Pomegranate (Punica granatum L.), from the family Punicaceae, is one of the oldest edible fruits and is commonly cultivated in many tropical and subtropical countries (Boroushaki et al., 2016; Białek et al., 2021a). Pomegranate fruits are mainly consumed fresh or processed, however, significant amounts of pomaces are generated during processing, which causes serious environmental hazards (Białek et al., 2021a). Recently, the utilization of these wastes as a source of valuable compounds which could be used as an ingredient in animal nutrition has received particular attention (Saki et al., 2014; Boroushaki et al., 2016; Białek et al., 2019, 2021a).

It is estimated that pomegranate seeds contain approximately 24% oil (Khoddami et al., 2014) and the fatty acids present in them are of particular interest (Białek et al., 2021a). Punicic acid (9‐cis, 11‐trans, 13‐cis or trichosanic acid) is the dominant form of the C18:3 class, which has a positive effect on health due to its therapeutical properties (Khoddami et al., 2014; Boroushaki et al., 2016). Studies have shown that pomegranate seed oil (PSO) can affect multiple signaling pathways involved in inflammation, cellular transformation, hyperproliferation, angiogenesis, initiation of tumorigenesis, and eventually suppressing the final steps of tumorigenesis and metastasis (Sharma et al., 2017). For example, Białek et al. (2021b) and Teh et al. (2019) demonstrated that PSO could improve cardiovascular health by reducing total cholesterol. Likewise, Mehta & Lansky (2004) described that PSO could be a potential breast cancer prevention, and Lansky et al. (2005) proposed that PSO could be a potent inhibitor of human PC-3 prostate cancer cells.

Japanese quails are valuable animals for avian research. Their small size makes them easy to handle, which allows them to be stored in limited spaces (Minvielle, 2004; Alkan et al., 2010). Moreover, farmer interest in raising quail for marketing continues to grow in Japan, France, Indonesia, Spain and Brazil (Minvielle, 2004; Santos et al., 2011). Japanese quails are commonly raised not only to produce eggs but also to produce meat in some countries. It is expected that in the near future, quail will become the main poultry used for meat production, due to its widespread demand around the world (Sabow, 2020). Thus, researchers should focus on improving the meat quality and productive performance of these birds.

Changes in animals’ feeding are the most commonly studied and applied way to modify meat properties and quality (Sarmiento-García et al., 2021; Vieira et al., 2021). It is also an indirect method of improving the diet, which in turn will have a health-promoting effect, and the appearance of the product (Saki et al., 2014). PSO also has significant effects on meat quality and the development of livestock species (Saki et al., 2014; Karampour & Kafilzadeh, 2016; Szymczyk & Szczurek, 2016; Emami et al., 2017; Białek et al., 2021b) no study has been conducted on the effects of pomegranate as a feed additive on the yield and instrumental meat quality of quails. The aim of this study was to evaluate the effects of dietary PSO on performance, carcass traits, as well as the instrumental quality of quail’s thigh and breast meat.

No mortality or illness symptoms were observed during the entire trial, and all quails were alive at the end of the experiment. According to the data in Table 2, the absence of statistical differences between the initial weights of the quails indicates that the subjects were randomly assigned to the experimental groups. PSO-supplemented diets linearly affected quail body weight gain and FI (p<0.05). These parameters decreased linearly with the addition of PSO to the diet. Likewise, a trend (p=0.092) was observed for final weight, which decreased as PSO concentration in the diet increased. However, a linear effect of PSO inclusion (p <0.05) on final weight was observed.

The effects of the dietary supplementation of PSO on the carcass traits are given in Table 3. Although there was a trend in final body weight between the experimental groups, no statistically significant differences in carcass traits were found between the groups (p>0.05). The minimum and maximum values for those parameters were as follows: carcass yield (59.39–60.38 %), abdominal fat (1.21–1.72 %), breast (53.04–54.28 %), thigh and drumstick (34.86–36.63 %), liver (1.33–1.43 %), heart (0.79–0.82 %), and pancreas (0.17–0.18 %).

