Effects of Dietary Supplementations of Synbiotics on Growth Performance, Carcass Characteristics and Nutrient Digestibility of Broiler Chicken

ABSTRACT

The study aimed to explore the effect of dietary supplementation of synbiotics on growth performance, carcass characteristics and nutrient digestibility in broiler chicken. For this purpose, three hundred 1-day-old Cobb-500 broiler chicks were purchased from the hatchery and randomly distributed into five dietary treatment groups. Each treatment had six replicates, each containing 10 chicks. The experimental diets were supplemented with 0, 700, 1200, 1700 or 2200 g/ton of feed synbiotics and respectively designated as A, B, C, D and E, with A being the control diet. Feed intake, weight gain and feed conversion ratio data were recorded on a weekly basis. At the research trial’s end, two birds from each pen were randomly selected and slaughtered to get data on carcass characteristics. Results showed that group C’s feed intake was reduced (p<0.05) when compared to control. Body weight was similar (p>0.05) among all treatments. However, feed conversion ratio was significantly improved (p<0.05) in group C as compared to other dietary treatments. Nutrient digestibility was improved (p<0.05) in group B and C, as compared to control. Carcass characteristics were not significantly affected and remained the same across all treatments. However, liver weight decreased in birds fed diet C. Meat quality and antibody titer were not affected in any of the dietary treatments. It is concluded that synbiotics can be safely used up to 1200 g/ton of feed, improving bird performance without harmful effects on bird health.

Keywords:
Synbiotic; Nutrient digestibility; Meat quality and Antibody titer

INTRODUCTION

Pakistan’s poultry industry is continuously growing, making a marvelous contribution to bridging the gap between the supply and demand of animal protein requirements. In spite of this, per capita consumption of meat is only 7.20 kg in Pakistan, while developed countries have a 40 kg per capita consumption (PPA., 2019).

Although the poultry industry is potentially growing to meet nutrient requirements, it is facing various problems in the form of diseases, due to extensive production. That is why the use of antimicrobial and antibiotic growth promoters (AGPs) for therapeutic and prophylactic purposes has become popular since 1940 (Edens, 2003; Pelicano et al., 2004; Castanon, 2007). Growing antibiotic resistance and ban on AGPs in many countries have led to a great concern in finding alternatives to antibiotics in chicken production (Obajuluwa et al., 2021). An alternative to therapeutic and prophylactic antibiotics is the usage of prebiotics, probiotics or the combination of both, known as synbiotics (Hassan et al., 2018). Probiotics are described as live microbes present in gut that improve host health by supporting beneficial bacteria (Mizock, 2015). Ahmad (2006) found the most appropriate level of Probiotic (Bacillus toyoi) to be 1 g/kg of feed, which improved digestibility of protein, fat, and dry matter. In another study, Nawaz (2014) concluded that Probiotics (50 g/100 kg of diet) improved the dressing and breast meat yield. Most beneficial organisms are Lactobacillus species, Bifidobacterium species and yeasts (Saccharomyces cerevisiae and Saccharomyces boulardii) (Patterson & Burkholder, 2003; Macfarlane et al., 2008). Probiotic supplementation in broiler diets is suggested as an economical and growth-promoting agent that leaves no residual effect like antibiotic growth promoters (Irshad, 2014). Saccharomyces cerevisiae (SC) is one of the extensively commercialized species (Ezema & Ugwu, 2015). It contains crude protein (40-45%) and various other water soluble vitamins like pantothenic acid, niacin, and biotin (Khan & Naz, 2013), increasing the nutrition quality of the compound feed. Saccharomyces cerevisiae secretes numerous other enzymes, which helps digestive enzymes increase the productive response, nutrient digestibility Jin et al. (2000), feed conversion ratio (FCR), and growth rate performance (Gibson et al., 2017).

