Pheasant Egg Case Study

Arch.Geflügelk., 73 ( 3). S. 201- 207, 2009, ISSN 0003-9098. © Verlag Eugen Ulmer, Stuttgart

Quality of pheasant (Phasianus colchicus L.) eggs with different shell colour

Qualität von Fasaneneiern ( Phasianus colchicus L.) mit unterschiedlichen Schalenfarben

R. Kożuszek1, Helena Kontecka1, S. Nowaczewski1, G. Leśnierowski2, J. Kijowski2 and A. Rosiński1

a.rosinski@hubbard-polska.pl

1Department of Poultry Science, University of Life Sciences in Poznań, Poland

2Department of Food Quality Management, University of Life Sciences in Poznań, Poland

Manuskript eingegangen am 15. August 2008, angenommen am 2. Oktober 2008

Introduction

Profitability of pheasant rearing depends, primarily, on their reproductive possibilities, i.e. the number of obtained eggs of high biological value and, consequently, the number of chicks. So far, the results obtained from artificial hatchings of pheasant eggs have not been quite satisfactory (Deeming and Wadland, 2001; Kirikçi et al., 2003) as they may have been affected by a number of factors. Experiments have shown that hatching results of birds depend, to a considerable extent, on egg quality, especially of the eggshell quality (Ipek and Sahan, 2002; Farooq et al., 2004). Positive correlation between number of hatched chicks and thickness or strength of eggshell can be explained by the fact that eggs with thicker shell show lower water vapour conductance (Fabijańska and Fabijańska et al. after Dohnal et al., 1986). Arad and Marder (1982), Christensen (1983) and Bennett (1992) obtained similar results. Mentioned scientists affirmed better chicks’ hatchability in hens and turkeys which laid eggs with thicker eggshell. The same was observed by Szczerbińska (1996). Hens’ eggs with thicker shell were characterised by higher values of hatchability results. Some authors suggested that a relationship between hatchability and egg specific gravity exists. For example, Dohnal et al. (1989) observed a positive correlation between these traits. According to Muambi et al. and Sergeeva (after Różycka and Wężyk, 1985) a significant improvement in hatchability rates is primarily dependent on the quality of the egg contents, i.e. of the egg albumen and yolk. Benton and Brake (1996) claimed that as the blastoderm is located adjacent to the albumen, changes in the pH and viscosity of albumen may play an integral role in determining the viability of the embryo during incubation. In turn, studies conducted on wild ducks indicate higher survival rates of ducklings hatched from bigger eggs (Anderson and Alisauskas, 2002; Pelayo and Clark, 2002). This correlation, however, has not been fully clarified.

On the other hand, correlations have been observed between eggshell colour and some egg physical traits (Scott and Silversides, 2000; Krystianiak and Kontecka, 2002; Silversides and Budgell, 2004) as well as egg fertilisation and chicks hatching (Mróz and Pudyszak, 2000). Moreover, the course of embryogenesis and, consequently, hatching results can also be influenced by the lysozyme content in the egg white. It is a basic globular protein which is characterised by high enzymatic activity and which exhibits considerable bactericidal and fungicidal activity and is also capable of inactivation of viruses (Salton and Pavilik after Świerczewska et al., 1998).

The shell colour of eggs laid by the pheasant female is preconditioned genetically and the colour intensity decreases with the duration of the laying period. The following four basic pheasant eggshell colours can be distinguished: dark-brown, light-brown, olive and blue (Hulet et al., 1978; Richards and Deeming, 2001). Krystianiak (2002) observed in some pheasant populations that 8, 20, 24 and 48% of females laid eggs with the following eggshell colour: blue, olive, dark-brown and light-brown. However, the other authors found a few shades of mentioned eggshell colours (Mróz and Pudyszak, 2000; Richards and Deeming, 2001; Kirikçi et al., 2005). There are few articles in literature on the subject concerning pheasant egg quality depending on the eggshell colour (Mróz and Pudyszak, 2000; Richards and Deeming, 2001; Kirikçi et al., 2005; Krystianiak et al., 2005). In addition, no data was found in the literature on the subject about the content and activity of lysozyme of the albumen of pheasants’ eggs.

The aim of the experiments was to compare pheasant eggs of different eggshell colour with regard to their external and internal traits which might be correlated with hatching results.

