1- Ardabil Agricultural and Natural Resources Research and Education Center, AREEO, Ardabil, Iran.
2- Animal Science Research Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran.
2- Animal Science Research Institute of Iran, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran.
Abstract: (85 Views)
Introduction and Objective: Feed restriction is a method to control problems caused by rapid growth in the broiler industry. After the feed restriction period, the use of growth promoters can be a suitable option to compensate for the effects of the restriction. Due to the increase of antibiotic resistance in recent decades, the use of antibiotics as growth promoters has been limited. Therefore, it seems that the use of plant extracts such as thyme and oregano are a suitable and low-complication alternative to antibiotics due to their antibacterial, antifungal, anti-coccidial, anti-inflammatory and microbial flora modulation properties. The use of herbal additives and growth promoters is a strategy to strengthen the compensatory growth phenomenon in broilers. Meat and bone quality in broiler chickens are economic traits. This study aimed to investigate the effects of using thyme, oregano, thyme-oregano and probiotic on meat quality and tibia bone status in broiler chickens after a feed restriction period.
Material and Methods: To perform the current study, a total of 480 one-day-old Ross-308 male broiler chickens were used. This experiment was conducted as a factorial experiment (2×5) in a completely randomized design including two feeding methods (full feed and restricted) and four types of additives (thyme extract, 300 g/ton of basal diet; oregano extract, 300 g/ton of basal diet; equal weight ratio of thyme+oregano extract, 300 g/ton of basal diet; probiotic protoxin, 250 g/ton of basal diet) along with control diets (without additives). In the first step, chickens were divided into two separate experimental groups, the first group was fed freely as a control group, but in the second group, from the age of 8 to 14 days, the quantitative restriction was applied for 7 days (25% less than the control group). After the end of the restriction period, herbal additives and probiotic were added to the diet of both mentioned groups. The factors of acidity, water holding capacity, oxidative stability, peroxide index and color were used to measure meat quality. Also, for sensory evaluation of the meat, the right side of the breast from each repetition after preparation was cooked at 170 ċ in an electric oven for 40-45 minutes depending on the weight of the samples. The evaluated traits in the experiment included smell, taste, crispness, juiciness and general acceptability. To determine the ash, calcium and phosphorus content of the tibia bone in different treatments, at the end of the period, by selecting two samples from each replicate, their left tibia bone was separated and defatted by an autoclave. In the next step and after preparing the samples, the percentage of ash, calcium and phosphorus was determined by atomic absorption method. Statistical analysis of data was done using the GLM procedure in SAS 9.1 software.
Results: Based on the results, acidity and meat redness (a*) in the feed restricted group were higher than in free feeding chickens and the TBA index in the free feeding method was higher than restricted group (P≤0.05). The water holding capacity of the carcass in the treatment without additive was lower than the treatments that received the additive (P≤0.05). Also, carcass acidity was the lowest in the probiotic receiving group and the highest in the group without additives (P≤0.05). The peroxide index in the treatment without additives was higher than the others (P≤0.05). The combination of thyme and oregano significantly increased the lightness of the breast meat compared to other additives. The overall acceptability of meat in the treatment containing thyme, the combination of thyme-oregano and probiotic had a higher score than the treatment without additives (P≤0.05). The use of the additive after the restriction period had significant effects on the smell, juiciness, taste, crispiness and overall acceptability of the breast meat, so that in terms of smell, the oregano had a lower score than the others (P≤0.05). Also, the juiciness, taste and crispness scores of the oregano and the treatment without the additive were lower than the other treatments (P≤0.05). Determining tibia bone content showed that the type of additive had statistically significant effects on ash and calcium percentage (P≤0.05), so that the ash percentage in the group without additive was lower than the other treatments except for the oregano treatment. The percentage of calcium was lower in the treatments without additives and higher in the probiotic receiving treatment (P≤0.05).
