Effects of dietary addition of synbiotic on the performance , carcass traits , and serum parameters of Japanese quails

This study aimed to evaluate the effects of different levels of synbiotic (Syn) on the growth performance, carcass traits, and serum parameters of Japanese quails. A total of 1,500 (750 male and 750 female) Japanese quails were assigned to five treatments, including the control (basal diet) and basal diets with the addition of 0.1, 0.2, 0.3, and 0.4% Syn according to a completely randomized design. Each treatment in the male and female experiment groups consisted of five replicates, with 30 chicks for each replicate. The addition of Syn had no effect on body weight (BW), while the BW of female quails was higher than that of male quails at day 42. The addition of Syn reduced feed intake (FI) and improved the feed conversion ratio (FCR) (P<0.000). The daily body weight gain and FI were significantly higher in female than in male quails and Syn also improved the FCR in the overall experiment. The effect of the addition of Syn on carcass parameters (except for abdominal fat) was not determined. The addition of Syn decreased abdominal fat weight and percentage when compared with the control group. Male quails were found to have higher carcass yield, wing, neck, and other percentages than female quails. However, female quails were found to have higher breast, breast skin, abdominal fat, and visceral organ percentages. The addition of 0.1% Syn to quail ration reduced serum aspartate aminotransferase, high-density lipoprotein (HDL), total protien (TP), and albumin (ALB) levels at day 42 of the trial. The addition of Syn decreased the serum total cholesterol level. Gender was found to have an effect in that female quails were found to have higher total cholesterol, HDL, TP, and ALB levels than male quails. In both genders, the addition of Syn improved the BWG, FC, and FCR in the overall experiment, reduced abdominal fat, decreased the total cholesterol levels, improved the HDL levels, and increased the TP and ALB levels at day 42. The addition of 0.3 and/or 0.4% synbiotic has a positive effect on quails by improving performance and enhancing some serum lipids and protein parameters.


Introduction
Commercial poultry production has a short and critical intensive feeding period, ranging from the chick stage to slaughter.During this period, the gastrointestinal tract of a chick requires fast development and colonized intestinal bacteria vary frequently (Edens et al., 1997).Densely settled intestinal bacteria play a critical role in health and growth performance due to its effect on nutrition, gut morphology, and immune response of animals (Lee et al., 2002).Antibiotic supplementation had been utilized for many years to protect against pathogens in the gut and enhance performance in poultry until the EU ban took effect (Tufan et al., 2015).Research is being carried out on the use of prebiotic, probiotic, and synbiotic as feed additives instead of antibiotic in poultry nutrition (Gibson and Roberfroid, 1995;Patterson and Burkholder, 2003).
Prebiotics are functional foods that do not hydrolyze in the digestive system; they are not absorbed or digested, but increase the development or activity of a limited number of bacteria selectively in the colon and positively affect the health of humans and animals (Gibson and Roberfroid, 1995).Probiotics are alternative living biological agents for antibiotics that suppress pathogen microorganisms with bacteriocin secretion, decrease the intestine pH (Gillor et al., 2008), and improve microbial balance (Fuller, 1989), positively affecting the digestive system.It has been reported in the literature that the use of preprobiotics in poultry improves the intestinal flora (Gibson and Roberfroid, 1995), strengthens the immune system (Hong et al., 2005), increases the digestibility of nutrients (Li et al., 2008a;Yasar and Akıncı, 2014), and enhances growth performance (Bolacali and Irak, 2017;Pelícia et al., 2004;Yasar and Akıncı, 2014).
Synbiotics that improve fattening performance are natural ingredients and are called functional products, along with prebiotics and probiotics.Synbiotics show the biological activity that is evident when pre-probiotics are used alone at a higher level (Junqueira et al., 2009).They encourage the development and growth of beneficial bacteria in the intestines through prebiotics and probiotics, stimulate their activities, improve intestinal flora, and increase the digestibility and absorption of nutrients (Gibson and Roberfroid, 1995).
The use of Syn in poultry production encourages a healthy gut via certain possible mechanisms, such as enhancing the immune system (Hamasalim, 2016), lowering pH, and increasing protective gut mucus (Nikpiran et al., 2014), creating an antimicrobial effect (Likotrafiti et al., 2016), increasing the digestibility of nutrients (Awad et al., 2008), and enhancing nutrition performance (Elfaki and Mukhtar, 2015;Pelícia et al., 2004).In previous studies conducted on poultry, it was reported that the use of Syn enhances growth performance (Vahdatpour et al., 2011;Min et al., 2016) and carcass yield (Pelícia et al., 2004).Sahin et al. (2008) reported that the addition of Syn to broiler rations did not have any effect on total serum protein, albumin, and total cholesterol levels.
It is known that probiotics on the small intestine, prebiotics on the large intestine, and synbiotics on both small and large intestines have a positive effect (Gibson and Roberfroid, 1995;Hamasalim, 2016).The objective of this study was to determine the effects of different levels of Syn on performance, carcass traits, and blood parameters of both genders of Japanese quails.

