Open-access The Influence of Physical Characteristics of Pheasant Egg on Incubation Results

ABSTRACT

The aim of this study was to determine the influence of physical characteristics of pheasant eggs (egg weight, egg length, egg width, egg shape index) on incubation results. The study was performed on 150 randomly chosen pheasant eggs from the parent flock at 45-50 weeks of age. The birds were bred at the pheasant station „Ub“ (44°28’N, 20°03’E, 97 m a.s.l.). Eggs were incubated and divided into three groups: all eggs, eggs lighter than average (< 28 g), and eggs heavier than average (> 28 g). Each group was subdivided into three categories: all eggs, hatched eggs, and eggs that did not hatch. Significant correlation (p<0.001 and p<0.01) between egg weight and length were found across all groups and categories. Similar significance was observed between egg weight and width, except in the lighter than average eggs across all categories, and in the hatched heavier than average eggs (p>0.05). In all groups and categories of pheasant eggs, correlation between weight of eggs and egg shape index was not statistically confirmed (p>0.05), except in hatched eggs with lower than average weight (p<0.05). It can be concluded that egg weight significantly impacts incubation results, but egg length and shape index should also be considered to improve hatchability and offspring vitality. Overall, incorporating all examined physical parameters of pheasant eggs into the selection criteria for incubation is essential for optimizing hatchability and offspring vitality.

Keywords: Egg length; egg shape index; egg weight; incubation; pheasant

INTRODUCTION

Breeding of pheasants (Phasianus colchicus) was previously con-sidered a privilege of the higher class, with birds of this species being bred for their beauty and hunting purposes. Today, however, the breeding of pheasants is gaining global importance. Pheasants are used in commercial poultry production for various reasons in different parts of the world (Yamak et al., 2016). While production is still primarily directed towards developing hunting tourism, it is also becoming increasingly important in meat production. Pheasants are bred mainly as hunting material, meat for human consumption, and release into the wild to prevent the decline of this wild species’ population (Kırıkçı et al., 2004; Ozbey et al., 2004; Caglayan et al., 2010). Meat of wild birds, including pheasants, is a high quality food that has some advantages compared to meat of domestic birds.

In poultry breeding, high fertility, hatchability and low embryonic mortality are the main goals for profitability and productivity (Uğurlu et al., 2017). The success in one-day-old bird offspring production depends on many factors, such as: age of the parent flock, period of laying, technology applied in parent flock breeding, egg collection operations, egg manipulation, egg and incubation station hygiene, technology of incubation, and quality of eggs used for incubation (Đermanović et al., 2016). In order to obtain offspring from the fertilized eggs, several factors are crucial for the development of embryo, such as adequate temperature, ventilation, relative humidity of air and rotation of eggs in the incubator. Nutrition and proper manipulation of the parent flock and their offspring influence birds’ reproduction processes, increasing the percentage of hatching and the vitality of hatched birds (Đermanović et al., 2012; 2013; 2016; 2018; Đermanović & Mitrović, 2013).

For a long time, the quality of eggs for incubation has been determined solely based on egg weight. However, recent studies have shown that other egg characteristics should also be considered, such as egg length, egg width and egg shape index (Olajide & Ade-Omowaye, 1999; Narushin & Romanov, 2002; Narushin, 2005; Altuntas & Sekeroglu, 2008; 2010). Besides the evaluation of egg quality, it is also neccesary to evaluate the quality of hatched offspring, with egg weight loss and relative share of chicken within the egg being the most important characteristics. Similar to other poultry species, particularly chickens, egg weight loss and the relative share of the chick within the egg indicate better or poorer vitality, which correlates with the survival rate of the hatched offspring (Đermanović et al., 2016).

The aim of this study was to determine the influence of pheasant eggs’ physical characteristics on incubation results. In addition to egg weight, the length and width of eggs, the weight of one-day-old chicks and the relative share of the chick withing the egg were monitored. To obtain more accurate results and conclusions, egg weight loss in specific stages of incubation was determined.

MATERIALS AND METHODS

The study was performed on 150 randomly chosen pheasant eggs from the parent flock bred at the pheasant station „Ub“ (44° 28’N, 20° 03’E, 97 m a.s.l.). Birds of the parent flock were 45-50 weeks old. The birds were housed in a communal aviary with a sex ratio of 1 male to 9 females. Each bird had approximately 2 square meters of floor space. Natural lighting conditions were maintained throughout the egg-laying cycle, with no artificial lighting used in the aviaries. They were fed a commercial mixture containing 18% crude protein and 11 MJ/kg metabolic energy, and had free access to water. Eggs were collected in the end of March and the beginning of April, 2023. The weight of each egg was measured in order to determine the average weight. Each egg was marked and placed in the incubator. Eggs were divided into three groups: all eggs, eggs lighter than average (<28 g), and eggs heavier than average (>28 g). Each group was subdivided into three categories: all eggs, hatched eggs, and eggs that did not hatch.