Prebiotics are described as “substrate act[ing] as a fertilizer by supporting the colonization of beneficial bacteria” (Gibson et al., 2017). Abundantly used prebiotics are carbohydrates and oligosaccharides that should be non-digestible (Gaggìa et al., 2010). Prebiotic includes mannan-oligosaccharides (MOS), fructo-oligosaccharides (FOS), xylo-oligosaccharides (XOS), inulin, lactulose, stachyose, and raffinose (Macfarlane et al., 2008). Prebiotic potentially promote host health by interacting with beneficial bacterial growth as well as preventing enteric infections (Sugiharto, 2016). Ramzan (2014) reported that prebiotic supplementation in diets improved birds’ growth performance in comparison to the control diet.

Synbiotics are the combination of probiotics and prebiotics. Probiotics usually depend on the substrate known as Prebiotic. Probiotics’ viability are therefore improved with the supplementation of appropriate non-digestible Prebiotics (Sekhon & Jairath, 2010). Prebiotics improve gut health and the beneficial bacterial count, reduce pH and boost the host animal’s immunity (Haq, 2018). Using synbiotics as a feed supplement could increase feed efficiency in comparison to prebiotics and probiotics used separately (Abdel-Raheem et al., 2012; Tayeri et al., 2018). The removal of AGPs from the compound feed resulted in poor feed conversion and growth performance, increasing production costs in about 3% and leaving poultry more vulnerable to mortality and diseases. Safe and economic strategies capable of reducing the microbial load are of utmost importance to poultry producers (Hruby & Cowieson, 2006). Due to extensive poultry production and the increased concern with safer and healthier chicken, efforts have been continuously made to use AGP alternatives as feed supplements. Most of the studies made an effort to use probiotics and prebiotics separately on broilers, experimenting with different combinations. Limited data is available on synbiotics’ (Synerall™) effect on broiler chickens’ digestibility and to which extent it could be used without compromising bird performance. This research was conducted to evaluate the impact of different levels of a synbiotic product (Synerall™) with a unique combination (Saccharomyces cerevisiae, mannanoligosaccharide and galacto-oligosaccharide) on growth performance, carcass characteristics, and nutrient digestibility of broiler chickens.

MATERIALS AND METHODS

Location and duration

The research trial was conducted at the Poultry Research Center, University of Agriculture Faisalabad, during the months of February and March 2019. Birds were initially weighed on delivery and after that weekly body weight, feed intake and feed conversion ratio were determined. Mortality was recorded on a daily basis. This trial lasted for 35 days.

Experimental birds and management

Day-old Cobb 500 broiler birds (300) were obtained from a local hatchery and were randomly distributed among five different treatments, with 6 replicates per treatment, each of them containing 10 birds. All distributed birds remained in the separate pens till the end of the trials. The broiler birds were raised in 30 different pens measuring 4×3 sq. feet. The birds were divided into five experimental groups (Figure 1) and were reared on commercial starter (Table 1) and grower feed (Table 2). The poultry shed maintenance for broiler production was conducted 10 days before chick’s arrival. House preparation initially consisted of shed cleaning and white washing, followed by pen structuring using iron mesh. Equipment was cleaned using tap water and subsequently placed in the sunlight to dry. Sawdust was used in each pen as bedding material, having a depth of about 3 inches. Chick paper was cut and placed according to pen requirements. All equipment was placed inside the poultry house. Fumigation and sanitization of the house were performed with formalin and a KMnO₄ solution, using a ratio of 35 ml and 17.5 g for every 100 cubic feet, respectively.

Table 1
Ingredient/nutrient composition of basal diet for COBB-500 broilers (1-21 days).

