Does the marketing age impact growth performance, carcass traits, economic feasibility and hemato-biochemical properties of genetically-modified quails?

Abstract

The meat of the quail is one of the most delicious types, as it is rich in minerals and vitamins, especially vitamin K, which is useful in treating nervous diseases. In the present investigation, based on their live body weight, 270 genetically-enhanced white quail chicks of mixed sex were randomly assigned to 3 groups, each with 90 chicks. The first group's birds were slaughtered at 28 d of age. The birds in the second group were slaughtered at 31 d, and the birds in the third group were slaughtered at 34 d. Results showed no significant difference between the various groups in the overall mortality rate index at the end of each fattening stage (P > 0.05). There were substantial variations (P ≤ 0.05) in the average live weight index between the first and both groups at each group's marketing age. With increasing marketing age, body weight increases. Quail chicks raised for 34 d received the lowest EPEF (28.90 points), followed by those raised for 31 d and 28 d, which received 33.37 and 37.32 points, respectively. The economic feasibility of the 3 groups, no significant differences in the profit index were observed at the age of 28 d. Compared to the marketing age of the other 2 groups, it was noted that the profit index decreased as the birds advanced in age. Delaying marketing to 31 d leads to a decrease in profit by 5.7%, and delaying marketing to 34 d reduces the profit index to 26.36% compared to marketing at 28 d. For blood hematology parameters, a significant increase in the studied indicators with the age of the birds was observed through the study of blood indicators. Still, it did not reach the significance level. It could be concluded that 28 d is the ideal marketing age for the enhanced white quails, as it yielded the highest economic return and the best performance.

INTRODUCTION

Quail has grown economically as an agricultural animal over the past ten years, producing meat and eggs valued for their distinct flavor (Abd El-Hack et al., 2016,2017,2024a,b; Soomro et al., 2019; Taha et al., 2019; Abou-Kassem et al., 2020; Abd Elzaher et al., 2023). The Japanese quail is a common laboratory bird for genetic studies because of its small size, ability to resist pathogens, rapid development, ease of handling, and short generation time (Alagawany et al., 2017; Hamad and Kareem, 2019).

Quail need less feed than other bird species because they are smaller; at four weeks old, their average live body weight (LBW) is 200 g (Sabow, 2020). Furthermore, quail can convert feed sources into meat and eggs (Arthur and Bejaei, 2017; Mnisi et al., 2023). In addition, quail birds are resistant to diseases, and the costs of establishing private pens for raising them are low (Minvielle, 2004). Also, its waste can be used as organic nitrogen fertilizer with a high fertilizing value (the percentage C/N ratio was 6.35). The profit achieved from raising it is more than 30% of the capital employed in the project (Boni et al., 2010; Suppadit et al., 2011; Aminzade et al., 2012). Japanese quails are currently being utilized in managerial research to measure specific physiological, biological, behavioral, and productivity traits as indicators of the concept of bird care (Ramankevich et al., 2022).

Quail meat is of good quality because it contains 23% protein and a fat content of less than 3% (Daikwo et al., 2013; Alagawany et al., 2014). The age of quail birds significantly affects live weight (Boni et al., 2010), carcass (Kumar et al., 2011; Sartowska et al., 2014), and the quality of the meat (Genchev et al., 2008; Choi et al., 2012). The growing interest in producing Japanese quail in emerging nations results from the tremendous chance for diversity and early marketability that quail breeding provides. Despite the Japanese quail's diminutive size, its meat and eggs are frequently consumed, which helps to solve the issue of a lack of animal protein (Daikwo et al., 2014).

According to Gharib et al. (2023), socioeconomic factors, an absence of institutional support, and other obstacles cause medium-to-low financial performance for those owned by small-scale broiler chicken farms in rural Egypt. Policy recommendations include increased institutional support, encouraging rural women to adopt new management technology, and providing appropriate input supplies. Gender factors only affected flavor score, according to Avcilar and Yilmaz (2023) research, which also found that slaughter age significantly impacted the pH and color values of meat. Similar data might have resulted from the small difference in slaughter ages. Furthermore, Lukanov et al. (2021) indicated that the color and pH levels in the breast muscle of meat-type quail (WG line) ranged from 5.75 to 6.26 and were unaffected by gender or the age when the quail was slaughtered (28, 35, and 42 d).