The meat colour was expressed as lightness (L∗), redness (a∗), and yellowness (b∗) values (Table 4). Breast meat from quail supplemented with PSO was paler and yellower than breast meat samples collected from control quails (p<0.001). Similar results were observed for the thigh meat, where the highest L* value (p<0.05) was observed in the group that had received the highest amount of PSO (38.97). The addition of PSO to the diet had a quadratic effect on redness index (a*) (8.26-9.09) of breast meat (p=0.042), but not of thigh meat (p>0.05). Moreover, increasing amounts of PSO in the diet caused a gradual rise (p<0.05) in the yellowness index (b*) in the thigh.

According to Table 5, breast meat’s instrumental parameters had the following minimum and maximum values: pH (5.61-5.74), cooking losses (9.06-11.06 %), and drip losses (13.83-14.05 %). For the instrumental parameters of the thigh meat, the minimum and maximum values were as follows: pH (6.17-6.29), cooking losses (6.62-14.96%), and drip losses (14.17-15.76 %). As shown in Table 5, the pH of breast and thigh meat was higher for the control diet compared to the PSO diet. However, those differences were not significant (p>0.05). In the group supplemented with 100 mg kg^-1 of PSO, breast cooking losses were reduced (p=0.022) compared to the control group (9.06 vs. 11.06). The highest cooking losses in thigh meat were found for the 200 mg kg^-1 PSO treatment, compared to the control and 100 mg kg^-1 PSO treatments. Regarding drip losses, no differences were observed between the study groups for either thigh or breast meat (p>0.05).

Pomegranate by-products may have the potential to be a good source of nutrients and antioxidants for livestock nutrition (Emami et al., 2015). In the current experiment, PSO had an impact on some performance parameters such as body weight gain and FI. In addition, it was observed that levels of 200 mg kg^-1 of PSO resulted in the lowest value of final body weight and abdominal fat. Although these differences were not significant (Table 3), a trend was observed for final body weight. Similar to the results of the current study, adding PSO to high-fat diets decreased body weight, body weight gain, fat, and biomarkers of cholesterol profile in rats (McFarlin et al., 2008; Vroegrijk et al., 2011). These authors proposed PSO supplementation in the diet would reduce leptin and increase adiponectin concentration, leading to lower weight and body fat content. Furthermore, McFarlin et al. (2008) speculated that PSO supplementation can alter the way that dietary fat interacts with the brain. These authors suggested that PSO could increase fat metabolism, resulting in the attenuation of weight gain that they observed. However, further research is needed to explain the effect of PSO on pathways that mediate body weight gain. These results were in disagreement with Szymczyk & Szczurek (2016) who have shown that body weight gain was not affected by PSO (from 5000 to 15000 mg kg^-1) supplementation to the diet in broilers, while Saleh et al. (2016) mentioned the addition of 100, 200, and 300 mg kg^-1 of pomegranate peel extract or 1, 2, and 3 g kg^-1 of pomegranate peel to the diet resulted in the reduction of growth performance for broilers up to 42 days. Nekooeian et al. (2014) showed that 200 or 600 mg kg^-1 PSO per day did not cause significant changes in the body weight of diabetic rats. Probably, those differences could be attributed to the different animal species included in the trials and the total amount of PSO included in the diet.

In addition, this study showed that FI decreased linearly as dietary PSO levels increased. This fact seems likely to be related to the palatability of the feed. The decrease in FI also affected the final body weight and body weight change of male quails. Pomegranate is a rich source of hydrolysable tannins, although the content of tannins is lower in the seed (Bar-Ya’akov et al., 2019). The reduction in FI can be explained by reduced diet palatability due to the presence of tannin in the PSO (Gungor et al., 2021) and body weight gain and final body weight could be affected. In agreement with these results, the lowest FI was observed by previous authors at the highest concentration of PSO in laying hens (Kostogrys et al., 2017) and broilers (Gungor et al., 2021). Rezvani et al. (2018) found that PSO negatively affected FI and growth performance, especially in young broilers. There is a possibility that these results are due to the amount of pomegranate seed extract provided in the diet and that the animals may not be able to adapt to the new diets.

