Introduction
⌅The production of poultry eggs, especially chicken eggs, has gained substantial interest due to their nutritional benefits, price, and the lack of any religious or traditional condemnation. Moreover, the recent rise in the global economic crisis, especially in developing and underdeveloped countries, has increased the global demand for chicken eggs as the main source of animal protein (Abdallah et al., 2022Abdallah N, Boga YE, Kursun K, Baylan M, 2022. Automation in layer hen production. Int Conf on Research of Agricultural and Food Technologies, Adana (Türkiye), Dec 22. pp: 9.). Additionally, the demand for poultry products, especially eggs has increased tremendously due to increasing levels of income and standard of living (Pomaah et al., 2023Pomaah AN, Abdallah N, Kurşun K, Baylan M, 2023. Egg production and consumption: a case study in Teshie municipality (Ghana). OKÜ Fen Bil Ens: 12 (6 Ek Sayı):454-66. 10.47495/okufbed.1265446). This has led to an increased interest in the production of other alternative poultry species such as quails for both eggs and meat. For instance, in India, the Japanese quails (Coturnix japonica) have been reported as promising poultry species for rural farmers due to their low cost of production and management (Bagh et al., 2016Bagh J, Panigrahi B, Panda N, Pradhan CR, Mallik BK, Majhi B, Rout SS, 2016. Body weight, egg production, and egg quality traits of gray, brown, and white varieties of Japanese quail in coastal climatic condition of Odisha. Vet World: 9(8): 832. 10.14202/vetworld.2016.832-836). Japanese quails are the smallest farmed poultry species in terms of size (Panda & Singh, 1990Panda B, Singh RP, 1990. Development in Processing Quail. Worlds Poult Sci J: 46: 219-234.), and are becoming highly significant for their eggs and meat (Dahouda et al., 2013Dahouda M, Adjolohoun S, Montchowui EH, Senou M, Hounsou NMD, Amoussa S, Vidjannagni DS, Abou M, Toleba SS, 2013. Growth performance of quails (Coturnix coturnix) fed on diets containing either animal or vegetable protein sources. Int J Poult Sci: 12(7): 396-400. 10.3923/ijps.2013.396.400; Mahrose et al., 2021Mahrose KM, Michalak I, Farghly M, Elokil A, Zhang R, Ayaşan T, Mekawy A, Fazlani S, 2021. Role of clay in detoxification of aflatoxin B 1 in growing Japanese quail with reference to gender. Vet Res Commun: 45:363-371. 10.1007/s11259-021-09817-z).
One of the most important sources of nutrients is eggs and some authors have reported that the eggs of Japanese quails are rich in minerals, vitamins, and antioxidants with 3-4 times superior nutritional value compared to chicken eggs (Lalwani, 2011Lalwani, 2011cited from Tunsaringkarn T, Tungjaroenchai W, Siriwong W, 2013. Nutrient benefits of quail eggs. IJSRP: 3(5):1-8.; Tunsaringkarn et al., 2013Tunsaringkarn T, Tungjaroenchai W, Siriwong W, 2013. Nutrient benefits of quail eggs. IJSRP: 3(5): 1-8.; Cadillo et al., 2023Cadillo AE, Malaver RH, Herrera FF, Degollar EM, Julca AC, Lara RT, Martineza RP, 2023. Analysis of Quality and Shelf Life of Quail Eggs in Sauce of Beta Vulgaris” Beterraga”. Chem Eng Trans: 101:247-52. 10.3303/CET23101042). An average quail egg weighs around 11g (Tolik et al., 2014Tolik D, Poawska E, Charuta A, Nowaczewski S, Cooper R, 2014. Characteristics of egg parts, chemical composition and nutritive value of Japanese quail eggs–a review. Folia Biol (Kraków): 62(4):287-292. 