Material and Methods
The synbiotic used in this study (SynbioticerAll™) was provided by the manufacturing company Global Nutritech LLC, Richmond, VA, USA.It included live Saccharomyces cerevisiae (strain NCYC R618), mannan, and glucan.
The research was conducted in Siirt, Turkey, between November and December of 2016.The research on animals was conducted according to the institutional committee on animal use (2016/09).A total of 1,500 (750 male and 750 female) one-day-old Japanese quail chicks for which two different experimental designs were designed -for male and female quails -was randomly allocated to one control group and four main groups with five pen replicates of 30 birds each.Over the experimental period, the quails were fed starter (1 to 21 days) and grower (22 to 42 days) basal diets (Table 1) formulated to meet the nutrient requirements specified by the National Research Council (NRC, 1977).
The treatments were conducted as follows: control (basal diet), basal diet + 0.1% Syn, basal diet + 0.2% Syn, basal diet + 0.3% Syn, and basal diet + 0.4% Syn.The chicks in each replicate group were housed in cages with dimensions of 45.5 × 68.8 × 177 cm (width × length × height).The required heating and 24-hour lighting were provided during the study and feed and water were given ad libitum.The study lasted 42 days and was conducted in cages.
The body weight (BW) of birds was recorded weekly and body weight gain (BWG) was calculated daily.Weekly feed intake (FI) was determined according to the daily feed and increasing feed and weekly FI was divided by the number of the animals and seven days to calculate the daily FI.The FI was divided by BWG to calculate the FCR.
On the 42nd day of the study, 300 quails were slaughtered to determine slaughtering and carcass parameters.The quails were slaughtered from both female and male experiment groups, six quails from each replicate group and 30 from each main group.The process of slaughtering and the separation into carcass parts were performed according to the method of Genchev and Mihaylov (2008).Carcass parameters were determined as hot and cold carcass, leg, breast, wing, back, neck, other, and breast skin weights/ percentages.The parameters of the visceral organs were determined according to the heart, liver, gizzard, intestine weight, and abdominal fat weight/percentage.
To determine the serum parameters, two blood samples from each subgroup and 10 blood samples from each main group were taken in anticoagulant-free tubes from the male and female study groups at days 21 and 42 of the study.The blood samples were centrifuged at 3,000 rpm for 10 min, and the serum was kept at −20 °C until the analyses were conducted.The aspartate aminotransferase (AST), total cholesterol, high-density lipoprotein (HDL), total protein (TP), and albumin (ALB) levels in the serum were analyzed with an auto analyzer (ADVIA 1800 Chemistry System).
Data were analyzed using a factorial model of the general linear model procedure of Minitab software (Minitab, 2017).The statistical model included the feed additive (Syn) and gender and their interaction effect.Differences within a significant effect were separated using Duncan's Multiple Range Test.Data points bearing different letters were considered significantly different at P≤0.05.

