article · Annals of Animal Science
Testing alternative feed ingredients is critical for aquaculture sustainability. In a 90-day feeding trial, genetically-improved farmed tilapia received diets supplemented with Azolla meal at concentrations of 10, 20, or 30 percent. Fish fed diets containing 10 percent and 20 percent Azolla meal achieved final body weights, weight gains, and feed conversion ratios that did not differ significantly from the control group. Conversely, a 30 percent inclusion level significantly suppressed growth performance and increased the feed conversion ratio. Digestive enzyme activities, proximate body composition, and immune markers such as lysozyme and phagocytic activity remained unaffected by Azolla across all levels. Supplementation also influenced gut morphology, increasing midgut villus length and goblet cell counts at higher inclusion rates, while sustaining normal haematological and biochemical functions.
Aquaculture producers continuously seek sustainable plant-based alternatives to standard feed ingredients to manage production costs. Demonstrating that Azolla meal can be incorporated into tilapia diets at up to 20 percent without impairing growth performance, digestive enzyme function, or vital immune responses provides fish producers with evidence on how to integrate alternative forage into aquafeeds safely.
This research provides applied dietary limits relevant to aquafeed manufacturers and tilapia farmers seeking alternative feed formulations. Given the specific inclusion testing, the approach is ready for farm-level feeding trials at up to 20 percent Azolla meal. Broader commercialisation will require reliable sourcing and processing of Azolla biomass, alongside formulation controls to prevent exceeding inclusion levels that impair feed efficiency.
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Abstract Azolla meal was included in fish feed at different levels (10%, 20%, and 30%) and was fed to genetically-improved farmed tilapia (GIFT) for 90 days. The obtained results demonstrated that the final body weight, weight gain, and specific growth rate decreased significantly in fish fed 30% Azolla (P<0.05), while tilapia fed 10% and 20% did not differ significantly from those of the control (P>0.05). However, the feed conversion ratio increased significantly in fish fed 30% Azolla (P<0.05), while tilapia fed 10% and 20% did not differ significantly from those of the control (P>0.05). The body proximate analysis, amylase, lipase, protease, blood phagocytic index, and phagocytic and lysozyme activity were not affected by the inclusion of Azolla in tilapia diets and remained similar to those of the control group (P>0.05). The villus length of the foregut was not significantly affected by Azolla inclusion in tilapia diets (P>0.05). In the midgut, the villus length significantly (P<0.05) increased in fish fed Azolla at 20% and 30% compared to the control, with no differences from those fed at 10% (P>0.05). The villus length significantly (P<0.05) increased in the hind gut in fish fed Azolla at 30 % compared to the control, with no differences from those fed at 10% and 20% (P>0.05). The mucosal length of the tilapia foregut significantly (P<0.05) increased in fish fed Azolla at 10% compared to the control, with no differences from those fed at 20% and 30% (P>0.05). In the foregut and hindgut, the number of goblet cells significantly increased in fish fed Azolla at 3% compared to the control, with no differences from those fed at 10% and 20% (P>0.05), while in the midgut, the number of goblet cells significantly (P<0.05) increased in fish fed Azolla at 20% and 30% compared to the control, with no differences from those fed at 10% (P>0.05). Feeding tilapia with Azolla resulted in normal hematological and biochemical functions, with insignificant differences for the measured parameters except for the red blood cell count, which significantly (P<0.05) increased in fish fed Azolla at 20% compared to the control, with no differences from those fed at 20% and 30%.
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DOI: 10.2478/aoas-2020-0016
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