10.3409/fb62_4.287). A higher albumen protein content (Genchev, 2012Genchev A, 2012. Quality and composition of Japanese quail eggs (Coturnix Japonica). TJS: 10(2): 91-101.) and lower yolk fat content (Sınanoglou et al., 2011Sınanoglou VJ, Strati IF, Miniadis-Meimaroglou S, 2011. Lipid, fatty acid and carotenoid content of edible egg yolks from avian species: A comparative study. Food Chem: 124(3): 971-977. 10.1016/j.foodchem.2010.07.037) in quail eggs have been reported. Female Japanese quails have a high egg production rate and can lay around 300 eggs per year with their egg production cycle starting around 6 weeks of age (Kaur et al., 2008Kaur S, Mandal AB, Singh KB, Kadam MM, 2008. The response of Japanese quails (heavy body weight line) to dietary energy levels and graded essential amino acid levels on growth performance and immuno-competence. Livest Sci: 1:117(2-3):255-62. 10.1016/j.livsci.2007.12.019; Dzuriatmono et al., 2019Dzuriatmono ST, Widyas N, Cahyadi M, Wati AK, Dewanti R, 2019. Egg production of black and brown Japanese quails raised under battery cage system. The 8th Int Sem on Tropical Animal Production, Yogyakarta (Indonesia), Sept 23–25(Indonesia). pp:012042. 10.1088/1755-1315/387/1/012042). Other authors also reported that sexual maturity in Japanese quails may vary between 35 and 45 days (Thomas & Ahujam, 1988Thomas PC, Ahuja SD, 1988. Improvement of broiler quails of CARI through selective breeding. Poultry guide: 25(10): 45-47.; Mınvıelle et al., 2000Minvielle F, Monvoisin JL, Costa J, Maeda Y, 2000. Long-term egg production and heterosis in quail lines after within-line or reciprocal recurrent selection for high early egg production. Br Poult Sci: 41(2): 150-157. 10.1080/713654914; Camci et al., 2002Camci, O, Erensayin C, Aktan S, 2002. Relations between age at sexual maturity and some production characteristics in quails. Arch fur Geflugelkd: 66(6): 280-282.; Reddish et al., 2003Reddish JM, Nestor KE, Lilburn MS, 2003. Effect of selection for growth on onset of sexual maturity in random bred and growth-selected lines of Japanese quail. Poult Sci: 82(2):187-191. 10.1093/ps/82.2.187; Sezer et al., 2006Sezer M, Berberoglu E, Ulutas Z, 2006. Genetic association between sexual maturity and weekly live-weights in laying-type Japanese quail. S Afr J Anim Sci: 36(2): 142-148. 10.4314/sajas.v36i2.3997; Alkan et al., 2009Alkan S, Karabag K, Galic A, Balcioğlu MS, 2009. Effects of season and line on sexual maturity and some egg yield traits in selected Japanese quails. J Appl Anim Res: 35(2): 105-108. 10.1080/09712119.2009.9706997; Karabağ et al., 2010Karabağ K, Alkan S, Balcıoglu MS, 2010. The differences in some production and clutch traits in divergently selected Japanese quails. Kafkas Univ Vet Fak Derg: 16(3):383-387.). Additionally, a peak production ratio of 88-98% with the peak egg production cycle around 3 months of age has been identified in quails (Nestor & Bacon, 1994Nestor KE, Bacon WL, 1994. Changes in the frequency and size of smooth muscle tumors in Japanese quail lines differing in body weight. Poult Sci: 73(7):947-952. 10.3382/ps.0730947; Mınvıelle et al., 2000Minvielle F, Monvoisin JL, Costa J, Maeda Y, 2000. Long-term egg production and heterosis in quail lines after within-line or reciprocal recurrent selection for high early egg production. Br Poult Sci: 41(2): 150-157. 10.1080/713654914; Matos et al., 2023Matos Júnior JJ, Furtado DA, Ribeiro NL, Marques JI, Leite PG, Nascimento JW, Rodrigues VP, Lopes Neto JP, Rodrigues LR, Santos SG, Oliveira AG, 2023. Productive performance, egg quality and the morphometry of the organs of Japanese quails (Cotournix cotournix Japônica) kept at different temperatures. Food Sci Technol: 43: e117822. 10.1590/fst.117822).
