Abstract
African catfish (Clarias gariepinus) were subjected to a 30-day feeding trial to determine the appropriateness of using plant protein (PP) (soybean and sunflower meal) as a fishmeal (FM) replacement in the diet and its effects on immune status, antioxidant activity, pituitary adenylate cyclase-activating polypeptide (PACAP) gene expression, and disease resistance. A total of 150 C. gariepinus (51.01 ± 0.34 g) were randomly distributed among five groups in triplicate. Five experimental diets were formulated to replace 0 (control), 33.5, 50, 66.5, and 100% FM with soybean and sunflower meal to form the experimental diets (R0, R33.5, R50, R66.5, and R100, respectively). After 30 days, the diet containing PP for FM had no significant impact on total, and differential leukocyte counts determined at the end of the feeding period. The total globulin concentration showed significantly greater differences in the following order R0 > R33.5 > R50 > R66.5 > R100. The R0 group had the highest concentration of serum γ-globulin, while R100 had the lowest concentration. The antioxidant status complements 3 (C3), lysozyme activity (LYZ), and antiprotease activity were not significantly different between R0, R33.5, and R50 groups, while they were significantly lower in R100. The serum nitric oxide activity (NO) exhibited significantly greater differences in the following order R0 > R33.5 > R50 > R66.5 > R100. PACAP was significantly higher in the R33.5 group. The highest cumulative mortality caused by Aeromonas sobria was recorded in the R100 group (60%) and the lowest in the R0 group (30%). In conclusion, the results indicate that the immunological responses and antioxidant status of C. gariepinus were not affected when they consumed a diet with FM replaced by up to 50% with PP (SBM and SFM) with methionine and lysine supplementation, but total globulin, NO, and cumulative mortality were impaired with a diet containing a 100% FM replacement.
Highlights
The development of the fish industry and the expansion of aquaculture have become necessary internationally, in developing countries, because of the nutritional, social, and economic value of fish
The serum ß- globulin concentration was significantly higher in the serum of R0 and R33.5 groups, followed by the R50 group, while the lowest concentration was recorded in the R66.5 and R100 groups
The effects of the interaction between feeding duration and levels of FM substituted with plant protein (PP) were assessed, and the results reveal that, in all groups, the total antioxidant capacity (TAC) level was dependent on time and level of FM substitution except in the R66.5 and R100 groups, where the TAC demonstrated better results after 15 days than 30 days of feeding (Figure 2A)
Summary
The development of the fish industry and the expansion of aquaculture have become necessary internationally, in developing countries, because of the nutritional, social, and economic value of fish. A settled source of fish is crucial for the nutrition and health of a wide segment of the globe [1] This sector provides employment and income in many developed and developing countries [2]. C. gariepinus is mainly characterized by its high growth rate, which is estimated to be at least three times that of other fish species [3]. It can be raised in a high-intensity culture without daily water exchange because its airbreathing capacity allows it to withstand poor water quality and low dissolved oxygen [4]. C. gariepinus is distinguished by a wide range of tolerance to high salinity levels [5], the ability to withstand various stresses [6], high fecundity [7], and high palatability
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