ABSTRAK Penelitian ini bertujuan untuk mengetahui pengaruh dosis probiotik RABAL yang terbaik pada media pemeliharaan benih Udang windu (Penaeus monodon Fab.) terhadap kelangsungan hidup, konversi pakan, pertumbuhan udang windu dan perubahan sel usus benih udang windu. Penelitian ini dilakukan pada bulan februari sampai dengan maret 2019 di Balai Perikanan Budidaya Air Payau (BPBAP) Ujung Batee, Kabupaten Aceh Besar, Provinsi Aceh, selanjutnya dilakukan pengukuran histomorfometri yang bertepatan di Labolatorium Patologi Fakultas Kedokteran Hewan Universitas Syiah Kuala. Penelitian ini menggunakan metode Rancangan Acak Lengkap (RAL) dengan 4 perlakuan dan 4 kali ulangan. Perlakuan yang diuji yaitu pemberian RABAL dengan dosis (A) 0 ppm, (B) 75 ppm, (C) 150 ppm, dan (D) 225 ppm. Frekuensi pemberian RABAL yaitu sekali sehari. Benih udang windu yang digunakan dengan rata-rata bobot 0,02 g/ekor. Berdasarkan hasil uji ANOVA diperoleh nilai terbaik pada perlakuan D (225 ppm) dengan nilai pertumbuhan bobot mutlak 0,46 g, pertumbuhan panjang mutlak 23,51 mm, laju pertumbuhan spesifik 11,35, kelangsungan hidup 72,92, rasio konversi pakan 1,3 dan diameter vili 0,82. Hasil penelitian menunjukkan bahwa pemberian RABAL dengan dosis berbeda ke dalam media pemeliharaan berpengaruh nyata (P0,05) terhadap kelangsungan hidup benih udang windu. Nilai parameter kualitas air pada penelitian ini masih pada kisaran normal untuk pemeliharaan udang windu. Kata kunci : Udang windu, probiotik (RABAL), kelangsungan hidup, konversi pakan, pertumbuhan dan vili udang windu. ABSTRACT This study aims to determine the effect of the best dose of RABAL probiotics on the maintenance media of tiger shrimp (Penaeus monodon Fab.) On survival, feed conversion, growth of tiger prawns and changes in intestinal cells of tiger shrimp. This research was conducted in February until March 2019 at the Pavau Aquaculture Fisheries Center (BPBAP) Ujung Batee, Aceh Besar Regency, Aceh Province, then conducted histomorphometric measurements which coincided at the Pathology Laboratory of the Faculty of Veterinary Medicine, Syiah Kuala University. This study uses a Completely Randomized Design (CRD) method with 4 treatments and 4 replications. The treatment that is administered is RABAL with a dose (A) of 0 ppm. (B) 75 ppm. (C) 150 ppm, and (D) 225 ppm. The frequency of giving RABAL Vaitu once a day. Tiger shrimp seeds used with an average weight of 0.02 g of tail. Based on the ANOVA test results obtained the best value in treatment D (225 ppm) with absolute weight growth value of 0.46 g, growth of 11.35, survival 99.58, feed conversion ratio of 1.3 and villi diameter 0 82. The results showed that the administration of RABAL with different doses into the maintenance media significantly influences (P-0.05) the growth and conversion ratio of wmdu shrimp feed but does not significantly affect (P> 0.05) on the survival of tiger shrimp. The value of water quality parameters in this study are still at normal levels for the maintenance of indu shrimp. absolute length 23.51 mm, specific growth rate of 11.35, survival of 72,92, feed conversion ratio of 1.3 and villous diameter of 0.82. The results showed that the administration of RABAL with different doses into the main tenance media had a significant effect (P 0.05) on the survival of tiger shrimp. The value of water quality parameters in this study is still in the normal range for the maintenance of tiger prawns. Keywords : Tiger prawns, probiotics (RABAL), survival, feed conversion, tiger shrimpgrowth and villi.