Dietary inclusion of vegetable oil, with or without quercetin was supplied to broilers for 35 days, in order to determine its influence on carcass characters and meat quality attributes. Vencobb strain of broiler chickens (n=192) were assigned in to four dietary treatment groups on 7th day of age. All the birds were supplied with corn soya-based diet as a basal feed. Group T1 served as control without any supplementation. T2 and T3 supplied with quercetin at 1 g kg-1 and 33 g kg-1 vegetable oil to raise 10% ME of the feed, respectively, whereas, both in combination at same dose rate were supplied in T4. At the end (42 days age) 8 birds from each respective group (2 birds per replicates) were sacrificed for carcass characters and meat quality assessment. Results revealed that dressing percentage relative to body weight was significantly differ among the dietary treatment groups, whereas % relative weight of all major organs was found comparable. Moisture % was significantly low whereas, pH and % cooking loss were comparatively high (P<0.05) in T3. CP, EE and TA content and physico-chemical composition of meat were not affected by treatments. The noteworthy (P<0.05) influence had been observed on sensory attributes of broiler meat with dietary treatments and overall palatability was improved in T1 and T2. Overall findings showed that 10% raised in ME by inclusion of oil was adversely influences the meat quality and quercetin supplementation exhibited positive impact on carcass characters and meat quality attributes of chickens.
Modern poultry production has common practice to use fat and oil for raising the energy density in poultry diets (Khatun et al., 2018). Besides supplying energy, inclusion of oils results in better absorption of fat-soluble vitamins, diminishes the pulverulence, improves the palatability of feeds, increase absorption and hydrolysis of essential fatty acids furnishing lipoproteins thereby increases the efficiency of the consumed energy (Nobakht et al., 2011). The source and type of dietary fat and its fatty acids composition influences on fatty acid profile and carcass quality of poultry meat (Khatun et al., 2018). Assimilating the demand of consumer unsaturated fatty acids (UFA) (like ω-3 and ω-6) in poultry ration improves the meat quality (Raza et al., 2016). These meats are more liable to oxidative spoilage, with retardation of meat product quality and had an unfavourable effect on consumer health (Adeyemi et al., 2015). The use of dietary saturated fatty acid (SFA) are stable against the oxidative damages by lipid peroxidation and has an effective strategy to enhance the product quality with reducing spoilage and increased abdominal fat deposition (Ayad et al., 2015).
However, poultry meat enriched with many nutritional properties such as low intramuscular fat and relatively high concentration of polyunsaturated fatty acids (PUFA). Oxidation by free radical is one of the primary mechanisms of quality deterioration in foods especially in meat products (Kanner, 1994). To prevent deterioration and maintain the meat quality, interest has been focussed to the use of natural antioxidants such astocopherols, carotenoids, flavonoids, phenolic acids (Yanishlieva-Maslarova et al., 2001). The antioxidant from natural sources can extend shelf life, reducing lipid peroxidation and increased the acceptability and quality of meat (Fellenberg and Speisky, 2006). Quercetin (2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy- 4H-chromen-4-one), a flavonoid compound, belongs to the class of flavonols having a strong antioxidant potential, found ubiquitous in plant and plant food sources (Sikder et al., 2014). The present experiment was designed to evaluate the influence of dietary SFA rich vegetable oil and potential of quercetin as an antioxidant supplementation on carcass characters, meat quality and sensory attributes of broiler chickens.
Materials and Methods
The present research was conducted after approval of the Institutional Animal Ethics Committee (IAEC/065-VCN-ANN-2018), College of Veterinary Science and Animal Husbandry, Navsari Agricultural University, Navsari, Gujarat, India.
In present experiment, quercetin was commercially procured from Sigma Aldrich Life Science (P) Ltd. The energy level was increased 10% than the recommendation (BIS, 2007) which was 3410 and 3520 Kcal metabolizable energy (ME) per kg feed, respectively in starter and finisher phase. The ME level (Kcal/kg feed) has been raised by introducing 33 g hydrogenated vegetable oil from 7th day onward.