According to Pavlova et al. (2023), the productive variety of quail has a major effect on both live weight and carcass weight. The slaughter yield of female sex quail decreases with age, especially between 28 and 35 d. A total of 11% of the productive types of birds determine the slaughter yield. The primary determinant of harvested meat from valuable carcass parts is live weight, with the productive type having the greatest influence.

The present study hypothesized that marketing age may affect productivity indicators of genetically-improved quails. So, this investigation aimed to evaluate the effect of the marketing age of improved white quail in Egypt on the most important productivity indicators, carcass traits, economic feasibility and hemato-biochemical properties.

MATERIALS AND METHODS

Ethical Approval

The current study complied with the Cairo University Faculty of Agriculture's Ethics Committee guidelines (CU-11-F23 23).

Experimental Birds, Feeding, and Management

The research was carried out at the Stino quail farm in Egypt. A total of 270 genetically improved white quail chicks, unsexed at 1- day-old, were randomly distributed according to their live body weight into 3 groups with 3 replicates per group (30 chicks per replicate). All housing and care conditions were the same for all groups during the period of care that lasted from 1 d to 34 d. Quail chicks were brooded at 35°C on the first day of age, then decreased to 3°C weekly, and then kept at 24°C after the fourth week of age. Quails were exposed to continuous light for the first 2 d of age and then supplemented with 23 h of light and 1 h of darkness afterwards. House humidity ranged from 60 to 65% throughout the experimental period. Feeding and watering of the birds were allowed ad libitum.

The productivity indicators were assessed at 28 d for the birds in the first group, 31 d for the birds in the second group, and 34 d for the birds in the third group. As stated by the NRC (1994), the starter diet, or basal nutrition, was created to satisfy the nutrient needs of developing chicks. The structure and calculated composition of the diet at the base and the energy-to-protein ratio (ME/P) are presented in Table 1.

Table 1.

The components and estimated nutritional values of the diets for Japanese quail.

Ingredients %	Starter diets	Grower diets	Finisher diets
Argentine yellow corn	48.4	56.2	64.2
High-fat soybean meal (43%)	40	33	26
Limestone	0.41	0.49	0.68
Corn gluten meal (60%)	7	6.5	6
Oil	0.2	0.25	0.3
Dicalcium Phosphate	2	1.6	1.2
Vitamins premix	0.4	0.4	0.4
Minerals premix	0.3	0.3	0.3
Threonine	0.25	0.265	0.28
Sodium chloride	0.13	0.115	0.1
Methionine %	0.15	0.125	0.1
Sodium bicarbonate	0.1	0.125	0.15
Choline chloride	0.1	0.05	0
Antifungal and toxins	0.05	0.05	0.05
manganese sulfate	0.02	0.01	0
LINCO MEX	0.01	0.01	0.01
Silica	0.1	0.025	0
Multivitamins AD3E	0.03	0.125	0
Yeast	0.1	0.125	0
Lysine	0.25	0.235	0.23
Total	100	100	100
Calculated analysis:
ME (kcal/kg)	3245	3269	3298
Crude Protein %	25.56	22.92	20.23
ME/P	126	142.63	163.03
Fat %	5.11	4.97	4.83
Crude fiber%	3.51	3.23	2.96
Ca	0.72	0.64	0.42
P	0.76	0.66	0.42
Lysine %	1.58	1.36	1.13
Methionine %	0.43	0.39	0.35
Cystine %	0.47	0.42	0.37
linoleic acid	1.17	1.31	1.45
Cost	11.92	11.41	10.78

Experimental Measurements

Data Collection

Every quail in the trial was exposed to the same procedure for gathering data. Each chick in each replicate was weighed individually every week and after the rearing period. Along with the European Production Efficiency Factor (EPEF), feed intake (FI), and bird mortality were recorded.

Measures of performance like body weight gain (BWG), feed efficiency (FE), FCR, mortality, and livability % were calculated according to the following formulas: BWG (g) = Final BW (g) at the end period – Initial BW (g) at the start, FI (g/bird) = (Feed offered – Feed residue)/No. of bird, FE (g/g) = BWG ÷ FI, FCR (g feed/g gain) = FI ÷ LBW, Mortality (%) = (No. of dead birds/Total number) × 100, Livability (%) = 100 – Mortality %, EPEF=[((Average live body weight by g) x (100 – mortality %)) / (Marketing age (day)) x (FCR)] /10.

