PENGARUH PENAMBAHAN ASAM HUMAT PADA PAKAN MENGANDUNG KADMIUM (Cd) DARI KERANG HIJAU TERHADAP BIOELIMINASI Cd, STATUS KESEHATAN, DAN PERTUMBUHAN IKAN KAKAP PUTIH Lates calcarifer

Abstract

Asam humat (AH) terdiri atas AH alami (AHA) dan sintetik (AHS), namun efektivitasnya sebagai feed additive pada pakan ikan kakap putih belum dikaji. Tujuan penelitian ini untuk mengetahui efektivitas penambahan AH pada pakan yang mengandung kadmium (Cd) dari kerang hijau Perna viridis terhadap status kesehatan dan pertumbuhan ikan kakap putih, Lates calcarifer. Percobaan dirancang menggunakan rancangan acak lengkap (RAL) dengan lima perlakuan dan tiga ulangan. Perlakuan terdiri atas lima pakan uji mengandung AH yang berbeda, yaitu 0; 1.600; 10.000; dan 20.000 mg.kg-1 (AHA) dan sebagai pembanding menggunakan AHS sebesar 1.600 mg.kg-1 pakan. Benih ikan kakap putih (4,18 ± 0,25 g) dipelihara dalam akuarium ukuran 80 cm x 35 cm x 28 cm yang diisi air laut dengan sistem resirkulasi selama 70 hari. Ikan diberi pakan uji sesuai perlakuan tiga kali sehari sampai kenyang. Hasil penelitian menunjukkan penambahan AH baik jenis AHA maupun AHS pada pakan dapat menurunkan akumulasi Cd dalam daging, ginjal, dan hati; kedua jenis AH tersebut mampu mengeliminasi Cd di dalam daging ikan. Pada dosis 1.600 mg.kg-1 kedua jenis AH tersebut mampu meningkatkan performa pertumbuhan dan kelangsungan hidup ikan, namun pada dosis AHA > 1.600 mg.kg-1 pertumbuhannya relatif menurun. Pola respons pertumbuhan ikan bersesuaian dengan parameter hematologi, enzim pencernaan, dan status antioksidan di hati ikan. Kesimpulan penelitian ini, penambahan asam humat pada dosis yang sama (1.600 mg.kg-1) pada pakan, AHS lebih efisien dibandingkan AHA dalam hal meningkatkan pertumbuhan. Penambahan AH dari jenis asam humat alami dan sintetik dalam pakan uji dapat meningkatkan status kesehatan dan mengeliminasi Cd di dalam daging ikan. Penambahan AHA pada dosis tinggi pada pakan memberikan respons negatif terhadap status kesehatan, kelangsungan hidup, dan kinerja pertumbuhan ikan kakap putih.

Humic acids (HAs) are available in natural and synthetic forms. HA has potential applications in aquaculture, yet its effectiveness as a feed additive in Asian seabass, Lates calcarifer has not well studied. The purpose of this study was to asses the effectiveness of the addition of natural and synthetic humic acids to reduce cadmium (Cd) concentration in green mussels Perna viridis used for Asian seabass feed and evaluate the fish health status and growth performance. The experiment was designed using a completely randomized design (CRD) with five treatments and three replications. Five test feeds containing different levels of humic acid, i.e., 0; 1,600; 10,000; and 20,000 mg natural humic acid kg-1 feed. As a comparison, a test feed was added with 1,600 mg synthetic humic acid kg-1 feed. Asian seabass juveniles (4.18 ± 0.25 g) were cultivated in seawater aquarium equipped with a recirculation system for 70 days. Fifteen aquaria of 80 cm x 35 cm x 28 cm were used as the culture tanks. The fish were fed with the experimental diet three times every day at the satiation level. The results showed that the addition of both HAs (natural, AHA and synthetic, AHS) in feed could reduce Cd level in the fish meat, kidneys, and liver. At a dose of 1,600 mg.kg-1, both HAs were able to improve the growth performance and survival of fish. However, at doses > 1,600 mg.kg-1, fish growth was relatively suppressed. Fish growth response patterns were concomitant with the hematological parameters, digestive enzymes, and antioxidant status in fish liver. This study concludes that the addition of AHS at 1,600 mg.kg-1 feed is more efficient in terms of increasing growth compared with the same AHA level. The addition of HA, either natural and synthetic humic acid in the feed, can improve the health status of Asian seabass and eliminate Cd in the fish meat. The addition of AHA at higher doses (> 1,600 mg.kg-1 feed) might cause a negative response to health status, survival, and growth performance of Asian seabass.