Conclusion: The obtained results showed that the use of herbal additives (thyme and oregano) and probiotic after a feed restriction period in the second week have favorable effects on various parameters of meat quality and also the strength of tibia bone in boilers. The combination of thyme and oregano, compared to their separate use, had a better effect on the sensory properties of the meat from broiler chickens, including aroma, juiciness, flavor, and tenderness. Since traits such as the quality of the tibia bone influence the health, welfare, and production of broiler chickens, as well as the sensory and chemical quality of the produced meat, which in turn affect marketability and customer satisfaction, using the findings from studies such as the present research can help improve these aspect. However, more studies are needed to identify appropriate additives, combining them and the extent of their use.
Material and Methods: To perform the current study, a total of 480 one-day-old Ross-308 male broiler chickens were used. This experiment was conducted as a factorial experiment (2×5) in a completely randomized design including two feeding methods (full feed and restricted) and four types of additives (thyme extract, 300 g/ton of basal diet; oregano extract, 300 g/ton of basal diet; equal weight ratio of thyme+oregano extract, 300 g/ton of basal diet; probiotic protoxin, 250 g/ton of basal diet) along with control diets (without additives). In the first step, chickens were divided into two separate experimental groups, the first group was fed freely as a control group, but in the second group, from the age of 8 to 14 days, the quantitative restriction was applied for 7 days (25% less than the control group). After the end of the restriction period, herbal additives and probiotic were added to the diet of both mentioned groups. The factors of acidity, water holding capacity, oxidative stability, peroxide index and color were used to measure meat quality. Also, for sensory evaluation of the meat, the right side of the breast from each repetition after preparation was cooked at 170 ċ in an electric oven for 40-45 minutes depending on the weight of the samples. The evaluated traits in the experiment included smell, taste, crispness, juiciness and general acceptability. To determine the ash, calcium and phosphorus content of the tibia bone in different treatments, at the end of the period, by selecting two samples from each replicate, their left tibia bone was separated and defatted by an autoclave. In the next step and after preparing the samples, the percentage of ash, calcium and phosphorus was determined by atomic absorption method. Statistical analysis of data was done using the GLM procedure in SAS 9.1 software.
Results: Based on the results, acidity and meat redness (a*) in the feed restricted group were higher than in free feeding chickens and the TBA index in the free feeding method was higher than restricted group (P≤0.05). The water holding capacity of the carcass in the treatment without additive was lower than the treatments that received the additive (P≤0.05). Also, carcass acidity was the lowest in the probiotic receiving group and the highest in the group without additives (P≤0.05). The peroxide index in the treatment without additives was higher than the others (P≤0.05). The combination of thyme and oregano significantly increased the lightness of the breast meat compared to other additives. The overall acceptability of meat in the treatment containing thyme, the combination of thyme-oregano and probiotic had a higher score than the treatment without additives (P≤0.05). The use of the additive after the restriction period had significant effects on the smell, juiciness, taste, crispiness and overall acceptability of the breast meat, so that in terms of smell, the oregano had a lower score than the others (P≤0.05). Also, the juiciness, taste and crispness scores of the oregano and the treatment without the additive were lower than the other treatments (P≤0.05). Determining tibia bone content showed that the type of additive had statistically significant effects on ash and calcium percentage (P≤0.05), so that the ash percentage in the group without additive was lower than the other treatments except for the oregano treatment. The percentage of calcium was lower in the treatments without additives and higher in the probiotic receiving treatment (P≤0.05).
Conclusion: The obtained results showed that the use of herbal additives (thyme and oregano) and probiotic after a feed restriction period in the second week have favorable effects on various parameters of meat quality and also the strength of tibia bone in boilers. The combination of thyme and oregano, compared to their separate use, had a better effect on the sensory properties of the meat from broiler chickens, including aroma, juiciness, flavor, and tenderness. Since traits such as the quality of the tibia bone influence the health, welfare, and production of broiler chickens, as well as the sensory and chemical quality of the produced meat, which in turn affect marketability and customer satisfaction, using the findings from studies such as the present research can help improve these aspect. However, more studies are needed to identify appropriate additives, combining them and the extent of their use.
Keywords: Compensatory growth, Growth promoters, Herbal additives, Meat acceptability, Water holding capacity
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