Results
The interaction between Syn and gender had no effect (P>0.05) on hatching at days 7, 14, and 42, but significantly influenced the BW at days 21, 28, and 35 (Table 2).The lowest BW was detected in the female control group at day 21 (P<0.039).The highest BW was determined in the female group fed 0.2% Syn at day 28 (P<0.024)and in the female group fed 0.1% Syn at day 35 (P<0.000).In terms of the addition of Syn in the study, the lowest BW was detected in the control group at day 21 (P<0.014)and in the group fed 0.3% Syn at days 28 and 35 (P<0.008 and P<0.000, respectively).It was determined that gender was effective on liveweight in later periods after day 21 (P<0.05).While BW was significantly higher in male quails than in female quails at day 21 (P<0.007), it was significantly higher in female quails than in male quails at days 28, 35, and 42 (P<0.000).
The interaction between Syn and gender had an effect on BWG, FI, and FCR of the birds at all rearing stages (except for the starter period of the FI) (P<0.05;Table 3).The highest BWG was detected in the male group fed 0.1% Syn in the starter period (P<0.028) and in the female group fed 0.1% Syn in the grower period and throughout the trial (P<0.003 and P<0.048, respectively).The addition of Syn to quail rations increased BWG in the starter period (P<0.042).The best performance was in the control group in the grower period (P<0.007).It was determined that the addition of Syn between 1-42 days had no effect (P>0.05) on BWG.While male quails had a higher BWG than female quails in the starter period (P<0.019),female quails had a higher BWG than male quails in the grower and overall period (P<0.000).
The highest FI was determined in the female group fed 0.2% Syn in the grower period and throughout the trial (P<0.000).The addition of Syn reduced FI in all periods (P<0.000).Female quails had a higher FI than male quails in the grower period and throughout the trial (P<0.000).The addition of Syn to quail rations improved the FCR in both male and female quails in all breeding periods of the study (P<0.000).While the FCR improved for males in the starter period (P<0.000), it improved for females in the grower period (P<0.017) and throughout the trial (P<0.000).
There were no effects of the interaction between Syn and gender on the weights and percentages of carcass parameters (P>0.05)(Tables 4 and 5).The addition of Syn to quail rations had no effect on other carcass weights and percentages except for abdominal fat weight and percentage (P>0.05), in which it reduced abdominal fat weight (P<0.001) and percentage (P<0.000).The slaughter weight, hot carcass, cold carcass, leg, breast, breast skin, and abdominal fat weights of female quails were higher than those of male quails (P<0.000).The hot carcass (P<0.000),cold carcass (P<0.000),other (P<0.006),wing (P<0.020),and neck (P<0.008)percentages were higher in male quails than in female quails.However, female quails were found to have higher breast, breast skin, and abdominal fat percentages (P<0.000).
There were no effects of feed additive (Syn) and the interaction between Syn × gender on the percentage of the visceral organs (P>0.05)(Table 6).Female quails were found to have higher visceral organ percentages than male quails (P<0.000).
The Syn × gender interaction had no effect on AST, serum total cholesterol, and HDL (P>0.05), but had an effect on TP (P<0.029) and ALB (P<0.046) at day 21 (Table 7).The highest TP and ALB were in the male group fed 0.4% Syn.The effect of feed additive on AST, total cholesterol, HDL, and TP was not observed at day 21.Female quails were found to have lower AST, total cholesterol, and HDL levels than male quails.The Syn × gender interaction had an effect on AST (P<0.000),serum total cholesterol (P<0.002),HDL (P<0.001),TP (P<0.007), and ALB (P<0.007) at day 42.The lowest total cholesterol level was found in the male group fed 0.2% Syn and the highest serum HDL level in the female group fed 0.4% Syn.The highest TP and ALB levels were found in the female group fed 0.4% Syn.The addition of 0.1% Syn to quail ration reduced serum AST, HDL, TP, and ALB levels (P<0.000).The addition of Syn to quail ration also reduced the total cholesterol level (P<0.000).Gender had no effect on the serum AST level (P>0.05),but had an effect on total cholesterol (P<0.002),HDL (P<0.000),TP (P<0.000), and ALB (P<0.000)levels.Female quails were found to have higher total cholesterol, HDL, TP, and ALB levels than male quails.

