Feeding containing the aerial part of Scutellaria baicalensis promotes the growth and nutritive value of rabbit fish Siganus fuscescens

Abstract

The root of Scutellaria baicalensis (Scutellaria Radix) has been used as herbal medicine for years, while its stem and leaf (aerial part) are considered as waste. The water extract from the aerial part of S. baicalensis (named as SBA) being included in the feeding of Siganus fuscescens (grey rabbit fish) has been shown to replace antibiotics in aquaculture with excellent outcome. To strengthen the usage of SBA in fish feeding, the total fish output and its nutritive value were determined here. Feeding the fishes with different doses of SBA for a month, the body length and weight were significantly increased after intake of standard feed containing 1% SBA. In parallel, the expressions of alkaline phosphatase and growth-related factors in bone, liver, and muscle of 1% SBA-fed fishes were markedly increased, suggesting the beneficial effects of SBA. The composition of amino acid and fatty acid in fish muscle, after intaking 1% SBA-containing feed, was altered. In SBA-fed fish muscle, the amounts of threonine and methionine were increased, while the amount of leucine was decreased, as compared with control group. The amounts of fatty acids, including docosahexaenoic acid, phosphatidylcholine, and phosphatidylethanolamine, were increased in the 1% SBA-fed fish, while the amounts of triglycerides were decreased. The results indicated the growth-promoting activity of SBA in an in vivo culture of S. fuscescens, as well as to increase the nutritive values of the muscle. Thus, the re-cycle of waste products during the farming of S. baicalensis herb in serving as fish feeding should be encouraged.

Keywords: Scutellaria baicalensis; feed additive; growth promotion; nutrient content analysis.

FIGURE 1

The growth performance of S. fuscescens after treatment. The body length and weight of S. fuscescens (rabbit fishes) were measured every week (see Table S1). The final measurement of 4‐week treatment was presented here. The notations are as follows: 0.5% SBA extract (SBA_0.5), 1.0% SBA extract (SBA_1.0), 5.0% SBA extract (SBA_5.0), 0.1% enrofloxacin (ENR_0.1), and control (standard feed). Values are expressed as % of change to control group (as 0, control diet), in Mean ± SEM, where n = 4–5. Statistical comparison was made with the control group; *p < .05; **p < .01

FIGURE 2

The quality of muscle after different diets. The dorsal muscle was collected from 4‐week cultured fishes. The notations are as follows: 0.5% SBA extract (SBA_0.5), 1.0% SBA extract (SBA_1.0), 5.0% SBA extract (SBA_5.0), 0.1% enrofloxacin (ENR_0.1), and control (standard feed). (a): The water content in percent of muscle wet weight. (b): The content of soluble protein in muscle in mg/m. (c): The ash content in percentage of total wet weight. Values are in Mean ± SEM, where n = 6. Statistical comparison was made with the control group; *p < .05; **p < .01

FIGURE 3

Expression of ALP, MyoD, and LPL and growth‐related factors in fish after SBA feeding. The dorsal muscle was collected from 4‐week cultured fishes. The notations are as follows: 0.5% SBA extract (SBA_0.5), 1.0% SBA extract (SBA_1.0), 5.0% SBA extract (SBA_5.0), 0.1% enrofloxacin (ENR_0.1), and control (standard feed). (a): ALP enzymatic activity in bone and muscle. (b): The expression levels of MyoD and lipoprotein lipase (LPL) in muscle. The liver and dorsal muscle were collected from 4‐week cultured fishes. The expression levels of growth hormone receptor (GHR), insulin‐like growth factor I (IGF‐I), and insulin‐like growth factor II (IGF‐II) in liver (c) and muscle (d) were measured by RT‐PCR. The values are expressed as percentage of change to control. The values are normalized to the protein amount and expressed as percentage of change to control reading (as 0, control diet), in Mean ± SEM, where n = 6. Statistical comparison was made with the control group; *p < .05; **p < .01

FIGURE 4

The contents of amino acid in muscle after SBA feeding. The dorsal muscle was collected from 4‐week cultured fishes. The amounts of 12 kinds of amino acids (both D, L forms) were calculated. The values are expressed as percentage of change to control reading (as 0, control diet), in Mean ± SEM, where n = 4. Statistical comparison was made with the basal group; *p < .05; **p < .01

FIGURE 5

The contents of fatty acids in muscle after SBA feeding. The dorsal muscle was collected from 4‐week cultured fishes. (a): Eight fatty acids having significant difference between control group and SBA_1.0 group were shown here. FA 22:6 (docosahexaenoic acid), PC 34:1 (1‐oleoyl‐2‐palmitoyl‐sn‐glycero‐3‐phosphocholine), PC36:4 (1,2‐di‐octadecadienoyl‐sn‐glycero‐3‐phosphocholine), and PE40:6 (1,2‐diacyl‐sn‐glycero‐3‐phosphoethanolamine). And four triglycerides including TG 52:2 (1,2‐dioctadecenoyl‐3‐hexadecanoyl‐sn‐glycerol), TG 50:2 (1‐linoleoyl‐2‐isoheptadecanoyl‐3‐isopentadecanoyl‐sn‐glycerol), TG50:1 (1,3‐dipalmitoyl‐2‐oleoylglycerol), and TG 52:3 (1‐palmitoyl‐2‐linoleoyl‐3‐oleoyl‐sn‐glycerol). The values are expressed as the relevant amount, in Mean ± SEM, where n = 4. Statistical comparison was made with the control group; *p < .05; **p < .01. (b): The principal components analysis (PCA; upper panel) and orthogonal projections to latent structures discriminant analysis (OPLS‐DA; lower panel) on MS result from control diet and SBA_1.0 diet, where n = 6. (c): Metabolic pathway analysis by using MetaboAnalyst 4.0. The x‐axis represents the pathway impact value computed from pathway topological analysis, and the y‐axis is the log of the p‐value obtained from pathway enrichment analysis. The glycerophospholipid metabolism pathway shows the most significantly change with both a high‐log(p) value and high impact value