Poultry farming has mainly focused on the production of chicken eggs and broiler chickens. In 2012, the poultry sector supplied 103 million tons of meat and 66.4 million tons of eggs for consumption worldwide [1]. According to FAO estimates, the food needs of the world's population will increase by 70% by 2050 [2]. Short-cycle animal husbandry, such as quail farming, can be an important asset in meeting animal protein requirements and reducing pressure on chicken and hen egg production. Improvements in quail rearing have been undertaken in order to take advantage of their characteristics, notably the early age of the bird in meat production (5 weeks), its laying performance (200 - 300 eggs per year) and its relatively short generation interval compared to other avian species [3]. Quail is reared for its meat and eggs, for its therapeutic virtues, taste and high nutritional value [4] [5]. The need of eggs for consumption is increasing and consumers are looking at the quality of poultry products. Thus, depending on the objectives, each farm has developed a strain with its own characteristics, which explains the great heterogeneity of populations and zootechnical [6]. On the whole, studies have been carried out on growth performance, egg laying and egg quality [7] [8], as well as the effect of genotype on the characteristics of Japanese quail eggs [9]. In Cameroon studies have been carried out on the effect of crude protein level on growth and carcass in quail (Coturnix sp.) in the finishing phase in the Cameroonian highlands [4], also on the characteristics of quail breeding [10]. However, no research has been focused on egg-laying performance as a function of age and phenotype of quail, hence the need for this study in the Sudano-Guinean zone of Cameroon. The general objective of this study is to contribute to the better management of quail reproduction by knowing the appropriate phenotype and age for better reproduction and quality of quail eggs in order to meet the food needs of populations.

Specifically, the effect on quails will be evaluated on the laying rate and egg characteristics.

Our results revealed that laying rate is higher between 4 pm and 8 pm whatever the age of birds and the genetic type considered. These results are in agreement with the observations made by Sauveur [12] who states that unlike hens whose laying is done in the morning, oviposition in quails is generally done in the afternoon between 4 pm and 8 pm with little oviposition in the morning.

Quails of the spotted white phenotype had the highest laying rate compared to other phenotypes. This could be attributed to the breed of the birds being more prone to lay eggs than the other phenotypes. These results do not agree with the findings of Jessy et al. (2016) who found that laying rate is higher in grey quails (86.65%) compared to brown (76.0%) and white (67.16%) quails. The values found in our study are lower than those reported by these authors and could be explained by genetic and environmental factors.

In brown and grey quails, laying rates were higher at six months of breeding (78.75% and 74% respectively). These results are similar to those obtained by Jessy et al. (2016) who indicate that in the 8th week, laying rate of brown quails (58.9%) increases with animal age up to 89% at around the 12th week and drops to 76% by the 20th week. Hantanirina et al. [13] also showed that laying rates vary from 78% to 43% between the 6th and the 32nd week of life of grey quails. In white quails, the highest laying rates (72% and 71%) were respectively recorded at 1 and 10 months of breeding. Hantanirina et al. [13] obtained similar results at 14 weeks of age in white and grey quails. In spotted white quails, the highest laying rate was recorded in quails that had been laying for 1 month (93.34%). These results are similar to findings of Hantanirina et al. [13] and Jessy et al. (2016) which respectively show a laying rate between (80% - 90%) and (60% - 99%) at the 4th week of breeding in all quail strains. This variation of results with other authors may be due to the genetic types of quails as well as environmental and managerial factors.

The significantly higher laying rate (72%) was recorded with birds of one- month breeding age. These results are close to those obtained by Hantanirina et al. [13] who found that the laying performance at the beginning of the laying period was between 15.12% and 29% and reached 80% - 90% at one month of laying. Overall, more or less significant differences were found between results of the authors with regard to the overall quality of laying. This is influenced by a combination of both intrinsic (strain, age, body weight) and extrinsic factors (sex ratio, diet, temperature, photoperiod etc.). The fact that the laying rates obtained at one (72.00% ± 9.80%) and 10 months (71.00% ± 10.5%) were similar and significantly higher than the rate recorded at 6 months of laying could be explained by some fluctuation of the oviposition during the laying carrier of hen. Indeed, laying is characterized by some cyclicity that leads to some reduction of the egg production inside a flock [12].

