The Effect of Spraying Duck Eggs with Different Solutions During Incubation on Hatching and Post-Hatch Performance

ABSTRACT

This study investigated the effect of spraying duck hatching eggs with distilled water or apple vinegar solution on the hatching and post-hatch performance. 120 eggs from breeder Pekin ducks at 64 weeks of age were used. The eggs were weighed using a scale with a precision of 0.1 g and divided into three groups with 40 eggs per group. The eggs of group 1 (Non-sprayed, NS) were incubated without any spraying practices. The eggs of group 2 (Water-sprayed, SW) and group 3 (Sprayed with apple vinegar, SA) were sprayed with distilled water and a solution of distilled water (250 mL) + apple cider vinegar (5 mL) between embryonic days (ED) 8 and 24, respectively. The eggshell temperature, hatchability of set and fertile eggs, and chick yield were significantly higher in the SW and SA compared to eggs of the NS eggs (p≤0.05). However, the best hatching traits, eggshell temperature, and chick yield were identified in SW. Body weight and body weight gain at 14 days of age and the total average body weight were significantly highest, and lowest in ducks of the SW and SA, respectively (p≤0.05). In addition, the metatarsal temperature was significantly lowest and highest in ducks of the NS and SW, respectively (p≤0.05). The hot carcass weight and breast weight were higher in ducks of the SW and SA groups compared to NS ducks (p≤0.05). The thigh and wing yield were significantly higher in SA ducks compared to ducks from the other incubation treatments. However, the back weight and yield were significantly higher in NS ducks than in ducks in the SW and SA treatments (p≤0.05). Spraying duck eggs with water and apple vinegar solution between ED 8-24 improves embryonic heat loss, hatching traits, chick yield, and chick weight at hatch. Moreover, spraying with water is more beneficial for improving post-hatch growth performance, while the application of both apple vinegar solution and water during incubation seemed beneficial for adaptation to post-hatch stress conditions. Additionally, spraying eggs with water and apple vinegar solution had the potential to improve most of the carcass and organ traits. It also tended to increase most of the texture profile values of the breast meat, cooking loss, and meat pH, as well as improve breast meat color traits.

Keywords:
Carcass; ducks; embryogenesis; in-ovo spray; hatchability; growth; meat quality; stress

INTRODUCTION

Pekin ducks have been identified as an alternative poultry species with low production and maintenance costs, but a high egg and meat nutritive value (Abdallah et al., 2024a). Ducks are reared in many parts of the world, but their production is mostly concentrated in Asia (Baéza & Huang, 2022). It has been reported by Aronal et al. (2012) that in Southeast Asia, duck meat is the second most consumed poultry meat. Compared to chicken eggs, duck eggs have been reported to have higher protein, energy, carbohydrate, vitamins, iron, and sodium content (Jalaludeen & Churchil, 2006). Several authors have also reported duck eggs to be a good source of protein and other nutrients, representing a food with high nutritional quality (Al-Obaidi & Al-Shadeedi, 2016; Ahmad et al., 2017). Moreover, a higher amount of total essential and non-essential amino acids in duck meat compared to chicken meat has been reported (Aronal et al., 2012).

Ducks are characterized by a high egg production rate and in some species, egg production varies between 200-250 per year (Abd El-Hack et al., 2019). Idahor et al. (2015) have identified that ducks could lay between 43 and 150 eggs per year. However, the hatchability of duck eggs has been reported to be very low compared to that of chicken and quail eggs. For instance, the hatchability of Pekin duck eggs in the winter, spring, and summer months has been reported at 57.68%, 78.0%, and 54.14%, respectively (Abd El-Hack et al., 2019). Ipek & Sozcu (2017) identified that the hatchability of fertile eggs for medium, large, and small Pekin duck eggs were 86.5±3.4%, 72.7±2.7%, and 84.7±5.3%, respectively. The same study reported the hatchability of set (total) eggs to be 77.80±5.0%, 65±23.1%, and 77.1±6.3% for medium, large, and small-size pekin duck eggs, respectively. Awad (2013) also identified the hatchability of duck eggs to be 65.21% in March and 34.96% in August.

The reduction in the hatchability of duck eggs is associated with the thickness of the eggshell and its membrane, which interferes with the eggshell conductance, embryonic development, and the ability of chicks to hatch (Christensen et al., 2005; Balkan et al., 2006). Additionally, the eggs of waterfowl possess a strong waxy coating cuticle that completely covers the eggshell pores, thereby preventing adequate water and gaseous exchange between the developing embryo and its environment (The Poultry Site, 2020). Changkang et al. (1999) reported that duck eggs are characterized by larger size, thicker eggshells, and a higher number of pores, making the hatching of duck eggs harder than chicken eggs. Moreover, embryos produce high metabolic heat during the latter stages of incubation, which could result in oxidative stress due to inappropriate eggshell conductivity. Therefore, research has focused on finding natural disinfectants and nutritive solutions with the potential ability to degrade the eggshell thickness and the waxy coating structure of the cuticle of waterfowl eggs to ensure better embryonic development, hatching traits, and post-hatch performance.

The in ovo application of natural exogenous materials, disinfectants, or nutritive solution to eggs before or during incubation has been identified to be an effective approach to improve the hatching and post-hatch performance traits of duck eggs. This process may include injecting, dipping, washing, or spraying eggs with water or other solutions before or during embryogenesis (He et al., 2020; El-Kholy et al., 2022; Salama, 2022; Eroglu et al., 2024). The provision of nutrients to developing embryos to aid body tissue formation as well as to mitigate stress during incubation has been identified as the overall objective of in ovo feeding techniques (Peebles, 2018; Tainika & Şekeroğlu, 2020; El-Kholy et al., 2021; Tainika & Bayraktar, 2021).

Apple vinegar as a natural solution contains several bioactive compounds and organic acids (Yagnik et al. 2018; Ousaaid et al. 2021a) with the potential to degrade eggshell thickness and the waxy coating of the cuticle, while also inhibiting oxidative stress during embryogenesis. Apple vinegar has been identified by several authors to possess antioxidant (Bakir et al., 2016; Yagnik et al., 2018; Ousaaid et al., 2021b) and antimicrobial properties (Hindi, 2013; Hindi et al., 2014; Yagnik et al., 2018; Ousaaid et al., 2021a). Additionally, it contains vitamins and minerals (del Campo et al. 2008), providing nutritional support (Ousaaid et al., 2021a), while also eliminating harmful intestinal microbes (Nazıroğlu et al., 2014).

This is an intriguing topic for further research, as very few studies have focused on how treating hatching eggs with apple vinegar affects parameters like eggshell temperature, post-hatch growth performance, body region temperature, carcass, and meat quality traits.Therefore, in the current study, it was hypothesized that spraying duck eggs with apple vinegar would improve hatching and post-hatch performance traits.

