Egg quality parameter of Naked Neck chicken and commercial layer strains in Bangladesh

Egg quality parameter is important for determination of egg quality, grading of egg and pricing. To conduct this study, 50 eggs of Hy-line Brown, 50 eggs of ISA Brown, 50 eggs of Saver-579 Brown and 50 eggs of Novogen Brown and 50 eggs of Naked Neck were collected from different poultry farms of Sylhet. Egg shape index (ESI) of Hy-line Brown, ISA Brown, Saver-579, Novogen Brown and Naked Neck were 78.86±1.24, 78.85±0.5, 78.45±1.20, 81.43±1.56 and 76.85±0.92 respectively. Egg weight of Hy-line Brown, ISA Brown, Saver-579, Novogen Brown and Naked Neck were 62.48±1.54g, 61.89±1.2g, 61.41±1.47g, 64.76±1.37g and 37.45±1.2g respectively. Yolk weight of Hy-line Brown, ISA Brown, Saver-579, Novogen Brown and Naked Neck were 18.09±0.62g, 18.26±0.29g, 19.33±0.32g, 19.73±0.21g and 15.12±0.48g respectively. Among the different strains/breed, Novogen Brown has the highest value and Naked Neck has the lowest value for ESI, egg weight and yolk weight. So that the grading value of Novogen Brown has the highest among other strain/breed. Future research is necessary to see the internal egg quality parameter (albumen index, yolk index, Haugh Units (HU) and yolk colour) of different strain/breed, which will help for grading of egg.


Introduction
Poultry is a good source of meat and egg which are used for human consumption. Fertile egg is used for reproduction of poultry species. The embryo inside the egg fully depends on the egg for nutrition. Egg also protect the embryo from adverse environmental effect (Abanikannda et al., 2007). Egg shell, albumen and yolk are the main part of an egg. The weight of an egg depends on egg shell, albumen and yolk. The weight of egg vary between breed or strain of different poultry species (Jones et al., 2010). Egg shell is important because it covers the egg and prevent invasion of microbes in egg. The quality of an egg is decreased if there are cracks in egg shell. During the time of processing and marketing of eggs a higher proportion of egg shell is ruptured (Qiu et al., 2020). Cracked and broken egg shells are major source of economic loss for farmer in two ways-cracked and broken egg can't be sold as quality egg, and cracks in egg shell increases the chances of microbial invasion which decreases the egg quality (Kemps et al., 2006). Cracked and damaged egg are responsible for economic loss of commercial layer farms, which is 6-8% of total egg production (Hamilton et al., 1979). Albumen is the white part of an egg and protect the embryo from different microorganism until the development of immune system. It also provides nutrition for developing embryo. Yolk is the main source of different nutrients for embryo. It is also a major source of different minerals (Na, K, P, Zn, Cu, Mn and Fe) for embryo, whereas albumen only provides Na and K for developing embryo (Yair and Uni, 2011). In the egg processing plant, the weight of egg, shell, albumen and yolk as well as their rate is important to set up the price of an egg. Asian J. Med. Biol. Res. 2020, 6 (3)

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The egg production, size of the egg, internal and external quality of egg has significant effect in breeder farm for breeding policy of commercial layers. Egg weight is an important egg quality parameter to determine some quality traits-albumen, yolk and shell weight. Weight of albumen, yolk and shell depends on egg weight. In case of Brown egg producing commercial strain, if the egg weight is 63.4 g, then the albumen, yolk and shell will be 64.3%, 26.1% and 9.6% respectively of egg weight (Grashorn, 2018). Egg shape index is also important egg quality parameter which ranges from 0 to 100 (Duman et al., 2016). Egg quality parameter consists of some characteristics (external and internal characteristics) of an egg which have a great impact on consumers. Nowadays consumers are very concern about what they buy and what they eat. So, we need to give more attention about different egg quality parameter. It is also important to reduce the problem related to production, processing, preservation and marketing of eggs (Kejela et al., 2019). Thick albumen and less air cell area (broader end of an egg) are two important characteristics for freshness of an egg. Consumers prefer clean, fresh and large egg and for this reason we need to give more attention on different external egg quality parameter-cleanliness, freshness and egg weight (Toussant and Latshaw, 1999). Egg is accepted as a staple food, which contains all important ingredients for balanced human diet. Biological value of chicken egg is 94 (scale: 0 to 100), which indicates that the different amino acids of egg are stay in proper proportion which is good for human body. To maintain superiority in overall egg quality, continuous genetic evaluations of egg quality traits in different breed and strains are essential. Therefore, this study was carried out to estimate different egg quality parameters-egg weight, shell weight, albumen weight, yolk weight and egg shape index of Naked Neck chicken and different commercial layer strains.

Study area, duration and collection of eggs
This study was conducted in Sylhet, Bangladesh from July to December, 2019. A total of 250 eggs of different strain/breed were collected from different poultry farms of Sylhet. In our study we used eggs of four different commercial layer strains-50 eggs of Hy-line Brown, 50 eggs of ISA Brown, 50 eggs of Saver-579 Brown and 50 eggs of Novogen Brown. We also collected 50 eggs of Naked Neck from the indigenous chicken project of Sylhet Agricultural University, Sylhet, Bangladesh.