Material and methods

The experimental material comprised pheasant eggs derived from the Export Hunting Corporation “MANISZEWO”. The birds were kept in aviaries and fed complete diets which contained 11.7 MJ/kg metabolisable energy, 18.0% crude protein and 3.05% calcium. From among eggs laid on a given day, 120 eggs were selected randomly, 30 eggs from each eggshell colour group, i.e. blue, olive, light- and dark-brown. The following traits were assessed in the selected eggs:

1.

Egg structure, i.e. its weight (g) and specific gravity (g/cm3) as well as shape index. Egg specific gravity (g/cm3) was determined using a set for the density determination of solids and liquids – WPS 360 C. Egg shape index (%) was calculated on the basis of measurements of the egg length and width using slide callipers with 0.02 mm accuracy according to the formula:

Egg shape index = egg width (mm) × 100%/length (mm)

2.

Eggshell, i.e. its area (cm2) according to Paganelli et al. (1974), mean (pcs/0.25 cm2) and total (pcs) number of pores according to Tyler (1953), weight (g), thickness (mm), density (g/cm3) as well as the share of the eggshell in the egg mass. Eggshell density was determined using a set for the density determination of solids and liquids – WPS 360 C and its elasticity using the set Marius.

3.

Egg content i.e. weight (g) of egg yolk and white (including thick and thin white) and their share in the egg mass (%), yolk and thick white pH, height of the yolk and thick white (mm) as well as Haugh units.

Haugh units was calculated according to the formula:

HU = 100 log (h – 1,7 W0,37 + 7,6)

where:

HU – Haugh units

h – average thick white height (mm)

W – egg weight (g)

The evaluation of the lysozyme content and activity in the egg white was carried out twice during the reproductive period of pheasants (May, June). At each date of assessment 24 eggs (6 eggs from each colour group) were analysed. The lysozyme content (% proportion in liquid white) was determined employing the electrophoretic method (Leśnierowski and Kijowski, 1995), while the hydrolytic activity of this enzyme (U/ml liquid white) was determined using the spectrophotometric method.

Mean values as well as standard error of the mean (SEM) were calculated for the examined traits. The differences between eggs with different shell colour as regards examined traits were determined using a linear model in one-way analysis of variance with the following form:

ykl = µ + bk + ekl,

where:

ykl – trait phenotype value for l-th egg of k-th colour,

µ – mean value of the trait for a given group,

bk – effect of k-th colour (k = 1, 2, 3, 4),

ekl – effect of experimental error.

For all traits, Fisher’s test was applied to verify the significance of differences between means for egg groups differing with regard to the eggshell colour. Calculations were conducted with the assistance of the SAS® v. 9.1 statistical package.

Results

Egg structure

Table 1 presents structural traits of pheasants’ eggs of different eggshell colour. No statistically significant differences in the egg weight were observed, although the highest weight was recorded in olive eggs, while the lowest in light-brown ones. On the other hand, eggs of light-brown eggshells were characterised by about 2.1 percentage points smaller shape index values in comparison with olive- and blue-coloured ones. Eggs of dark-brown eggshells were found to have statistically significantly higher (by 0.005 g/cm3) mean specific gravity than eggs with light-brown and blue shells.

Table 1. Characteristics of pheasants eggs external traits with different shell colour

Gewicht, Form und spezifisches Gewicht von Fasaneneiern mit unterschiedlicher Schalenfarbe

Trait

Eggshell colour

dark-brown

light-brown

olive

blue

(n = 30)

(n = 30)

(n = 30)

(n = 30)

SEM

SEM

SEM

SEM

egg weight (g)

33.2

0.62

32.0

0.37

33.3

0.46

32.5

0.52

egg shape index (%)

79.3 ab

0.52

77.7 b

0.68

80.0 a

0.6

79.5 a

0.57

egg specific gravity (g/cm3)

1.071 a

0.001

1.066 b

0.001

1.070 ab

0.001

1.066 b

0.002

Mean values designated in rows with different letters differ significantly at the level P ≤ 0.05

Eggshell

Table 2 presents mean eggshell trait values of pheasant eggs of different colour. No differences were found between eggs with regard to the shell surface. Eggs with dark-brown and olive colour shells had fewer pores per 0.25 cm2 than the remaining ones. The difference was statistically significant and on average amounted to 7.4 pcs. On the other hand, the highest mean total pore number was recorded in the shells of blue-coloured eggs and this difference was higher than values obtained for the light-brown, olive and dark-brown eggs by: 440, 1268 and 1761 pcs., respectively. No statistically significant differences between eggs of different eggshell colour were determined with regard to their weight, density and elasticity as well as percentage proportion in the egg mass. Significantly thicker eggshells (by about 0.027 mm) were determined in dark-brown and olive coloured eggs in comparison with the remaining ones.