Before placing for incubation, weight (W), length (EL) and width (EW) were monitored for each egg. The weight was measured on a scale with ±1 g precision, while length and width of eggs were determined with a ±0.02 mm precision caliper. Measurement of egg parameters was performed on 3-to-5-days-old eggs. Based on determined exterior quality parameters, egg shape index (ESI) was calculated as follows:

E S I ( % ) = ( E W / E L ) x 100

(Olajide & Ade-Omowaye, 1999; Narushin, 2005; Narushin & Romanov, 2002; Altuntas & Sekeroglu, 2008; 2010).

Eggs were placed in individual cells of the incubator with automatically regulated functions.

Within each group, average values and variability parameters for all eggs, hatched eggs and unhatched eggs were determined.

At the end of the incubation period, the weight of hatched and dried one-day-old pheasant chicks (PW) was measured on a scale with ±1 g precision, followed by the determination of chicken share in the egg (PSE) according to the formula:

P S E ( % ) = ( P W / W ) x 100

Statistical parameters (mean, standard error of the mean, standard deviation, and coefficient of variation) were calculated for each group and category of the studied eggs. Based on the obtained results, the correlation between observed characteristics, egg quality parameters and quality of one-day-old chicken quality was determined. Statistical analysis was performed using the IBM SPSS statistics Version 22 (2013) package.

RESULTS

The average values and variability of exterior quality characteristics of pheasant eggs across the three analyzed groups and three categories are presented in Table 1. The results show that the average weight of pheasant eggs was 28.81 g, while the average weights of eggs lighter and heavier than average were 26.76 g and 30.26 g, respectively. Basic physical characteristics of pheasant eggs were similar among the three groups: egg length was equal to 4.43 cm, 4.33 cm, and 4.50 cm, while egg width was 3.51 cm, 3.43 cm, and 3.56 cm in the respective groups. The egg shape index was nearly identical among groups: 79.24% for all eggs and eggs >28 g, and 79.25% for eggs <28 g. On the 21st day of incubation, the weight of eggs varied from 22.94 g to 26.20 g.

All investigated eggs Hatched eggs Unhatched eggs Parameter Average C.V. SE Average C.V. SE Average C.V. SE All eggs n 150 102 48 W (g) 28.81 7.63 0.18 29.05 7.24 0.21 28.31 8.25 0.34 EL (cm) 4.43 3.77 0.01 4.45 3.53 0.02 4.38 4.06 0.03 EW (cm) 3.51 2.78 0.01 3.52 2.63 0.01 3.49 3.03 0.02 ESI (%) 79.24 3.53 0.23 79.03 3.44 0.27 79.69 3.69 0.42 W21 (g) 24.85 10.22 0.21 25.05 8.36 0.21 24.44 13.42 0.47 PW (g) - - - 17.83 10.26 0.18 - - - PSE (%) - - - 61.43 7.96 0.48 - - - Eggs < 28 g n 62 36 26 W (g) 26.76 4.82 0.16 26.89 5.09 0.23 26.62 4.52 0.24 EL (cm) 4.33 3.77 0.02 4.35 3.58 0.03 4.3 3.98 0.03 EW (cm) 3.43 1.93 0.01 3.43 1.62 0.01 3.42 2.24 0.02 ESI (%) 79.25 3.94 0.4 78.88 3.73 0.49 79.49 4.13 0.64 W21 (g) 22.94 8.57 0.25 23.25 6.61 0.26 22.5 10.69 0.47 PW (g) - - - 16.53 7.99 0.22 - - - PSE (%) - - - 61.51 7.14 0.73 - - - Eggs > 28 g n 88 66 22 W (g) 30.26 4.66 0.15 30.24 4.42 0.16 30.24 5.42 0.35 EL (cm) 4.5 2.89 0.01 4.51 2.78 0.02 4.46 3.2 0.03 EW (cm) 3.56 2.06 0.01 3.56 2.1 0.01 3.57 1.99 0.02 ESI (%) 79.24 3.24 0.27 79.01 3.23 0.31 80.01 3.22 0.55 W21 (g) 26.2 7.5 0.21 26.03 6.39 0.2 26.67 10.16 0.58 PW (g) - - - 18.53 9.14 0.21 - - - PSE (%) - - - 61.29 8.4 0.63 - - - n - number of eggs; W - egg weight; EL - egg length; EW - egg width; ESI - egg shape index; W21 - egg weight on day 21; PW - weight of one-day-old pheasant chick; PSE - chicken share in the egg