The internal and external quality of hatching and table eggs are very important for the egg industry (Kocevski, et al., 2011Kocevski D, Nikolova N, Kuzelov A, 2011. The influence of strain and age on some egg quality parameters of commercial laying hens. 3rd Int Conf “New Perspectives and Challenges of Sustainable Livestock Production, Belgrade (Republic of Serbia), Oct 5–7. pp: 1649-1655.; Hatab et al., 2024Hatab MH, Chen W, Abouelezz K, Elaroussi M, Badran A, Zoheir K, El-Komy E, Li S, Elokil A, 2024. Effects of exposing Japanese quail eggs to a low dose of gamma radiation and in ovo feeding by two sources of trace elements on embryonic development activities. Poult Sci:103(3):103364. 10.1016/j.psj.2023.10336). For instance, Khurshid et al. (2003Khurshid A, Farooq M, Durrani FR, Sarbiland K, Chand N, 2003. Predicting egg weight, shell weight, shell thickness and hatching weight of Japanese quail using various egg traits as regressors, Int J Poult Sci: 2: 164-167. 10.3923/ijps.2003.164.167) elaborated that traits such as yolk and albumen weight, shell thickness, shell and egg weight influence hatching performance if other management conditions and fertility are not the limiting factors. Additionally, the breeder’s body weight is also an important factor that influences egg-laying performance, hatching and egg quality traits. Martin et al. (1998Martin AG, Franklin WM, Maffiol A, 1998. Quail: An egg and meat production system. ECHO, USA: 1-14.) reported that female Japanese quails deposit 8% of their body weight in their eggs as compared to only 3% in the case of laying hens. Although, an increase in egg weight has been achieved through selection for higher live weight, this could have negative implications on egg production. To ensure maximum egg production with better egg quality and hatching traits, the selection of breeder parents with the appropriate body weight is very important. Breeder parents with higher body weight are more likely to have higher abdominal fat content, which has an inverse association with hormones related to reproduction. On the other hand, the selection of breeder parents with lower or medium body could have detrimental limitation on the amount of body weight deposited in the egg, resulting in a negative effect on egg quality, hatching traits and egg production. This could also compromise the welfare of the breeder parents.
Therefore, this study investigated the effect of breeder body mass on laying performance, quality, and hatching traits of Japanese quail eggs.
Material and Methods
⌅Housing facility and experimental animals
⌅This study was carried out at the Research and Experimental Unit of Çukurova University in the Republic of Türkiye with a total of 216 quails. Chick and grower conventional cages were used for rearing of the quails for the first 2 weeks (wk) of age and from 2-5 wk of age, respectively. The quails were then transferred to egg-laying cages on the 5 wk (age).
Experimental treatments and replicates
⌅During the 5 wk of age, the young breeder pullets and cockerels were weighed individually using a scale (SCALTEC SBA 41, Germany) with a precision of 0.1 g. After determining their body mass, the birds were allocated to one of the experimental body weight groups: high body mass (HBM) (>310 g), medium body mass (MBM) (290- 310 g), and low body mass (LBM) (<290 g); with three replicates per group. For each replicate, the ratio of male to female was 6:18. The ratio of male to female used in each experimental group and replicate is shown in Table 1.
Composition of animal feed used during the experimental period
⌅During the rearing or growing period, a diet containing 22% crude protein, 3000 kcal/kg metabolic energy (ME), 1.1% calcium and 0.43% phosphorus was used. A diet containing 17% crude protein, 2750 kcal/kg ME, 3.5% calcium and 0.42% phosphorus was used during the egg production period. Feed and water were provided ad libitum.
