Effects of Dietary Rosemary Extract on Growth Performance, Immunity and Antioxidant Function in Broiler Chickens

 Abstract:The purpose of this article is to investigate the effects of adding rosemary extract to diets on the growth performance, immunity and antioxidant function of broilers. The 120 broilers were randomly divided into 6 groups with 4 replicates each and 5 chickens in each replicate, the control group was fed with basal diet, and the broilers in groups 1, 2, 3, 4 and 5 were fed with 100, 200, 300, 400 and 500 mg/kg of rosemary extract in the basal diet, respectively, and the experiment lasted for 60 d. The results showed that the average daily weight gain of the broilers in groups 1, 2, 3, 4 and 5 increased significantly (P＜0.05) and the feed-to-weight ratio decreased significantly (P＜0.05) compared with that of the control group.

 

The results showed that compared with the control group, the average daily weight gain of groups 1, 2, 3, 4 and 5 was significantly higher (P < 0.05), the feed-to-weight ratio was significantly lower (P < 0.05), the average daily feed intake of groups 1 and 2 was significantly lower (P < 0.05), and the average daily feed intake of groups 4 and 5 was significantly higher (P < 0.05). In addition, CD3+, hepatic glutathione peroxidase (GSH-Px), hepatic total antioxidant capacity (T-AOC), serum GSH-Px, and serum T-AOC were significantly increased (P < 0.05), and hepatic MDA and serum MDA were significantly decreased (P < 0.05) in groups 1, 2, 3, 4, and 5, as compared with the control group. Compared with group 1, hepatic GSH-Px, hepatic MDA and serum MDA in groups 2, 3 and 4 were significantly higher (P < 0.05) and lower (P < 0.05).

 Compared with Group 1, hepatic GSH-Px, hepatic T-AOC and serum GSH-Px in Groups 2, 3 and 4 were significantly higher (P < 0.05), hepatic malondialdehyde (MDA), serum MDA and serum T-AOC were significantly lower (P < 0.05), hepatic GSH-Px and serum GSH-Px in Group 5 were significantly higher (P < 0.05), hepatic MDA, serum MDA and serum T-AOC were significantly lower (P < 0.05), compared with Group 1 Liver MDA, serum MDA and serum T-AOC decreased significantly (P < 0.05) compared with Group 1. Conclusion: Under the present experimental conditions, the addition of 100 mg/kg of rosemary extract to the basal diet helped to increase the growth performance of broilers and improve their immunity and antioxidant functions.

 

Antibiotics used to play an important role in promoting growth and improving feed utilization in livestock farming. Although the wide application of antibiotics has greatly promoted the progress of livestock and poultry farming, problems such as bacterial resistance, environmental pollution and drug residues in food of animal origin have arisen as a result of their long-term application and even abuse (Li et al., 2019; Wang et al., 2018). In order to ensure food safety and safeguard public health, since 2020, the Ministry of Agriculture and Rural Affairs of China has completely banned the use of medicated feed additives as additives to promote animal growth in feed, so the search for a suitable alternative to antioxidants has become a great concern for the majority of scholars (Li Aike et al., 2020).

 

Plant extracts are substances obtained from plants, and their ingredients are green, safe and do not produce drug residues. In recent years, as people's demand for the quality of livestock products continues to increase, plant extracts have been more and more widely used in the animal husbandry industry. A large number of studies have shown (Bianchin et al. 2021; Baron et al. 2020; Goncalves et al. 2020) that adding plant extracts to livestock feed can not only enhance their antioxidant capacity, but also strengthen their immune function.

 

Rosemary is a source of several phenolic antioxidants that have been shown to have antioxidant, anti-inflammatory, and anti-glycemic benefits (Fu et al.  2022; Saton et al. 2022; Ghasemzadeh et al. 2020). However, until now, the research on rosemary and its extracts in broiler chickens has been insufficient, mainly focusing on pharmaceuticals for the treatment of human diseases. Therefore, the present study was designed to investigate the effects of the inclusion of rosemary extracts in diets on the growth performance, immunity and antioxidant functions of broiler chickens with the aim of providing a reference to the use of rosemary extracts in broiler chickens rearing.

 

1 Materials and Methods

1.1 Experimental materials 120 1-day-old white-feathered broilers with similar body weights were purchased from local breeding farms, and the rosemary extract was provided by a biotechnology company in Jiangsu Province, China. The main components of the rosemary extract included rosemarinic acid (≥5%), ursolic acid (≥3%), chlorophyll (≥4%), and flavonoids (≥16%). The basal diets used in this experiment were formulated with reference to the nutritional requirements of NRC broilers, and the specific composition of the diets is shown in Table 1.

 

1.2 Experimental design and feeding management  

The 120 broilers were randomly divided into 6 groups, with 4 replicates in each group and 5 chickens in each replicate. The control group was fed a basal diet, while the broilers in groups 1, 2, 3, 4, and 5 were supplemented with 100, 200, 300, 400, and 500 mg/kg of rosemary extract in the basal diet, and the nutritional levels of the broilers in each group were basically the same, except for the different amounts of rosemary extract added to the diet. The experiments lasted for 60 d. The broilers in each group were housed in 4-layer three-dimensional cages, with free feeding, free watering, natural light, and relative humidity of 50%-60%, and were protected from epidemics and immunized routinely.

