Enzymatic hydrolysis is a technology that is widely used to enhance the biological and functional characteristics of plant proteins and deactivate anti-nutritious components. In order to tackle this pressing issue, considerable research has been conducted on plant-based proteins as a potential substitute. This study sought to comprehensively examine the impacts of replacing fish meal with enzymatically hydrolyzed jojoba meal (EHJM) in the Nile tilapia, Oreochromis niloticus diets. After the enzymatic hydrolysis process for jojoba meal, hydrolyzed amino acid content increased in enzymatically hydrolyzed jojoba meal (EHJM), while fiber content, phytic acid, saponins, and trypsin inhibitors dramatically decreased. A thorough evaluation of key parameters included growth, gene expression, digestive enzyme activity, digestibility, intestinal histomorphometry, biochemical indicators, and antioxidant enzyme activity. Fish (n = 360, 6.41 ± 0.05 g fish−1) were allocated at random to four groups consisting of four replacement levels of fishmeal protein content with EHJM: 0 % (control diet), 25 % (EHJM25), 50 % (EHJM50) and 75 % (EHJM75) for 74 days. The results showed both the control diet and the EHJM25 groups showed remarkable improvements in performance metrics such as final body weight, specific growth rate, weight gain, feed conversion ratio, and protein efficiency ratio, with no discernible variations between them. The inclusion of EHJM up to 50 % produced a noteworthy (P < 0.05) rise in the intestinal lipase and amylase activities. Furthermore, a high apparent digestibility coefficient for crude lipid and protein values was observed in EHJM25% and EHJM50%. The presence of EHJM up to 25 % in tilapia diets, as a substitute for FM, had a significant impact (P < 0.05) on various parameters in the intestine, including goblet cells, muscularis mucosa, villi height, villi width, absorption area, and height muscularis. Moreover, the inclusion of EHJM with different levels in tilapia diets resulted in a noticeable reduction (P < 0.05) in alkaline phosphatase (ALP) and serum alanine aminotransferase (ALT) levels, with fish given the EHJM75% diet showing the lowest amounts in their plasma. In addition, the amount of plasma total protein, albumin, and globulin were found to rise sharply with the escalating replacement of EHJM in fish diet, reaching the highest values in the EHJM25% and EHJM50% diets. Interestingly, the catalase (CAT) and superoxide dismutase (SOD) levels in fish that were given the control diet and EHJM25% showed a remarkable increase compared to the other treatments (P < 0.05). Fish fed EHJM50% diet had the highest glutathione peroxidase and the lowest malondialdehyde levels. In addition, the fish that were fed the control diet exhibited the highest expression of insulin-like growth factor and growth hormone genes, compared to those fed the EHJM25% diet. Based on the results, the EHJM25% and EHJM50% diets were more effective than the EHJM75% diet in improving the efficiency of Nile tilapia. The inclusion of EHJM in Nile tilapia diets had a neutral effect on growth indices compared to a fishmeal diet (control diet). The optimal replacement level is 55.3 %.
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