Using natural nutraceuticals is a key strategy for aquafeed sustainability (Paray et al., 2021; Zhu, 2020). Diverse of medicinal herbal plants and microalgae have been validated as growth-promoting and immunostimulant agents in aquaculture (Adel et al., 2021; Mahmoud et al., 2018; Mohammadiazarm et al., 2021; Zahran et al., 2020; Zahran et al., 2021; Zhu, 2020). In this study, fish fed Cu-NPs and SP containing diets for 56 days exhibited pronounced improvements in the growth rate, SGR, and FCR of Nile tilapia fed Cu-NPs and SP. Dietry including of Cu-NPs has resulted in enhanced growth performance in Nile tilapia (O. niloticus) (Abdel-Tawwab et al., 2022), white leg shrimp (Litopenaeus vannamei) (Bhoopathy et al., 2021). Besides, dietary inclusion of curcumin improved the growth parameters in gilthead seabream in a dose-dependent manner for 150 days (Ashry et al., 2021). Enhanced growth performance was also reported in the juveniles of rainbow trout (Akdemir et al., 2017), common and grass carp fed curcumin diets (Giri et al., 2021; Ming et al., 2020). The curcumin growth-promoting effect could be related to its enhanced digestion activity via increasing the activities of lipase, trypsin, and amylase enzymes in intestine and hepatopancreas to facilitate absorption of nutrients and consequently amended nutrient utilization and feed efficiency (Abd El-Hakim et al., 2020; Jiang et al., 2016). Curcumin has an attractive flavor, concurrently it could augment the palatability of feed and therefore increased the feed intake (Alagawany et al., 2021).
It is well described that the dietary supplementation of Spirulina Arthrospira platensis has enhanced the growth performance of Nile tilapia (Awad et al., 2022), Caspian brown trout (Roohani et al., 2019), as well as Oscar fish, Astronotus ocellatus (Mohammadiazarm et al., 2021). These outcomes are attributed to the high contents of bioactive compounds in spirulina, involving polyunsaturated fatty acids, mainly γ-linolenic acid, polysaccharides, and also pigments such as total carotenoids; Zeaxanthin, β-carotene, chlorophyll, and phycocyanin (Awad et al., 2022; Roohani et al., 2019; Rosas et al., 2019). Furthermore, improved digestive enzyme activities in the intestine of aquatic species were assayed by dietary spirulina (Rosas et al., 2019; Teimouri et al., 2013). In this regard, the incorporation of Cu-NPs and SP in diets of Nile tilapia induced the serum activities of amylase, lipase, and protease enzymes. In similar studies, curcumin supplementation increased the activities of digestive enzymes as represented in fingerlings of Oreochromis mossambicus (Midhun et al., 2016), crucian carp (Jiang et al., 2016), and gilthead seabream larvae (Xavier et al., 2021). Recently, increasing the efficacy of digestive enzymes activities has improved the growth performance of Nile tilapia fed with graded levels of Cu-NPs for 60 days (Abdel-Tawwab et al., 2022). Moreover, dietary SP improved the digestive enzyme activities in the intestine of rainbow trout (Oncorhynchus mykiss) (Teimouri et al., 2013; Teimouri et al., 2016), and Oscar fish, Astronotus ocellatus (Mohammadiazarm et al., 2021), resulting in enhanced feed intake and decreased nutrient retention.
In the present study, fish body protein and ash contents were increased by dietary supplementation of Cu-NPs and SP after 56 days of feeding trial with no marked change in the lipid content. Recent studies demonstrated that long-term feeding with curcumin markedly enhanced the protein and ash contents of Nile tilapia muscles (Abd El-Hakim et al., 2020; Amer et al., 2022). Similar results were reported in Oscar fish, Astronotus ocellatus fed SP powder (Mohammadiazarm et al., 2021). Dietary SP increased the ash content of whole body and dorsal muscles along with significant decreased in lipid content in the juvenile gibel carp (Cao et al., 2018b). Data of growth performance with Cu-NPs and SP diets were confirmed by those findings.