Carcass Traits

Birds were chosen at 28, 31, and 34 d of age, then weighed individually to determine the live weight (LBW), fasted for 8 h, and slaughtered. Birds were slaughtered by slitting the throat and cutting the carotid arteries, jugular veins, esophagus, and trachea without severing the head (Sams, 2001). After slaughtering, each bird was hanged in a bleeding funnel for 3 min and weighed again to obtain the blood weight. Birds were then scalded in a 68°C water bath for 30 s, and then the feathers were removed by an automatic circular feather plucker. The birds were then weighed again to get the feathers' weight. The shanks and head (without neck) were removed, and the birds were eviscerated and chilled. Each empty, chilled carcass was weighted to obtain the dressed weight. Carcass yield was expressed as the percentage of dressed weight to LBW.

The wings with bones were then removed from the front parts and weighed. Also, the skinless pectoralis major and minor muscles were removed to obtain breast muscle weight. The bones from the thighs and drumsticks were removed, and then the skinless leg muscles were weighed as leg meat. The liver, heart, and gizzard (empty) were weighed. All previous muscles and organs were also calculated as percentages of LBW.

Blood Biochemical Analysis

Blood samples were taken at 28, 31, and 34 d of age to determine hematological parameters. Serum was examined after specimens of blood were spun at 4,000 rpm for 10 min to assess the serum content of RBCs, PCV, hemoglobin, WBCs, total protein, glucose, uric acid, calcium, phosphorus, triglycerides, and cholesterol, which was calculated via Young and Friedman (2001).

The Economic Feasibility

The economic feasibility study for fattening the following ages (28, 31, and 34 d) was based on the price of feed materials, the cost of 1 kg of live weight, and the chick price during the research period, where the following indicators were calculated:

• 1.The cost of chicks to produce 1 kg of live weight = (the price of the chick / the average live weight of the bird kg) x (100 / the safety of birds).
• 2.Feed cost to produce 1 kg of live weight = (federation conversion factor x price of 1 kg of feed consumed) x (100/safety of birds).
• 3.Production cost of 1 kg of live weight = (the cost of chick to produce 1 kg of live weight + the cost of nutrition to produce 1 kg of live weight) x (100/75), as the cost of chick and feed constitutes about 75% of the total costs of production.
• 4.Realized profit = selling price for 1 kg of live weight minus production cost for 1 kg.
• 5.Profit index (%) = (profit achieved from 1 kg of live weight/production cost of 1 kg of live weight) x 100.

Note: the price of a 1-day-old chick is 5 Egyptian pounds, and the selling price for 1 kg of live weight is 90 Egyptian pounds.

Statistical Analysis

The general linear model in the SAS software was utilized to analyze the data (Xlstat, 2014). The following model was used:

$${\mathrm{Y}}_{\text{ij}}=\mu +{\mathrm{L}}_{\mathrm{i}}+{\mathrm{e}}_{\text{ij}}$$

Where:

• Y_ij: The j^th observation within the i^th group.

• μ: The overall mean.

• L_i: The effect of the i^th groups (28, 31, and 34 d of age).

• E_ij: Random error.

When significance was found, mean values were divided using Duncan's multiple-range test (Duncan, 1955) at a significant level of 5%.

Before evaluation, percentage data underwent an arc-sine transformation. The results obtained from this research were subjected to statistical analysis. The significance of differences between mortality percentages between groups was tested according to Fisher's (F) test for the significance of differences between percentages. A simple random design was used to analyze the differences in the remaining indicators. Only the least significant difference (L.S.D.) test was calculated at the 5% and 1% levels when the indicator showed a significant difference between the groups.

RESULTS

The overall mortality rate of birds by feeding stage is displayed in Table 2. Our results show no significant difference between the various groups in the overall mortality rate index at the end of each fattening stage (P > 0.05). Delaying the marketing age to extend the rearing period indicates a significant increase in mortality among different groups living in the same environment.

Table 2. Mortality rate (%) in the experiment period.

Group 3	Group 2	Group 1	Age (days)
1.11	1.11	1.11	14
1.11	1.11	2.22	21
1.11	2.22	2.22	28
1.11	2.22		31
1.11			34

Table 3 shows no significant variations (P > 0.05) in the mean live weight, daily FI, or FCR between the groups after each fattening stage. Furthermore, significant variations (P ≤ 0.05) in the average live weight index between the first and both groups at each group's marketing age. With increasing marketing age, body weight increases.