Within the group of hatched eggs, the average weight was 29.05 g for all eggs, 26.89 g for eggs <28 g, and 30.24 g for eggs >28 g. The length and width of eggs in this group were nearly the same; which is understandable, as these quality parameters do not change according to the incubation technology applied. However, some small differences within groups were observed, likely due to the different number of examined eggs within each group. The average values of the egg shape index were 79.03% for all eggs, 78.88% for eggs <28 g, and 79.01% for eggs >28 g. The weight of eggs on the 21st day of incubation varied from 23.25 g to 26.03 g. For this group of eggs, evaluating the quality of eggs and the quality of hatched offspring, as well as their correlation, is highly important. Therefore, special attention was given to parameters such as pheasant weight and the relative share of the pheasant in the egg. The determined pheasant weight was 17.83 g for all eggs, 16.53 g for eggs <28 g, and 18.53 g for eggs >28 g. Depending on the weight of one-day-old chicks and the weight of eggs, as well as weight loss during incubation, the observed values of the relative share of the chick in the egg were 61.43%, 61.51%, and 61.29% in the respective groups.

In the group of unhatched eggs, the average egg weight was 28.31 g, the weight of eggs lighter than average was 26.62 g, and the weight of eggs heavier than average was 30.24 g. As in other groups, the parameters of egg length and width did not differ significantly among categories. However, the egg shape index varied among categories, amounting to 79.49% (egg <28 g), 79.69% (all eggs) and 80.01% (eggs >28 g). Similarly to other groups, the lowest egg weight on the 21st day of incubation (22.50 g) was observed in eggs lighter than average, and the highest (26.67 g) in the eggs heavier than average.

The incubation value of eggs generally refers to the percentage of fertilization, i.e., the percentage of chicks hatched from incubated eggs. Therefore, investigating egg weight loss during incubation and the weight of one-day-old offspring significantly contributes to the evaluation of egg quality for incubation. Determining the correlation between examined characteristics is crucial for evaluating the quality of incubation eggs and the achieved results of incubation, as shown in Tables 2, 3, and 4.

Table 2
Phenotypic correlation between physical characteristics of eggs.
Table 3
Phenotypic correlation between physical characteristics of hatched eggs.
Table 4
Phenotypic correlation between physical characteristics of unhatched eggs.

Based on determined correlation coefficients, it might be concluded that in all three groups and categories there was a significant correlation between weight and length of eggs (p<0.001 and p<0.01). A similar correlation existed between weight and width of eggs, except in eggs lighter than average, and in hatched eggs heavier than average (p>0.05). However, in all groups and categories of eggs, correlation between weight and egg shape index was not statistically significant (p>0.05), except in hatched eggs of lower weight than average (p<0.05).

Egg length is one of the most important parameters of incubation quality, and showed a very significant statistical correlation with egg shape index (p<0.001). This parameter was significantly correlated to egg width (p<0.01 and p<0.05), except in eggs of lower weight than average, especially in hatched eggs.

Similarly to egg length, egg width, which is another important characteristic for incubation quality, showed significant correlation with egg shape index (p<0.01 and p<0.05). The only deviation from this finding was observed among the unhatched eggs (p>0.05).

Examination of correlation between physical characteristics of egg quality and incubation results showed a statistically significant correlation (p<0.01 and p<0.05) between egg weight and weight of hatched chicks. Similar results were obtained between egg length and weight of hatched chicks, as well as between egg width and weight of hatched chicks in all eggs. The same parameters in heavier and lighter than average eggs were not correlated to the weight of hatched chicks (p>0.05). Egg shape index and weight of hatched chicks were not correlated (p>0.05). Similar results were obtained for the correlation of physical characteristics of eggs and the relative share of the pheasant in the egg (p>0.05). A remarkably high statistical significance (p<0.001) was determined for the correlation between weight of hatched chicks and share of the pheasant in the egg.

DISCUSSION

To achieve the main goals in chicken reproduction, huge attention should be given to laying egg quality, i.e. their physical characteristics, such as egg weight, egg length, egg width, egg shape index, egg volume, egg area, egg shell thickness, specific weight of egg, length circumference, and width circumference (Narushin & Romanov, 2002; Narushin, 2005; Altunaş & Şekeroğlu, 2008; 2010; Đermanović et al., 2012; 2013; 2015; Đermanović & Mitrović, 2013). Understanding the physical characteristics of eggs is crucial for improving reproductive efficiency and egg quality, which directly impacts the success of incubation and the health of future chicks.