A total of 192-day-old broiler chicks of Vencobb-400 strain were randomly assigned into four dietary treatment groups with four replicates and 12 birds in each based-on body weight. The birds were housed under deep litter system with uniform managemental practices. Nutrient requirement of birds were fulfilled as per ICAR, (2013). Birds were provided with ad libitum water and fed weighed quantity of basal diets with ensuring left over. Dietary treatments and pattern of supplementation are depicted as per Table 1. The ration was formulated by using listed ingredients (Table 2) following BIS, (2007) for the starter and finisher phases.
Table 1: Outline of experimental designs and treatment regimen of broiler chickens
|Treatment Groups||Diet||Vegetable oil||Quercetin|
|I. T1 (CON)||Basal Diet||—||—|
|II. T2 (Q)||Basal Diet||—||1 g kg-1|
|III. T3(HFD)||Basal Diet||33 g||—|
|IV. T4 (HFD+Q)||Basal Diet||33 g||1 g kg-1|
(T: Treatment; CON: Control; Q: Quercetin; HFD- High fat diet)
At the end of experiment (35th day), eight birds from each group (2 birds/replicate) were sacrificed by cervical dislocation as per standard protocols to study carcass characteristics. The influences of dietary treatments on dressed weight and relative weight of internal organs were estimated by using following formula.
|% Dressing on live body weight|
|% Relative weight of organs|
Meat Quality Attributes
The meat quality was evaluated through a series of parameters viz. chemical composition, physico-chemical properties and sensory evaluation. The breast pieces (pectoral muscle) of meat were stored at -40°C in air tight pre-labeled polythene bags to evaluate the quality attributes.
The chemical composition viz. moisture, dry matter, crude protein, crude fat and total ash content of meat samples were analyzed as per the standard methods (AOAC, 2002).
Table 2: Ingredients and nutrient composition of experimental diets
|(g)||(8-22 days)||(23-42 days)||(8-22 days)||(23-42 days)|
|(T1 and T2)||(T1 and T2)||(T3 and T4)||(T3 and T4)|
|Deoiled Rice Bran||90||100||90||100|
|De-Oiled Soya Cake||87||50||87||50|
|Ground Nut Cake||90||75||90||75|
1Tracemin CB: Each 1 kg contain–Manganese – 90 g, Zinc – 80 g, Iron – 90 g, Copper -15 g, Iodine – 2 g and Selenium – 300 mg; **calculated values
Meat samples were analyzed for their physico-chemical properties like pH, water holding capacity (Wardlaw et al., 1973), tyrosine value (Strange et al., 1977), thiobarbituric acid reactive substances as malondialdehyde production (Witte et al., 1970) and cooking loss (Pearson and Dutson, 1994). The pH was measured using pH meter (pH Tester 30, Thermo Fisher scientific, USA). TBARS (thiobarbituric acid reactive substances) was estimated by using solvent trichloroacetic acid for extraction.
Meat sample (g muscle) from each was further reduced by 1.5-2.0 cm size and cooked by electric microwave oven at the temperature range of 180-200°C for 30 minutes. The cooked meat samples were served to a panel consisting seven semi trained panelist. The products were evaluated for their appearance, color, flavor, texture, juiciness and overall palatability using a 9-point hedonic scale to anticipate the acceptability of meat products on quality bases.
The data generated were analyzed for their statistical significance using package for the social sciences (SPSS, version 20.0 Chicago, USA). Analyzed data were used to draw interpretations and conclusions. The means were compared using Duncan’s multiple range test (Duncan, 1955).
The findings of influence of dietary oil or quercetin supplementation on carcass characters of broiler chickens are being presented in Table 3. Majority of organs relative weight were not affected on supplementation of oil, quercetin or both, however dressing per cent were significantly affected with dietary treatments. Quercetin supplementation (T2) revealed higher dressing percentage, followed by T4, T3 and low in unsupplemented group (T1). The % relative weight of large intestine was high in T1(P<0.05), which were similar to T2 and T4, while low in T3.The weight of the whole sell cuts like neck, back, thigh, breast, drumstick and wing were not influenced (P>0.05) by supplementing either oil or quercetin or inclusion of both together in birds.
Meat Quality Attributes
Results for chemical composition of breast meat of broilers supplemented with oil or quercetin are shown in Table 3. The moisture and dry matter percent were significantly influenced by the dietary treatments. The moisture level was significant improved in T2 and T1, while poor in T3. Intermediate level of moisture was observed in T4 groups. The other proximate components of meat were not affected with either oil or quercetin in broilers. However, apparently higher EE was found in T3 groups.
