The benefits of blend essential oil for GIFT tilapia on the digestion, antioxidant, and muscle quality during cold storage

Essential oils have been used commercially as feed additives on livestock and poultry due to their broad spectrum antioxidant and disease resistance effects. However, their effects have not been well studied in fish. To this end, this study was conducted in two parts to evaluate the roles of blend essential oil (BEO, cinnamaldehyde, thymol, carvacrol) in fish. First, the growth inhibition effects on two typical pathogens and one beneficial bacterial of tilapia in vitro. Second, a feeding trial of tilapia with or without BEO (300 mg/kg) for 8 weeks (first phase), and further feeding trial of tilapia selected from phase first with or without BEO (300 mg/kg feed), florfenicol (200 mg/kg feed) for 2 weeks (second phase). The results showed that BEO has a broad-spectrum antibacterial effect on tilapia pathogens (Streptococcus agalactiae and Streptococcus iniae) and beneficial bacterial (Bacillus subtilis), but B. subtilis was a bit more sensitive to BEO than florfenicol. BEO added to feed significantly increased the intestine and serum amylase (AMS) activity (P < 0.05), decreased MDA content (P < 0.05) during 8 weeks feeding. In addition, BEO significantly increased the SOD activity (P < 0.05), decreased glycated albumin (GSP) and albumin (AIB) content (P < 0.05) of tilapia under hypoxia stress. Besides, BEO significantly decreased tilapia fillet MDA content (P < 0.05) after cold storage for 14 days. Contrast, BEO has no significant effect on growth and immunity and decreased the disease resistance (morality, 81% VS 41%) (P < 0.05) when compared to that of control group. In short, this study presents the positive effects of BEO on tilapia digestion, serum antioxidant and fillet freezing quality.

Automated summary

The study found that blend essential oil (BEO) has broad-spectrum antibacterial effects on tilapia pathogens and beneficial bacteria. It also showed positive effects on tilapia digestion, serum antioxidant levels, and fillet quality.