MATERIALS AND METHODS

Ethical statement

This study was conducted under the guidelines for animal experiments of the Ministry of Food, Agriculture and Livestock, Türkiye. Approval was granted by the Animal Experiments Local Ethics Committee of Çukurova University (Approval number: No 10/ 29.11.2024).

Animal material and experimental groups

This study was carried out at the Animal Research and Experimental Unit of Çukurova University, Adana, Türkiye. 120 eggs from breeder Pekin ducks at 64 weeks of age were used. The eggs were weighed using a scale with a precision of 0.0 1 g and divided into three groups with 40 eggs per group. The average incubation temperature and humidity between ED 0-24 were 37.8^oC and 55%, respectively. At hatch, the average temperature and humidity of the hatchery machine was 37.5^oC and 65-70 %. The eggs of group 1 (control) were incubated without any spraying practices (NS). The eggs of group 2 and group 3 were sprayed with distilled water (SW) and a solution of distilled water + apple cider vinegar (SA) between embryonic day (ED) 8 and 24, respectively.

Preparation of apple cider vinegar + distilled water solution

Apple cider vinegar made up of apple cider and sodium metabisulphite (antioxidant) was purchased from a certified local company. Using a syringe, 5 mL of the apple cider vinegar was mixed with 250 mL of distilled water at a temperature of 30 ±1^oC. The temperature of the distilled water was measured using a TP101 digital food thermometer (50 -+ 300^oC). The preparation of the solution was conducted in a transparent spraying plastic bottle. The solution was then thoroughly mixed by hand shaking for approximately 3 minutes to ensure the uniformity of the mixture. The composition of the apple cider vinegar used in this experiment is given in Table 1.

Table 1
Energy and nutrients per 100 g of the apple cider vinegar used in this study.

Energy (kcal/g)	26.60
Saturated fat (g)	0.00
Fat (g)	0.00
Sugar (g)	1.15
Protein	0.00
Carbohydrate (g)	1.50
Salt (g)	0.03
Acidity (acetic acid) %	4-5

Application of in ovo spraying practices

Between embryonic days (ED) 8 and 24, eggs of group 2 (SW) and group 3 (SA) were withdrawn from the incubator, allowed to cool to an eggshell temperature of 30±1^oC on a rectangular table, and sprayed thoroughly with distilled water and apple vinegar solution, respectively. The eggshell temperature reached 30±1^oC between 25 to 30 minutes, which was measured using a WOHLER ST-D2 (±0.3^oC) infrared thermometer. After achieving the required eggshell temperature, the spraying practices were conducted for 10 minutes. The entire processes were carried out at the same time throughout the incubation period (10:00 am-10:40 am). To ensure that the only variable having an effect on hatching and post-hatch traits were the spraying effects, the eggs of group 1 (NS) were also withdrawn from the incubator together with the eggs of group 2 and 3 and cooled to the same eggshell temperature during the entire spraying practices (ED0-24). Once the praying practices were done, all the eggs were returned to the incubator.

Determination of egg weight loss, hatching traits, chick weight and chick yield at hatch, eggshell temperature, and eggshell thickness

On ED 15, 22, and 24, all the eggs in each experimental treatment were weighed separately using a balance with 0.1 g precision. After identifying egg weight on ED 24, a fertility test was conducted using the candling method, and fertile eggs were transferred to the hatcher. On ED 28, the last day of hatch, all the hatched ducklings per experimental treatment were counted and weighed separately using a balance with 0.1 g precision. The percentage of egg weight loss, hatchability of set and fertile eggs, and chick yield were identified with the respective formulae below (Abdallah et al., 2024b; Abou-Kassem et al., 2024; Ozkan et al., 2024). The hatchery machine used was a Cimuka T1280H, with the capacity of hatching 1280 chicken eggs at a time.

$\begin{array}{c}Percentageofegg\\ weightloss(\%)\end{array}=\frac{Eggweightbeforeincubation-EggweightonED24}{Eggweightbeforeincubation}\times 100$

$Hatchabilityofseteggs(\%)=\frac{Totalofnumberofhatchedchick}{Totalnumberofeggs}\times 100$

$Hatchabilityoffertileeggs(\%)=\frac{Totalofnumberofhatchedchick}{Totalnumberoffertileeggs}\times 100$

$Chickyield(\%)=\frac{Averageweightofhatchedchicks}{Averageeggweightatsetting}\times 100$

The eggshell temperature of 16 eggs per treatment was identified on ED 16, 19, 21, and 22, using a WOHLER ST-D2 (±0.3^oC).

At hatch, 16 shells of hatched eggs from each treatment were collected for the measurement of eggshell thickness. Portions of each eggshell from the broad, middle, and narrow parts were first identified. The thickness of each part was then determined using a digital shell thickness gauge with a precision of 0.01 mm (Model 100823, Russia), and the mean average value of the three portions was identified.

The formula below (Baylan et al., 2024; Kurşun et al., 2024a) was used to evaluate the eggshell thickness.

$Eggshellthickness(mm)=\frac{narrow+middle+broadportions}{3}$

Post-hatch housing and feeding

During the rearing stage, ducklings were first brooded in a floor system with the dimensions of 150cm x 150cm x 29 cm (Length, width, and height, respectively) between 1 and 14 days of age. Between 14 and 50 days of age, the brooder was removed and the dimension of the production system (litter system) was 219 cm x 263 cm x 205 cm (length, width, and height, respectively). There were three replicates per incubation treatment, with 12 ducks per replicate. Ducklings were fed broiler starter and grower diets between 1 and 14 days of age and between 15 and 28 days of age, respectively. The broiler finisher diet was used between 29 and 50 days of age. Feed and water were provided ad libitum. The composition and the ingredients of the diets used in this study are given in Tables 2 and 3, respectively. The photoperiodic lightning [Light (L) and Dark (D) phase] used throughout the experimental period was 21 L: 3 D from day-old till slaughter age.

Table 2
Nutritional composition of the diet used in this experiment.

Composition	Feed type
	Starter diet (1-14 d)	Grower diet (15-28 d)	Finisher diet (29-50 d)
Lysine (%)	1.44	1.15	1.05
Methionine (%)	0.56	0.47	0.47
Metabolic energy (kcal/kg)	3000	3200	3200
Vitamin D3 (IU/kg)	2000	2000	2000
Vitamin A (IU/kg)	10,000	10,000	10,000
Crude protein (%)	23.00	19.50	19.5
Crude cellulose (%)	3.60	3.60	3.07
Crude fat (%)	5.40	7.20	7.20
Crude ash (%)	6.30	5.30	5.30
Calcium (%)	3.96	0.78	0.78
Phosphorus (%)	0.48	0.39	0.39
Sodium (%)	0.16	0.16	0.16
Manganese (mg/kg)	80.00	80.00	80.00
Zinc (mg/kg)	60.00	60.00	60.00
Cobalt (mg/kg)	0.50	0.50	0.50
Selenium (mg/kg)	0.15	0.15	0.15
Iodine (mg/kg)	2.00	2.00	2.00
Iron [iron sulphate monohydrate] (mg/kg)	60.00	60.00	60.00
Copper [copper sulphate pentahydrate] (mg/kg)	5.00	5.00	5.00

Table 3
The composition of raw materials (ingredients) in feeds used in the experiment (%).