Table 2. Characteristics of pheasants eggshell traits with different shell colour

Struktur und Qualität der Schalen von Fasaneneiern mit unterschiedlicher Schalenfarbe

Eggshell colour

dark-brown

light-brown

olive

blue

Trait

(n = 30)

(n = 30)

(n = 30)

(n = 30)

SEM

SEM

SEM

SEM

eggshell surface (cm2)

47.8

1.43

47.9

0.37

49.2

0.45

47.2

1.26

no of pores

24.0 a

1.2

30.9 b

1.7

25.9 a

1.2

33.7 b

1.1

(per 0,25 cm2 of surface)

total number of pores

4610 a

283

5931 b

338

5103 c

241

6371 d

269

eggshell weight (g)

2.96

0.09

2.82

0.04

2.90

0.08

2.90

0.08

eggshell proportion (%)

8.9

0.2

8.8

0.1

8.7

0.2

8.9

0.2

eggshell density (g/cm3)

1.962

0.019

1.959

0.015

1.970

0.024

1.958

0.025

eggshell thickness (mm)

0.288 a

0.004

0.265 b

0.005

0.283 a

0.008

0.253 b

0.006

eggshell elasticity (µm)

28.9

1.56

29.9

1.59

28.2

1.81

29.8

1.37

Mean values designated in rows with different letters differ significantly at the level P ≤ 0.05

Egg content

Table 3 shows pheasant egg yolk and white traits of egg with different colour. Blue eggs were characterised by a significantly lower (on average by 0.77 g) yolk weight in comparison with dark- and light-brown eggs. On the other hand, no differences were found between the examined eggs with regard to yolk height. In comparison with the light-brown eggs, dark-brown, olive and blue eggs were characterised by a similar and statistically significantly smaller mean yolk proportion in the egg mass (by 2.6 percentage points) and its pH (on average by 0.47). On the other hand, eggs with light-brow shells were characterised by a significantly smaller egg white weight in comparison with the remaining eggs. Similar and the highest egg white proportion in the egg mass was determined for eggs with olive and blue shells ( = 59.2%). Eggs with olive and light-brown shells, in comparison with the remaining eggs, were characterised by similar and significantly smaller (by about 1.42 g) weight of thick white and, consequently, also significantly smaller percentage proportion of this white in the egg mass. Olive-coloured eggs had the greatest weight of the thin egg-white as well as its percentage proportion in the egg mass. The smallest mean thick egg-white height was determined for blue eggs and the greatest for dark-brown eggs. The difference between these eggs was significant and reached 0.66 mm. The highest pH of the thick egg-white was found in dark-brown eggs, while the lowest in olive-coloured eggs. Only dark-brown and blue eggs differed significantly with regard to the JH number. The value of this trait in blue eggs was by about 5.33 units lower.

Table 3. Characteristics of pheasants eggs internal traits with different shell colour

Merkmale der inneren Qualität von Fasaneneiern mit unterschiedlicher Schalenfarbe

Trait

Eggshell colour

dark-brown

light-brown

olive

blue

(n = 30)

(n = 30)

(n = 30)

(n = 30)

SEM

SEM

SEM

SEM

yolk weight (g)

11.0 a

0.28

11.2 a

0.19

10.8 ab

0.22

10.3 b

0.21

yolk height (mm)

14.8

0.24

14.6

0.22

15.0

0.2

14.7

0.19

yolk proportion (%)

33.2 a

0.6

35.0 b

0.73

32.2 a

0.46

31.8 a

0.56

pH of yolk

5.82 a

0.07

6.37 b

0.07

5.77 a

0.09

6.11 a

0.05

total white weight (g)

19.2 a

0.46

18.02 b

0.38

19.7 a

0.32

19.3 a

0.43

white proportion (%)

57.8 ab

0.7

56.2 a

0.7

59.0 b

0.6

59.3 b

0.6

thick white weight (g)

