The optimum thymol requirement in diets of Channa argus : effects on growth, antioxidant capability, immune response and disease resistance

Abstract

In the present study, we aimed to evaluate the effects of dietary thymol on growth, antioxidant status, liver health, immune response and disease resistance of snakehead fish (Channa argus) (initial weight, 11.86 ± 0.15 g). The fish were fed for 56 days with a basal diet supplemented with thymol at 0, 150, 300, 450, 600 and 750 mg/kg, leading to six experimental diets. The final body weight (FBW), weight gain (WG), protein efficiency ratio (PER) and specific growth rate (SGR) were increased as dietary thymol level increased, arriving a summit value at 450 mg/kg dietary thymol level, and then, values of these indices started to decrease when dietary thymol level further rose, and feed conversion ratio (FCR) is the opposite state. Our results showed a significant increase (p < .05) in the superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH‐Px) activities in liver, spleen, head kidney and intestine with diets supplemented with 300 and 450 mg/kg thymol compared to the control and significantly decrease (p < .05) in the malondialdehyde (MDA) activity. Results showed that dietary supplementation with 300 and 450 mg/kg thymol significantly increased (p < .05) the serum acid phosphatase (ACP), alkaline phosphatase (AKP), lysozyme (LZM) activities and immunoglobulin M (IgM), complement 3 (C3), complement 4 (C4) concentrations of C. argus compared to the control, and decreased (p < .05) the serum glutamic‐pyruvic transaminase (ALT) and glutamic‐oxaloacetic transaminase (AST) activities. Moreover, the expression of HSP70, TNF‐α, IL‐1β and IL‐8 were down‐regulated in liver, head kidney and intestine by dietary supplementation with 300 and 450 mg/kg thymol, and the expression of IL‐10 and TGF‐β was up‐regulated. After challenge with Aeromonas veronii, survival rates in all thymol treatment groups were significantly increased (p < .05). Consequently, our results indicate that adequate dietary supplementation thymol can effectively enhance the growth, antioxidant status, immune response and disease resistance of C. argus, and the optimum dietary thymol requirement for maximum WG of C. argus was estimated to be 356 mg/kg.

Effects of thymol:carvacrol association on health and zootechnical performance of tambaqui Colossoma macropomum

“…Morselli et al (2020) revealed an increase in carp weight gain using thymol at concentrations of only 100 mg/kg. Kong et al (2021) defined a thymol concentration of 356 mg/kg for the best performance of snakehead fish, and Silva et al ( 2021) observed a better zootechnical performance of tambaqui fed 10 g/kg of carvacrol. The results of zootechnical performance in this study did not indicate differences between treatments, but the regression analysis revealed that there was a significant increase in the final weight of the fish as the level of supplementation with thymol:carvacrol increased.…”

Phytogenic Bioactive Compounds Shape Fish Mucosal Immunity

“…The effect of some single specific bioactive compounds related to aromatic plants of the Lamiaceae family, such thymol or carvacrol, upon mucosal tissues were also reported (Table 1). Although these studies have the advantage to associate a specific mucosal response to the administration of a specific compound, once again it is observed that most of them only reported the analysis of few immune and oxidative markers (97,98,101,103), or a limited microbiological examination (99, 100). In fact, few studies were observed to apply complementary analysis, or achieved to successfully discuss the multifactorial impact exerted by such nutritional strategies upon mucosal tissues (107,108).…”

Dietary Thymol Improved Growth, Body Composition, Digestive Enzyme Activities, Hematology, Immunity, Antioxidant Defense, and Resistance to Streptococcus iniae in the Rainbow Trout (Oncorhynchus mykiss)

“…Thymol (2-isopropyl-5-ethylphenol) (TYM), is the main phenolic compound of Thymus vulgaris essential oil, with antimicrobial properties [9], anti-inflammatory [10], and antioxidant [11] functions. Some studies have studied the effect of thymol as a dietary supplement on fish growth, hematology, and immunity ( [12][13][14][15]). However, there is a limited data on commercial fishes such as rainbow trout with thymol.…”

“…The antioxidant system is a vital part of fish immunity since it makes the first line of enzymatic and nonenzymatic defense against free radicals [16,17]. Although the enhancing effects of TYM on the antioxidant defense of vertebrates have been reported in many studies [14,[18][19][20][21], little is known with fish [13,[22][23][24]. TYM appears to stimulate the activity of the enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), and glutathione peroxidase (GPx) [15,25].…”

“…Inflammatory responses in fish are activated by cytokines such as Interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α), while other cytokines, such as transforming growth factor-β (TGF-β) and IL-10, act as anti-inflammatory molecules and prevent extra activation of the inflammatory responses and prompt tissue recovery processes [27]. TYM has been shown to moderate inflammatory reactions [10,[28][29][30], however, this is somewhat unknown in fish [13]. Apart from immune components, hematological indices are also used to evaluate the overall health of fish.…”