Photoperiod during rearing and egg-laying cycle
⌅The birds were exposed to a photoperiod (L, light: D, darkness) of 22 hours (h) of L:2h of D from the first 0-3 days (d) of age, and 21h L:3h D from 4-7 d of age. From 2-5 wk of age, a photoperiod of 10h L:14h D was practiced. Thereafter, 16h L:8h D was ensured throughout the entire egg-laying phase.
Evaluation of egg laying performance
⌅Eggs from the various experimental replicates were collected, counted, and weighed individually every day in the morning throughout the egg-laying period. The collected eggs were weighed using a scale (SCALTEC SBA 41, Germany) with a precision of 0.1 g, and the overall egg weight was evaluated at group level. Additionally, the percentage of total egg production was evaluated at group level using the formula below (Baylan et al., 2024Baylan M, Kursun K, Abdallah N, Celik LB, Yenilmez F, Kutay H, 2024. The effect of housing systems on the growth, egg production, overall egg weight and egg quality traits of a new Turkish laying hen hybrid, Akbay. Rev Bras Cienc Avic:26(3):eRBCA-2024. 10.1590/1806-9061-2024-1924).
Incubation conditions and evaluation of hatching traits
⌅A total of three trays with 50 eggs per tray were incubated for each experimental group. The collected fertile eggs were incubated at a standard incubation temperature (37.7 ˚C) and humidity (65%) up to day (d) 15 of incubation. At d 15 of incubation, the eggs were transferred to the hatchery machine at a humidity of 75% and a temperature of 37.5 ˚C. The hatchability of set eggs, hatchability of fertile eggs, and fertility for each replicate tray were calculated, and the overall hatchability of set eggs, hatchability of fertile eggs, and fertility were evaluated at the group level. The formula below was used for evaluating the respective parameters (Allanah et al., 2014Allanah TO, Okonkwo JC, Omeje SI, 2014. Fertility and hatchability characterization of three strains of egg type chickens. J Biosci: 3(6) 59-68. 10.14196/sjbs.v3i6.1537; Fathi et al., 2022Fathi M, Abou-Emera O, Al-Homidan I, Galal A, Rayan G, 2022. Effect of genotype and egg weight on hatchability properties and embryonic mortality pattern of native chicken populations. Poult Sci: 101(11):102129. 10.1016/j.psj.2022.102129).
Evaluation of egg quality traits
⌅On the 18 wk of age, the internal and external quality traits of 15 egg samples per experimental group were analysed. Each egg per group was assessed individually for the egg quality trait and the overall average value was evaluated based on group level. The external quality traits included egg weight, shape index, and shell thickness, while the internal quality traits comprised the yolk colour traits (L*; brightness, a*; redness, b*; yellowness), albumen pH, Haugh unit, yolk index and albumen index. The egg weight was measured using a scale with a precision of 0.1 g (SCALTEC SBA 41, Germany) and a digital Vernier calliper with a precision of ± 0.01 mm (INSIZE 1112-150, Brazil) was used in measuring the egg length and width, the albumen height, width, and length as well as the yolk height and width. Shell thickness was measured by taking portions of eggshells from the broad, middle, and narrow parts. The thickness of each part was then measured with a digital shell thickness gauge with a precision of 0.01 mm (ORKA 100823, Russia) and the mean value of the three portions was recorded. The albumen pH was recorded by separating the albumen from the yolk. The albumen was then collected in a disposable transparent cup and a pH meter (Desc ST300-G, China) was inserted in it for 20-30s. The yolk was collected into a petri dish and then placed into a Konica Minolta Colorimeter device (ColorFlex EZ CR-300, USA) to determine the yolk colour values. The formulae below were used in calculating the respective parameters (Abdallah et al., 2024Abdallah N, Kursun K, Baylan M, 2024. Egg quality traits of French pekin ducks reared under the indoor housing systems. In 8th Int Student Science Conf, Izmir (Türkiye), May 23-24. pp: 23-24. 10.52460/issc.2024.029; Kurşun et al., 2024Kurşun K, Abdallah N, Baylan M, 2024. Egg quality characteristics of Sussex chickens reared under the housing conditions of Cukurova University farm. Int Conf on Research of Agricultural and Food Technologies, Adana (Türkiye), Oct 4-6. pp: 01047. 10.1051/bioconf/20248501047; Tainika et al.,2024Tainika B, Şekeroğlu A, Akyol A, Şentürk YE, Abaci SH, Duman M, 2024. Effects of Age, Housing Environment, and Strain on Physical Egg Quality Parameters of Laying Hens. Rev Bras Cienc Avic: 26(03), eRBCA-2024. 10.1590/1806-9061-2024-1911).
