Countering the negative effects of dietary soybean (SB) meal in Nile tilapia with organic acid salts.

Abstract

While soybean meal (SBM) is a cost-effective protein source for Nile tilapia, its anti-nutritional factors require dietary interventions such as the supplementation of organic acid salts to maintain health and gut functions. Therefore, this study evaluated the dietary effects of organic acid salts as sodium propionate (PR), sodium butyrate (BT), and their mixture (PR + BT) on the growth, digestive enzymes, hepatic antioxidant responses and intestinal histomorphology of Nile tilapia fed a high SBM diet. Fingerlings (average initial weight ~ 19.65 ± 0.1 g) were assigned to five triplicate diets for 12 weeks: a negative control (CNT, contains 350 g/kg SBM), a high SBM diet (SB, contains 550 g/kg SBM), SB + PR (2.0 g/kg), SB + BT (6.25 g/kg), and their mixture (SB + PR + BT). Results revealed that fish fed solely on SB diet had significantly reduced growth, feed efficiency, and digestive enzyme activities, alongside higher levels of oxidative stress markers (MDA malondialdehyde levels) and intestinal inflammatory lesions (enteritis). Supplementation with PR, BT, or their mixture improved final body weight, weight gain, and feed conversion ratio. Digestive enzyme activities (lipase, amylase, protease) and antioxidant defenses (T-AOC, SOD, CAT, and GPx) were improved, while lipid peroxidation (MDA) was reduced in the treated groups. The histological examination confirmed that organic acid salts supplementation, especially PR + BT, alleviated SB-induced enteritis. Gene expression analysis revealed enhanced growth (IGF-2, GHR1, IGF-1, and GHR2) and immune-related markers (TLR2, and IFN-γ) and suppression of inflammatory (IL-1β, TNF-α, and caspase-3) related genes in the treated groups. In conclusion, PR and BT supplementation, especially in combination, effectively counteracted the negative impacts of high SB diets, supporting growth, alleviating inflammation, mitigating oxidative stress, and improving intestinal health of fish. These effects underscore the fascinating roles of organic acid salts in the improvement of aquafeed for tilapia culture.