Ingredients	Treatment
	A	B	C	D	E
Corn	56.52	56.52	56.52	56.52	56.52
SBM 46%	35.92	35.92	35.92	35.92	35.92
Fish Meal	1.95	1.95	1.95	1.95	1.95
Molasses	0.50	0.50	0.50	0.50	0.50
Vegetable Oil	1.90	1.90	1.90	1.90	1.90
Synerall ™	0.00	0.070	0.120	0.170	0.220
Limestone	0.80	0.80	0.80	0.80	0.80
Di-Calcium phosphate	1.60	1.60	1.60	1.60	1.60
Sodium bicarbonate	0.10	0.10	0.10	0.10	0.10
Common salt	0.22	0.22	0.22	0.22	0.22
Lysine Sulphate, 55%	0.17	0.17	0.17	0.17	0.17
DL-Methionine, 99%	0.20	0.20	0.20	0.20	0.20
L-Threonine	0.02	0.02	0.02	0.02	0.02
Vitalink ®	0.05	0.05	0.05	0.05	0.05
Nutrimin ®	0.05	0.05	0.05	0.05	0.05
Total	100	100	100	100	100
Nutrient composition
CP	21.99	21.99	21.99	21.99	21.99
ME (KCal/Kg)	3009.11	3009.11	3009.11	3009.11	3009.11
EE	4.53	4.53	4.53	4.53	4.53
CF	2.54	2.54	2.54	2.54	2.54
Lysine, digestible	1.19	1.19	1.19	1.19	1.19
Methionine, digestible	0.51	0.51	0.51	0.51	0.51
M+C, digestible	0.82	0.82	0.82	0.82	0.82
Threonine, digestible	0.78	0.78	0.78	0.78	0.78
Tryptophan, digestible	0.25	0.25	0.25	0.25	0.25
Sodium	0.15	0.15	0.15	0.15	0.15
Calcium	0.95	0.95	0.95	0.95	0.95
Phosphorous, available	0.45	0.45	0.45	0.45	0.45

• Synerall ™ is a synbiotic developed by Global Nutritech, Richmond, VA, USA.
• Vitalink^® is a vitamins premix; each Kg of it supplied the following: Vitamin A 20000 KIU; Vitamin D₃ 5400 KIU; Vitamin E 48000 mg; Vitamin K₃ 4000mg; Vitamin B₁ 4000 mg; Vitamin B₂ 9000 mg; Vitamin B₆ 7600 mg; Vitamin B₁₂ 20 mg; Niacin 60000 mg; Pantothenic acid 20000 mg; Folic acid 1600 mg; Biotin 200 mg
• Nutrimin^® is a minerals premix; each Kg of it supplied the following: Iron 10000 mg; Zinc 120000 mg; Manganese 140000 mg; Copper 12000 mg; Iodine 1800 mg; Cobalt 400 mg; and Selenium 360 mg

Table 2
Ingredient and nutrient composition of basal diet for Cobb-500 broilers (22-35 days).

Ingredients	Treatment
	A	B	C	D	E
Corn	62.95	62.95	62.95	62.95	62.95
SBM 46%	28.00	28.00	28.00	28.00	28.00
Fish Meal	2.20	2.20	2.20	2.20	2.20
Molasses	1.00	1.00	1.00	1.00	1.00
Vegetable Oil	3.30	3.30	3.30	3.30	3.30
Synerall ™	0.00	0.070	0.120	0.170	0.220
Limestone	0.50	0.50	0.50	0.50	0.50
Di-Calcium phosphate	1.35	1.35	1.35	1.35	1.35
Sodium bicarbonate	0.09	0.09	0.09	0.09	0.09
Common salt	0.20	0.20	0.20	0.20	0.20
Lysine Sulphate, 55%	0.12	0.12	0.12	0.12	0.12
DL-Methionine, 99%	0.19	0.19	0.19	0.19	0.19
Vitalink ®	0.05	0.05	0.05	0.05	0.05
Nutrimin ®	0.05	0.05	0.05	0.05	0.05
Total	100	100	100	100	100
Nutrient composition
CP	19	19	19	19	19
ME (KCal/Kg)	3170.61	3170.61	3170.61	3170.61	3170.61
EE	6.05	6.05	6.05	6.05	6.05
CF	2.33	2.33	2.33	2.33	2.33
Lysine, digestible	0.97	0.97	0.97	0.97	0.97
Methionine, digestible	0.47	0.47	0.47	0.47	0.47
M+C, digestible	0.74	0.74	0.74	0.74	0.74
Threonine, digestible	0.66	0.66	0.66	0.66	0.66
Tryptophan, digestible	0.21	0.21	0.21	0.21	0.21
Sodium	0.14	0.14	0.14	0.14	0.14
Calcium	0.76	0.76	0.76	0.76	0.76
Phosphorous, available	0.39	0.39	0.39	0.39	0.39

