dietary conjugated linoleic acid on the quality characteristics of chicken eggs during refrigerated storage. Poult. Sci. 78:922-928.

Alewi, M, Melesse, A. and Teklegiorgis, Y. (2012). Crossbreeding effect on egg quality traits of local chickens and their F1 crosses with Rhode Island Red and Fayoumi chicken breeds under farmers’ management conditions. Journal of Animal Science Advances , 2 (8): 697-705.

Anderson, K. E.; Tharrington, J. B.; Curtis, P. A. and Jones, F. T. (2004). Shell characteristics of eggs from historic strains of single comb white leghorn chickens and relationship of egg shape to shell strength. Int. J. Poult. Sci. (3): 17-19.

Butcher G.D. and Miles R.D. (2013). Concepts of egg shell quality. University of Florida. Available at: http://edis.ifas.ufl.edu/pdffiles/VM/VM01300pdf.

Campo, J.L; Gil, M.G and Dávila, S.G. (2007) Differences among white-, tinted-, and brown-egg laying hens for incidence of eggs laid on the floor and for oviposition time. Arch Geflügelkd 71: 105-109

Colin G S; GB and ME Ensminger, (2004). Poultry Science. Fourth edition. Upper Saddle River, New Jersey.

Carvalho, F.B.; Stringhini, J. H.; Jardim Filho, R.M. (2003). Influência da conservação e do período de armazenamento sobre a qualidade interna e da casca de ovos comerciais. Revista Brasileira de Ciência Avícola, Supl. 5, p.100.

Carter J.C. (1975). The hens egg estimation of shell superficial area and egg volume using measurements of fresh weight and shell length and breadth alone or in combination. Br. Poult. Sci. (16): 541-543.

Curtis, P.A., F.A.Gardner, andD. B. Mellor, (1985). Acomparisonof selected quality and compositional characteristics of brown and white shell eggs. II. Interior quality. Poultry Sci. 64:302–306.

Curtis, P.A., F.A.Gardner, andD. B.Mellor, (1986). Acomparison of selected quality and compositional characteristics of brown and white shell eggs. III. Composition and nutritional characteristics. Poultry Sci. 65:501–507.

Duncan D.B. (1955). New multiple range test. Biometrics. 11, 1-42.

Daviloo, R. V., (2000). Effect of hen’s age on quality of hatching eggs and embryonic development. Proceeding of 21th World’s Poultry Congress. Montreal, Canada.

Gentry, R. F. and Quarles, C. L. (1972). The measurement of bacterial contamination on eggshells. Poultry Science 51: 930-933.

De Reu, k., Grijspeerdt, k., Heyndrickx, m., Uyttendaele, m. and Herman, l. (2005a). The use of total aerobic and Gram-negative flora for quality assurance in the production chain of consumption eggs. Food Control 16: 147-155.

Gavril R and MG Usturoi, (2012). Effect of storage time and temperature on hen egg quality. Seria Zootehnie, 57: 221-229.

Halaj M. and Grofík R. (1994): The relationship between egg shell strength and hens features. Živoc. Výr., 39, 927–934.

Hasan, A and Okur, A. A. (2009). Effect of storage time, temperature and hen age on egg quality in free-range layer hen. J Anim Vet Adv, 8 (10): 1953-1958.

Haugh R.R. (1937): The Haugh Unit for measuring egg quality. US Egg Poult. Mag., 43, 552–555, 572–573.

Hurnik, J. F.; Summer, J. D.; Reinhard, B. S. and Sweirczewks, A. (1997). Effects of age in the performance of laying hens during the first year of production.Poultry Sci. 56:222-230.

Johnston S A and Gous, R M (2007). Modelling the changes in the proportions of the egg components during a laying cycle. Br Poult Sci 48: 347-353.

Jones DR and MT Musgrove, (2005). Effects of extended storage on egg quality factors. Poult Sci, 84:1774-1777.

Ledvinka, Z.; Tumová, E; Arent, E.; Holoubek, J and Klesalová L (2000). Egg shell quality in some white-egg and brown-egg cross combinations of dominant hens. Czech J Anim Sci 45: 285-288.

Leyendecker M; Hamann H; Hartung J; Kamphues J; Ring C; Gluender G; Ahlers C, Sander I; Neumann U and Distl O (2001b). Analysis of genotype-environment interactions between layer lines and housing systems for performance traits, egg quality and bone breaking strength - 2 nd communication: Egg quality traits. Züchtungskunde 73: 308-323.

Leandro, N.S.M.; Deus, H.A.B.; Stringhini, J.H. (2005). Aspectos de qualidade interna e externa de ovos comercializados em diferentes estabelecimentos na região de Goiânia. Ciência Animal Brasileira, v.6, p.71-78, 2005.

Lukáš Zita; Eva Tumová and Ladislav Štolc (2009). Effects of Genotype, Age and Their Interaction on Egg Quality in Brown-Egg Laying Hens. ACTA VET. BRNO, 78: 85–91.