Research on quality of pheasant eggs for reproduction performed by Usturoi et al. (2010) has shown that the average weight of eggs was 28.64 g in the beginning of the laying period, 31.02 g at the peak of laying, 31.87 g at the middle of laying, and 32.16 g at the end of egg production. The average egg weight in this research was 30.92 g. Like egg weight, egg shape index was equal to 78.14%, 78.89%, 79.09% and 79.22% in the respective periods, with an average value for the whole period of production of 78.83%. The average egg weight, regardless of the laying period studied by Usturoi et al. (2010), was higher when compared to our results, while the average egg shape index had similar or slightly higher value.

A similar investigation of egg quality was conducted by Mangiagalli et al. (2003), who weighed eggs laid on the 43rd, 48th and 54th weeks of flock age. The authors determined the average egg weights of 34.4 g (43rd week), 34.6 g (48th week) and 34.5 g (54th week). The average egg weight for the whole laying period was 34.5 g, which was higher than the egg weight observed in our research with a flock of similar age (45-50 weeks).

Górecki et al. (2020) investigated the basic physical and biochemical characteristics of pheasant eggs depending on the period of laying. The authors have determined the average egg weights of 32,73 g in April and 33,35 g in June, the average lengths of 45,64 mm (April) and 46,35 (June), the average width of 36,09 mm (April) and 36,16 mm (June), and the average egg shape index of 79,13% in April and 78,10% in June. The laying-period-dependent differences observed were statistically significant (p<0.1). Although egg length, egg width, and egg shape index from the group of eggs laid in April in the research by Górecki et al. (2020) were very similar to our results, the average egg weight in this research was somewhat higher compared to weight of eggs in our research (32.73 g vs. 28.81 g), which is probably due to the different diets of birds from the parent flock and the breeding conditions.

Ashraf et al. (2016) have given detailed results on basic physical characteristics of pheasant eggs and one-day-old offspring. The authors have divided eggs in three weight categories: heavy, medium and light eggs, with average weights for each category of 36.18 g, 26.88 g and 22.86 g, respectively. The average lengths of eggs in each category were respectively 4.37 cm (heavy eggs), 4.20 cm (medium eggs) and 4.09 cm (light eggs); while the average egg widths were respectively 3.48 cm, 3.41 cm and 3.25 cm. The average egg shape indexes were 79.68% (heavy eggs), 81.22% (medium eggs) and 79.53% (light eggs). After the incubation period, the authors determined that the average pheasant chicks weighted 14.80 g among males, and 15.70 g among females. The average weight of hatched eggs obtained in our study was similar to the weight of medium eggs, egg shape index had nearly the same value, and the weight of hatched chicks was slightly higher in our research compared to results of Ashraf et al. (2016). With same weight categories, Ipek & Dikmen (2007) have determined the following average egg weights: 22.6 g (heavy eggs), 21.8 g (medium eggs) and 19.5 g (light eggs).

Esen et al. (2010) investigated basic parameters of reproduction eggs quality in one-, two-, and three-year-old breeding flocks. The average laying rates for the one-, two-, and three-year-old flocks were respectively 47.58%, 53.27%, and 42.69%. The percentage of hatching from all laid eggs ranged from 63.35% (one year old flock) to 71.45% (three-year-old flock), while the hatching rate from fertilized eggs was between 67.13% (one year old flock) and 76.12% (three-year-old flock). The average egg weights determined in this research were 28.74 g (one year old flock), 32.11 g (two-year-old flock) and 33.83 g (three-year-old flock). Unlike egg weight, which increased with flock age, the authors have observed a decrease of egg shape index, equalling 84.14%, 78.59% and 77.49% in the respective groups. The same parameters in different pheasant strains were investigated by Błaszccyk & Pohorecki (2015), who have determined the average weight of pheasant egg to be 27.67 g, and egg shape index to be 74.86%, which is perfectly in line with the results obtained in our research. Moreover, the average weight of eggs obtained in our research is in accordance with results by Krystianiak et al. (2007), who found that one-year-old flocks had significantly (p<0.05) lower average egg weight (29,4 g) compared to two-year-old flocks (30,5 g).