8.91 a

0.40

7.34 b

0.32

7.59 b

0.26

8.86 a

0.32

thick white proportion in egg mass (%)

26.9 a

1.1

22.9 b

1,0

22.8 b

0.8

27.3 a

0.9

thin white weight (g)

10.30 a

0.49

10.7 a

0.42

12.1 b

0.37

10.5 a

0.48

thin white proportion in egg mass (%)

30.9 a

1.1

33.2 ab

1.1

36.2 b

0.9

31.9 a

1.2

thick white height (mm)

4.12 a

0.18

3.77 ab

0.16

3.96 ab

0.24

3.46 b

0.18

pH of thick white

8.90 a

0.05

8.27 b

0.04

8.16 c

0.06

8.61 d

0.06

Haugh units (JH)

73.42 a

1.44

71.37 ab

1.37

71.39 ab

2.06

68.09 b

1.62

Mean values designated in rows with different letters differ significantly at the level P ≤ 0.05

The content and activity of lysozyme at the two dates of evaluation in relation to the eggshell colour are shown in Table 4. In the case of both dates of assessment, a significantly higher content (on average by 0.06%) and activity (on average by 12824 U/ml) of this enzyme was found in eggs with light-coloured shells, i.e. blue and light-brown in comparison with the remaining ones. In addition, in blue and olive eggs values of these traits were significantly higher at the second date of assessment.

Table 4. Lysozyme content and activity in the albumen of pheasant eggs of different eggshell colour

Lysozymgehalt und –aktivität im Eiklar von Fasaneneiern mit unterschiedlicher Schalenfarbe

Trait

Eggshell colour

Date

dark-brown

light-brown

olive

blue

(n = 6)

(n = 6)

(n = 6)

(n = 6)

SEM

SEM

SEM

SEM

Lysozyme content in liquid white (%)

May

0.25a

0.002

0.32b

0.004

0.22c*

0.002

0.28d*

0.003

June

0.25a

0.005

0.31b

0.006

0.25a*

0.004

0.30b*

0.005

overall

0.25a

0.003

0.32b

0.004

0.24a

0.004

0.29b

0.004

Lysozyme activity (U/ml)

May

52041 a

332

67356 b

768

47570 c*

174

59662 d*

420

June

53174 a

1102

65693 b

1117

51966 a*

1005

63335 b*

935

overall

52608 a

574

66525 b

693

49768 c

822

61499 d

738

Mean values designated in rows with different letters differ significantly at the level P ≤ 0.05

*Means of first and second date within eggshell colour are significantly different at p ≤ 0.05

Discussion

Egg structure

No significant differences between the examined pheasant eggs were observed with regard to their weight. Different results were reported by Krystianiak et al. (2000, 2005), Krystianiak and Kontecka (2002), Kuźniacka et al. (2005a) and Kirikçi et al. (2005). The above researchers reported that pheasant eggs with dark eggshells were characterised by greater weight in comparison with light-coloured shells. Olive, blue and dark-brown eggs were more round than eggs with light-brown shells. Kirikçi et al. (2005) found that brown, blue and olive-green eggs were characterised by about 3.1 percentage points higher shape index in comparison with eggs with white shells. On the other hand, Mróz and Pudyszak (2000) failed to show significant differences between eggs of different eggshell colour with regard to the discussed trait. Dark-brown eggs were characterised by greater specific gravity than the remaining ones, which is in accordance with the results obtained by Krystianiak and Kontecka (2002). On the other hand, Ipek and Sahan (2001) showed that eggs of broiler breeders of lower specific gravity were characterised by higher embryos’ mortality during incubation and worse hatchability results.