Hematological features are reliable tools to assess the impact of herbal products on the health and nutritional status of fish (Vazirzadeh et al., 2017; Yonar et al., 2019). Our current study displayed that fish fed on Cu-NPs and SP diets improved RBCs and WBCs counts, including neutrophils and monocytes, as well as Hb concentration and Ht level compared with the control fish with no significant change in MCH level. These findings are consistent with previous researches, which assayed the positive effects of dietary curcumin and its nanoparticles analogues on the hematological parameters in a variety of fish species (Abdel-Tawwab et al., 2022; Ashry et al., 2021; Mohamed et al., 2020; Yonar et al., 2019). The enhanced hematological indices emphasized the salutary role of curcumin nanoparticles and spirulina on the health of Nile tilapia with no anemic symptoms with promoted mechanism of erythropoiesis and hemosynthesis, indicating the positive link of curcumin to the metabolic functions and availability of nutrients in the blood of Nile tilapia (Ashrafizadeh et al., 2020; Ashry et al., 2021; Fazio, 2019). Besides, increasing the percentages of neutrophils and monocytes in curcumin and Cu-NPs diets are associated with ameliorated properties of both innate and adaptive immune system of fish (Abdel-Tawwab et al., 2022; Moniruzzaman and Min, 2020; Pereira et al., 2020). Curcumin can probably activate the neutrophils and macrophages, to release reactive oxygen species (ROS) subsequent with increased the phagocytic activity, which is involved in immunity (Ashry et al., 2021; Jagetia and Aggarwal, 2007). In this regard, spirulina platensis had also ameliorated Hb, HCT, MCH and MCHC in Oscar fish (Mohammadiazarm et al., 2021), and this improvement is attributed to phycocyanin of spirulina platensis is known for its beneficial effects on the stem cells in the bone marrow, which promoted the cellular immune system and red blood cells of fish (Meng-umphan, 2008).
Lysozyme is a substantial hydrolytic enzyme of the innate immunity of fish, causing lysis of bacterial pathogens with triggering of the complement system and phagocytes (Saurabh and Sahoo, 2008). Serum immunoglobulins play a vital role in phagocytosis and killing of pathogenic microrganisms inside the fish body (Magnadottir, 2010). Our existing data indicated remarkable increase in lysozyme, and total Ig levels in Nile tilapia fed with C-NPs and SP. Curcumin administration showed marked augmentation of IgM values in rainbow trout (Yonar et al., 2019), as well it promoted serum immunity parameters (IgM and lysozyme) in snakehead fish (Channa argus) (Li et al., 2022). The highest lysozyme activity was detected in rainbow trout fed curcumin supplemented diets (Kohshahi et al., 2019). Curcumin nanomicelles-enriched diets displayed higher levels of lysozyme in L. vannamei (Moghadam et al., 2021), and in Nile tilapia (Abdel-Tawwab et al., 2022). Furthermore, a significant increment in the lysozyme mRNA expression was observed in the Cu-NPs fed L. vannamei shrimp (Bhoopathy et al., 2021). Affirmative effects of spirulina platensis on the inherent immunity of fish, including lysozyme activity were noticed earlier (Awad et al., 2022; Cao et al., 2018a; Mohammadiazarm et al., 2021). Our finding may be accompanied by the induction of the humoral immunity of Nile tilapia after Cu-NPs and SP administration as curcumin provokes cytokines production with activating of macrophages and neutrophils, which regulate the immunity response of fish (Jagetia and Aggarwal, 2007).
A holistic view is documented between the antioxidant property and fish immunity. Antioxidative enzymes, such as SOD, CAT, and GPx protect the cellular components from oxidative stress through induce the reduction of ROS into less reactive approach (Xavier et al., 2021). The product marker of lipid peroxidation, MDA indicates the oxidative damages to the lipids. Notable increases in the activity of SOD, CAT, and GPx enzymes together with significant reduction in levels of MDA were assayed in our study, indicating to the inducing effect of antioxidant activity of Cu-NPs and SP. Higher activity of SOD and CAT enzymes coupled with lower MDA levels were documented in L. vannamei fed with curcumin nanoparticles additives (Bhoopathy et al., 2021; Moghadam et al., 2021). Recent study investigated the enhanced effect of antioxidant activity of Nile tilapia fed Cu-NPs (Abdel-Tawwab et al., 2022). Comparable studies investigated the enhanced effects of spirulina platensis on antioxidant capacity of fish species (Awad et al., 2022; Mahmoud et al., 2018; Mohammadiazarm et al., 2021; Sayed et al., 2015; Teimouri et al., 2019). The antioxidant properties of curcumin are related with stimulating antioxidant enzymes and free radicals’ removal through activating the transcription of nuclear factor erythroid 2 (Nrf2) signaling pathway (Abdel-Tawwab et al., 2022; Xu et al., 2018). Besides, polyphenols donate hydrogen or electron with capability to maintain unpaired electrons, as well as they are nitrosation reaction inhibitors, preventing oxidative deterioration via ROS scavenging and promoting the antioxidant activities (Bishayee et al., 2011; Moskaug et al., 2005). Otherwise, the chemical compounds, such as β-carotene, C-phycocyanins, vitamins, and minerals are attributed to the antioxidant property of spirulina. In specific concern, phycocyanin is a biliprotein, having the ability to modulates cyclooxygenase-2, a prostaglandin-catalyzing enzyme and so it protects against oxidative deterioration (Awad et al., 2022; Karadeniz et al., 2009).
