The Use of Cinnamon Essential Oils in Aquaculture: Antibacterial, Anesthetic, Growth-Promoting, and Antioxidant Effects

Dietary supplementation of cinnamaldehyde positively affects the physiology, feed utilization, growth, and body composition of striped catfish Pangasianodon hypophthalmus

The study evaluated the effects of diverse cinnamaldehyde (CIN) supplementation doses on the physiological attributes, feed utilization, growth, and body composition of striped catfish Pangasianodon hypophthalmus. The study incorporated five doses of CIN supplementation, namely 0, 0.5, 1, 1.5, and 2 g kg-1 feed, with four replicates per group. Commercial extruded isonitrogenous and isoenergetic feeds with crude protein and gross energy levels of 28.46% ± 0.23% and 3858.70 ± 18.06 kcal kg-1, respectively, were used as test feeds. The initial weight of striped catfish was 5.57 ± 0.02 g, and 30 fish were maintained in each cage (2 × 1 × 1 m3) for 60 days. The results illustrated that the incorporation of CIN into the diet increases amylase and lipase levels and the ability of striped catfish to accumulate glucose, as the glucose tolerance test revealed that CIN 1.0 and 1.5 g kg-1 reduced glucose content to its basal level at 3-4 h postinjection and upregulated the insulin receptor, hexokinase, and hormone-sensitive lipase genes. CIN 1.5 g kg-1 also increased plasma total protein and high-density lipoprotein levels and reduced triglyceride and cholesterol levels. CIN 1.0-2.0 g kg-1 increased antioxidant capacity by increasing the levels of superoxide dismutase and glutathione and decreasing malondialdehyde levels. CIN 1.5 g kg-1 was the best treatment for increasing final weight, the specific growth rate, protein retention, and the protein efficiency ratio and for decreasing the feed conversion ratio. CIN additionally increased meat protein and decreased meat and liver lipid content. This study concluded that 1.24 g kg-1 is the optimal CIN dose calculated from the equation Y =  - 0.1487x2 + 0.3702x + 5.0724 (R2 = 0.71) to increase growth and feed efficiency in striped catfish by increasing nonprotein catabolism and exerting antioxidant effects.

Growth Performance and Disease Resistance against Vibrio parahaemolyticus of Whiteleg Shrimp (Litopenaeus vannamei) Fed Essential Oil Blend (Phyto AquaBiotic)

Acute Hepatopancreatic Necrosis Disease (AHPND) is a serious and emerging disease caused by a group of strains of Vibrio parahaemolyticus and affects farmed shrimp, particularly whiteleg shrimps (Liptopenaeus vannamei). The objective of this study is to assess the effect of dietary supplementation with two dosages of an essential oil mixture (Phyto AquaBiotic, abbreviated as PAB) on growth performance and mortality reduction after challenge against V. parahaemolyticus. PAB was mixed with basal diets at rates of 0, 1 and 2 g/kg and fed for 42 days. Each tank was stocked with 100 individuals with experimentation performed in triplicate. The results showed an improvement in growth performance in a dose-dependent manner, specifically regarding daily weight gain, specific growth rate and total biomass, which were significantly improved compared to control (p < 0.05). Further, PAB significantly reduced mortalities when challenged against Vibrio parahaemolyticus (p < 0.05) and decreased Vibrio spp. count in the hepatopancreas of infected shrimp. Overall, PAB was efficient in reducing mortalities in cases of disease outbreaks at a rate of 2 g/kg.

Tea Tree Oil Improves Energy Metabolism, Non-Specific Immunity, and Microbiota Diversity via the Intestine-Hepatopancreas Axis in Macrobrachium rosenbergii under Low Fish Meal Diet Administration

