Introduction
Freshwater species like the giant river prawn (Macrobrachium rosenbergii) are a promising alternative to other farmed crustaceans due to their high market value and significant production, which reached 294,000 tons in 2020 (2.6% of total crustacean farming) (FAO, 2022). However, optimizing their nutrition remains a challenge, particularly in identifying sustainable protein sources.
Among the alternatives to fish meal, hydrolysed proteins from processed animal by-products (PAPs) such as hydrolysed feather meal (HFM) could offer a viable solution, improving feed efficiency while reducing waste. Despite their potential, research on the use of PAPs in freshwater prawn diets, particularly during early developmental stages like post larvae, is still limited.
This study evaluates the effects of HFM inclusion in M. rosenbergii post larvae diets, assessing growth performance, digestive enzyme activity, antioxidant status, and whole-body composition
Material and Methods
A total of 1600 M. rosenbergii postlarvae (0.021 ± 0.006 g) were distributed into 20 aerated 250-L tanks, each connected to a recirculating system with a Bead filter (1200 L h⁻¹ flow rate). Prawns were randomly assigned to five diets with different HFM inclusion levels (0.0%, 1.5%, 3.0%, 4.5%, 6.0%) and four replicates per diet. Diets were formulated to be isonitrogenous (44.2 ± 0.4% crude protein) and isolipidic (14.8 ± 0.1% crude lipids). Ingredients were ground (0.5 mm sieve), mixed, pelleted, and feeds stored at 4 °C until use. A 32-day feeding trial was run, which included five daily feedings (9:00, 11:00, 14:00, 17:00, 21:00). Tanks were siphoned before the first feeding to remove faeces and uneaten food. The initial feeding rate (10% of biomass) was daily adjusted daily based on consumption. Mortality was recorded twice daily. A 12 h light/12 h dark photoperiod was maintained. Temperature and dissolved oxygen were measured daily; total ammonia nitrogen and nitrite, three times a week; hardness and alkalinity, biweekly. Water parameters were within the recommended range for M. rosenbergii farming (mean ± SD): temperature 29.35 ± 0.91 °C, dissolved oxygen 6.10 ± 1.05 mg L−1, pH 8.34 ± 0.09, hardness 108 ± 19 mg CaCO3 L −1, alkalinity 107 ± 11 mg CaCO3 L −1, total ammonia nitrogen 0.011 ± 0.015 mg L−1, and nitrite 0.003 ± 0.29 mg L−1. At the end of the trial, survival, final weight, length, antenna length, biomass gain, and feed conversion rate were assessed. Hepatopancreases from 100 prawns (20 per diet) were collected to analyse digestive enzyme activity, antioxidant activity, and lipid peroxidation. Data were tested for homogeneity (Levene’s test) and normality (Shapiro–Wilk’s test). One-way ANOVA followed by Tukey’s test was used for analysis. Results are expressed as mean ± SEM, with p<0.05 considered statistically significant.
Results and discussion
Survival rates ranged from 73.3±5.4 % to 83.3±3.8 % without significant differences among treatments (p>0.05). All treatments with HFM inclusion showed significant higher final weight in comparison with the control treatment (p<0.05). Final weight, final length, and biomass gain were significantly higher in prawns fed diets with 6.0% HFM (p<0.05) and the feed conversion rate was significantly improved by the same diet (p<0.05). Additionally, prawns fed diets containing 4.5% or 6.0% HFM inclusion had significantly longer antennae (p<0.05), suggesting improved welfare conditions (Furtado et al., 2015).
Antioxidant status did not change according to the dietary treatment (p>0.05), suggesting that HFM did not induce oxidative stress or disrupt prawn redox balance. In details, thiobarbituric acid reactive substances (TBARS) averaged 0.94 ± 0.13 µM/mg protein; reduced glutathione (GSH) 1.70 ± 0.37 µM/mg protein; glutathione S-transferase (GST) 0.18 ± 0.04 nMol tioeter/min/mg protein; glutathione peroxidase (GPx) 0.88 ± 0.16 µM NADPH/min/ mg protein; and glutathione reductase (GR) 0.73 ± 0.18 µM NADPH/min/mg protein.
The lack of differences in digestive enzyme activity according to the diet suggests that HFM inclusion of up to 6% did not significantly alter the digestive physiology of prawns post larvae, both at carbohydrate (maltase: 11341 ± 2902 U/mg protein, on average; sucrase: 4266 ± 1233 U/mg protein) and protein (chymotrypsin: 4.94 ± 0.73 µmol/min/mg protein; trypsin: 1.54 ± 0.25 nmol/min/mg protein) digestion level. On the other hand, in Pacific white shrimp (Penaeus vannamei) fed 6% of HMF during the grow-out phase, higher levels of trypsin activity were recorded compared with the control diet, suggesting a potentially enhanced protein digestion (Negrini et al., 2024a), while no changes were observed in Pacific white shrimp fed similar diets during the nursery phase (Negrini et al., 2024b).
Conclusions
Hydrolysed feather meal inclusion up to 6% improved growth performance, feed conversion, and welfare in giant freshwater prawns without compromising digestive enzyme activity or antioxidant status. These findings suggest that HFM is a viable alternative protein source that supports efficient digestion and shrimp health. Additionally, its use promotes circularity also in crustacean aquaculture by valorising poultry by-products, reducing reliance on traditional protein sources, and enhancing the sustainability of prawn production.
References
FAO 2022 - FAO. The State of World Fisheries and Aquaculture 2022; Towards Blue Transformation: Rome, Italy, 2022.
Furtado P.S., Campos B.R., Serra F.P., et al., 2015. Effects of nitrate toxicity in the Pacific white shrimp, Litopenaeus vannamei, reared with biofloc technology (BFT). Aquacult. Int. 23, 315–327 https://doi.org/10.1007/s10499-014-9817-z
Negrini C., Nascimento Ferreira C.H., Kracizy R.O., et al., 2024a. Different protein hydrolysates can be used in the Penaeus vannamei (Boone, 1934) diet as a partial replacement for fish meal during the grow-out phase. Fishes 9, 73. https://doi.org/10.3390/ fishes9020073
Negrini C., Nascimento Ferreira C.H.d., Kracizy R.O., et al., 2024b. Partial replacement of fish meal with protein hydrolysates in the diet of Penaeus vannamei (Boone, 1934) during the nursery phase. Fishes 9, 75. https://doi.org/10.3390/fishes9020075
Financial Support
CONFAP - Secretaria de Ciência, Tecnologia e Ensino superior, Fundação Araucária e CNPq.