Sargassum sp. extract improve hematological profile of tilapia fish ( Oreochromis niloticus ).

Background: Strategies to increase body resistance and prevent disease in aquaculture 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 Sargassum sp. Methods: This research was conducted from March to May 2022 at the Biotechnology Laboratory, Faculty of Fisheries and Marine, Universitas Riau, in two stages: 1) the sensitivity of extracts of Sargassum sp. and 2) the application of Sargassum sp. extract orally in tilapia ( O. niloticus ). The parameters measured were clear zone, minimum inhibitory concentration, LD 50 test of leaf extract of Sargassum sp. in tilapia ( O. niloticus ), hemoglobin levels, hematocrit, total leukocytes, total erythrocytes, leukocyte differentiation, and survival rate. Data on hematology parameters were tabulated and analyzed using a One-Way ANOVA followed by a Student Newman Keuls (SNK) test when deemed necessary. Results: The results showed that the extract of Sargassum sp. inhibited the growth of Aeromonas hydrophila 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 (LD 50 ). Hematological parameters can be a sign of the health status of fish. Tilapia given Sargassum sp. in different doses gave an effect between treatments, both after 30 days of rearing and post-test against A. hydrophila bacteria (p<0.05). The results showed that the hematology of fish fed with Sargassum sp. extract was in the normal or healthy range. Healthy tilapia had erythrocyte counts ranging from 1.34-2.11×10 6 cells/mm 3 , hematocrit 26.17-33.19%, hemoglobin 6.26-11.2 g/dL and total leukocytes 1.01-1.50×10 4 cells/mm 3 and total erythrocytes 5.88-9.13×10 4 cells/ mm 3 . Conclusions: A dose of 3000 ppm provided the highest health improvement against A. hydrophila bacterial infection.