 

1.3 Sample Collection  

At the end of the test, two broilers in each group were randomly selected from each repetition to collect 10 mL of blood from the wing vein with a disposable syringe and collect it into an anticoagulation tube, mix it up and down, then centrifuge it at 3000 r/min for 10 min, and store the separated serum at -20℃. After cleaning, 1.0 g of liver tissue was mixed with saline to make a homogenate of 100 g/L, centrifuged at 2500 r/min for 10 min, and stored at -80℃.

 

1.4 Measurement indicators and methods

1.4.1 Growth performance measurements  

During the experiment, we observed the growth of broilers in each group, weighed the broilers in each group, recorded the remaining feed amount of broilers once a week, stopped feeding at 20:00 the night before weighing, and weighed the broilers on an empty stomach at 8:00 a.m. the next morning, and calculated the average daily intake of broilers in each group (g), the average daily gain of broilers (g), and the feed-to-weight ratio.

 

1.4.2 Determination of immune function  

CD3+, CD4+/CD8+, and blood lymphocyte activity were determined by flow cytometry, and the procedure was performed according to Yan Lidong (2013).

 

1.4.3 Determination of antioxidant function  

Antioxidant markers, including glutathione peroxidase (GSH-Px), malondialdehyde (MDA), and total antioxidant capacity (T-AOC) levels in liver and serum were determined by ELISA.

 

1.5 Statistics and analysis of data  

The results were organized by Excel and then analyzed by SPSS 22.0 software for analysis of variance (ANOVA), and Duncan's for multiple comparisons, and the results were expressed as "mean ± standard deviation", with P＜0.05 indicating a significant difference between the groups.

 

2 Results

2.1 Effects of dietary rosemary extract on the growth performance of broilers As shown in Table 2, the average daily feed intake of broilers (Groups 1 and 2) with lower dosage of rosemary extract decreased significantly (P < 0.05), while that of broilers with higher dosage (Groups 4 and 5) increased significantly (P < 0.05), and the average daily weight gain of broilers (Groups 1, 2, 3, 4, and 5) with rosemary extract increased significantly (P < 0.05) and the feed-to-weight ratio decreased significantly (P < 0.05), as compared to that of broilers without rosemary extract. The average daily feed intake of broilers with higher doses of rosemary extract (Groups 4 and 5) increased significantly (P < 0.05), while the average daily weight gain of broilers with higher doses of rosemary extract (Groups 1, 2, 3, 4 and 5) increased significantly (P < 0.05), and the feed-to-weight ratio decreased significantly (P < 0.05).

Table 2 Effect of dietary inclusion of rosemary extract on the growth performance of broiler chickens

 

2.2 Effect of dietary supplementation with rosemary extract on the immune function of broilers  

As shown in Table 3, significant increases in CD3+ were observed in groups 1, 2, 3, 4, and 5 compared with the control group (P < 0.05).

 

2.3 Effect of dietary addition of rosemary extract on oxidative function in broiler chickens

 As shown in Table 4, hepatic GSH-Px, hepatic T-AOC, serum GSH-Px, and serum T-AOC in groups 1, 2, 3, 4, and 5 were significantly higher (P < 0.05) than those in the control group, whereas hepatic MDA and serum MDA were significantly lower (P < 0.05) than those in the control group.  

 

3 Discussion

In this study, the significant increase in growth performance of broilers after adding rosemary extract to the basal diet may be attributed to its ability to regulate the intestinal function, as shown by Norouzi et al. (2015), which showed that rosemary could promote the growth of Lactobacillus lactis in the intestinal tract of broilers, and at the same time, control the reproduction of Escherichia coli, which improved the intestinal environment and aided the growth and development of broilers.

 

Rosemary extract contains phenolic components, which can regulate the leakage of intracellular proteins and reducing sugars from bacteria, and selectively regulate the leakage of proteins and reducing sugars, thus effectively inhibiting the activity of bacterial intracellular enzymes and their transcriptional replication. Schönfeld et al. (2018) showed that rosemary is metabolized to caffeic acid and its derivatives in the animal intestinal tract, and trans-caffeic acid inhibits the expression of STAT3, which inhibits the proliferation and differentiation of CD4+ T lymphocytes, leading to the suppression of the immune response. The results were similar to the present study.

 

In addition, the excessive production and accumulation of reactive oxygen species in the body can lead to an imbalance in the oxidative system, resulting in oxidative stress, which may have a serious impact on the performance of the animals. In the present study, the addition of rosemary extract to the basal diet significantly improved the antioxidant function of broiler chickens, which may be related to the hepatoprotective effect of rosemary.Fadlalla and Galal (2020) showed that rosemary extract significantly reduced the serum AST, ALT and triacylglycerol levels and improved the oxidative function of paracetamol model rats, similar to the present results. The results were similar to the present study.

 

4 Conclusion

The addition of rosemary extract to the basal diet can help to increase the growth performance of broilers and improve their immunity and antioxidant functions, but too high a dose of rosemary extract will not improve the immunity and antioxidant functions of broilers, and may inhibit the growth performance of broilers. However, too high a dose of rosemary extract would not improve the immunity and antioxidant functions of broilers, and might inhibit the growth performance of broilers.

 

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