Raw materials (%)	Starter feed	Grower feed	Fininsher feed
Corn 6.2% CP	49.01	49.97	51.55
Soybean Meal 47 CP%	37.81	32.24	27.07
Barley 12% CP	4.00	7.00	9.00
Soybean Oil	3.17	4.23	5.28
Sunflower Meal 33CP%	3.00	4.00	5.00
Limestone	0.75	0.65	0.55
Mineral Premix	0.20	0.20	0.20
DL Methionine	0.36	0.32	0.28
L-Lysine HCL	0.17	0.16	0.15
Dicalcium Phospahte	0.73	0.44	0.15
Sodium Bicarbonate	0.11	0.12	0.13
Phytase	0.12	0.12	0.12
L-Threonine	0.15	0.13	0.10
Vitamin Premix	0.10	0.10	0.10
Choline Chloride-75%	0.05	0.05	0.05

Determination of post-hatch growth performance traits

Body weight (BW) and feed intake (FI) were determined at 14, 28, 42, and 50 days of age using a scale with a precision of 0.0 1 g. The body weight gain (BWG) was identified by subtracting the body weight of a particular week from the body weight of the subsequent week. Additionally, the FI was calculated by subtracting the feed left at the end of a particular week from the total feed given at the beginning of that week. The feed conversion ratio (FCR) was calculated by dividing the FI by the BWG. BWG, FI, and FCR were evaluated using the formulae below:

$\begin{array}{l}BWG=(Bodyweightofsubsequentweeks-bodyweightofpreviousweeks)\\ FI=(Feedgivenatthebeginningofaparticularweek-feedleftattheendofthatweek)\\ FCR=\frac{Feed\mathrm{int}ake(g)}{Bodyweightgain(g)}\end{array}$

Measurement of body region temperature and fluctuating asymmetry of the leg

The footpad, beak, and metatarsal temperature of 15 ducks per treatment (5 ducks per replicate) were identified at 45 days of age using a WOHLER ST-D2 (±0.3^oC) infrared thermometer under post-hatch heat stress conditions (30±1^oC, 30%RH). The cloacal temperature was identified by inserting an MT101 clinical thermometer (±0.1^oC) 3cm inside the cloaca for 20-30s (Kursun et al., 2024b). The fluctuating asymmetry (FA) of the leg was determined after the ducks were slaughtered and the legs were separated from the carcass. The metatarsal length, width, and middle toe length were determined using an INSIZE digital calliper (± 0.01 mm). Twelve ducks per incubation treatment were used for the identification of the FA. The FA was evaluated using the formula below (Archer et al., 2009).

All the measurements were conducted in mm.

$FA=\frac{ML(L-R)+MW(L-R)+MTL(L-R)}{3}$

Where: R (Right); L (Left); ML (Metatarsal length); MTL (Middle Toe length); MW (Metatarsal width).

Measurement of carcass traits

At 50 days of age, four ducks per replicate (12 ducks per incubation treatment) whose live weights were close to the average live weight of each replicate were slaughtered. At slaughter, the weight of the hot carcass, heart, spleen, gizzard, and liver were determined using a scale with 0.0 1 g precision. The hot carcass was then stored in a refrigerator at +4^oC for 24 hours. After the 24-hour cold storage, the weight of the cold carcass, abdominal fat, and carcass parts (breast, thigh, wings, and back) were identified with a scale of 0.0 1 g precision. The cold and hot carcass yield, and the percentage of each portion of the carcass (breast, thigh, wing, and back percent) were evaluated according to the formulae below (Duman et al., 2024; Bashir et al., 2023):

$Hotcarcassyield(\%)=\frac{Hotcarcassweight(g)}{Slaughterweight(g)}\times 100$

$Coldcarcassyield(\%)=\frac{Coldcarcassweight}{Slaughterweight(g)}\times 100$

$Percentageofcarcassparts(\%)=\frac{Weighofaspecificcarcasspart(g)}{Slaughterweight(g)}\times 100$

Meat quality analysis

Six breast meat samples from each experimental group were used for the identification of breast meat quality traits. The traits identified were pH24, cooking loss, breast meat color, and sensory properties (Texture Profile Analyses). The left and right breast muscle pH was identified after the +4^oC 24h cold storage using an ST272 Spear pH electrode, and the mean average value of the two was recorded. 100 g of the uncooked (raw) breast meat samples were taken and ground using an electronic Arcelik K 1261 RHB hand blender. After that, 50g of the homogenized ground meat was wrapped in a plastic bag and boiled in a container with distilled water at 80^oC for 20 minutes. After the boiling process, the weight of the boiled meat (WBM) was determined and the meat weight loss (MWL) was calculated by subtracting the weight of the boiled meat (WBM) from the weight of the fresh meat (WFM). The WBM and WFM were used to calculate the cooking loss (CL). Additionally, samples of the ground meat were collected into a petri dish and then placed in a Konica Minolta Colorimeter device (ColorFlex EZ CR-300, USA) to determine the meat color values (L*, a*, and b*).

Texture profile analysis of the meat was carried out in a TA.XT-2 Plus™ texturometer (Stable MicroSystem Ltd., Surrey, UK) using cylindrical samples (1cm height and 1cm diameter). Samples were compressed twice at 50% of their height with a 36mm diameter cylindrical probe at 3mm/s, with a 5s delay between compressions. Hardness, cohesiveness, springiness, and resilience values were calculated from the corresponding force vs distance curves, while chewiness was calculated as the product of hardness, cohesiveness, and springiness with the software of the device (Texture Exponent 32).

Statistical analysis

The normality test and test of homogeneity were conducted using Shapiro-Wilk and Levene’s tests, respectively. It was confirmed that all the data showed normal distribution. After confirming the normality of the data, the analysis of variance (ANOVA) was applied to the data. Inter-group comparisons were conducted using Duncan`s multiple comparison test at p≤0.05. The statistical software package JMP 17 (SAS, 2017) was used for data analysis.

RESULTS

The effect of the incubation treatments on egg weight (g) at ED 15, 22, and 24, and total egg weight loss (ED 0-24) are presented in Table 4. It was identified that the egg weights at ED 15, 22, 24, and the total egg weight loss (ED 0-24) were not significantly different among the incubation treatments (p>0.05).

Table 4
The influence of incubation treatments on egg weight (g) at ED 15, 22, and 24, and total egg weight loss (%) (Mean ± SEM).