G: Egg weight.
H: Albumen height.
Statistical analysis
⌅With the software SPSS version 22, the test of normality of the data was conducted using the Shapiro-Wilk test and all the data showed normal distribution. One-way ANOVA analysis, Duncan test was conducted to analyze the significant difference among the experimental groups. The significant level was accepted at p≤0.05.
Results
⌅The effect of breeder body mass on average egg weight and total egg production is presented in Table 2. A statistical difference among the experimental groups in relation to overall egg production and egg weight was identified (p≤0.05). The MBM and HBM groups had the highest and lowest rate of egg production, respectively. However, the highest and lowest average egg weight was observed in the HBM and LBM groups, respectively.
The influence of breeder body mass on external and internal egg quality traits is given in Table 3. There was no significant difference in terms of the egg quality traits among the groups (P>0.05) however; shape index, shell thickness, egg weight, yolk and albumen index, and Haugh unit were all numerically higher in the HBM group than the other groups. Furthermore, the egg weight nearly approached a significant level (p=0.080), which was highest in the HBM group and lowest in the LBM group.
The effect of breeder body mass on yolk colour traits is presented in Table 4. The yolk colour traits were not statistically different between the experimental groups (P>0.05). However, eggs from the MBM group had numerically higher yolk colour trait values than those from the other groups. The redness of the yolk colour nearly reached a significant level (p=0.067), which was highest in the MBM group and lowest in the LBM group.
The effect of breeder body mass on hatching traits is given in Table 5. A significant difference (p≤0.05) in terms of the hatchability of set eggs and fertility among the groups was identified. The LBM and HBM groups had the highest and lowest fertility and hatchability of set eggs, respectively. Although the hatchability of fertile eggs did not differ significantly among the groups (P>0.05), numerically it was highest in the LBM and lowest in the HBM group.
Discussion
⌅The HBM group in the current study had the lowest overall egg production but the highest overall egg weight. Similar to our observations, other authors also reported lower egg production but a higher egg weight among hens, and Japanese quails with high body mass (Ipek et al., 2004Ipek A, Sahan U, Yilmaz B, 2004. The effect of live weight, male to female ratio and breeder age on reproduction performance in Japanese quails. S Afr J Anim Sci: 34(2): 130-134.; Alkan et al., 2010Alkan S, Karabağ K, Galiç A, Karsli T, Balcioğlu MS, 2010. Effects of selection for body weight and egg production on egg quality traits in Japanese quails of different lines and relationships between these traits. Kafkas Univ Vet Fak Derg: 16 (2): 239-244. htpps://doi.org/10.9775/kvfd.2009.633; Taskin et al., 2017Taskin A, Karadavut U, Tunca RI, Genc S, Cayan H, 2017. Effect of selection for body weight in Japanese quails on some production traits. Indian J Anim Res: 51 (2): 358-364. 10.18805/ijar.11466; Ekinci et al., 2023Ekinci O, Esenbuga N, Dagdemir V, 2023. The effects of body weight and age on performance, egg quality, blood parameters, and economic production of laying hens. J Hell Vet Medical Soc: 74(2): 5809-5816. 10.12681/jhvms.30324). Additionally, Jatoi et al. (2013Jatoi AS, Sahota AW, Akram M, Javed K, Jaspal MH, Hussain J, Mirani AH, Mehmood S, 2013. Effect of different body weight categories on the productive performance of four close-bred flocks of Japanese quails. J Anim Plant Sci: 23(1): 7-13.) confirmed that imported and local hens with high body masses laid eggs with heavier weights compared to their counterparts with medium or low body masses. Contrary to the findings of the present study, Ocak et al. (2004Ocak N, Sarica M, Erener G, Garipoglu AV, 2004. The effect of body weight prior to molting in brown laying hens on egg yield and quality during second production cycle. Int J Poult Sci: 3(12): 768-72. 