Discussion
The objective of the present study was to study the efficacy of Syn on the performance, carcass characteristics, and serum parameters of Japanese quails.In the current study, the dietary inclusion of Syn increased BW of 21-day-old chicks and increased BWG and decreased FI and FCR during the starter period (1 to 21 days) when compared with the control group.In the present study, it was observed that the use of Syn as an additive in the early period improved the fattening performance, but there was no dose response.Research shows that the use of Syn, prebiotics, probiotics, and combination of Syn as feed additives improves growth performance and health by regulating intestinal microflora (Gibson and Roberfroid, 1995;Li et al., 2008b).A number of researchers have previously demonstrated the useful effect of Syn on BW, BWG, and FCR in poultry in the early period of chicks (Dizaji et al., 2012;Yasar and Akıncı, 2014).
The addition of a Syn supplement in the quail diet improved FCR in the grower and overall periods, which is consistent with the findings of Dizaji et al. (2012) and Yasar and Akıncı (2014).The Synbiotic feed additive reduced FI in the grower period, which is consistent with the findings of Dizaji et al. (2012), but inconsistent with the findings of Yasar and Akıncı (2014).In the present study, it was found that the improvement in the FCR depended on the dose of Syn used as a feed additive (Elfaki and Mukhtar, 2015).
Body weight, at day 21, and BWG and FCR, during the starter period (1 to 21 days), of male improved compared with female quails.On the contrary, the gender of quails plays a role in their fattening performance.Kul et al. (2006) reported that females had a higher BW at day 21 and higher BWG between days 14-21 compared with males.Ayasan et al. (2000) reported that gender had no effect on quail BW at day 21 nor on the FI and FCR between days 1 and 21.Kul et al. (2006) reported that females had a higher BW at day 21 and higher BWG between days 14 and 21 compared with males.
In the present study, female quails showed better improvement in the BWG and FCR in the grower period of this study than male quails, which is consistent with the findings of some studies (Ayoola et al., 2014;Kul et al., 2006).The increase in the FI was found to be incompatible with the results of Ayoola et al. (2014).The improvement in the BWG throughout the experiment was shown to be similar to the results of Kul et al. (2006).These authors found that the FI and FCR of female quails were not affected between 14 and 42 days compared with those of male quails, which is inconsistent with the results of the current study.Ayasan et al. (2000) reported that female quails had higher BWG at day 35 compared with male quails and that gender had no effect on the FI and FCR between days 1 and 35.In the present study, the growth parameters were inconsistent with those of previous findings.This may be attributed to the use of different strains and doses of probiotics and prebiotics in combination with Syn or different experiment conditions and durations.
The interaction between the Syn feed additive and gender significantly influenced BWG, FI, and FCR throughout the experiment (1-42 days).In this study, the improvement in the BWG, FI, and FCR of male quails in the period of the experiment (1-42 days) is caused by the growth-promoting effect of Syn.The improvement in growth performance found in this study may be associated with the dose of the feed additive.The positive effects of probiotics and prebiotics on intestinal flora are well known.In this study, the improvement in growth performance may be associated with Syn assistance in digestion and absorption, such as with protein (Hamasalim, 2016).This improvement in growth performance may be explained by the positive effect of the use of Syn as an additive on protein metabolism in the present study.In terms of performance, synbiotics were effective in improving the growth of poultry, which corresponded to the effect of supplementation of either probiotics or prebiotics in the diet of chickens.The fact that the addition of Syn had no effect on other internal organs and carcass parameters, except for abdominal fat weight and percentage, is consistent with other studies on quails (Sahin et al., 2008;Sharifi et al., 2011) and broilers (Elfaki and Mukhtar, 2015;Saiyed et al., 2015).Moreover, the fact that the addition of Syn reduced abdominal fat weight and percentage is consistent with the results of Saiyed et al. (2015) and Mokhtari et al. (2015).Fattening is an undesirable condition in commercial poultry production; abdominal fat is one of the carcass parameters that is not consumed.We found that the addition of Syn reduced abdominal fat, which shows that it can be used as an alternative additive in commercial poultry production in which fattening caused by high-energy rations is seen.
The result of the current study is consistent with the outcome of Alkan et al. (2013), who found that carcass yield was higher in male quails than in females, but inconsistent with the finding of Alkan et al. (2013) that breast, wing, and abdominal fat percentages were higher in female quails than in males.In accordance with the results of the present study, Ojedapo and Amao (2014) found that breast percentage was higher in female quails than in males.In the current study, supplementation with Syn decreased the abdominal  fat weight and percentage in the male group compared with the control group.In accordance with the present results, Mokhtari et al. (2015) established that significantly reduced abdominal fat was observed with broiler diets, depending on the addition of Syn.According to Beserra et al. (2015), the administration of Syn is efficient in improving lipid profiles.
Studies on quails have found that female quails had higher rates of heart, liver, and stomach than male quails, which is consistent with the current study (Alkan et al., 2013;Ojedapo and Amao, 2014).
Blood parameters are important for observing metabolic changes in an organism.The fact that the use of Syn as a feed additive had no effect on AST, total cholesterol, HDL, TP, and ALB levels at day 21 is consistent with the result of Sharifi et al. (2011).The fact that the addition of 0.4% Syn at day 42 increased the AST level is similar to the result of Vahdatpour et al. (2011).However, the addition of 0.1% Syn reduced the AST level, being inconsistent with the results of Cakir et al. (2008) and Vahdatpour et al. (2011).The addition of Syn reduced total cholesterol level (Mousa et al., 2014) and increased the HDL level (Sharifi et al., 2011), which is consistent with the results of this study.The supplementation of Syn increased the serum HDL level which is the "good" cholesterol and decreased the abdominal fat percentage, showing positive effect of Syn on the lipid mechanism.Although the effect mechanisms of probiotics and prebiotics are not well known, it is known that they have a regulatory effect on lipid and cholesterol metabolism (Gibson and Raberfroid, 1995;Hamasalim, 2016).Probiotic and prebiotic supplementations that decrease absorption in the gastrointestinal tract and/or the synthesis of cholesterol in the liver can lead to a reduction in the serum cholesterol of broiler chickens fed probiotic-and prebiotic-supplemented diets (Mohan et al., 1996).Contrary to these results, some other studies have reported that this does not have an effect on the total cholesterol and HDL levels (Sahin et al., 2008;Sharifi et al., 2011).The addition of Syn increased the TP and ALB levels, which is consistent with the results of Tufan et al. (2015).In the present study, an improvement in the serum protein levels of the study groups, which is associated with dosage, was observed.The high TP and ALB levels of male quails in the groups fed 0.3 and 0.4% Syn and of female quails in the group fed 0.4% Syn may be associated with the positive effect of the addition of Syn on protein metabolism.However, the manner in which Syn affects protein metabolism is not fully known.In contrast to the present results, some studies have reported that adding Syn does not affect the TP and ALB levels (Sahin et al., 2008;Sharifi et al., 2011).