Experimental group	Egg weight (g) classification			Total egg weight loss (%) (ED 0 - ED 24)
	ED 0	ED 15	ED 22	ED 24
NS	88.20±0.92a	81.49±0.87a	78.11±0.85a	76.43±0.87a	12.81±0.25a
SW	89.27±0.92a	82.31±0.87a	78.84±0.85a	77.70±0.87a	12.75±0.25a
SA	88.05±0.92a	81.54±0.87a	78.40±0.85a	76.81±0.87a	12.47±0.28a
p-value	0.595	0.757	0.831	0.572	0.637

• Values with different superscript letters differ significantly. NS (Non-sprayed); SW (Sprayed with distil water); SA (Sprayed with apple vinegar solution); ED (Embryonic day); SEM (Standard error of mean).

The influence of the incubation treatments on eggshell temperature (^oC), hatchability of set and fertile eggs (%), chick weight (g), chick yield (%), and eggshell thickness (mm) is given in Table 5. The eggshell temperature was significantly different among the incubation treatments (p<0.05), lowest in SW on ED 16, 19, and 22, and in SA on ED 21. The hatchability of set and fertile eggs and chick yield were significantly highest in SW and lowest in NS (p<0.05). Additionally, chick weight nearly reached a significant level (p=0.0648), with the highest and lowest in ducklings of SW and NS, respectively. However, the incubation treatments did not have any significant effect on eggshell thickness among the experimental groups (p>0.05).

Table 5
The influence of incubation treatments on eggshell temperature (^oC), hatchability of set and fertile eggs (%), chick weight (g), chick yield (%), and eggshell thickness (mm) (Mean ± SEM).

Experimental group	Eggshell temperature (EST, oC)			Hatchability of set eggs (%)		Hatchability of fertile eggs (%)	Chick weight (g)	Chick yield (%)	EGST (mm)
	ED 16	ED 19	ED 21	ED 22
NS	38.35±0.09a	39.53±0.10a	39.73±0.13a	38.37±0.14a	80.00±0.79a	86.49±0.80a	55.59±0.85a	63.03±0.35a	368.17±7.56a
SW	37.09±0.09c	39.03±0.10b	39.43±0.13ab	37.64±0.14b	92.50±0.79b	94.87±0.80b	58.32±0.85a	65.33±0.35c	361.21±7.56a
SA	37.99±0.09b	39.28±0.10ab	39.25±0.13b	38.21±0.14a	85.00±0.79c	89.47±0.80ab	56.21±0.85a	63.84±0.35b	363.04±7.56a
p-value	<0.001	0.004	0.038	0.002	<0.001	<0.001	0.065	<0.001	0.798

• Values with different superscript letters differ significantly.
• NS (Non-sprayed); SW (Sprayed with distil water); SA (Sprayed with apple vinegar solution); EGST (Eggshell thickness); SEM (Standard error of mean).

The effect of the incubation treatments on body weight (g), body weight gain (g), feed intake (g), and feed conversion efficiency is presented in Table 6. The body weight at 14 days of age and the total average (0-50 d of age) body weight were found to be significantly different (p<0.05), with the highest and lowest values in ducks of SW and SA, respectively. Additionally, the body weight at 28 days of age nearly reached a significant level, being highest in ducks of SW and lowest in SA ducks (p=0.099). However, the body weights at 42 and 50 days of age were not significantly different among the experimental groups (p>0.05).

Table 6
The effect of incubation treatments on body weight (g), body weight gain (g), feed intake (g), and feed conversion efficiency (Mean ± SEM).

Groups		Age of ducks (days)
		14	28	42	50	Total average
BW (g)	NS	203.00±6.72ab	1104.00±28.36a	2399.50±42.54a	3156.10±50.16a	6918.19±78.21ab
	SW	215.67±6.72a	1163.00±28.36a	2477.80±42.54a	3210.13±50.16a	7124.92±78.21a
	SA	191.23±6.72b	1077.10±28.84a	2351.17±43.27a	3086.07±50.16a	6850.82±79.54b
	p-value	0.041	0.099	0.114	0.221	0.042
BWG (g)	NS	147.41±6.43ab	901.00±25.91a	1295.50 ±54.06a	756.60±60.08a	3100.51±49.38a
	SW	157.35±6.43a	947.33±25.91a	1314.80±54.06a	698.28±61.11a	3151.81±49.38a
	SA	135.03±6.43b	871.57±26.82a	1282.30±54.06a	742.79±61.11a	3047.21±50.22a
	p-value	0.050	0.128	0.913	0.778	0.337
FI (g)	NS	7567.00±180.41a	14423.33±963.77a	25728.33±1195.92a	20618.33±115.69a	17084.25±4072.09a
	SW	7453.33±180.41a	15982.00±963.77a	27443.67±1195.92a	20925.00±115.69a	17951.00±4072.09a
	SA	7682.00±180.41a	15126.33±963.77a	26766.67±1195.92a	20845.67±115.69a	17605.17±4072.09a
	p-value	0.686	0.553	0.618	0.231	0.989
FCR	NS	5.15±0.56a	1.60±0.04a	1.59±0.03a	4.08±0.23a	3.11±0.52a
	SW	4.87±0.56a	1.69±0.04a	1.59±0.03a	4.44±0.23a	3.15±0.52a
	SA	5.83±0.56a	1.67±0.04a	1.63±0.03a	3.95±0.28a	3.43±0.52a
	p-value	0.504	0.402	0.753	0.403	0.893

• Values with different superscript letters differ significantly.
• Total average for BW and BWG (0-50 d). Total average for FI and FCR (14-50 d).
• NS (Non-sprayed); SW (Sprayed with distil water); SA (Sprayed with apple vinegar solution); SEM (Standard error of mean).

Moreover, the body weight gain at 14 days of age was significantly highest and lowest in ducks of SW and SA, respectively (p=0.05). Differences in body weight gain on days 28, 42, and 50 of age and the total average body weight gain (14-50 d of age) were determined to be insignificant among the experimental groups (p>0.05). Additionally, the feed intake during the experimental period (14, 28, 42, and 50 days of age) and the overall average feed intake were not statistically significant among the experimental groups (p>0.05). Moreover, in the present study, the weekly feed conversion ratio, as well as the total feed conversion ratio were statistically insignificant among the experimental groups (p>0.05).

The effect of the incubation treatments on body region temperature (rectal, footpad, metatarsal, and beak) under post-hatch stress conditions (30±1^oC, 30% RH) at 45 days of age and fluctuating asymmetry (FA) of the leg is given in Table 7. The fluctuating asymmetry of the leg, footpad, and beak temperature were not statistically different among the incubation treatments (p>0.05); however, the rectal temperature nearly reached a significant level, being highest in NS ducks and lowest in SA ducks (p=0.099). Additionally, the metatarsal temperature was significantly highest and lowest in SW and NS ducks, respectively (p=0.05).

Table 7
The effect of incubation treatments on body region temperature under post hatch high temperature conditions and fluctuating asymmetry (FA) of the leg (Mean ± SEM).

