ARTICLE 66 FEED & ADDITIVE MAGAZINE January 2023 utilization of fish. The nutrient digestibility of fish increases with dietary inclusion of FPH with small molecular weight fractions in diets. Hence, the higher inclusion of FPH may negatively influence the digestibility in fish. Growth performance In order to the higher palatability and suitable peptide fractions (<10 kDa) produced from enzymatic process and molecular weight profile that improved the growth performance fish when fishmeal replaced by FPH. The replacement at 5-10 % of fishmeal with FPH improving growth performance of yellow croaker, Asian seabass and South American catfish juveniles. However, fish fed with higher FPH (≥20%) diets have been reported to decrease growth performance (Xu et al 2016; Siddik et al. 2018a). The higher hydrolysate levels leading to reduction in the growth performance may be due to an excessive number of short-chain peptides and free amino acids in these hydrolysed products, which could cause saturation of the peptide transport mechanism in the intestine. Also, higher amount of free amino acids could alter the absorption of amino acids leading to an increase of amino acid oxidation and reduced retention of dietary protein. Biochemical responses The replacement of low FM diet by FPH led to an increase in haematocrit, haemoglobin, total protein and cholesterol levels, and decrease level of plasma glucose and triglyceride levels may indicate that the dietary inclusion of FPH leads to better absorption of the hydrolysed protein and enhancement of the general health condition of fish. Dietary inclusion of FPH in fish diets may trigger the innate immune system and disease resistance of fish. Immunoglobulin M, lysozyme activity and complement C4 were significantly higher in fish fed with diets containing 10% and 15% FPH when compared to fish fed with the basal diet (Tang et al., 2008; Siddik et al., 2019b). The low molecular weight bioactive peptides in FPH may have immune stimulating and antibacterial property. CONCLUSION Consider the amount of by-products produced from fish processing industries every year. FPH is one of these by-products which has potential effects on growth and biochemical responses in aquaculture due to their strong functional and bioactive characteristics. Hence, further research needs to develop the hydrolysis process without rendering the characteristics of the FPH. References 1. Bhaskar, N., Benila, T., Radha, C., & Lalitha, R. G. (2008). Optimization of enzymatic hydrolysis of visceral waste proteins of Catla (Catla catla) for preparing protein hydrolysate using a commercial protease. Bioresource technology, 99(2), 335-343
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