β‐Carotene of Arthrospira platensis versus vitamin C and vitamin E as a feed supplement: Effects on growth, haemato‐biochemical, immune‐oxidative stress and related gene expression of Nile tilapia fingerlings

Abstract

Microalgae are one of the most important sources of natural bioactive compounds, especially those revealing antioxidant activity such as β-carotene. Thus, this study was to compare the effects of dietary Vitamin C (L-ascorbic acid) or Vitamin E (α-tocopherol) with β-carotene extracted from Arthrospira platensis on Nile tilapia (Oreochromis niloticus) on growth, feed utilization, blood indices, antioxidant activity, non-specific immunological indices and related gene expression. Three hundred and sixty apparent healthy Nile tilapia (5.80 ± 0.286 g) were randomly distributed into four groups. Four isonitrogenous and isoenergetic diets were performed. A control diet was compared against three experimental diets supplemented with Vitamin C (0.5 mg kg−1 diet), Vitamin E (1 g kg−1 diet) or β-carotene (0.5 g kg−1 diet) for 10 weeks. According to the results, there was no significant difference in feed intake (p > 0.05) between experimental diets. Dietary Vitamins C and E and β-carotene significantly (p < 0.05) enhanced the weight gain, final body weight, protein efficiency ratio, specific growth rate and apparent protein utilization in all groups, whereas the best FCR (p = 0.017) and the highest weight gain (p = 0.007) were detected in the β-carotene diet. Fish survival rates differed significantly (p < 0.05) amongst treatments, whilst fish fed a diet supplemented with β-carotene recorded the highest survival rate. The supplemental diet with β-carotene boosted the values of the biochemical and haematological parameters (p < 0.05) compared with the control diet. The activities of catalase, superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in the liver (p = 0.0560; p = 0.0032; p = 0.0353 respectively) and tilapia muscles were higher in fish fed either β-carotene or Vitamin E (p = 0.0579; p = 0.1494; p = 0.2145 respectively) than other groups. The highest values of SOD, CAT and immune globulin M-2 gene expression (p < 0.05) were found in fish fed a diet enriched with β-carotene. These results suggested that the dietary incorporation of β-carotene had a superior impact on growth performance, haemato-biochemical and immune-oxidative stress biomarkers in addition to the associated gene expression of Oreochromis niloticus.