• Synerall ™ is a synbiotic developed by Global Nutritech, Richmond, VA, USA.
• Vitalink^® is a vitamins premix; each Kg of it supplied the following: Vitamin A 20000 KIU; Vitamin D₃ 5400 KIU; Vitamin E 48000 mg; Vitamin K₃ 4000mg; Vitamin B₁ 4000 mg; Vitamin B₂ 9000 mg; Vitamin B₆ 7600 mg; Vitamin B₁₂ 20 mg; Niacin 60000 mg; Pantothenic acid 20000 mg; Folic acid 1600 mg; Biotin 200 mg
• Nutrimin^® is a minerals premix; each Kg of it supplied the following: Iron 10000 mg; Zinc 120000 mg; Manganese 140000 mg; Copper 12000 mg; Iodine 1800 mg; Cobalt 400 mg; and Selenium 360 mg

Figure 1
Experimental layout.

Data recording for performance parameters

Feed intake was measured at the difference between offered refused feed on a weekly basis. Weekly feed intake per replicate helps finding the feed intake per bird every week through the following formula:

$Feed\mathrm{int}ake(g)=Feedoffered-Feedrefused$

Body weight was initially measured when chicks arrived at the poultry shed. However, weekly body weight was measured at the end of each week. Weight gain after each week for each treatment was calculated by subtracting the initial weight. Average weight gain per bird was also determined by dividing the total pen weight by the number of birds in a pen at the end of each week.

The feed conversion ratio (FCR) was used to determine bird’s growth efficiency. The FCR per bird was initially determined using weekly data, and then using the following formula for the overall research period:

$FCR=\frac{Feed\mathrm{int}akeingrams}{Weightgainingrams}$

Nutrient digestibility analysis

The indirect method was used to determine nutrient digestibility. External marker acid insoluble ash (Celite^®) was thoroughly mixed in diets (1%). Feces samples were collected from each pen on the 21^st and 35^th days. Polythene sheets were used to collect feces twice a day. Samples were preserved at -10°C until further analysis. Nutrient digestibility was determined using the following equation:

Antibody titer and meat quality investigation

At the end of trial, two birds from each experimental pen were selected randomly and slaughtered to get data on carcass characteristics and antibody titer. After the slaughter, collected blood serum samples were immediately transferred to the laboratory for investigation of antibody titer against Newcastle disease using the standard HA/HI method (Majiyagbe & Hitchner, 1977).

After the slaughter, breast meat samples were collected and conveyed to the National Institute of Food and Technology (NIFSAT), University of Agriculture, Faisalabad, to study the breast meat’s water holding capacity and pH. Meanwhile, crass characteristics including dressing percentage, breast and thigh yield, and weight of visceral organs were determined immediately after carcass dressing.

Statistical Analysis

Results were analyzed with the use of JMP software (version 5.0.1a; SAS Institute, 2000). Analysis of Variance (ANOVA) technique under Completely Randomized Design was employed and means were compared using Tukey’s test.

RESULTS AND DISCUSSION

In the recent study era, most efforts have been focused on producing feed additive products that have a positive effect on growth performance, feed intake, FCR, and gut health of birds. At this point, synbiotics have gained more importance as growth promoters due to the positive effects of enhancing broiler performance, increasing the resistance against intestinal bacterial infection, and improving the immune status in broiler chickens (Deraz, 2018).

Feed intake

The feed intake was not affected in birds fed diet A, B, C, D and E during both starter and finisher phase (Table 3). However, feed intake was significantly reduced in birds offered diet C (p<0.05) for the whole period of 35 days. The present study was in line with the findings of Al-Sultan et al. (2016), who found that supplementation of synbiotics in broiler diet significantly reduced the feed intake at 35 days of age (p<0.05). These additives improved feed efficiency by growing intestinal microflora population, improving intestinal integrity, and stimulating the immune system. Contrasting results were found by Sarangi et al. (2016), who reported that synbiotic supplementation at 500 g/ton of feed has no effect on feed intake. The studies have demonstrated that dietary synbiotic supplementation could improve intestinal integrity and barrier function, a key factor in nutrient utilization and adsorption, by inhibiting the colonization of pathogenic bacteria and stimulating the proliferation of beneficial bacteria in the intestine, beneficial consequences that may eventually contribute to the enhanced nutrient utilization (Cheng et al., 2017). Abdel-Raheem et al. (2012) found that synbiotic supplementation in broiler diets significantly increased the feed intake as compared with the control group (p<0.05). This increase in feed intake might be due to the different management or feed nutrient profile.