Experimental group	Body region temperature (oC)				FA (mm)
	Rectal	Footpad	Metatarsal	Beak
NS	41.99±0.12a	34.41±0.18a	34.65±0.07b	34.70±0.09a	3.53±0.58a
SW	41.74±0.13a	34.23±0.20a	34.89±0.06a	34.67±0.09a	2.76±0.58a
SA	41.61±0.12a	34.30±0.17a	34.77±0.07ab	34.65±0.09a	2.43±0.56a
p-value	0.099	0.790	0.050	0.929	0.383

• Values with different superscript letters differ significantly. NS (Non-sprayed); SW (Sprayed with distil water); SA (Sprayed with apple vinegar solution); ED (Embryonic day); SEM (Standard error of mean).

The influence of the experimental treatments on carcass traits is given in Table 8. The hot carcass yield, cold carcass weight, cold carcass yield, breast yield, wing weight, and neck weight were statistically insignificant among the experimental groups (p>0.05). The thigh yield was significantly higher in SA compared SW and NS ducks (p<0.05). However, the thigh weight nearly reached a significant level, being higher in SW and SA ducks than in NS (p=0.069). Similarly, the hot carcass and breast weight were identified as significant, being highest and lowest in SW and NS ducks, respectively (p<0.05). The wing yield was also statistically highest and lowest in SA and SW ducks, respectively (p<0.05). Additionally, the neck yield nearly reached a significant level, being highest in NS ducks and lowest among SW ducks (p=0.057). The back weight and yield were determined to be significant, both being higher in NS ducks than in SW and SA ducks (p<0.05).

Table 8
The influence of experimental treatments on carcass traits (Mean ± SEM).

Groups	HCW (g)	HCY (%)	CCW (g)	CCY (%)	TH-W (g)	TH-Y (%)	BR-W (g)	BR-Y (%)	WG-W (g)	WG-Y (%)	NK-W (g)	NK-Y (%)	BK-W (g)	BK-Y (%)
NS	2183.33 ±23.61b	70.48 ±0.72a	2209.58 ±26.33a	71.32 ±0.66a	456.08 ±7.14a	14.72 ±0.21b	864.00 ±17.58b	27.89 ±0.58a	211.50 ±4.10a	6.83 ±0.13ab	167.08 ±4.03a	5.39 ±0.12a	280.10 ±5.64ab	9.05 ±0.12a
SW	2318.58 ±23.61a	71.30 ±0.72a	2281.75 ±26.33a	70.85 ±0.71a	478.58 ±7.14a	14.71 ±0.21b	926.73 ±18.36a	28.46 ±0.61a	210.25 ±4.10a	6.47 ±0.13b	163.08 ±4.03a	5.02 ±0.12a	274.58 ±5.14a	8.61 ±0.12b
SA	2195.83 ±23.61b	72.50 ±0.72a	2215.83 ±26.33a	72.57 ±0.71a	475.42 ±7.14a	15.70 ±0.21a	872.00 ±17.58ab	28.81 ±0.58a	215.33 ±4.10a	7.11 ±0.13a	162.83 ±4.03a	5.37 ±0.12a	260.50 ±5.64b	8.56 ±0.12b
p-value	<0.001	0.150	0.116	0.223	0.069	<0.001	0.040	0.536	0.662	0.004	0.707	0.057	0.050	0.015

• Values with different superscript letters differ significantly.
• NS (Non-sprayed); SW (Sprayed with distil water); SA (Sprayed with apple vinegar solution); HW (Heart weight); HY (Heart yield); LW (Liver weight); HCW (Hot carcass weight); HCY (Hot carcass yield); CCW (Cold carcass weight); CCY (Cold carcass yield); TH-W (Thigh weight); TH-Y (Thigh yield); BR-W (Breast weight); BRY (Breast yield); WG-W (Wing weight); WG-Y (Wing yield); NK-W (Neck weight); NK-Y (Neck yield); BK-W (Back weight); BK-Y (Back yield); SEM (Standard error of mean).

The effect of the incubation treatments on internal organ trait is given in Table 9. The heart weight, heart yield, liver yield, spleen weight, spleen yield, abdominal fat weight, abdominal fat yield, gizzard weight, and gizzard yield were statistically insignificant among the ducks from the various incubation treatments (p>0.05). In addition, the liver weight nearly reached a significant level, being highest and lowest in SA and SW ducks, respectively (p=0.074).

Table 9
The effect of incubation treatments on internal organ traits (Mean ± SEM).

Groups	HW (g)	HY (%)	LW (g)	LY (%)	SP-W (g)	SP-Y (%)	ABF-W (g)	ABF-Y (%)	GZ-W (g)	GZ-Y (%)
NS	18.43±0.70a	0.59±0.02a	67.36±2.70a	2.16±0.08a	1.92±0.14a	0.06±0.01a	21.36±1.46a	0.71±005a	96.57±3.68a	3.19±0.11a
SW	17.37±0.70a	0.56±0.02a	61.71±2.82a	1.99±0.08a	1.870±0.14a	0.06±0.01a	21.53±1.46a	0.70±0.05a	96.13±3.85a	3.09±0.12a
SA	18.99±0.73a	0.58±0.02a	70.93±2.70a	2.18±0.08a	1.94±0.15a	0.06±0.01a	24.01±1.46a	0.74±0.05a	101.30±3.68a	3.12±0.11a
p-value	0.281	0.526	0.074	0.187	0.945	0.823	0.369	0.811	0.558	0.835

• Values with different superscript letters differ significantly.
• NS (Non-sprayed); SW (Sprayed with distil water); SA (Sprayed with apple vinegar solution); HW (Heart weight); HY (Heart yield); LW (Liver weight) ; Liver yield (LY); SP-W (Spleen weight); SP-Y (spleen yield); ABF-W (Abdominal fat weight); ABF-Y (Abdominal fat yield); ABF-Y (Abdominal fat yield); GZ-W (Gizzard weight); GZY (Gizzard yield); SEM (Standard error of mean).

The influence of the incubation treatments on meat quality traits is given in Table 10. The pH24, CL, HA, CH, SP, GU, RS, and ADH were not statistically different among the experimental groups (p >0.05); however, CO nearly reached a significant level, similar between NS and SA ducks and lowest in SW (p=0.055). Additionally, the a* and b* color traits were not significantly different among the experimental groups (p >0.05), but the L* value nearly reached a significant level, being highest and lowest in the breast meat of SA and NS, respectively (p=0.081).

Table 10
The effect of incubation treatments on meat quality traits (Mean ± SEM).

