Effects of dietary vitamin C on growth, antioxidant activity, and immunity in ricefield eel (Monopterus albus)

Abstract

A 10‐week feeding trial aimed to investigate the effects of dietary vitamin C (l‐ascorbic acid) on growth, antioxidant activity, and immunity in ricefield eel, Monopterus albus. Six diets were formulated with different levels of vitamin C supplementation (0.1, 17.5, 34.8, 68.6, 139.7, and 278.5 mg/kg). The results indicated that the weight gain (WG) of the M. albus fed the diets with vitamin C was remarkably higher than that of the M. albus fed the control diet (p < .05), and the quadratic analysis showed an optimal vitamin C level of 80.66 mg/kg. Compared with the control group, serum lysozyme activities, the complement pathway, red blood cell counts, white blood cell counts, immunoglobulin M, and phagocytosis percentage were significantly increased (p < .05) in the treatment groups, and superoxide dismutase activity, serum glucose, and malondialdehyde content were significantly decreased (p < .05) in the treatment groups. The challenge trial with Aeromonas hydrophila showed that the M. albus fed the diets with vitamin C had remarkably reduced cumulative mortality compared with those fed the control diet (p < .05), and mortality in the 68.60 mg/kg diet group was the lowest. Based on WG, the optimal vitamin C supplementation level for M. albus was estimated to be 80.66 mg/kg.

Extreme temperature differently alters the effects of dietary vitamin C on the growth, immunity and pathogen resistance of Waigieu seaperch, Psammoperca waigiensis

“…Indeed, we found that the food conversion ratio was lower, and protein efficiency ratio and protein productive value were higher in fish fed with dietary vitamin C than those fed with basal feed diet. These results are in line with the findings of previous studies on cobia (Q. Zhou et al, 2012), ricefield eel (Hu et al, 2020) and Chu's croaker (Zou et al, 2020); all showed higher protein efficiency ratio when fed with vitamin C supplementary diets.…”

“…These results are in line with the findings of previous studies on cobia (Q. Zhou et al, 2012), ricefield eel (Hu et al, 2020) and Chu's croaker (Zou et al, 2020); all showed higher protein efficiency ratio when fed with vitamin C supplementary diets.…”

“…Plasma compositions such as triglyceride, glucose and total protein, as well as haematological components such as red and white blood cells, haematocrit, haemoglobin and platelets, are good indicators of animal health and immune response (Dawood & Koshio, 2018; Hu et al, 2020; Liang et al, 2017; Q. Zhou et al, 2012). In our study, the haematological parameters were strongly reduced under extreme temperatures.…”

“…White blood cells involve directly in cell-mediated immune response and phagocytosis to fight infections (Fazio, 2019;Qiang et al, 2013). Lysozyme is one of the most critical components of the innate immune system of fish, enabling them to act as the first-line defence against a broad spectrum of pathogens, particularly bacteria Hu et al, 2020;Saurabh & Sahoo, 2008). The reduced white blood cells and lysozyme activity at 32℃ suggest that P. waigiensis may be more susceptible to bacterial diseases as temperature rises.…”

“…The white blood cells of yellow catfish are not affected by dietary vitamin C levels (Liang et al, 2017), but it increases in ricefield eel (Hu et al, 2020). The lysozyme activity is positively correlated with supplements of vitamin C in the diet of Japanese seabass (Ai et al, 2004), large yellow croaker (Ai et al, 2006), cobia (Zhou et al, 2012), yellow catfish (Liang et al, 2017) and ricefield eel (Hu et al, 2020). In our study, the number of white blood cells and the lysozyme activity increased with increasing vitamin C in diets in a dose-dependent manner, suggesting that the supplement of vitamin C enhances the immunity of P. waigiensis.…”