Table 3
Growth performance for finisher phase (22-35) and overall period (1-35) of broilers fed varying levels of synbiotics.

Parameters				Dietary Treatments
		Day		A		B		C		D		E		SEM		p-value
Feed intake (g)		1-21		1292		1285		1245		1308		1309		10.9		0.35
		22-35		2050a		1917ab		1909b		1922ab		1958ab		18.7		0.010
		1-35		3343a		3202ab		3154b		3158ab		3196ab		22.2		0.032
Body weight (g)		1-21		844		918		873		901		891		9.79		0.14
		22-35		1150		1142		1178		1085		1071		16.2		0.165
		1-35		1994		2061		2052		1986		1961		17.8		0.329
Feed conversion ratio		1-21		1.53		1.40		1.42		1.45		1.47		0.01		0.26
		22-35		1.79		1.68		1.63		1.71		1.77		0.02		0.066
		1-35		1.68a		1.55ab		1.54b		1.59ab		1.63ab		0.01		0.029
Mortality (%)		1-21		0.00		3.33		0.00		1.67		0.00		0.73		0.53
		22-35		1.67		1.67		3.33		1.67		0.00		0.692		0.705
		1-35		0.167		5.00		0.333		0.333		0.000		0.951		0.553

• SEM = Standard error of mean.
• Diet A, B, C, D and E having synbiotic supplementation 0, 700, 1200, 1700 and 2200g/ton of feed, respectively.
• Values having different super-scripts show significant difference (p<0.05)

Body weight

Body weight during the starter and finisher phases remained unaffected (Table 3). This could be due to the proper direct-fed microbial supplementation that promotes favorable intestinal conditions for the colonization of beneficial microflora, which in turn facilitate a better growth performance in broiler chicks (Sarangi et al., 2016). In agreement with our findings, Yalçinkaya et al. (2012) and Khalaji et al. (2011) also showed that MOS (0.5, 1 and 1.5 g/kg) had no significant effect on growth performance of broiler chicks. However, in contrast to our results, Al-Sultan et al., 2016 found that synbiotics significantly increased the birds’ weight gain as compared to the control group. The findings of Bozkurt et al. (2014) were also that MOS at 1 g/kg improved the body weight gain in broilers. It could be postulated that a synbiotic or prebiotic may provide a healthy environment in the broiler intestine (e.g. balanced intestinal microflora) and consequently improve growth performance. This is due to the multiplication of useful bacteria because of probiotics’ beneficial effects against the adverse effects of the harmful microbial populations in the digestive system (Abdel-Hafeez et al., 2017).

Feed conversion ratio

In the present study, feed conversion ratio was improved (p<0.05) at the 35^th day of age in birds offered diet B and C, as compared to other dietary treatments (Table 3). The feed conversation ratio was not affected by the treatment during the starter and finisher phases. Similar results were found by Nikpiran et al. (2013), and they reported that FCR was increased by 1.5%. Similar results were also reported by Dizaji et al. (2013), who found that prebiotic (MOS) and synbiotic (Amax) supplementations at 1 g/kg in the diet resulted in better FCR in broiler birds. Nawaz et al. (2016) reported that FCR was improved with the incorporation of microbial or yeast-based probiotics. The improvement in feed conversion ratios might be due to the feeding of synbiotics to which are attributed better nutrient digestibility (Pelicano et al., 2004) and improvement of morphologic characteristics viz. increased villus height, villus width and their ratio in the small intestine (Al-Sultan et al., 2016). In contrast, Yalçinkaya et al. (2012) reported that a prebiotic supplemented diet at 1 g/kg diet resulted in poor FCR in broiler birds. Awad et al., 2009 reported no effect of synbiotic supplementation on broiler feed conversion ratio. Present findings conflict with Sarangi et al., 2016, who reported that the addition of synbiotic neither improved nor negatively impacted the feed conversion ratio of broiler birds.