Table 3.

The live weight (g), feed intake (g), and feed conversion ratio for the duration of the experiment.

Traits	Age	Group 1	Group 2	Group 3	p-value
Live body weight (g)	1	11.90 ± 0.24	11.99 ± 0.02	12.15 ± 0.21	0.663
	14	147.92 ± 1.95	141.59 ± 5.25	142.35 ± 1.96	0.416
	21	253.25 ± 1.61	251.97 ± 6.81	242.91 ± 2.89	0.288
	28	335.59 ± 4.35	330.21 ± 7.42	320.39 ± 6.83	0.378
	31		356.54 ± 6.61	343.97 ± 5.49	0.27
	34			370.64 ± 8.54
Feed intake (g)	14	25.26 ± 0.27	25.28 ± 1.68	26.25 ± 2.22	0.886
	21	41.61 ± 0.27	38.42 ± 1.00	38.54 ± 1.97	0.244
	28	52.97 ± 2.03	51.93 ± 3.33	53.24 ± 3.84	0.953
	31		58.94 ± 4.48	54.73 ± 3.96	0.52
	34			63.60 ± 2.27
Feed conversion ratio
(g feed/ g gain)	14	2.60 ± 0.01	2.73 ± 0.13	2.82 ± 0.20	0.671
	21	2.76 ± 0.03	2.60 ± 0.14	2.75 ± 0.09	0.803
	28	3.14 ± 0.002	3.10 ± 0.08	3.26 ± 0.23	0.713
	31		3.37 ± 0.13	3.51 ± 0.24	0.621
	34			3.73 ± 0.14

Means within the same row different superiors are different (p ≤ 0.05).

It was observed from Table 4 that there wasn't a significant difference in the EPEF in quail birds in the different groups at the age of 28 d, while the reduction in the studied index was observed with the age of the birds. Quail chicks raised for 34 d received the lowest EPEF (28.90 points), followed by those raised for 31 d and 28 d, which received 33.37 and 37.32 points, respectively. The means connected to EPEF marketing age are considered performance indices.

Table 4.

The European Production Efficiency factor (EPEF) of birds in different groups.

Age	Group 1	Group 2	Group 3
28	37.32	37.19	34.71
31		33.37	31.26
34			28.90

According to Table 5, the only relative weights that differ significantly are the gizzard and carcass percentages; the gizzard percentage increases with the age of the birds. At the same time, the weight of the feathers, blood, liver, heart, abdominal fat, chest, and thighs as a percentage of carcass weight for each group did not differ significantly (P > 0.05) between the groups under study.

Table 5.

Carcass traits as a percentage of the carcass weight for each group as well as the live body weight (g) and carcass weight (g).

Traits	Group 1	Group 2	Group 3	p-value
Live body weight	331.67c ± 4.41	362.33b ± 6.74	372.67a ± 3.71	0.004
Carcass weight	254.0c ± 4.58	272.0b ± 6.56	286.33a ± 2.96	0.004
Leg meat %	23.89 ± 0.33	21.84 ± 0.82	21.19 ± 0.47	0.088
Breast meat%	28.32 ± 2.16	26.16 ± 1.79	25.14 ± 0.16	0.383
Blood%	5.68 ± 1.01	5.26 ± 0.39	4.76 ± 1.01	0.833
Feathers%	4.06 ± 0.28	3.67 ± 0.15	4.07 ± 0.29	0.337
Liver%	4.72 ± 0.15	4.53 ± 0.23	4.19 ± 0.17	0.096
Heart%	3.68 ± 0.12	3.68 ± 0.25	3.50 ± 0.24	0.786
Gizzard%	2.10b ± .012	2.22b ± 0.26	3.03a ± 0.10	0.034

^a-dMeans within the same row with different superiors are different (p ≤ 0.05).

Table 6, Table 7, Table 8 presented the results of an analysis of the economic viability of fattening birds in various groups according to the cost of feed ingredients, as well as the cost of chicks, 1 kg of feed, average LBW of the birds, average FCR for the duration of the fattening period, average FC per bird, and cumulative mortality rate in each of the groups during the research period (group 1st 28, group 2nd 31, and group 3rd 34 d). When studying the economic feasibility of the 3 groups at the age of 28 d, no significant differences in the profit index were observed. When compared to the marketing age of the other 2 groups, it was noted that the profit index decreased as the birds advanced in age.