Ozbey et al. (2011a) have studied egg quality in four parent flock age groups: up to 34, 35-36 weeks, 37-38 weeks, and more than 39 weeks of age. The average weights of eggs in the respective groups were: 28.52 g, 31.64 g, 32.48 g and 30.86 g. Egg shape indexes were respectively 80.48%, 82.34%, 78.75% and 76.58%. The influence of age on physical characteristics of pheasant eggs, i.e. increase of average values for the observed characteristics, have been confirmed by Günlü et al. (2018). Furthermore, Ozbey et al. (2011b) have investigated pheasant reproductive eggs quality depending on the weight of hatched chicks. Authors have divided chicks into three weight groups: up to 20.00 g, 20.01 - 22.00 g, and more than 22.01 g. The average egg weight in birds from the first group was 28.32 g, from the second group it was 31.23 g, and from the third group it was 32.89 g. The average egg shape indexes were 83.54%, 79.71% and 75.73% in the respective groups.

Kirikçi et al. (2003) determined the average weight of pheasant eggs of 31.03 g and the egg shape index of 80.69%. Garip et al. (2010) obtained similar results, reporting an average weight of pheasant eggs of 31.02 g, and egg shape index of 80.58%. Both authors obtained somewhat higher results than those of our research. When studying egg quality in relation to egg shell color, i.e. different strains of pheasants, Kirikçi et al. (2005) obtained the following results: average egg weights were 33.2 g (dark brown eggs), 32.0 g (light brown eggs), 33.3 g (olive eggs) and 32.5 g (blue eggs); while egg shape indexes were 79.3%, 77.7%, 80.0% and 79.5%, respectively. Further insight into differences in quality of eggs of different colors was given by Nowaczewski et al. (2013). These authors have found egg weights of 32.46 g (blue), 31.35 g (light brown), 31.98 g (olive) and 32.34 g (dark brown), with an average weight for all observed eggs of 32.03 g. Reported egg lengths and widths were 4.56 cm and 3.58 cm (blue), 4.42 cm and 3.72 cm (light brown and dark brown), 4.22 cm and 3.62 cm (olive), with the average of 4.41 cm and 3.66 cm for all eggs. Based on measured egg length and width, egg shape indexes were calculated to be 78.72% (blue), 84.21% (light brown), 87.63% (olive) and 84.19% (dark brown), with the average value for all eggs of 83.69%.

Differences in the weight and physical characteristics of eggs in our study can be attributed to several factors. The first and most likely reason is the diet of the parent flock. As demonstrated by Kokoszyński et al. (2011), increased protein intake in the diet can significantly increase egg weight, length, and width, indicating that varying protein contents in the feed may be one of the causes of the observed differences. Another significant factor is the age of the birds. It is well known that as birds age, egg size increases, which could explain the increase in egg weight in older flocks. Additionally, the housing conditions of the birds (such as temperature, humidity, and overall microclimatic conditions in the facilities) can further influence the physical characteristics of the eggs. Finally, genetic differences between the pheasant lines used may have contributed to variations in the results, as different genetic lines can have different reproductive characteristics. All these variations together may explain the specific outcomes observed in our study.

CONCLUSIONS

Based on the obtained results, it can be concluded that egg weight plays a significant role in determining their quality and selecting eggs for incubation. However, the results also indicate that other indicators, such as egg length and egg shape index, should not be overlooked when assessing the quality of hatching eggs and, consequently, hatched offspring. Furthermore, the research results suggest that egg length has a more significant impact on embryonic development and the hatchability of high-vitality pheasant chicks than egg width. Taking this into account, selecting eggs for incubation based on all the examined physical parameters would lead to higher fertility, hatchability, and vitality of the hatched offspring.

However, the limitations of this study include focusing on a single genetic line and specific environmental conditions, which indicates the need for further research encompassing different genetic lines and environmental conditions. This would allow for the verification and expansion of these findings to various genetic populations and environments, thereby improving the accuracy and applicability of the criteria for egg selection for incubation.

ACKNOWLEDGMENTS

The authors are grateful to the Ministry of Education, Science and Technological Development of the Republic of Serbia for sponsoring part of the study within project (contract number 451-03-65/2024-03/200116).

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  • Data availability statement
    The data used in this study will be available upon request.
  • Disclaimer/Publisher’s Note
    The published papers’ statements, opinions, and data are those of the individual author(s) and contributor(s). The editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content.

Edited by

  • Section editor:
    Maria Fernanda Burbarelli

Data availability

The data used in this study will be available upon request.

Publication Dates

  • Publication in this collection
    25 Nov 2024
  • Date of issue
    2024

History

  • Received
    20 May 2024
  • Accepted
    08 Sept 2024
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