Conclusions
The addition of 0.3 and/or 0.4% synbiotic has a positive effect on quails by improving performance and enhancing some serum lipids and protein parameters.

Table 1 -
Ingredient composition and analyzed content of the nutrients in the diets used in the trial 2 Calculated according to NRC (1977) table values.

Table 2 -
Effects of dietary supplementation of synbiotic (Syn) on live body weights of quails at various periods (g) 1 SEM -standard error of mean. 1 Means were obtained from five replicate cages.a-d -Means within a column with different letters are significantly different at the level shown.

Table 3 -
Effect of adding various levels of synbiotic (Syn) to the rations of male and female quails on BWG (g/day), FI (g/day), and FCR (g/g) 1 BWG -daily body weight gain; FI -feed intake; FCR -feed conversion ratio; SEM -standard error of mean. 1 Means were obtained from five replicate cages.a-g -Means within a column with different letters are significantly different at the level shown.

Table 4 -
Effect of dietary synbiotic (Syn) supplementation on weights of carcass traits of quails (g) 1 SEM -standard error of mean. 1 Means were obtained from six quails of each replicate group and 30 quails of each main group.a,b -Means within a column with different letters are significantly different at the level shown.R. Bras.Zootec., 46(10):805-813, 2017

Table 5 -
Effect of dietary synbiotic (Syn) supplementation on relative organ ratio (percentage of cold carcass mass) of male and female quails (%) 1 1 Means were obtained from six quails of each replicate group and 30 quails of each main group.a,b -Means within a column with different letters are significantly different at the level shown.

Table 6 -
Effect of dietary synbiotic (Syn) supplementation on relative organ percentage in male and female quails (g) 1 SEM -standard error of mean. 1 Means were obtained from six quails of each replicate group and 30 quails of each main group.

Table 7 -
Effects of synbiotic (Syn) supplementation on some quail blood serum parameters at days 21 and 42 1 AST -aspartate aminotransferase; CHOL -cholesterol; HDL -high-density lipoprotein; TP -total protein; ALB -albumin; SEM -standard error of mean. 1 Means were obtained from two quails of each replicate group and 10 quails of each main group.a-e -Means within a column with different letters are significantly different at the level shown.R. Bras.Zootec., 46(10):805-813, 2017