Physico- Chemical Composition
The findings pertaining to influencing effect of oil or quercetin or both on physicochemical compositions was mentioned in Table 3. The pH of meat sample significantly affected with dietary treatments. However, other physico-chemical characters namely water holding capacity, tyrosine and thiobarbituric acid reactive substances values were not influenced (P>0.05) by supplementation. Cooking loss was noticed greater (P<0.05) in T3 and found low in T2 and T4 groups.
The effects of oil with or without quercetin on sensory evaluation of meat are displayed in Table 3. The dietary treatments have significant influenced on all the sensory characters except color of cooked meat. All sensory attributes in T1 and T2 groups were scored highest (P<0.05) than the T3 and T4.
Table 3: Influence of dietary oil with or without quercetin on carcass characteristics (% relative weight) of broiler chickens
|% Relative Weight||T1||T2||T3||T4|
|Dressing||57.40c ±0.82||65.34a±0.74||60.62b ±0.64||62.31ab ±0.78||0.61|
|Large intestine||2.01a ±0.11||1.92ab ±0.09||1.34b ±0.33||1.78ab ±0.10||0.43|
abMeans with different superscript in a row differ significantly (P<0.05); T1= Control; T2= Quercetin (1g kg-1 feed); T3=33 g kg-1 Vegetable oil; T4=33 g kg-1 Vegetable oil + Quercetin (1g kg-1 feed)
Carcass characters were not significantly influenced by the dietary treatment except relative dressing percent and large intestine. Dressing % was increased (P<0.05) in quercetin supplemented group (T2 and T4), which might be due to apparent increase in relative weight of internal organs. Similar response was observed by Soomro et al. (2016) who found significant differences in values of carcass weight and dressing percentage of broiler fed varying level of dietary fat from different sources. Findings of relative weight of breast and leg were consistence with Zhang et al. (2013), who supplemented varying level of olive oil to broilers. In same trend, Ayed et al. (2015) reported comparable (%) relative weight of thigh, heart and gizzard on supplementation of either soybean or palm oil in broilers. Similarly, Somade et al. (2016) found comparable finding on relative weight of heart in broiler on supplementation of quercetin with sodium azide (SAZ) induced extra hepatic oxidative stress in rat. However, Nobakht et al. (2011) reported significant effect of different level and oil sources on relative weight of gizzard.
Many researchers revealed that polyphenolic compound from varying sources like Moriga olifera, grape seed, Allium sativum, Allium cepa, Zingiber officinal having potential to improved dressing percent of broiler carcass (Arslan et al., 2017 and Abu Hafsa and Ibrahim, 2018). Contradictory of present finding, Goliomytis et al. (2014) reported that higher relative weight of heart while rest of the internal organ like liver, spleen and fat pad were found similar in chickens supplied with quercetin. They suggested that increased % relative heart weight might be due to the exhibition analogues effect of quercetin on cardiovascular function.
Water holding capacity, pH, color and tenderness are crucial for the culinary value and technological properties of chicken meat (Nissen and Young, 2006). The pH value plays a vital role for maintaining the meat keeping quality and that directly relay on muscle energy metabolism balance (Li et al., 2017). In present study, the pH of breast muscle was significantly differ among dietary treatments, however, the values of pH were within the range of 5.5 to 6.5 suggested by Mir et al. (2017). Increasing in meat pH on supplementation of oil was also noticed by Zaki et al. (2018). In agreement with present study, quercetin supplementation did not showed any influence on meat pH, TBARS level and cooking loss in broilers (Goliyomytis et al., 2015). Inconsistence to present findings, Tasdelen and Ceylan, (2017) and Kalakuntla et al. (2017) reported significantly increase TBARS level in breast muscle on vegetable oil supplementation in broilers, which might be due to the increased lipid peroxidation for sack of higher dietary oil supplementation in the muscles. The cooking loss was found highest in the T3 group that might associate with the changes in meat pH.