Table 6.

The economic feasibility of fattening birds up to 28 d of age.

28 d	Group 1	Group 2	Group 3
The cost of the chick to produce 1 kg live weight (Egyptian pounds)	15.05	15.61	15.82
Feed cost to produce 1 kg live weight (Egyptian pounds)	36.00	35.79	36.69
The cost of chick and feed to produce 1 kg live weight (Egyptian pounds)	51.05	51.40	52.51
The production cost of 1 kg live weight (Egyptian pounds)	68.06	68.53	70.00
The profit achieved from the production of 1 kg live weight (Egyptian pounds)	21.93	21.46	19.99
Profit index %	32.22	31.32	28.55

Table 7.

The economic feasibility of fattening birds up to 31 d of age.

31 d	Group 1	Group 2	Group 3
The cost of the chick to produce 1 kg live weight (Egyptian pounds)	-	14.51	14.73
Feed cost to produce 1 kg live weight (Egyptian pounds)	-	38.84	39.34
The cost of chick and feed to produce 1 kg live weight (Egyptian pounds)	-	53.35	54.08
The production cost of 1 kg live weight (Egyptian pounds)	-	71.13	72.10
The profit achieved from the production of 1 kg live weight (Egyptian pounds)	-	18.87	17.90
Profit index %	-	26.53	24.83

Table 8.

The economic feasibility of fattening birds up to 34 d of age.

34 d	Group 1	Group 2	Group 3
The cost of the chick to produce 1 kg live weight (Egyptian pounds)	-	-	13.67
Feed cost to produce 1 kg live weight (Egyptian pounds)	-	-	50.09
The cost of chick and feed to produce 1 kg live weight (Egyptian pounds)	-	-	63.77
The production cost of 1 kg live weight (Egyptian pounds)	-	-	85.02
The profit achieved from the production of 1 kg live weight (Egyptian pounds)	-	-	4.98
Profit index %	-	-	5.86

It is noted from Table 9 that when studying the economic feasibility of the different groups at the end of the marketing life for each group, it was found that delaying marketing to the age of 31 d leads to a decrease in profit by 5.7%, and delaying marketing to the age of 34 d leads to a reduction in the profit index to 26.36% compared to marketing at the age of 28 d. A significant increase in the studied indicators with the age of the birds was observed through the study of blood indicators (Table 10), but it did not reach the significance level.

Table 9.

The economic feasibility of fattening birds for each group.

	Group 1, 28 d	Group 2, 31 d	Group 3, 34 d
Profit index %	32.22	26.53	5.86

Table 10.

The hemato-biochemical characteristics of developing Japanese quails according to age.

Items	Group 1	Group 2	Group 3	p-value
RBCs (× 106/mm3)	2.71 ± 0.31	2.78 ± 0.30	2.83 ± 0.08	0.549
PCV (%)	31.66 ± 0.85	32.76 ± 1.43	33.8 ± 1.74	0.291
Hemoglobin, g/dL	12.38 ± 0.39	13.00 ± 0.47	13.40± 0.75	0.081
WBCs (× 103/mm3)	25.17 ± 1.45	25.20 ± 0.47	25.23 ± 1.15	0.134
Total protein, g/dL	4.42 ± 0.24	4.59 ± 0.54	4.67 ± 0.41	0.128
Glucose, mg/dL	299.13 ± 8.27	301.78 ± 7.54	304.7 ± 8.47	0.324
Total cholesterol, mg/dL	161.32 ± 4.23	163.41 ± 5.47	166.71 ± 5.43	0.07
Triglycerides, mg/dL	493.88 ± 16.78	525.62 ± 16.80	637.65 ± 18.45	0.241
Uric acid, mg/dL	8.14 ± 0.59	8.31 ± 0.86	8.45 ± 0.86	0.356
Calcium, mEq/L	7.52 ± 1.47	7.65 ± 1.24	8.00 ± 1.51	0.086
Phosphorus, mEq/L	5.51 ± 0.29	5.64 ± 0.38	5.70 ± 0.44	0.079

RBCs: Red blood cells; PCV: Packed cell volume; WBCs: White blood cells.

Means within the same row different superiors are different (p ≤ 0.05).