Dressed poultry carcasses, which are dead poultry bodies after being partially butchered without internal organs, heads, and legs, are influenced by both genetic and environmental factors including age, sex, line, and livestock management (Ali et al., 2019). The values obtained for carcass yield agree with those published by Ali et al. (2019) which are between 55.73 and 58.86 (%). Conversely, these results were relatively lower than those published by Raji et al. (2015) for mature Japanese quail, which can reach 89.82%. Several factors may contribute to this difference, including genetics and environment. In addition, carcass percentage may be directly affected by live body weight. A higher body weight of quail results in a higher dressed carcass weight and carcass percentage. These findings are consistent with those observed in our study, which showed a lower final weight of quails. The values obtained for breast percent (54.28 to 53.04%) were higher than those found by Raji et al. (2015), although these authors evaluated deboned breasts in their study. In line with the current findings are those published by previous authors for bone-in breast, which range from 40 to 50% (Alkan et al., 2012; Lukanov et al., 2018; Hussen, 2020). Similar results are observed for the thigh value, which was higher in the current study because the thigh and drumstick were evaluated together. The rest of the parameters evaluated (including organs and fat) are in line with those shown by Raji et al. (2015) for Japanese quails. However, slight differences can be found which, according to these authors, could be justified by the genetics of the quail. Quail meat with excellent dressed carcass characteristics could be produced by crossbreeding quails that are genetically superior to quail meat.

Despite the reduction in final body weight, no changes were observed in the slaughter yield of quails with the dietary addition of PSO at 100 and 200 mg kg^-1. Moreover, in the current study proportions of breast, thigh, drumstick, liver, heart, and pancreas in the carcasses did not differ among the groups. Also, the findings of the current study are consistent with those get by Szymczyk & Szczurek (2016) who replaced soybean oil with PSO in chicken diets. Those authors did not find significant differences in carcass yield, breast and leg muscles, liver, gizzard, and heart weights of chickens. The only exception was an abdominal fat percentage, which was found to be higher in broilers fed a diet containing 1500 mg kg^-1 PSO. Banaszkiewicz et al. (2018) did not find any influence of PSO supplementation in the slaughter yield, proportions of breast, thigh, total muscle, and abdominal fat. In the same trend, Jankowski et al. (2012) observed no differences in slaughter yield or breast, thigh, and drumstick muscle yield in turkeys fed diets containing soybean, linseed, and rapeseed oils. In partial agreement with our feedback Hamady et al. (2015) proved that the supplementation of pomegranate peel powder did not influence liver, gizzard, or heart weight percentages of broiler chickens. However, those authors noticed that the addition of pomegranate peel powder to the diet increased thigh and breast weight percentages. The findings of the current study on carcass traits disagree with Akuru et al. (2021), who reported the hat thigh, breast, and heart weight of broilers improved with pomegranate peel powder supplementation in the diet. Those differences are probably due to the different compositions of the pomegranate co-product included in the diet.