10.3923/ijps.2004.768.772) identified higher egg weight and egg production in hens and partridges with high body masses compared to those with low, and medium body masses. Akșit et al. (2003Akșit M, Yalçın S, Karul AB, 2003. Physiological stress parameters during food withdrawal period in force moulted hens. Arch fur Geflügelkd: 67 (5): 212 – 216.) reported higher egg production and egg weight in hens with low and medium body masses compared to those with high body mass. Additionally, Tyasi et al. (2024Tyasi TL, Sathekge LJ, Hlokoe VR, 2024. Association of Different Body Sizes and Egg Quality Characteristics in White Leghorn Chicken Breed of South Africa. Measurements. J World`s Poult Res: 14(2): 154-159. 10.36380/jwpr.2024.16) identified heavier egg weight in hens with low and medium body masses compared to those with high body mass.
It was reported that birds with high body mass ovulate heavier or larger egg yolks leading to heavier eggs however, their ovaries lose their function causing a reduction in egg production (Lacin et al., 2008Lacin E, Yildiz A, Esenbuga N, Macit M, 2008. Effects of differences in the initial body weight of groups on laying performance and egg quality parameters of Lohmann laying hens. Czech J Anim Sci: 53(11): 466-471.; Najib & Yousif, 2014Najib H, Al-Yousif Y, 2014. Egg size Saudi local layers as affected by line of the bird (body weight at sexual maturity) and Dietary fat level. Int J Poult Sci: 13(8): 442-448. 10.3923/ijps.2014.442.448; Muir et al., 2022bMuir WI, Akter Y, Bruerton K, Groves PJ, 2022. The influence of hen size and diet nutrient density in early lay on hen performance, egg quality, and hen health in late lay. Poult Sci: 101(10): 102041. 10.1016/j.psj.2022.102041). Moreover, it could be possible that the birds with the high body mass had higher abdominal fat content which has been reported to have a negative correlation with egg production performance (Whitehead et al., 1990Whitehead CC, Armstrong J, Herron KM, 1990. The growth to maturity of lean and fat lines of broiler chickens given diets of different protein content: body composition, plasma lipoprotein concentration and initial egg production. Anim Prod: 50: 183–190. 10.1017/S000335610000458X; Zhang et al., 2018Zhang XY, Wu MQ, Wang SZ, Zhang H, Du ZQ, Li YM, Cao ZP, Luan P, Leng L, Li H., 2018. Genetic selection on abdominal fat content alters the reproductive performance of broilers. Animal: 12(6): 1232-1241. 10.1017/S1751731117002658;). Indeed, Ocak et al. (2004Ocak N, Sarica M, Erener G, Garipoglu AV, 2004. The effect of body weight prior to molting in brown laying hens on egg yield and quality during second production cycle. Int J Poult Sci: 3(12): 768-72. 10.3923/ijps.2004.768.772) identified a higher significant abdominal fat in laying hens with high body mass compared to those with medium or low body masses. Robinson & Robinson (1991Robinson FE, Robinson NA, 1991. Reproductive performance, growth rate and body composition of broiler breeder hens differing in body weight at 21 weeks of age. Can J Anim Sci: 71(4):1223-31. 10.4141/cjas91-145) reported that at 22 and 62 weeks of age, body fat composition was higher in breeders with high body mass compared to those with medium and low body masses. Akşit et al. (2003Akșit M, Yalçın S, Karul AB, 2003. Physiological stress parameters during food withdrawal period in force moulted hens. Arch fur Geflügelkd: 67 (5): 212 – 216.) also reported higher levels of triglyceride in breeder hens with high body mass than those with medium and low body masses. Moreover, Walzem & Chen (2014Walzem RL, Chen SE, 2014. Obesity-induced dysfunctions in female reproduction: lessons from birds and mammals. Adv Nutr: 5: 199–206. 10.3945/an.113.004747) identified that the ovarian function of hens was compromised by fattening/obesity due to the fact that it caused a proapoptotic effect on granulosa cells and also altered hormone production. Since granulosa cells play a major role in ovarian functionality (Zhu et al., 2019Zhu G, Fang C, Li J, Mo C, Wang Y, Li J, 2019. Transcriptomic diversification of granulosa cells during follicular development in chicken. Sci Rep: 9(1): 5462. 