Nutrient digestibility

The results of the present study showed that the use of synbiotic at the levels of 700 and 1200 g/ton of feed significantly improved (p<0.05) broiler birds’ nutrient utilization (Table 4). These findings are supported by Mountzouris et al. (2010), who incorporated probiotic in diets and observed a significant increase in nutrient utilization. The present findings were further supported by the results of Yun et al., 2017, who declared that the addition of synbiotic in broiler diets had significantly improved (p<0.05) nutrient digestibility. Findings of Yang et al. (2008) are also in accordance with the present study, as they concluded that supplementation of MOS in broiler diets significantly improved starch and protein digestibility. Saleh et al. (2015) reported that nutrient utilization increased when synbiotic (Aspergillus awamori + FOS) was added to the broiler diet. This increase in digestibility was due to the intake of live gut environment modulation microorganisms that improved the gut barrier function via fortification of the beneficial members of the intestinal microflora, the competitive exclusion of pathogens, and the stimulation of the immune system (Mountzouris et al., 2010). Tuohy et al. (2003) reported that an increase in the nutrient digestibility in broilers supplemented with an oligosaccharide diet was due to an improvement in gut health. It is assumed that an increase in villus height is compensated by improvements in the digestive and absorptive functions of the intestine, due to increased absorptive surface area, expression of brush border enzymes, and nutrient transport systems (Awad et al., 2009).

Table 4
Nutrient digestibility of broiler birds during starter and finisher phase fed varying levels of synbiotics.

Parameters (%)				Dietary Treatments
		Day		A		B		C		D		E		SEM		p-value
Fat		21		83.51		82.44		82.26		82.02		82.16		0.906		0.184
		35		83.03		82.55		84.81		79.65		85.52		1.54		0.531
CP		21		60.37c		73.1a		69.25ab		63.75bc		60.66c		1.30		0.000
		35		61­.00b		70.2ab		77.29a		69.07ab		65.82b		1.11		0.003

• SEM = Standard error of mean.
• Diet A, B, C, D and E having synbiotic supplementation 0, 700, 1200, 1700 and 2200g/ton of feed, respectively.
• Values having different super-scripts show significant difference (p<0.05)

However, the results of this research contradicted the results of Sharifi et al. (2012), who incorporated probiotic at 150 mg/kg in the diet that reduced nutrient digestibility in broiler birds. The present findings were also contradictory with the results of Kırkpmar & Açikgöz (2004), who revealed that prebiotic addition at 0.5% in diets resulted in a reduced nutrient utilization by broiler birds. The results of this research were also in contrast with Swamy & Upendra (2013), who reported that prebiotic addition in the diet at 0.05% resulted in poor nutrient utilization in broiler birds.

Carcass characteristics

The results of the present study showed no significant effects of synbiotic supplementation on broiler dressing percentage, breast meat yield, and thigh meat yield (Table 5). Similar findings were reported by Sarangi et al. (2016), who showed that the supplementation of synbiotics did not affect the dressing percentage, breast meat yield, and thigh meat yield of broiler birds. Ashayerizadeh et al. (2011) also reported similar results as they supplemented synbiotics (Primalac and Biolex-MB) in the broiler diet and found no significant change in the carcass, thigh meat yield, and breast meat yield percentages. Opposite results were found by Abdel-Raheem et al. (2012), as they reported that dressing percentage, breast meat yield, and thigh meat yield increased as compared with other treatment groups.

Table 5
Carcass parameters (at 35 days) of broilers fed varying levels of synbiotics.

Parameters (%)		Dietary Treatments
		A		B		C		D		E		SEM		p-value
Dressing		62.81		63.58		63.65		63.88		63.0		0.42		0.942
Brest meat yield		36.33		41.39		37.23		37.90		37.05		0.74		0.220
Thigh meat yield		26.47		25.66		26.42		25.98		26.03		0.36		0.961
Heart weight		0.64		0.64		0.69		0.67		0.52		0.02		0.337
Liver weight		2.61a		2.38ab		2.09b		2.22ab		2.14b		0.05		0.008
Gizzard weight		2.00		2.00		1.65		1.73		1.74		0.04		0.017
Spleen weight		0.34		0.28		0.26		0.33		0.27		0.02		0.846