Egg shape index (ESI)
The egg shape index (ESI) was determined by using the following formula (Duman et al., 2016;Anderson et al., 2004) ESI Here, L means length of egg and W means width of egg. We used digital slide calipers for measurement of egg length (L) and width (W) in millimeter (mm). Eggs were classified on the basis of shape index (SI) (Altuntaş and Şekeroǧlu, 2008)sharp egg (SI < 72), normal (standard) egg (SI = 72-76) and round egg (SI > 76).

Measurement procedure of egg weight, shell weight, albumen weight and yolk weight
Electronic balance was used for weighing of egg, albumen, yolk and shell in gram (g). After taking all egg weight, eggs were broken and shell, yolk, and albumen were immediately separated and weighed. Albumen and yolk were separated by using funnel. We cracked the egg and put albumen and yolk together on a funnel, then the funnel separated the albumen from yolk.

Statistical procedure
Different egg quality parameter (length of egg, width of egg, egg shape index, egg weight, shell weight, albumen weight and yolk weight) were analyzed by ANOVA using the GLM procedure of Minitab statistical software (2019) at 5% level of significance. We did Tukey pairwise comparisons to see the variation among different strain/breed for different egg quality parameter.

Results and Discussion
Egg quality parameter (length of egg, width of egg, egg shape index, egg weight, shell weight, albumen weight and yolk weight) of different strain/breed are shown in Table 1. The length and width of egg is highest in Novogen Brown (57.2mm and 46.6mm) and lowest in Naked Neck (51.73mm and 39.73mm). Egg shape index (ESI) is highest for Novogen Brown (81.43) and lowest for Naked Neck (76.85). Shape of the eggs of different strain/breed is round (ESI is more than 76). The values obtained in this study for ESI of ISA Brown and Naked Neck is similar to the findings of Kabir et al., (2012) (9.90 ESI for ISA Brown and 78.10 ESI for Naked Neck). Egg weight of different strain/breed was given in Table 1. The weight of an egg is a direct proportion of shell, albumen and yolk that it contains and this varies significantly between breeds or strains of the bird species (Jones et al., 2010). Among the different strain/breed, egg weight is higher in Novogen Brown (64.76g) and lower in Naked Neck (37.45g). According to our observation the egg weight of Hy-line Brown, ISA Brown, Saver 579 Brown and Novogen Brown are similar with the standard egg weight Hy-line Brown, ISA Brown, Saver 579 Brown and Novogen Brown. Standard egg weight of Hy-line Brown, ISA Brown, Saver 579 Brown and Novogen Brown is 62.1g, 62.9g, 62g and 64g respectively (Table 2). Egg weight of Novogen Brown is higher than the findings of Cornwall-Thomas (2019) (60.3g for Novogen Brown) and Dawud Ibrahim Yimer (2019) (57.7g for Novogen Brown). Egg weight of Naked Necked and ISA Brown is higher from the findings of Kabir et al., (2012) (57.50g for ISA Brown and 20.20g for Naked Neck). Our findings for egg weight of ISA Brown is similar with the findings of Islam et al.,(2013) (egg weight of ISA Brown is 61.656g). However, egg weight of Naked Necked (37.45g) is lower than the findings of Islam and Dutta (2010) (egg weight of indigenous chicken is 40.04g) and Yakubu et al., (2008) (egg weight of Naked Neck is 43.04g). Egg shell weight of different strain/breed was given in Table 1. Among the different strain/breed, Hy-line Brown and ISA Brown strain has the highest egg shell weight (8.83g) and lowest for Naked Necked breed (4.42). Shell weight of different strain/breed is higher than the standard value except Naked Neck (Table 3). Standard egg weight of Hy-line Brown, ISA Brown, Saver 579 Brown, Novogen Brown and Naked Neck is 6.83g, 6.9g, 6.82g, 7.04g and 4.62g respectively (Table 3). Egg shell was weighted immediate after the breaking of the fresh eggs that's why some parts of albumen may attach with egg shell which was responsible for the higher egg shell weight than the standard egg shell weight. Albumen weight of different strain/breed was given in Table 1. Internal egg parameters such as albumen weight and yolk weight are very important from nutritional and health viewpoints (Sparks, 2006). Among the different strain/breed, albumen weight is higher in Novogen Brown (36.23g), however, it is slightly lower than the standard albumen weight for Novogen Brown (37.76g) ( Table 4). The lowest value of albumen weight is for Naked Neck (17.71g) which is also lower than the standard value of albumen weight for Naked Neck (20.53g). Albumen weight of different strain/breed is lower than the standard value because of albumen might be attached with the egg shell during separation procedure of egg shell and albumen. Albumen weight of Naked Neck is lower than the findings of Islam and Dutta (2010) (albumen weight of Naked Neck is 18.92g), but about two times higher than the findings of Kabir et al., (2012) (albumen weight of Naked Neck is 8.10g). Yolk weight of different strain/breed is given in Table 1. The higher yolk weight for Novogen Brown (19.73g) which is similar with the standard yolk weight of Novogen Brown (19.8g) ( Table 5). Among the different strain/breed, the lower yolk weight for Naked Neck (15.12g) which is also lower than the standard yolk weight of Naked Neck (16.95g) ( Table 5). Yolk weight of ISA Brown and Naked Neck both are relatively higher than the findings of Kabir et al., (2012) (yolk weight for ISA Brown and Naked Neck is 11.9g and 7.9g respectively). Moreover, yolk weight of Naked Neck is higher than the findings of Islam and Dutta (2010) (yolk weight of Naked Neck is 14.65g). This occurs for variation in egg weight and shell weight of different strain/breed.