10.1038/s41598-019-41132-1), the apoptotic death of the granulosa cells negatively affects ovarian functioning and follicular development. This reason might have contributed to the lower egg production observed in the group with high body mass. It could also be possible that high breeder body mass influences the normal functioning of the hypothalamic-adenohypophyseal-gonadal axis which in turn influences egg production rate. Probably, high body mass might have stimulated the mechanism that activates follicular atresia causing a reduction in the rate of follicular maturation with subsequent reduction in egg production.
In the current study, no significant difference was observed in relation to the external and internal egg quality traits among the experimental groups. In agreement with our findings, other authors have reported no significant effect of breeder body mass on yolk height, yolk index, shape index, Haugh unit and shell thickness in both Japanese quails and other poultry species (Altan et al., 1998Altan Ö, Oğuz İ, Akbaş Y, 1998. Effects of selection for high body weight and age of hen on egg characteristics in Japanese Quail. Turk J Vet Anim Sci: 22(6): 467-474.; Ocak et al., 2004Ocak N, Sarica M, Erener G, Garipoglu AV, 2004. The effect of body weight prior to molting in brown laying hens on egg yield and quality during second production cycle. Int J Poult Sci: 3(12): 768-72. 10.3923/ijps.2004.768.772; Lacin et al., 2008Lacin E, Yildiz A, Esenbuga N, Macit M, 2008. Effects of differences in the initial body weight of groups on laying performance and egg quality parameters of Lohmann laying hens. Czech J Anim Sci: 53(11): 466-471.; Ojo et al., 2019Ojo V, Ayorinde KL, Fatoki HO, 2019. Relationship between body weight and some egg production trait in the Japanese quail. NISEB: 11(1): 89-94.). Contrary to the results of the current study, Jatoi et al. (2015Jatoi AS, Sahota AW, Akram M, Javed K, Jaspal MH, Mehmood S, Hussain J, Ishaq HM, Bughio E, 2015. Egg quality characteristics as influenced by different body sizes in four close-bred flocks of Japanese quails. J Anim Plant Sci: 25(4): 921-926.) reported higher shell thickness and yolk index in eggs from breeder parents with high body mass. Moreover, higher eggshell thickness has been reported in broiler breeders with high body mass (Akşit et al., 2003Akșit M, Yalçın S, Karul AB, 2003. Physiological stress parameters during food withdrawal period in force moulted hens. Arch fur Geflügelkd: 67 (5): 212 – 216.). Furthermore, Kırıkcı et al. (2007Kırıkçı K, Günlü A, Cetin O, Garip M, 2007. Effect of hen weight on egg production and some egg quality characteristics in the partridge (Alectoris graeca). Poult Sci: 86(7):1380-3. 10.1093/ps/86.7.1380) reported that breeder body mass had no significant effect on shape and yolk index however, albumen index and Haugh unit was significantly higher in eggs from breeders with low and medium body masses compared to eggs from breeders with high body mass. From the same study, shell thickness was highest in eggs from breeders with medium body mass compared to eggs from breeders with low and high body masses. In addition, it was reported that eggs from pheasants with low body mass had significantly highest and lowest shape index and shell thickness respectively, while the yolk index and Haugh unit was significantly highest in eggs from breeders with higher body mass than eggs from breeders with low and medium body masses (Kırıkçı et al., 2004Kırıkçı K, Çetin O, Günlü A, Garip M, 2004. Effect of hen weight on egg production and some egg quality characteristics in pheasants (Phasianus colchicus). Asian-Australas J Anim Sci: 17(5):684-687. 10.5713/ajas.2004.684). The differences in the various reports could be attributed to the breed of quail used, the nutritional components of the experimental feed, and the age of the quails. Moreover, the type of housing system used could be an additional factor affecting the utilization of nutrients leading to variation in the results reported by the various authors.