• SEM = Standard error of mean.
• Diets A, B, C, D and E have synbiotic supplementation of 0, 700, 1200, 1700 and 2200g/ton of feed, respectively.
• Values with different super-scripts show significant difference (p<0.05)

The results of the present study showed no significant effects of synbiotics on giblets relative to organ weight percentage, except liver weight, which decreased in birds offered diets having synbiotic at the concentration of 1200 g/kg (Table 5). Similar results were reported by Yun et al. (2017). They found that the addition of synbiotics in broiler diets had no effect on giblet relative weight percentages. Salma et al. (2007) reported that, with supplementation of probiotics, liver weight decreased significantly (p<0.05) as compared to other broiler birds’ treatments.

The liver weight might be decreased, considering the reduced presence of serum enzymes, as their quantity in the serum can provide some indications of the degree of organ or tissue damage. The serum concentration of liver enzymes, such as alanine aminotransferase (ALT), agamma-glutamyl transpeptidase (GGT), and aspartate aminotransferase (AST) can be used to evaluate avian hepatic function because their synthesis occurs in the liver. Vahdatpour et al. (2011) found that the activities of ALT and ALP were lower in female Japanese quails fed with prebiotics (Fermacto^®), probiotics (Protexin^®) or synbiotics (the combination of Fermacto^® and Protexin^®) than in control quails. A similar result was reported by Salarmoini & Fooladi (2011), whereas broiler chickens supplemented with a probiotic (Bioplus2) or fermented milk containing L. acidophilus exhibited lower levels of serum ALT and ALP than the control broiler chickens. The activities of ALT and ALP may also increase in the serum if there is a cellular injury in the liver or muscle caused by excessive stress. In this context, probiotics and prebiotics have been reported to reduce chicken stress (Tang et al., 2017).

Meat quality

The results of the present study showed no effect of synbiotics on broiler meat water holding capacity (WHC) and pH at the varying levels included in broiler diets (Table 6). Similar results were found by Cheng et al., 2017, who reported that the addition of synbiotics had no effect on breast meat pH as compared to the control group. Similar findings were also reported by Mehdipour et al., 2013, who revealed that synbiotics at a concentration of 500 mg/kg added to quail diets had no effect on meat pH and WHC. Results of Park & Kim, 2014 were also in line with our findings, concluding that the supplementation of probiotics in broiler diets had no effect on broiler breast meat WHC and pH.

Table 6
Meat quality attributes and antibody titer of broiler birds (35 days) ) fed varying levels of synbiotics.

Parameters		Dietary Treatments
		A (Control)		B		C		D		E		SEM		p-value
Water holding capacity		36.66		36.41		36.41		36.41		36.01		0.618		0.99
pH		6.63		6.63		6.54		6.61		6.56		0.01		0.465
NDV		5.50		5.00		5.75		5.25		5.50		7.19		0.284

• SEM = Standard error of mean.
• Diets A, B, C, D and E have synbiotic supplementation of 0, 700, 1200, 1700 and 2200g/ton of feed, respectively.

New castle disease virus (NDV) anti-body titer

The results of the present study found that broiler birds’ immunity was not affected by supplementation of varying levels of synbiotics on day 35 (Table 6). Contrasting results were reported by Hassanpour et al. (2013), who increased humoral immune response through the administration of the synbiotics Biomin and Protexin + TechnoMos. Midilli et al. (2008) reported that the use of probiotic BioPlus, prebiotic BioMos and their combination did not have any effect on the concentration of IgG in broilers’ serum. A possible explanation for the differences between findings of different investigators may the differing doses of probiotics, prebiotics and synbiotics applied, animal species and study populations (e.g. in age, weight or breed), strains of micro-organism used, and composition of diets.

CONCLUSIONS

The current research concluded that synbiotics can be safely used at up to 1200 g/ton of feed in broilers’ diets to improve bird performance without any harmful effects on other health parameters.

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Publication Dates

• Publication in this collection
  25 June 2021
• Date of issue
  2021

History

• Received
  07 Sept 2020
• Accepted
  28 Feb 2021