DISCUSSION

The findings indicated no significant difference in the overall mortality rate index between groups at each fattening stage, but postponing the marketing age significantly increases mortality in the same environment. As a result, we can observe that the 28-d marketing age had the lowest death toll, and these findings are in line with Abougabal (2020), who found that the mortality rate increased from 0.0% for the early marketing age group (30 d) to 3.33% for broiler age at 50 d. This finding is consistent with that of Goliomytis et al. (2003) and Baeza et al. (2012), who found that the mortality rate rose starting at 42 d of age and reached values that were 5 to 7 times higher compared to broilers brought up for 35 or 42 d, for broilers brought up for 63 d.

Metabolic disorders associated with rapid growth may be the cause of rising age-related mortality (Rezaei et al., 2018). Also, Schmidt's (2008) findings showed that mortality rose by about 1% between 43 and 46 d of broiler age. Additionally, Al-Barzinji (2022) reported that the best crossbreeding for the economic characteristics of the local quail was between desert males and white females, resulting in quail with a high hatchability rate of 87.08% and sexual maturity after 34 d.

The live weight, daily FI, and FCR results were non-significant between fattening groups. Still, there was a significant difference in average live weight index between the first and both groups at each marketing age. The body weights of quails differed substantially compared to other studies, although the marketing age in the current study is smaller. Our results are consistent with the results of Jatoi and Dawood (2012) and Hassan and Fadhil (2019). Local Egyptian and imported quail flocks have considerably different slaughter weights at 4 wk of age. On the other hand, Alamuoye and Ojo (2015) found that Japanese quail had a greater LBW (P ≤ 0.05) at various ages. Sabow (2020) also noted that the brown kind had the highest slaughter weight and carcass yields compared to other quails.

Average body weight increased significantly with age. These outcomes support prior research on the effectiveness of expansion in birds at various slaughter ages (Goliomytis et al., 2003; Baeza et al., 2012; El-Waseif and Abougabal, 2017; Rezaei et al., 2018). The findings of this study also corroborated Szőllősi and Szucs's (2014) findings that live body weight rose gradually with age.

On the other hand, Goliomytis et al. (2003) and Wang et al. (2012) indicated that FI increased steadily with age. Also, according to Abougabal (2020), raising the quail marketing age from 30 to 50 d significantly affects all groups' mortality rate, FCR, and FI. Between 30 and 50 d of age, an approximate 1.62% daily increase in FCR resulted in a 32.5% difference in FCR values. These decreases in FCR values are detrimental because, according to Abougabal (2020), a higher FCR directly raises production costs.

It is well known that FCR rises with advancing age (Lesson, 2000). According to Schmidt (2008), the FCR will increase by 2.1% every day the market age increases. Given the ages of the birds, the FCR rises because body fat, body maintenance, and locomotion require more energy than the weight gain dose. Consequently, the bird's FCR decreases with age, consistent with the findings of Szőllősi and Szucs (2014), who found that broiler FCR increased progressively with age, going from 1.71 on the 35th d to 2.05 on the 49th d.

The study presented no significant variation in the EPEF in quail birds at 28-days-old. However, a reduction was observed with bird age, with 34-days-old chicks receiving the lowest EPEF. In agreement with the current study, Abougabal (2020) reported that early-marketing-age chicks had considerably greater levels of EPEF than other late-marketing age groups. The EPEF index, the most crucial indicator of all development features that reflect the whole production profile, provides a low-cost technical and productive efficiency management index.

The current findings emphasize the challenges associated with increasing quail ages, primarily due to higher death rates and lower FCR, which impacted the EPEF of quail production concerning the rise in LBW. In line with our results, Szőllősi and Szűcs (2014) found that EPEF declined gradually with age, going from 317.7 on the 35th d to 286.8 on the 49th d of broiler age. According to study findings by Abou-Kassem et al. (2019), male or female Japanese quails should be slaughtered at 5 or 6 wk to maximize carcass yields and achieve the best possible meat quality and composition.