Tea tree oil (TTO) is an essential plant oil with diverse antibacterial and antioxidant properties; however, whether the role played by TTO in low fish meal (LF) diets induced the observed effects in the farmed crustaceans remains unclear. Therefore, this study used Macrobrachium rosenbergii as the model crustacean, and an 8-week feeding experiment with NF (normal fish meal), LF (soybean meal replacing 40% fish meal), and LFT (LF with 200 mg/kg TTO) diets was conducted to evaluate the positive effects of TTO under the LF diet. Compared to the NF diet, the LF diet reduced hemolymph antioxidant capacity and non-specific immunity, and induced hepatopancreas apoptosis and damage. However, in comparison with LF, LTF significantly ameliorated morphological impairment in the hepatopancreas, improved hepatopancreas energy metabolism by upregulating the Bcl-2/Bax and Akt/mTOR pathways, and enhanced antioxidant and non-specific immune capacity by activating the NF-κB/NO pathway. In addition, LFT repaired intestinal barrier injury and the imbalance of intestinal microbiota induced by the LF diet. Moreover, the Pearson correlation revealed the variations of the above indicators, which were related to the abundance changes of Klebsiella, Clostridium sensu stricto 12, Thermobifida, Bifidobacterium, and Alistipes, indicating that these microbes might serve as prospective targets for the intestine-hepatopancreas axis to affect hepatopancreas apoptosis, metabolism, and non-specific immunity. In summary, 200 mg/kg TTO supplementation mediated gut microbiota and positively improved energy metabolism and non-specific immunity, thereby alleviating hepatopancreas dysplasia and damage induced by the LF diet in M. rosenbergii.

Dietary Cinnamaldehyde Enhances Growth Performance, Digestion, Immunity, and Lipid Metabolism in Juvenile Fat Greenling (Hexagrammos otakii)

Fat greenling (Hexagrammos otakii) is a kind of economic fish that is widely consumed by human, and its intensive farming technology is making important progress. However, high-density farming may cause the occurrence of diseases in H. otakii. Cinnamaldehyde (CNE) is a new feed additive for aquatic animals and has a positive effect on disease resistance. In the study, dietary CNE was evaluated on the growth performance, digestion, immune response, and lipid metabolism of juvenile H. otakii (6.21 ± 0.19 g). Six experimental diets were formulated containing CNE at levels of 0, 200, 400, 600, 800, and 1000 mg/kg for 8 weeks. The percent weight gain (PWG), specific growth rate (SGR), survival (SR), and feeding rate (FR) were significantly increased by including CNE in fish diets regardless of the inclusion level (P < 0.05). The feed conversion ratio (FCR) was significantly decreased among the groups fed CNE supplemented diets (P < 0.05). A significant decrease in hepatosomatic index (HSI) was observed in fish fed 400 mg/kg-1000 mg/kg CNE compared to the control diet (P < 0.05). Fish-fed diets containing 400 mg/kg and 600 mg/kg CNE had a higher level of crude protein in muscles than the control diet (P < 0.05). Moreover, the activities of lipase (LPS) and pepsin (PEP) in the intestinal were markedly increased in juvenile H. otakii-fed dietary CNE (P < 0.05). Apparent digestibility coefficient (ADC) of dry matter, protein, and lipid was significantly increased with CNE supplement (P < 0.05). The activities of catalase (CAT) and acid phosphatase (ACP) in the liver were markedly enhanced by including CNE in juvenile H. otakii diets compared with the control (P < 0.05). The activities of superoxide dismutase (SOD) and alkaline phosphatase (AKP) in the liver were markedly enhanced in juvenile H. otakii treated with CNE supplements 400 mg/kg-1000 mg/kg (P < 0.05). Additionally, the levels of total protein (TP) in the serum were markedly increased by including CNE in juvenile H. otakii diets compared with the control (P < 0.05). In the CNE200, CNE400, and CNE600 groups, albumin (ALB) levels in the serum were markedly higher compared with that in the control (P < 0.05). In the CNE200 and CNE400 groups, the levels of immunoglobulin G (IgG) in the serum were significantly increased compared with that the control group (P < 0.05). The juvenile H. otakii-fed dietary CNE had lower triglycerides (TG) and total cholesterol (TCHO) levels in the serum than fish-fed CNE-free diets (P < 0.05). The gene expression of peroxisome proliferator-activated receptor alpha (PPAR-α), hormone-sensitive lipase (HSL), and carnitine O-palmitoyltransferase 1 (CPT1) in the liver was significantly increased by including CNE in fish diets regardless of the inclusion level (P < 0.05). However, fatty acid synthase (FAS), peroxisome proliferator-activated receptor gamma (PPAR-γ), and acetyl-CoA carboxylase alpha (ACCα) in the liver were markedly decreased with CNE supplements 400 mg/kg-1000 mg/kg (P < 0.05). The glucose-6-phosphate1-dehydrogenase (G6PD) gene expression levels in the liver were markedly decreased compared with the control (P < 0.05). The optimal supplementation level of CNE was shown by curve equation analysis to be 590.90 mg/kg.