Dietary Supplementation with Fumaric Acid Improves Growth Performance in Nile Tilapia Juveniles

SIMPLE SUMMARY: The benefits of dietary supplementation with organic acids are commonly known in farm animals, especially swine and poultry, but these compounds are rarely exploited as additives to aquafeeds. Fumaric acid (FA) and its salts are among the most used organic acids in terrestrial animal feeds, but research with fish diets is limited. This study evaluated the inclusion of FA (0, 5, 10, 15, 20, and 30 g/kg) in the diets of Nile tilapia juveniles, and showed that supplementation improved growth, feed efficiency, protein use, and intestinal villi morphometry. Additionally, the population of undesirable intestinal bacteria was reduced (Gram-negative) or eliminated after 28 days (Enterobacteriaceae) in fish fed fumaric acid diets. Therefore, this study supports the addition of fumaric acid to the diet as a reliable strategy to improve the production and intestinal microbiota health of Nile tilapia juveniles. ABSTRACT: Organic acids have recently been identified as promising replacements for antibiotics in aquafeeds that promote fish growth and feed efficiency. This study evaluated the inclusion of fumaric acid (FA; 0, 5, 10, 15, 20, and 30 g/kg) in diets (350 g/kg CP; 3.4 kcal digestible energy/g) of Nile tilapia juveniles. Fish (average weight 1.7 ± 0.1 g) were distributed in three 40 L aquaria per treatment (13 fish/aquaria) in a completely randomized design. Over 35 days, the fish received the experimental diets three times daily to apparent satiety. The maximum weight gain, feed efficiency ratio, and protein efficiency ratio were recorded in fish supplemented with 14–15 g/kg FA. After 28 days, Enterobacteriaceae was registered only in the gut of tilapia without FA augmentation. Gram-negative bacteria in the fish gut decreased (p < 0.05) in fish receiving 17 g/kg of dietary FA, increased after this level. The intestinal villi height and width were affected (p < 0.05) by FA levels and feeding time. Thus, inclusion of 15 g/kg of FA was effective in promoting growth, improving intestinal morphometry, and decreasing negative gut bacteria of Nile tilapia juveniles after 35 days.