Menezes de, P.C.; Cavalcanti, V.F.T. and Lima, E.R (2009). Aspectos produtivos e econômicos de poedeiras comerciais submetidas a diferentes densidades de alojamento. Revista Brasileira de Zootecnia, v.38, n.11, p.2224-2229.

Menezes de; Evilda Rodrigues de Lima; Juliana Pinto de Medeiros; Wanessa Noadya Ketruy de Oliveira and Joaquim Evêncio-Neto (2012). Egg quality of laying hens in different conditions of storage, ages and housing densities. R. Bras. Zootec., v.41, n.9, p.2064-2069.

North, M. O. and Bell, D. D., (1990). Breeder Management. In: “Commercial Chicken Production Manual”. 4th Ed., Van Nostrand Reinhold. New York, USA.

NRC. (1994). Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC.

Rayan. G.N.; Mahrous, M.Y.; Galal,A. and El-Attar, A.H. (2013). Study of some productive performance and egg quality traits in two commercial layer strains. Egypt. Poult. Sci. Vol (33) (II): (357-369).

Rizzi, C. and G. M. Chiericato, (2005). Organic farming production. Effect of age on the productive yield and egg quality of hens of two commercial hybrid lines and two local breeds. Ital. J. Anim. Sci. 4: 160-162.

Samli, H. E.; A. Agma and N. Senkoylu, (2005). Effects of storage time and temperature on egg quality in old laying hens. J. Appl. Poult. Res. 14:548–553. SAS Institute (1998).

SAS Users Guide; Statistics. Version 8.1. SAS Institute Inc.,Cary, NC.

Scott , T. A. and F. G. Silversides (2000). Effect of storage and strain of hen on egg quality. Poult. Sci. 79: 1725-1729.

Silversides, F.G. and Scott, T.A (2001). Effect of storage and layer age on quality of eggs from two lines of hens. Poultry Science, v.80, p.1240-1245.

Singh, R., K. M. Cheng, and F. G. Silversides (2009). Production performance and egg quality of four strains of laying hens kept in conventional cages and floor pens. Poult. Sci. 88:256-264.

Siyar HSA, H Aliarabi, A Ahmadi and N Ashori, (2007). Effect of different storage conditions and hen age on egg quality parameters. Aust Poult Sci Symp. 19: 106-109.

Suk, Y. O and Park, C. (2001). Effects of broiler breeder age and length of egg storage on albumen characteristics and hatchability. Poultry Science 80: 855-858.

Silversides, F. G and Scott, T. A. (2001). Effect of storage and layer age on quality of eggs from two lines of hens. Poult Sci 80: 1240-1245.

Tabidi, M. H, (2011). Impact of storage period and quality on composition of Table egg. Adv Environ Biol, 5(5): 856-861.

Tebesi, T; Madibela, O.R and Moreki, J.C. (2012). Effect of storage time on internal and external characteristics of Guinea fowl (Numida meleagris) Eggs. J Ani Sci Adv,2(6):534- 542.

Tumová E, Skrivan M, Mandák K 1993: Technological value of eggs of Hisex Brown and D 29 laying hens. Sborník VŠZ v Praze, AF, rada B. 55: 245-251 (In Czech).

Tona, K., O. Onagbesan, B. De Ketelaere, E. Decuypere and V. Bruggeman. (2004). Effects of age of broiler breeders and egg storage on egg quality, hatchability chick quality, chick weight and chick posthatch growth to 42 days. J. Appl. Poult. Res. 13: 10-18.

Tumová E, Ledvinka Z (2009). The effect of time of oviposition and age on egg weight, egg component weight and eggshell quality. Arch Geflügelkd 73 (in print)

Van den Brand H; Parmentier, H. K and Kemp, B. (2004). Effects of housing system (outdoor vs. cages) and age of laying hens on egg characteristics. Br Poult Sci 45: 745-752.

Vits, A; Weitzenburger D; Hamann, H and Distl, O. (2005). Production, egg quality, bone strength, claw length, and keel bone deformites of laying hens housed in furnished cages with different group sizes. Poult Sci 84: 1511-1519.

Washburn, K. W., (1990). Genetic variation in egg composition. Pages 781–798 in: Poultry Breeding and Genetics. R.D. Craw-ford, ed. Elsevier Scientific Publishers, New York, NY.

Zemková, L; Simeonovová, J; Lichovníková, M and Somerlíková, K (2007). The effects of housing systems and age of hens on the weight and cholesterol concentration of the egg. Czech J Anim Sci 52: 110-115

 

Table (1): External egg quality traits affected by strain, flock age, storage period and their interactions.

 

Table (2): Internal egg quality affected by strain, flock age, storage period and their interactions.

 

Table (3): Shell microbial contaminations affected by strain, flock age, storage period and their interactions.