Introduction

Tilapias (dominated by Oreochromis niloticus) are the second largest group of farmed fish after carps and has become an integral part of human diets worldwide (FAO 2022). The sustainable production of tilapia is reliant on the provision of cost-effective formulated feeds. Although more prevalent in feeds for carnivorous fish and crustaceans, fish meal is also included in feeds for omnivorous fish like tilapia (Prabu 2019). However, fish meal has raised sustainability concerns as the wild fish supply will not meet the growing demand and will constrain aquaculture growth (Ghamkhar 2020).

In order to support the sustainable growth of global tilapia farming industry, a number of novel ingredients have been investigated as alternatives to fish meal, and these include fermented plant proteins, animal-derived protein, insect meals, and especially novel single cell proteins derived from bacteria, microalgae and yeasts (Hodar 2020). However, similar to plant ingredients, most of the novel ingredients are largely devoid of taurine as well (Gaylord 2006). Based on this information, the urrent study was undertaken to examine the effect of Nile tilapia when they are fed soy-based diets containing combination of single cell protein and taurine.

Experimental design

The experimental diets were divided into two diet formulas (Table 1): fish meal control diet (5%FM), and 50% of fish meal (2.5%FM) was replaced with UPF® with supplemented taurine at 0.5% (T0.5). The floating feeds (2mm) were produced at Feed Technology Center of Zhejiang NHU Co., Ltd., using typical extrusion process. The feeding trial was carried out at the RAS system in Aquaculture Research Station of Zhejiang NHU Co., Ltd. A total of 240 Nile tilapia (mean weight 56g) were randomly distributed to 8 400L fiberglass tanks, each holding 30 fish. The fish were exposed to continuous light (24 h) throughout the feeding trial, and the average water temperature was kept constant at 26-28°C. The daily feeding rate was 4.6%-5% of body weight, and the fish were fed one of the two diets in four replicate tanks for a feeding period of 49 days. During the experiment, the ammonia and nitrate were measured twice a week. At the end of the experiment, the fish performance was evaluated (survival, final body weight, specific growth rate, and feed conversion ratio). Also, five fish per tank were sampled for hematological analyses (triglyceride, acid phosphatase, alkaline phosphatase, aspartate transaminase and alanine transaminase) and antioxidant parameters (T-AOC, GSH-PX, SOD and MDA).

Results

Growth performance, feed utilization and body condition

The growth parameter and feed utilization results after fish were fed with various diets are listed in Table 2. The fish are in good condition and no mortality happened during the feeding period. Fish weight increased by a factor of 3-3.1 (FBW: 169-172g) at the end of feeding trial. Looking at fish performance, the trials showed that the T0.5 group performed better than the Control group (Table 2; Figure 1). SGR were higher in T0.5 group of fish compared with fish fed with the control diet (p < 0.05). No significant differences in feeding rate and FCR levels were found between the control group and other trial groups (p > 0.05). Significantly higher values of condition factor was observed in fish fed T0.5 diet (p < 0.05).

Hematological parameters

Results of serum parameters of fish fed experimental diets are shown in Table 3. The results revealed similar values of triglyceride (TG), acid phosphatase (ACP), alkaline phosphatase (ALP), aspartate transaminase (AST) and alanine transaminase
(ALT) among all dietary groups (p > 0.05).

Antioxidant Capacities

The results of antioxidant capacities of fish are presented in Table 4. No significant differences among treatments were observed for the antioxidant parameters in serum except for the T-AOC, which is higher in fish fed T0.5 diet (p < 0.05).

Taurine accumulation in fish fillet

There was a significantly higher response of taurine accumulation in T0.5 group compared with the control group (Figure 2, p < 0.05).

Economic Evaluation

The cost/benefit analyses of the experimented diets is presented in Table 5. The simple economic analysis of fish production in the present study showed that diet T0.5 had lower feed cost per kg fish and higher profit indices, in comparison with the value obtained with the control diet.

Conclusion

It is obvious from the results of the present study that supplementation of taurine does have a significant impact on growth and antioxidant capacity of Nile tilapia when they are fed soy-based diets containing single cell protein as partial replacement for fish meal. The economic analyses also show potential cost-competitiveness and culture profitability when adding taurine in the practical diets. Besides, dietary taurine attributes to taurine accumulation in farmed tilapia, meaning a better nutritional quality of the fish for the consumers (Bae 2022).

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Article made possible through the contribution of NHU Co., Ltd

The value of adding taurine in low-fish meal diet for tilapia