Introduction
Fish meal (FM) is often considered as neither eco-friendly nor sustainable. Therefore, feed nutritionists are actively seeking reliable and cost-effective protein sources to substitute for FM. Meat meal (MM) has a lower cost (USD 0.86/kg, USD 1 = 1400 KRW) compared to FM (USD 2.03/kg), and it is classified into low-quality [≤ 75% crude protein (CP)] and high-quality (≥ 80% CP) MM based on their protein content. Among them, high-quality MM has advantages including high CP and lipid content, and year-round availability as a FM alternative in fish diets.
Red sea bream (Pagrus major), a carnivorous fish species, is a valuable species of marine fish in Republic of Korea and Japan. Gunathilaka et al. (2023) proved that 50% of FM could be replaced with high-quality MM (CP: 84.2%) without compromising growth and feed consumption when fingerling (initial weight of 50.2 g) red sea bream were fed with a 60% FM-based diet or one of diets replacing 50% of FM with plants, animals, or their blends.
The size (or age) of fish can greatly influence the substitutability of FM by alternative proteins in diets. In general, smaller (younger) fish are less likely to tolerate higher level of FM substitution. However, no study on the substitutability of high-quality MM for FM in juvenile red sea bream diets has yet been performed.
Therefore, this study aims to evaluate the impact of partial or complete FM replacement with high-quality MM in the diet on the growth performance and feed utilization of red sea bream.
Materials and Methods
The control (Con) diet contained 55% FM (Table 1). In the Con diet, the partial (20%, 40%, 60%, and 80%) or complete (100%) levels of FM were replaced with high-quality MM, referred to the MM20, MM40, MM60, MM80, and MM100 diets, respectively. All experimental diets were formulated to be isoproteic at 51.5% and isolipidic at 14.5%. A total of 450 juvenile red sea bream (7.9 ± 1.85 g; mean ± SE) were distributed into 18 of 50-L flow-through tank (25 fish per tank) with triplicate. All fish were hand-fed to apparent satiation twice a day for 8 weeks. At the end of the 8-week feeding trial, growth performance, feed utilization, blood chemistry, proximate composition, and amino acid and fatty acid profiles were analyzed.
Data were subjected to One-way ANOVA and Tukey’s honestly significant difference test using IBM SPSS Statistics for Windows, version 24.0 (IBM Corp., Armonk, NY, USA).
Results
Weight gain, specific growth rate (SGR), and feed consumption of fish fed the Con, MM20, and MM40 diets were significantly (P < 0.0001 for all) higher than those of fish fed the MM60, MM80, and MM100 diets (Fig. 1 and Fig. 2). In regression analysis, linear relationships were revealed to be the most suitable model between dietary elevated MM replacement for FM (X) and weight gain (Y = – 0.145434X + 31.6540, R2 = 0.9253, P < 0.0001), SGR (Y = – 0.008442X + 2.9195, R2 = 0.9161, P < 0.0001), and feed consumption (Y = – 0.133145X + 32.5305, R2 = 0.9213, P < 0.0001), respectively. In orthogonal polynomial contrast, weight gain and feed consumption of red sea bream revealed linear (P = 0.0001 for both), quadratic (P = 0.002 and P = 0.014, respectively), and cubic (P = 0.030 and P = 0.019, respectively) relationships with dietary MM replacement levels for FM, but SGR revealed linear (P = 0.0001) and quadratic (P = 0.001) relationships with dietary elevated MM replacement for FM. However, blood chemistry, proximate composition, and amino acid profiles of fish were not significantly (P > 0.05) influenced by dietary FM replacement with MM.
Conclusion
FM up to 40% could be replaced with MM in a 55% FM-based diet without significantly impairing the growth performance and feed utilization of juvenile red sea bream.
References
Gunathilaka, B.E., Jeong, S., Cho, M., Kim, K., Hur, S., Lee, S., You, S., Lee, S., 2023. Effects of dietary fish meal replacement with alternative protein ingredients and their combinations on growth performance, feed utilization, fillet composition, and biochemical parameters of red seabream (Pagrus major). Aquac. Nutr. 2023.