Sargassum sp extract improve Hematological profile of Tilapia fish (Oreochromis niloticus)

Strategies to increase body resistance and prevent disease in cultivation include using vaccines, antibiotics, and probiotics. Today, the use of antibiotics with natural ingredients is becoming a trend. One of the natural ingredients that contain high antioxidants and antibiotics is <em>Sargassum</em> sp. This research was conducted from March to May 2022 at the Biotechnology Laboratory, Faculty of Fisheries and Marine, Universitas Riau. This research was conducted in two stages, namely 1) the sensitivity of extracts of <em>Sargassum</em> sp. and 2) the application of <em>Sargassum</em> sp. extract orally in tilapia (<em>O. niloticus</em>). The results showed that the extract of <em>Sargassum</em> sp. was able to inhibit the growth o<em>f Aeromonas hydrophila </em>bacteria with a clear zone of 6.5-15.0 mm, which is classified as resistant. At doses of 2000, 2500, and 3000 ppm, it did not cause death in fish for 96 hours (LD₅₀). Hematological parameters can be a sign of the health status of fish. Tilapia given to the addition of <em>Sargassum</em> sp. with different doses gave an effect between treatments, both after 30 days of rearing and post-test against <em>A.hydrophila</em> bacteria (p&lt;0.05). The results showed that the hematology of fish fed with <em>Sargassum</em> sp. extract was in the normal or healthy range. Healthy tilapia had erythrocyte counts ranging from 1.34-2.11 x10⁶ cells/mm³, hematocrit 26.17-33.19%, hemoglobin 6.26-11.2 g/dL and total leukocytes 1.01-1.50 x10⁴ cells/mm³ and total erythrocytes 5.88-9.13x10⁴ cells/ mm³. A dose of 3000 ppm provided the highest health improvement against <em>A.hydrophila</em> bacterial infection