Colour is one of the important quality traits influencing consumer preferences (Vieira et al., 2021). The addition of PSO led to significant differences in the colour parameters. Increased lightness (L*) was found in breast and thigh meat as PSO levels increased. According to Abdel Baset et al. (2022), meat weight might decrease due to reduced water-holding capacity (WHC), resulting in lighter meat, which is consistent with what was observed in this study. Moreover, an increase in yellowness index (b*) was observed in the breast and thigh when PSO was added to the diet. In different studies, pomegranate coproducts had a colour stabilizing effect on muscle food. However, the results are not conclusive. For example, Devatkal et al. (2010) found that the incorporation of pomegranate rind powder was effective in reducing L-values, but no differences were observed among pomegranate seed powder and control for L values. Conversely, redness was reduced when using pomegranate rind powder and pomegranate seed powder compared with the control goat patties. Similar results have been described in frankfurter samples containing white pomegranate juice concentrate, red pomegranate juice concentrate, and pomegranate rind powder extract (Das et al., 2021). It was observed that the inclusion of these ingredients reduced the L* and a* values concerning to the control. In a similar way, Serdaroğlu et al. (2021) reported a decrease in these values when pomegranate seed powder was used in chicken meat emulsion. Contrary, Gungor et al. (2021) did not find any difference in breast colour (in terms of lightness, yellowness or redness) among different PSO diets. Pomegranate is a good source of bioactive substances such as tocopherol and xanthophyll (Madrigal-Carballo et al., 2009). The consumption of natural ingredients rich in these substances has been linked to changes in meat colour. Processing and storing of these ingredients may alter their oxidation levels, resulting in a change in FI and consequently, a change in xanthophyll deposition in meat (Pertiwi et al., 2022). The differences in meat colour found among the studies consulted could be justified for this reason.

According to Terlouw et al. (2008) normal pH of quail breast meat ranged between 5.4 and 6.0. The pH in the current study was on average 5.67, regardless of the diet received, which can be characterized as normal breast pH. On the other hand, the values for thigh pH (6.22) were slightly lower than those reported by Nasr et al. (2017), which ranged between 6.24-6.37. Those differences could be attributed to slaughter age, strain, or line. The use of PSO in the current study did not significantly affect the pH of breast and thigh muscles, but the addition of PSO numerically decreased the pH in the breast and thigh muscles. These results are in line with those published by Banaszkiewicz et al. (2018), who showed that the use of PSO in a broiler diet did not influence meat pH. Likewise, Akuru et al. (2021) pointed out that dietary supplementation of pomegranate peel powder meal at four levels (2, 4, 6 and 8 g/kg) did not influence the pH of the broiler breast meat compared to the control diet.

Water holding capacity is determined as drip losses and cooking losses. The lowest value of cooking losses in the breast was found for the 100 mg kg^-1 dose. However, contrary to expectations, the value of cooking losses was increased in the thigh of quails that had received 200 mg kg^-1 of PSO. Kaur et al. (2015) reported that with the increase in the ratio of pomegranate seed powder added to chicken nuggets, there was a significant decrease in emulsion stability and cooking efficiency. The authors propose a decrease in WHC as a consequence of lower pH. In contrast, Keşkekoğlu & Üren (2014) described that there were no significant differences between the controls and the pomegranate seed extract containing meatball samples, which is consistent with those described by Kurt (2017) for beef patties. Moreover, a trend was observed for drip losses, which decreased as the concentration of PSO in the diet increased. Similar results had been reported by Emami et al. (2015), who showed that the inclusion of pomegranate seed powder in a goat diet decreased drip loss of meat. Those authors suggest a negative correlation between intramuscular fat content and drip losses. Intramuscular fat may act as ‘insulation’ and reduce water loss in meat. The same behaviour was observed by several authors, who proposed that the incorporation of pomegranate coproducts in meat enhances the WHC of raw beef sausage (Gullón et al., 2020), beef meatballs (Morsy et al., 2018), and beef burgers (Abdel-Fattah et al., 2016). However, since our results are not conclusive for WHC in the different parts of the carcass evaluated, further research is required.

In summary, pomegranate seed oil supplementation at a level of 200 mg kg^-1 reduced FI and body weight gain without affecting carcass traits. Compared to the control, PSO supplementation increased L* and b* in the thigh and breast meat. Likewise, dietary PSO at 100 mg kg^-1 significantly improved some characteristics of cooked meat. According to these findings, the inclusion of PSO at 100 mg kg^-1 level in the quails can be a promising method to increase some characteristics of meat quality, but a higher concentration has detrimental effects on quail performance and meat quality. Further research is needed to find the optimal dose of PSO for quails to improve these parameters.