Group	pH24	CL (%)	HA	CH	SP	CO	GU	RS	ADH	Meat color traits
										L*	a*	b*
NS	5.67±0.07a	29.33±1.40a	1748.77±220.65a	611.69±102.7a	0.69±0.03a	0.50±0.02a	887.83±152.2a	0.25±0.01a	60.82±8.02a	32.79±1.03a	10.75±0.46a	11.89±0.45a
SW	5.76±0.06a	31.68±1.40a	2144.79±201.42a	661.05±93.36a	0.71±0.03a	0.44±0.02a	941.05±138.97a	0.22±0.01a	62.85±8.79a	35.48±1.03a	11.37±0.46a	12.18±0.45a
SA	5.69±0.06a	29.45±1.40a	1737.96±246.69a	860.47±93.36a	0.73±0.03a	0.50±0.02a	1228.66±152.23a	0.26±0.01a	53.48±8.79a	36.18±1.03a	11.52±0.46a	12.14±0.45a
p-value	0.5312	0.5312	0.338	0.188	0.655	0.055	0.265	0.123	0.733	0.081	0.471	0.886

• Values with different superscript letters differ significantly.
• NS (Non-sprayed); SW (Sprayed with distil water); SA (Sprayed with apple vinegar solution); HA (Hardiness); CL (Cooking loss); CH (Chewiness); SP (Springiness); CO (Cohesiveness); GU (Gumminess); RS (Resilience); ADH (Adhesiveness); L* (Brightness); a* (Redness); b* (Yellowness); SEM (Standard error of mean).

DISCUSSION

In the current study, the egg weight at ED 15, 22, and 24, and the total egg weight loss (ED 0- ED24) were not statistically different among the experimental groups, but the groups sprayed with water and apple vinegar had the numerically lowest percentage of egg weight loss compared to the non-sprayed group. In line with our findings, He et al. (2020) also observed that eggs washed with acetic acid, vinegar, citric acid, or dipped in water had the lowest percentage of egg weight loss compared to unwashed eggs. Additionally, Fouad et al. (2018) identified the lowest percentage of weight loss in eggs sprayed with vinegar and water during incubation compared to the control (non-sprayed). Brah et al. (2024) also confirmed that treating eggs with vinegar has no effect on egg weight loss. The latest study by Mustafa et al. (2023) revealed eggs treated with either apple, lemon, or grape vinegar and stored for eight weeks at room temperature had a significantly higher egg weight compared to non-treated eggs.

Studies that have used other natural disinfectants have also confirmed results similar to those of the present study. For instance, Al-Asadi & Ibrahim (2020) also reported that dipping eggs in either basil or fenugreek solution had no significant effect on egg weight at ED 18 and on the percentage of egg weight loss. Shahein & Sedeek (2014) also reported no significant effect of spraying eggs with different liquids on the percentage of egg weight loss between ED 6-18, but eggs sprayed with other solutions (propolis, thyme oil, and ethyl alcohol) had the lowest percentage of egg weight loss compared to the non-sprayed eggs between ED 0-5 and ED 0-18.

It was therefore speculated that the dipping, spraying, or washing of eggs with different solutions (water, apple vinegar, vitamin C, or other solutions) interferes with the eggshell conductance by covering the air spaces/pores or interfering and altering the structural components (peptides and proteins) of the cuticle, affecting its permeability, and leading to lower evaporation and moisture loss. Indeed, He et al. (2020) reported that the dipping of eggs in different chemical solutions could alter the cuticle by interfering with its structural component, then dissolve and/or denature to form a viscous, less permeable substance that blocked the eggshell pores. This mechanism might have contributed to the lower egg weight/percentage of egg weight loss observed in eggs sprayed with apple vinegar or water during incubation in the present study.

On the contrary, different authors (Al-Hamed & Al-Eshaki, 2019) have identified higher weight in eggs sprayed with 10 g/L of vitamin C between ED 5 and 10 as compared to other groups (control, sprayed with water and sprayed with 5 g/L vitamin C). However, the eggs sprayed with vitamin C had the lowest weight compared to those sprayed with water and the control on ED 15. In addition, the percentage of egg weight loss was lower in the group sprayed with 10 g/L of vitamin C on ED 5. However, between ED 10 and 15, the eggs sprayed with vitamin C (10 or 5 g/L) had the highest percentage of weight loss. Similarly, some authors also identified a higher percentage of weight loss in eggs dipped in vitamin C (5 or 10 g/L) or water before incubation (Mohammed et al., 2011). Moreover, Abdel-Azeem et al. (2016) confirmed higher weight in non-sprayed eggs and eggs sprayed with water on ED 18 compared to those sprayed with vitamins (4 or 6 g/L) or L-carnitine (4 g/L). In addition, the egg weight loss was higher in the groups sprayed with vitamins and L-carnitine compared to the non-sprayed group or those sprayed with water. Rizk et al. (2022) confirmed no effect of spraying eggs with either water or garlic oil on the percentage of egg weight loss.

The washing, dipping, or spraying of eggs with water or other solutions (apple vinegar, vitamin C, etc.) has the potential to degrade the structural component of the eggshell and its cuticle, increasing eggshell conductivity and moisture loss which could contribute to the overall egg weight loss. The differences in results could be related to the type of in-ovo method (washing, dipping, spraying) used, the concentration of the solvent, and the type of eggs used (chicken quail, duck, or goose eggs).

The EST at ED 16, 19, 21, and 22 were all significantly lower in the sprayed groups than in the non-sprayed group in the current study. We did not find any article that has studied the effect of treating eggs with natural disinfectants or nutritive solution on eggshell temperature; however, apple vinegar is known for its antioxidant ability (Bakir et al., 2016; Yagnik et al., 2018; Ousaaid et al., 2021b), and water is also known to support thermoregulation or enhance heat loss. It is therefore speculated the regular spraying of apple vinegar improved the thermoregulatory mechanism of the developing embryo, contributing to the lower EST in that group. Additionally, the regular spraying of water might have enhanced or facilitated the heat dissipation of the developing embryo by modifying the eggshell conductance.

In the present study, the hatchability of set and fertile eggs, and chick yield were significantly higher in the sprayed groups compared to the control incubation treatment (non-sprayed). In line with the findings of the current study, higher hatchability, and chick weight in eggs sprayed with water or vinegar have been identified by Fouad et al. (2018). Eggs dipped in sugarcane vinegar or water have also been identified with the highest hatchability and chick weight at hatch compared to the control (El-Kholy et al., 2022; Salama, 2022). Eggs washed in either water, acetic acid, vinegar, or citric acid were identified to have the highest hatchability, chick weight, and chick yield (He et al., 2020). Similarly, Onbaşılar et al. (2014) also confirmed higher hatchability of set and fertile eggs in eggs sprayed with water either once or twice a day compared to non-sprayed eggs, with the highest chick weight in eggs sprayed once a day. Bordunova et al. (2024) also identified the highest hatchability in eggs treated with acetic or hydrochloric acid compared with untreated eggs. Furthermore, the dipping or spraying of organic acid or water on eggs was identified to increase the hatchability of set and fertile eggs and chick weight (Omer & Mustafa, 2023).

