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.