Average egg weight was 10.42g. Hrncar et al. [9] found higher values (11.48 g and 13.06 g) in Japanese quails for laying and meat respectively. The average shape index of 78.73% obtained is close to the 78.2% reported by Ouaffai et al. [7]. According to Nedeljka [14], shape index between 70% and 77% can be estimated as optimal in poultry and hens precisely. It should be however noted that younger laying birds give higher shape indexes and more rounded eggs; furthermore, the high values of the shape index obtained in our trial could be due to the poultry species used. White phenotype quail eggs had a volume of 12.60 ml, significantly higher than those of other phenotypes. This difference can be attributed to the higher weight, diameter and height of eggs of the same phenotype. These results are similar to those recorded by Kanagaraju et al. [15] who reported egg volumes between 10.36 and 11.64 ml depending on the phenotype.

Spotted white quail eggs had the largest egg albumen diameter (20.77 mm) compared to other phenotypes. White quail eggs, on the other hand, recorded the lowest yolk diameter value (22.50 mm). These results do not agree with those of Jessy et al. [16]; Begum et al. [17] who reported higher values (between 32 and 37 mm) that plumage colouring does not significantly affect egg albumen diameter in quails Şeker et al. [18], in a study on the effect of storage time on egg quality in laying hens, found that the diameter increased with storage time. These observations were also confirmed by Djitie et al. [19] by evaluating the effect of storage time on the physico-chemical characteristics of eggs from backyard systems. The genetic type and storage time of the eggs are the main factors that can justify the low values of the albumen diameter obtained in the present study.

Albumen height and eggshell thickness also varied significantly with the quail phenotype, corroborating the results obtained by Rasol et al. [20] and Kanagaraju et al. [15]. However, Jessy et al. [16] reported that feather coloration did not significantly affect height or thickness of Japanese quail egg constituents.

The overall yolk proportion was 32.27% with the lowest value reported in white quails and the highest in brown quails. This could be due to the fact that the brown quail egg yolk was heavier. These results are similar to those reported by Kanagaraju et al. [15]. Hrncar et al. [9] also reported similar values in laying (32.43%) and meat (35.84%) quails. With an average of 60.41%, the lowest proportion of egg albumen (57.79%) was obtained in brown quail eggs. Kanagaraju et al. [15] reported higher values for brown (62.67%), white (65.19%) and golden (62.50) plumage quails. Variations in the proportion of albumen egg from one quail phenotype to another could be explained by a variability in the process of setting of the different egg constituents according to the phenotype. The proportion of eggshell overall was 7.33% with the lowest value (6.73%) recorded in grey quail eggs and the highest (7.93%) in spotted white quail eggs. These results are not consistent with those of Begum et al. [17] who found higher (9% - 10%) and otherwise comparable values in white, grey, fawn, black and tuxedo quails.

Haugh’s index was higher with grey quail eggs (88.17%). This might be an indication that grey quail eggs age slower than those of other phenotypes. Similar results were reported by Kanagaraju et al. [15] in brown (87.68) and white (84.78) quails. Other authors [9] [21] rather noted that Haugh’s index did not vary significantly with genetic type. This difference in results with other authors could be explained by the egg storage duration and the age of the birds.

At the end of our study on the effect of quail phenotype and age on the laying rate and egg characteristics, it was found that:

· laying is concentrated between 4 pm - 8 pm on all phenotypes. Although the laying rate varies from one phenotype to another with age, white spotted quails showed significantly higher laying rates compared to other phenotypes throughout the survey;

· Except for egg volume, which was higher in white quails, external egg characteristics were generally similar between all quail phenotypes.

· The white spotted quails’ eggshells were significantly thicker than those of the other phenotypes. Grey quails had higher Haugh’s index eggs and a proportion of edible matter.

Considering these results, it can be concluded that although grey quails had high proportions of edible matter, white spotted quails are more suitable for reproduction since they have the best egg laying performance and better shell quality.

The authors declare no conflicts of interest regarding the publication of this paper.

Djitie, K.F., Akana, A.E., Radu-Rusu, R.M., Teodorescu, A., Usturoi, M.G., Ngoula, F. and Teguia, A. (2021) Effect of the Quail Phenotype and Breeding Age on Egg Laying and Characteristics. Open Journal of Animal Sciences, 11, 208-221. https://doi.org/10.4236/ojas.2021.112016