Although the LBM group had the smallest egg weight, the hatchability of set eggs and fertility were significantly higher in the LBM group compared to the other groups. Similarly, Cahaner et al. (1986Cahaner A, Nitsan Z, Nir I, 1986. Reproductive performance of broiler lines divergently selected on abdominal fat. Poult Sci: 65(7):1236-43. 10.3382/ps.0651236) observed that at 35 and 48 weeks of age, the fertility, hatchability of set and fertile eggs of hens from low-fat lines was higher than that of hens from high-fat lines. In addition, selection for higher body mass has been reported to decrease hatchability and fertility of Japanese quails (Rehman et al., 2022Rehman A, Hussain J, Mahmud A, Javed K, Ghayas A, Ahmad S, 2022. Productive performance, egg quality, and hatching traits of Japanese quail lines selected for higher body weight and egg number. Turk J Vet Anim Sci: 46(2): 322-335. 10.55730/1300-0128.4180). Furthermore, Zhang et al. (2018Zhang XY, Wu MQ, Wang SZ, Zhang H, Du ZQ, Li YM, Cao ZP, Luan P, Leng L, Li H., 2018. Genetic selection on abdominal fat content alters the reproductive performance of broilers. Animal: 12(6): 1232-1241. 10.1017/S1751731117002658) have reported higher fertility and hatchability in breeder parents from lean genetics lines compared to those from fat genetic lines. It was suggested that in the current study, the LBM group might have been characterised with lower levels of abdominal fat and Zhang et al. (2018Zhang XY, Wu MQ, Wang SZ, Zhang H, Du ZQ, Li YM, Cao ZP, Luan P, Leng L, Li H., 2018. Genetic selection on abdominal fat content alters the reproductive performance of broilers. Animal: 12(6): 1232-1241. 10.1017/S1751731117002658) speculated that the high level of hormones related to reproduction (luteinizing hormone, estrogen and follicle stimulating hormone) which in turn influences the growth of the reproductive system of the female and ovulation might have contributed to the higher rate of fertility in parents from lean female lines. This reason might account for the higher fertility observed in the LBM group than the other groups. Additionally, hatchability has been reported to be influenced by incubation conditions and egg quality, which in turns affect the quality of oocyte (Zhang et al., 2018Zhang XY, Wu MQ, Wang SZ, Zhang H, Du ZQ, Li YM, Cao ZP, Luan P, Leng L, Li H., 2018. Genetic selection on abdominal fat content alters the reproductive performance of broilers. Animal: 12(6): 1232-1241. 10.1017/S1751731117002658). Walzem & Chen (2014Walzem RL, Chen SE, 2014. Obesity-induced dysfunctions in female reproduction: lessons from birds and mammals. Adv Nutr: 5: 199–206. 10.3945/an.113.004747) reported that poor-quality oocytes in chickens has been linked to obesity/fattening and hence, it is suggested that the HBM group might have possessed higher abdominal fat content which negatively affected the expression of genes related to maturation and follicular development as well as reproductive hormones, leading to poor-quality oocytes and the subsequent reduction in hatchability.
Selection for high breeder body mass could improve egg weight however, it may have a negative correlation with egg production and hatching traits.