Contrary, to present results, supplementation of polyphenols (hesperidine shows significance improvement in TBARS value of stored broiler meat (Simitzis et al., 2011). Flavanols supplementation to broilers reduces the malondialdehyde level while did not exert any significant changes in meat pH and cooking loss (Goliomytis et al., 2015) which was inconsistence to present findings. This positive effect on malondialdehyde level might be attributed to strong antioxidant potential and accumulation of its metabolites in body tissues (Goliomytis et al., 2014). Changes in the water content of meat ensuring alterations in the key quality attribute such as color and texture (Ali et al., 2015). Similar to present result of meat chemical composition, Dorra et al. (2014) found non-significant effects on proximate composition, however, contrary results with non-significant alteration were noted for moisture (%) with inclusion of frying oil the diet of broilers. Similar effect on dry matter content (Ayad et al., 2015) and breast meat protein content (Kalakuntla et al., 2017) was observed with oil supplementation in broilers. Increased dietary fat resulting in to elevation in amount of energy consumed by the chickens (Ayad et al., 2015). The apparently higher fat content in T3 group might be due to the possible widening of calorie: protein ratio and high SFA content of vegetable oil this study.
Significant changes in sensory attributes under present study were might be the reflection of alteration in moisture content of meat. It indicated that supplementation of oil was influencing on physio-chemical and sensory parameters (Kalakuntla et al., 2017). The inclusion of oil or quercetin had found significant influence on all the sensory characters excluding color of cooked meat. Improvement in sensory score in T2 might be the flavor enhancing effects of quercetin and presence of its metabolites in the tissues (Li et al., 2016).
Table 4: Influence of dietary oil with or without quercetin on meat quality attributes of broiler chickens
|MO (%)||74.10a±0.48||74.23 a ±0.73||71.66 b ±0.94||72.79 ab ±0.85||0.41|
|DM (%)||25.89b±0.48||25.76 b ±0.73||28.33 a ±0.94||27.20 ab ±0.85||0.41|
|pH||5.58b ±0.12||5.80ab ±0.14||6.04a ±0.10||5.80ab ±0.01||0.06|
|TBARS (mg 100-1)||0.61±0.09||0.55±0.11||0.67±0.17||0.60±0.07||0.05|
|Cooking loss (%)||22.99ab±0.28||22.90b ±0.18||23.57a ±0.18||22.67b ±0.20||0.11|
|Appearance||7.75ab ±0.25||8.12a ±0.29||7.00ab ±0.0.37||7.37b ±0.74||0.16|
|Flavor||7.75a ±0.25||8.12a ±0.29||6.75b±0.31||6.50b ±0.37||0.19|
|Juiciness||6.37b ±0.49||8.25a ±0.31||5.62b ±0.32||5.87b ±0.29||0.28|
|Texture||6.12b ±0.29||7.50a ±0.32||6.12b ±0.39||6.25b ±0.52||0.24|
|Overall palatability||7.25b ±0.25||8.25a ±0.25||6.62b ±0.74||6.62b ±0.46||0.21|
abMeans with different superscript in a row differ significantly (P<0.05); T1= Control; T2= Quercetin (1g kg-1 feed); T3=10% Vegetable oil; T4=10% Vegetable oil + Quercetin (1g kg-1 feed), moisture; MO, dry matter; DM, crude protein; CP, ether extract; EE and total ash; TA., water holding capacity; WHC, thiobarbituric acid reactive substances; TBARS.
Consistence effect was noted by Takahashi et al. (2012) who reported significant effect on sensory characters like flavor, sweetness and taste in broilers supplemented with arachidonic acid enriched oil (AAO). Similar effect (P>0.05) on sensory attributes of meat with quercetin supplementation to broilers was observed by Jang et al. (2011). Contrary to present findings significant influence on juiciness, flavor, oxidized flavor and acceptability of breast meat samples were observed by Kirkpinar et al. (2014) with dietary oregano and garlic oils supplementation.
Dietary inclusion of oil with or without quercetin does not exerted significant influence on carcass characters. The oil inclusion had significantly reduced moisture level in meat, although overall either quercetin or oil supplementation did not affect the chemical composition of meat of broilers. Supplementation of oil without quercetin has showed increased the meat pH and cooking loss. The sensory attributes have found adverse influence with higher dietary oil supplementation whereas quercetin incorporation improved it.