Supplementation of Ulva lactuca in Feed Formulation to Enhance the Non-Specific Immune System of the Nile Tilapia Oreochromis niloticus

The Nile tilapia (Oreochromis niloticus) aquaculture faces numerous challenges, particularly bacterial infections caused by members of the Aeromonas genus. Such infections can result in high mortality rates within tilapia populations, especially when not promptly diagnosed and treated. The incorporation of natural ingredients such as Ulva lactuca into fish feed has been explored due to its potential to inhibit Aeromonas hydrophila, attributed to its antibacterial properties. Ulva lactuca contains ulvan with 12.80–23% sulfate, 12.73–45% rhamnose, 2–12% xylose, and 6.5–25.96% uronic acid, all of which contribute to its antibacterial activity. Therefore, this study aimed to evaluate the effect of dietary supplementation with Ulva lactuca on the growth performance of the Nile tilapia and its efficacy in suppressing Aeromonas hydrophila infection. The experiment consisted of four treatments with the addition of Ulva lactuca to feed formulation (treatment control (0%), A (8%), B (12%) and C (16)), and three replications were performed for each. The results showed that treatment B (12%) yielded the most favorable outcomes supported by a total leukocyte count of 98.000 cells/mm³ and phagocytic activity of 70% following the bacterial challenge. In addition, treatment B exhibited a high lymphocyte percentage on day 14 recorded at 102%.