The results showed gizzard weight increases with bird age, while feather, blood, liver, heart, abdominal fat, chest, and thigh weights are not significantly different between study groups. This shows that it is not profitable to raise the age of birds above that which is suitable for slaughter. However, Wilkkanowska and Kokoszynski (2011) discovered that the characteristics of quail carcass yield increased with age. Similarly, quail liver weight was greater at 42 wk of age than at 35 wk, according to Alves et al. (2014). El-Full (2001) further stated that Japanese quail carcass properties vary greatly with age. Bughio et al. (2020) found that the liver weight (g) of 4 quail breeds, each slaughtered at a different age, varies greatly. Similarly, Walita et al. (2017) discovered that at 5 to 6 wk of age, there was a significant difference (P < 0.05) in the slaughter weight of quail giblets.

Jatoi and Dawood (2012) found that giblet weight in quail varies significantly by the fourth week. El-Full (2001) also found that the age of slaughter had a significant (P ≤ 0.01) impact on the amounts of edible heart, gizzard, liver, carcass, breast, leg, wing, and edible inner weights. However, when the abdominal fat, organs, and percentages in BW were evaluated, Narinc et al. (2014) found that, in 2 lines of Japanese quail, mass selection and slaughter age raised BW, which in turn enhanced all slaughter and carcass traits, excluding the percentage of edible inner organs. Despite these enhancements, the issue of low economic effectiveness due to high production costs, as retail cuts (breast, legs, and wings) originate from broiler chickens with a longer marketing age (Beski et al., 2015). In 2020, 196 to 230 g of breast meat was extracted from a chicken carcass with a marketing age of 28 to 30 d, verifying the significant increase concerning the daily weight gain of retail cuts (Park et al., 2021). Therefore, when contrasted with broiler chickens with a typical marketing age of 28 to 32 d, these cuts' texture and flavor qualities derived from chickens raised to a more significant marketing age (36 d or higher) are less favorable (Wattanachant et al., 2004).

In the opinion of Maynard et al. (2023), smaller bird markets exhibit improvements in most quality parameters. Broiler carcass performance and meat quality are significantly impacted by strain, sex, and carcass size. According to Hammemi et al. (2024), at 35 d, the Cobb 500 strain of birds had greater BW, breast meat yield, and FC than the Ross 308 strain. Higher wooden breast scores, drip loss, and cooking loss also impact the breast meat quality of these birds.

Results of the current study showed no significant differences in the profit index at 28 d but decreased as birds aged. The remaining 2 groups show no significant difference in profit index. Also, delaying marketing for 31 d leads to a 5.7% decrease in profit, while delaying it for 34 d results in a 26.36% decrease in profit index. This is consistent with Pavlova et al. (2023), who indicated that feeding costs rise by 75% as quail slaughter age increases. The deterioration in feed conversion, particularly after 35 d, the slaughter production of female sex quail decreases with age, primarily affecting live weight.

Park and Kim (2021) assessed the quality of cured chicken breasts produced from broiler chicken breasts at varying marketing ages (28, 30, 32, and 34 d). Age increases pH, shear force, protein content, and water-holding capacity. A 34-d broiler marketing age was determined to be appropriate for the Korean market. On the other hand, Walita et al. (2017) reported that quails should be slaughtered around 5 to 6 wk of age compared to 8 to 11 wk of age to obtain higher carcass yields. Also, according to Petek et al. (2022), younger quail meat samples had greater pH levels, suggesting a decrease in water-holding capacity, while older quail carcasses had higher values. In contrast, Lukanov et al. (2021) found no significant differences in the pH value between the slaughter age (28, 35, and 42 d) and gender. According to Maynard et al. (2023), processing different live weights and straight-run broilers may have contributed to the higher yield of broilers in large bird markets, with quality varying between males and females at a given weight.

The findings of blood indicators revealed an increase in indicators with the bird's age, but the significance level did not reach the desired level. This result agrees with Abou-Kassem et al. (2019), who reported that advancing the age of quails (from 5 to 7 wk) leads to a significant increase in the values of erythrocytes, PCV, and Hb, while plasma cholesterol, total protein, triglycerides, and haemoglobin decreased linearly with age. According to Jinxue et al. (2023), growth performance is impacted by heat stress and the recovery that follows. These effects are accompanied by abnormalities in redox function, disruptions in serum nutrient metabolism, and temporal and gender-specific differences.

CONCLUSIONS

Based on the obtained results, it could be concluded that the ideal marketing age for improved quail in Egypt is 28 d, as it did not negatively impact the indicators or the productive efficiency of the birds. Rather, this reduced the cost of chicks and nutrition to produce 1 kg of live weight and thus raised the profit index from the fattening process.