Moreover, spraying, dipping, or washing eggs with other natural disinfectants and nutritive solutions has been reported to improve hatching traits, chick weight, and chick yield. For instance, Abuoghaba et al. (2021) identified that spraying eggs with curcumin during incubation increased the hatchability of fertile and set eggs and chick weight compared to the control. The hatchability of set and fertile eggs and chick weight were identified as higher in eggs sprayed with either water, vitamin C, ascorbic acid, or L-carnitine compared to the control (Mohammed et al., 2011; Yassein et al., 2014; Abdel-Azeem et al., 2016). Additionally, Shahein & Sedeek (2014) also confirmed the highest hatchability of set and fertile eggs, and chick weight in eggs sprayed with propolis, thyme oil, or ethanol alcohol compared to the eggs of the control incubation treatment.

These natural disinfectants and nutritive solutions (vinegar, garlic oil, acetic acid, vitamin, etc.) that are used for spraying, washing, or dipping eggs contain bioactive compounds with antioxidant and antimicrobial effects that are known to improve embryonic growth and development, and decrease embryonic mortality (Ghonim et al., 2008). He et al. (2020) confirmed lower microbial flora on eggs either washed with water, acetic acid, vinegar, or citric acid compared to unwashed eggs. Some authors also reported that the higher hatchability among eggs treated with organic acid, propolis, or formaldehyde may be related to the ability of these substances to kill microbes on the eggshell (Shahein & Sedeek, 2014; Omer & Mustafa, 2023). Again, these natural substances contain organic acids with the potential to degrade the eggshell and the structural components of the cuticle, promoting better eggshell conductance (Deeming, 2008; Mohammed et al., 2011), with a subsequent increase in embryonic development and a decrease in embryonic mortality. Additionally, spraying, washing, or dipping eggs in water might prevent excess embryonic heat production and dehydration, providing embryos with a more stable and sustainable environment for development and hatching, especially during the latter stages of embryogenesis. These reasons may explain the higher hatching traits, chick weight, and chick yield identified in the groups sprayed with water or apple vinegar compared to the control in the current study.

Contrary to the findings of the current study, Eroglu et al. (2024) reported that eggs from control incubation treatment and those sprayed with water acetic or boric acid did not differ significantly in terms of the hatchability of set and fertile eggs. Brah et al. (2024) also observed no significant effects of vinegar on the hatchability of set and fertile eggs.

The incubation treatments did not significantly influence the eggshell thickness in the current study, which is in line with the findings of Alhamed (2025), who also identified no significant effect on of spraying or immersing eggs in vinegar on eggshell thickness; however, treating (spraying or immersing) eggs with vinegar significantly decreased the shell weight. Mohammed et al. (2011) have also confirmed that dipping eggs in water or a nutritive solution (vitamin C) had no significant effect on eggshell thickness and shell weight.

On the other hand, significantly lower eggshell thickness in eggs sprayed with either water or vinegar has been reported by Fouad et al. (2018). Similarly, He et al. (2020) also confirmed significantly lower eggshell thickness and cuticle opacity in eggs either washed with water, acetic acid, vinegar, or citric acid. However, Al-Hamed & Al-Eshaki (2019) identified significantly higher eggshell thickness in eggs either sprayed or immersed in water or vitamin. Also, eggs stored for eight weeks at room temperature and coated with either apple, grape, or lemon vinegar were identified to have the lowest egg-breaking strength compared to uncoated eggs (Mustafa et al., 2023). Several factors such as the type of poultry species, age, housing, management conditions, nutrition, and welfare influence the formation and the thickness of the eggshell, which could have caused the differences in the findings of the current study compared to what was reported by other authors. Additionally, the type, composition, and concentration of the solution, as well as the method of application on eggs also plays a significant role in degrading the structural component of the eggshell.

Body weight and body weight gain at 14 days of age and the total average body weight was highest in ducks that hatched from the group sprayed with water (group 2) and lowest in ducks that hatched from the group sprayed with apple vinegar (group 3) in the present study, which is similar to the findings of Al-Hamed & Al-Eshaki (2019), who identified the highest total weight gain in quails that hatched from eggs sprayed or immersed in water. The same study confirmed similar body weight between the quails of the control group and those that hatched from eggs either sprayed or immersed in water, but both groups had higher body weight than those that hatched from eggs sprayed or immersed in vitamin C. It was therefore speculated that the lower body weight, body weight gain, and total body weight in the group sprayed with apple vinegar in the current study could be related to the concentration of the apple vinegar solution, which might be detrimental to the production, growth, and development of cells responsible for post-hatch muscle growth and development. Additionally, it could also be possible that the traces of the vinegar altered the gut microbiota, affecting its health and function and contributing to overall poor growth performance.

However, several authors identified higher body weight and body weight gain in chickens or quails that hatched from eggs sprayed with vinegar than in those from non-sprayed eggs or those sprayed with water (Fouad et al., 2018; Alhamed, 2025). El-Kholy et al. (2022) also reported that while the body weight and body weight gain were similar between ducks that hatched from eggs dipped in water or sugarcane vinegar, ducks from both groups had higher body weight and body weight gain than the ducks that hatched from the control incubation treatment. Higher body weight (35 d) and body weight gain (1-35 d) in broilers that hatched from eggs sprayed with water or vitamins compared to those from the control incubation treatment were also identified (Abdel-Azeem et al., 2016). Additionally, Salama (2022) confirmed higher body weight and body weight gain in ducks that hatched from eggs dipped in water or sugarcane vinegar compared to those that hatched from the control incubation treatment. Moreover, higher body weight (28 d) and total body weight gain (1-28) in chickens from eggs sprayed with ascorbic acid compared to non-sprayed eggs or those sprayed with water were reported (Yassein et al., 2014). Similarly, He et al. (2020) identified higher live weight in quails that hatched from eggs washed with either acetic acid, vinegar, citric acid, or water compared to those that hatched from the control incubation treatment.

The feed intake and feed conversion ratio evaluated in the present study were not statistically different among the experimental groups (p>0.05), which agrees with the findings of Brah et al. (2024), who identified no significant difference in terms of feed intake and feed conversion ratio of guinea fowls that hatched from eggs either treated with bleach or vinegar. Moreover, Alhamed (2025) confirmed no significant difference in terms of the feed intake between quails from the control incubation treatment and those from eggs sprayed with vinegar between the 2 wk and 4 wk of age however, the total feed intake was higher in quails from the control incubation treatment than in quails from eggs sprayed with vinegar. Other authors (Al-Hamed & Al-Eshaki, 2019) that used other solutions also identified no significant difference in terms of the feed intake between the quails from the control incubation and those sprayed or immersed in water however, their feed intake was higher than that of quails from eggs sprayed or immersed in vitamin C. Higher total (1-35d) feed intake in quails from eggs sprayed with water, vitamin C or L-carnitine compared to quails that hatched from controlled incubation treatment was identified with quails from the vitamin and L carnitine group characterized with better feed conversion ratio than quails from the other incubation treatments (Abdel-Azeem et al., 2016). Additionally, Yassein et al. (2014) identified that chickens from the control incubation treatment and those from eggs sprayed with ascorbic acid or water did not differ significantly in terms of post-hatch feed intake. However, the chickens from eggs sprayed with ascorbic had better feed conversion ratio than those from the other incubation groups. Rizk et al. (2022) found no significant effects in terms of the feed conversion ratio of chicks from eggs of the control incubation treatment compared to those from eggs either sprayed with water or garlic oil.