Eggshell

There were more pores per 0.25 cm2 of eggshell surface in light-coloured eggs, i.e. than in light-brown and blue ones. Blue-shelled eggs were characterised by the highest number of pores. Similar results were reported by Krystianiak and Kontecka (2002) as well as by Krystianiak et al. (2005). On the other hand, Kuźniacka et al. (2005a) reported that darker eggs were characterised by a greater total pore number than light-coloured eggs (4768 vs. 4594 pcs.). In the performed investigations, no significant differences were determined between weight, density and percentage proportion of eggshell in pheasant eggs of different colour. On the other hand, Krystianiak and Kontecka (2002) as well as Kirikçi et al. (2005) found that blue eggs were characterised by significantly lightest shells. Light coloured eggs, i.e. light-brown and blue eggs, were found to have thinner shells, which is in accordance with the results reported by Hulet et al. (1985), Krystianiak et al. (2000, 2005) and Krystianiak and Kontecka (2002) where it was demonstrated that blue eggs were also characterised by thinner eggshells. Presumably, cones in these eggshells merge early and papillary layer becomes shallow and, therefore, shells of blue eggs are thinner (Krystianiak et al., 2005). Moreover, Richards and Deeming (2001) demonstrated that papillae with concaved ends without papillary cores occurred in blue eggshells. Such defective shell structure can probably be attributed to an inappropriate binding of the sub-shell membrane with papillary cores. Borzemska (2005) claimed that eggshell structure is also disturbed, when a second egg is laid within 24 hours. An egg which does not stay in the oviduct sufficiently long is also characterised by a worse quality eggshell. The improper eggshell structure may exert a negative influence on embryo development by excessive water evaporation and impairment of gas exchange between the inside of the egg and the outside environment. Usually, hatching results of eggs characterised by thinner eggshells are worse (Roque and Soares, 1994). This was also confirmed by experiments carried out by Christensen (1983) and Bennett (1992) who obtained better hatching results of turkeys and broiler breeders from eggs with thicker eggshells. In addition, Kuźniacka et al. (2005b) observed that in pheasants with progressing reproductive season eggshell thickness as well as proportion of hatched healthy chicks decreased, while the percent of dead embryos increased.

Egg content

Eggs with light- and dark-brown shells, in comparison with blue-shelled eggs, were characterised by heavier yolks. The highest yolk percentage proportion was recorded in light-brown eggs, while the lowest in blue ones. Higher weight of yolks in dark-shelled eggs was also reported by Kirikçi et al. (2005), Kuźniacka et al. (2005a) as well as Mróz and Pudyszak (2000), whereas Silversides and Scott (2001) reported that brown eggs from laying hens were characterised by 0.5–1.0 percentage point smaller proportion of yolk in comparison with white-shelled eggs. In our experiments, the smallest egg-white weight was determined in eggs with light-brown shells. On the other hand, Kirikçi et al. (2005) found that blue eggs were characterised by the smallest albumen weight ( = 14.37 g). In experiments carried out on hens, Silversides and Budgell (2004) found that egg-white weight from eggs with white shells was by 8.89 g smaller in comparison with brown-shelled eggs.

Blue- and olive-shelled eggs were characterised by a higher percentage proportion of the white in comparison with light-brown eggs. Kirikçi et al. (2005) showed that blue-shelled eggs were characterised by the lowest value of these traits ( = 53.65 g), whereas Kuźniacka et al. (2005a)

served and three isoforms were identified. According to

Desert et al. [3], this polymorphism reflects the existence

of isoforms with no, one or two iron atoms per molecule.

Using IEF in the commercial gels with a pH ranging from

4 to 6, we could use gradient to differentiate the proteins

from eggs of different origins.

RP-HPLC has also been used to separate proteins from

different avian species. Figure 4, spectrum a shows a

typical elution profile at 214 nm of hen egg white pro-

teins. The method allowed to separate with different re-

tention times ovomucoid, lysozyme, ovotransferrin and

ovalbumin. The results obtained were similar to those

obtained with SDS-PAGE and we can see that the profile

of duck presents a very high relative concentration of

ovomucoid and a lower content of ovotransferrin. The

chromatogram profile that belongs to ostrich albumen

(Fig. 4, spectrum e) showed the most important differ-

ences. RP-HPLC and SDS-PAGE using Phast System

methods have been proved reliable methods to separate

the principal proteins from different avian species. Both

can be used as routine methods. In general terms the

drawback which has often been associated with gel

electrophoretic methods is the quantification of the bands.

The use of IEF using different gradients permitted to

differentiate isoforms of ovalbumin and ovotransferrin in

the different avian species .

In conclusion, all the techniques managed to separate

the main egg white proteins, and qualitative and quanti-

tative differences were observed between species. This

variability between species suggests advantages in the use

of proteins from different egg sources, which not only

have a similar protein richness to that of hen egg but may

also present other beneficial health properties. This work

constitutes a preliminary study on the different charac-

teristics of these proteins present in the albumen of dif-

ferent species. Nevertheless, more studies are required

using proteomic techniques to characterize novel proteins

and their properties.

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