The noteworthy lowering in the levels of glucose, total cholesterol, and triglycerides were observed in Nile tilapia fed with Cu-NPs and SP diets. Oreochromis mossambicus fed with curcumin enriched diets has significant lower levels of blood glucose (Sruthi et al., 2018). Many reports documented that curcumin promoted the glycogenesis with decreasing the blood glucose level in Nile tilapia (Alagawany et al., 2021; Manal, 2018). Specifically, the previously mentioned the levels biochemical indices (glucose, total cholesterol, and triglycerides) were notably diminished in Nile tilapia fed with different doses of Cu-NPs enriched diets (Abdel-Tawwab et al., 2022). The dietary addition of curcumin reduced the contents of triglyceride and total cholesterol in serum of grass carp, tilapia, and amberjack Seriola dumerili (Yang et al., 2022). Our current study assayed the favorable regulatory effect of curcumin on lipid metabolism, reducing the biosynthesis of plasma and hepatic cholesterol and triglyceride levels (Guan, 2015; Shin et al., 2011). Also, polyphenol compounds of spirulina species are identified as a fat reducer (Kim et al., 2013), that attributed to reduced total cholesterol and triglyceride levels in fish fed Spirulina platensis (Mohammadiazarm et al., 2021).
The results showed marked favorable effects of Cu-NPs and SP on the biochemical blood metabolites of Nile tilapia related to liver function (ALP, AST, ALT), renal tissue markers (creatinine and uric acid), indicating their healthy condition without liver failure or functional damage to the kidney. Including both of curcumin in gilthead sea bream (Ashry et al., 2021), and Cu-NPs in Nile tilapia diets, has resulted in similar findings (Abdel-Tawwab et al., 2022). In line with that, supplementing with Spirulina platensis improved the liver and renal functions in Nile tilapia (Awad et al., 2022).
In the present study, dietary Cu-NPs and SP markedly increased total protein, albumin, and globulin concentrations in the blood serum of O. niloticus. Substantial augmentation of serum total protein have been investigated in rainbow trout fed curcumin (Yonar et al., 2019), as well as in Nile tilapia fish supplemented curcumin (Manal, 2018), and Cu-NPs (Abdel-Tawwab et al., 2022). Also, feeding L. vannamei on Cu-NPs-enriched diets showed higher serum total protein and albumin levels (Moghadam et al., 2021). Moreover, Nile tilapia fed a diet containing live spirulina had higher levels of protein, albumin, and globulins (Abdel-Tawwab and Ahmad, 2009). Total serum proteins elucidate the vital index of fish’s health and nutritional status (Zahran et al., 2021). Additionally, raised serum protein and globulin levels are correlated with a potent innate immune response in fish species (Kumar et al., 2013).
Fish health is threatened by many diseases and environmental pollution that is inevitable (Taghreed, 2019). Furthermore, the stress of confinement can induce tissue damage and production losses by lowering disease resistance (Steckert et al., 2018). Similarly, in the current study, the histology of different organs of fish in the control group reported tissue alterations. On the other hand, both groups receiving Cu-NPs and SP had less severe histopathological alterations emphasizing the positive role of nutrition on disease resistance. Likewise, previous research reported that nutrition can play a major role in the incidence and severity of many fish diseases through the modulation of the immune system (Blazer, 1992).