On the other hand, higher feed intake and better feed conversion ratio have been observed in ducks from eggs sprayed with sugarcane vinegar compared to those from the control incubation treatment (El-Kholy et al., 2022; Salama, 2022).

In the current study, only the metatarsal temperature was significantly lower in ducks from the control incubation group than in those from eggs sprayed with apple vinegar or water. It is difficult to explain why the metatarsal temperature was lower in ducks from the eggs of the control incubation, but it was identified that those ducks had higher beak and footpad temperatures compared to those from the other incubation treatments, meaning that they might have been emitting more heat from other body parts than the metatarsus, contributing to the lower metatarsal temperature identified.

The majority of the articles that have studied the effect of spraying, washing, or dipping hatching eggs in disinfectants or nutritive solutions have not studied their effect on carcass traits and meat quality, making this section difficult to discuss. However, in the current study, the hot carcass weight and the breast weight were significantly higher in ducks from the sprayed incubation groups than in those from the control incubation treatment. Protein accretion and muscle cell proliferation are some of the processes that lead to muscle formation in farm animals (Mohammadabadi et al., 2021), so it could be possible that ducks from the eggs treated with vinegar and water were better in terms of acclimatization to post-hatch environmental stimuli, increasing the proliferation and differentiation of myoblasts and satellite cells, contributing to better muscle growth and development. In line with the findings of the present study, other authors (Al-Hamed & Al-Eshaki, 2019) have confirmed higher carcass and breast weight in quails from eggs sprayed or immersed in water or solutions with vitamin C compared to those from the control incubation treatment.

The thigh and wing yield in the current study were significantly higher in the ducks from eggs sprayed with apple vinegar than the other incubation treatments, which is similar to the findings of Al-Hamed & Al-Eshaki (2019), who identified higher thigh yield and wing yield in quails from eggs immersed in a solution containing 10 g/L and 5 g/L of vitamin C, respectively. Again, it is speculated that spraying eggs with apple vinegar might have accelerated the proliferation, differentiation, growth, and development of the muscle cells responsible for thigh and wing development during the post-hatch growing period.

The back weight and yield in the current study were significantly higher in ducks from the control incubation treatment compared to those from eggs sprayed with apple vinegar or water, which disagrees with the findings of Al-Hamed & Al-Eshaki (2019), who confirmed higher back yield in quails from eggs sprayed or immersed in water or vitamin C.

In the current study, the weight and yield (proportion) of the internal organs (heart, liver, spleen, abdominal, fat, and gizzard) did not differ among the ducks that hatched from the various incubation treatments. In line with the findings of the present study, Al-Hamed & Al-Eshaki (2019) also reported that the proportions of heart and gizzard of quails from eggs sprayed or immersed in water or vitamin C and that of those from the control incubation treatment did not significantly differ from one another. Nevertheless, quails from eggs sprayed with 5 g/L of vitamin C had the significantly highest liver and abdominal fat proportions. Additionally, Salama (2022) also confirmed that at hatch, ducklings from eggs dipped in sugarcane vinegar, water and those from the control incubation treatment did not significantly differ in terms of liver weight and liver proportion. Moreover, while the liver, gizzard, and heart weight were identified as insignificantly different among chickens from the control incubation treatment and those from eggs sprayed with water or garlic oil, the chickens from eggs sprayed with garlic oil had the highest spleen weight, but the lowest bursa weight (Rizk et al., 2022).

Contrary to the findings of the current study, Abdel-Azeem et al. (2016) confirmed a higher liver weight in broilers from eggs sprayed with vitamin C than in those from eggs sprayed with L-carnitine, water, and the control incubation treatment. However, broilers from the control incubation treatment and those from eggs sprayed with water had higher abdominal fat, gizzard, and heart weight than those from eggs sprayed with vitamin C or L-carnitine. Additionally, Yassein et al. (2014) confirmed a higher spleen weight in chickens from eggs sprayed with ascorbic acid than in those that hatched from eggs sprayed with water and the control incubation treatment. Quails from eggs sprayed with garlic oil were identified to have the highest liver, gizzard, and heart weight compared to those of the control incubation treatment and those from eggs sprayed with water (Fouad et al., 2018).

The meat quality traits (pH24, cooking loss, hardiness, chewiness, springiness, cohesiveness, gumminess, resilience, and meat color traits) in the current study were not significantly different among the ducks from the various incubation treatments. No literature on the effect of treating hatching eggs with natural disinfectants (vinegar, garlic oil, etc.) or nutritive solutions (vitamin C) on meat quality traits was available. However, cooking loss is caused by denaturing meat proteins, which leads to the eradication of cell filaments, shrinkage of cell strands, the total and gel formation of myofibrillar proteins, as well as the alteration of sarcoplasmic proteins and the solubilization of connective tissues (Tornberg, 2005). It could be possible that the effect of the incubation treatment (spraying with apple vinegar or water) was not long-lasting enough to cause a significant alteration in the structural component of the meat (cell filaments, cell strands, sarcoplasmic proteins, and connective tissues). Additionally, it is speculated that the effect of the incubation treatment was not lasting enough to cause a significant influence on the contraction of the intramuscular connective tissues, muscle fibres and intramuscular fat content, which has a profound effect on meat texture profile (hardiness, chewiness, springiness, cohesiveness, gumminess, resilience). Moreover, the lack of a significant effect of the incubation treatment on meat color traits (L*, a*, and b*) could be explained by the incubation treatment not influencing the pigmentation, or the mechanism that influences the pigmentation of the meat color.

CONCLUSION

The spraying, washing, and dipping of eggs in apple vinegar as a natural disinfectant on hatching and post-hatch traits has not been studied intensively. Overall, spraying eggs with distilled water and apple vinegar solution improved hatching and post-hatch growth performance, as well as carcass and meat quality traits, with the potential to improve the adaptability of ducks to post-hatch stress conditions.

ACKNOWLEDGEMENTS

We would like to thank AYDOĞDU GROUP ÖRDEK A.Ş. in Karaisali/Adana, Turkiye for providing us with the duck eggs used in conducting this scientific study/experiment.

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• FUNDING
  No funds were received for this study.
• DATA AVAILABILITY STATEMENT
  The data for this research is available with the corresponding author and will be shared 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:
  Tatiana Carlesso dos Santos

Data availability

The data for this research is available with the corresponding author and will be shared upon request.

Publication Dates

• Publication in this collection
  10 Nov 2025
• Date of issue
  2025

History

• Received
  08 Jan 2025
• Accepted
  25 Aug 2025