KEBUTUHAN ASAM AMINO LISIN UNTUK BENIH IKAN KERAPU BEBEK (Cromileptes altivelis)

Percobaan penentuan kebutuhan asam amino lisin untuk benih ikan kerapu bebek (Cromileptes altivelis) telah dilakukan dengan metode pemeliharaan ikan menggunakan pakan yang mempunyai kandungan lisin berbeda. Ikan dengan bobot rata-rata 4,4 ± 0,3 gram dipelihara dalam bak polikarbonat volume 100 L dengan kepadatan 12 ekor ikan per bak. Setiap bak dilengkapi dengan sistem air mengalir dan aerasi. Pakan percobaan dibuat dalam bentuk pelet kering dengan kandungan protein 49% yang bersumber dari kasein dan tepung ikan serta campuran asam amino murni sehingga menyerupai komposisi asam amino tubuh ikan kerapu bebek, kecuali untuk lisin. Pakan percobaan mempunyai kandungan lisin berbeda, yaitu 1,77%; 2,27%; 2,77%; 3,27%; 3,77%; dan 4,27%. Ikan diberi pakan percobaan 2 kali sehari pada level satiasi selama 63 hari. Hasil percobaan menunjukkan bahwa bobot ikan akhir, persen pertambahan bobot, laju pertumbuhan spesifik, efisiensi pakan, retensi protein, dan kandungan protein tubuh ikan dipengaruhi oleh kandungan lisin pakan. Kadar optimum lisin dalam pakan untuk benih ikan kerapu bebek dihitung dengan regresi broken line berdasarkan data persen pertambahan bobot. Dari perhitungan ini diperoleh bahwa kebutuhan lisin untuk benih ikan kerapu bebek mencapai 2,77% dalam pakan atau setara dengan 5,63% dari protein pakan.The experiment to find out an amino acid lysine requirement for growth of humpback grouper juvenile has been conducted in 18 polycarbonate tanks, 100 liters volume. Each tank is equipped with flow-through water system. Twelve juveniles of humpback grouper (4.4 ± 0.3 gram in body weight), which were produced in hatchery, were randomly selected, and stock in each tank. Fish fed with experimental diets twice everyday at satiation level for 63 days. Experimental diets were prepared as dry pellet with casein and fish meal as the intact protein sources, and the mixture of crystalline amino acids to reach protein level of 49% and the composition of amino acid similar to the amino acid composition of whole body protein of humpback grouper, except for lysine content. Basal diet (diet-1) contains 1.77% lysine that was supplied from casein and fish meal. Graded level (0.5%) of crystalline lysine was added to the basal diet to get the final lysine level in each diet of 1.77%, 2.27%, 2.77%, 3.27%, 3.77%, and 4.27%. The experiment was designed according to completely random design (CRD) with 6 treatments (lysine levels) and three replicates for each treatment. Result of the experiment showed that dietary lysine content influenced final weight, weight gain, specific growth rate, feed efficiency, protein retention, and body protein content of humpback grouper juvenile. Optimum dietary lysine for humpback grouper juvenile was calculated using broken line regression analysis. Optimum dietary lysine requirement for growth of juvenile humpback grouper is 2.77% or equal to 5.63% of dietary protein