Judul: Depuration of Lead (Pb) from Nirwana Tilapia (Oreochromis niloticus) Using Coconut Cake and Palm Oil Cake Substituted Feed
Abstrak: Nirwana Tilapia is not only a popular fish for consumption in Indonesia but also an important aquaculture species. Nirwana is widely cultivated in locations with different water characteristics that can make the fish contaminated by various toxic and hazardous substances, including lead (Pb). Fish have the ability to absorb and accumulate Pb from the water in their body tissues, especially the tissues of the body that contains a lot of fat and muscle tissue such as the organs of the viscera. The process of absorption and accumulation is a mechanism that is unique and different for each fish species with the level of concentration which is linear with time. The Pb compound that accumulates can bring an effect which is lethal, sub-lethal and chronic to cultured fish and may experience biomagnifications in the food chain and will have an impact on human. Therefore, it is necessary to carry out post-fish harvest treatment of the cultured fish to clean up or reduce the concentration of Pb. The cleaning up or Pb reduction of fish can be done by depuration. The depuration method used in this research was by providing coconut cake and palm oil cake as substituted feed which have the ability to absorb Pb from the body tissues of fish since coconut cake and palm oil cake are actually vegetable materials that generally have coarse fiber and high fat. The coarse fiber in the diet is needed to assist in the digestion of food. The fat in the feed is expected to absorb large amounts of heavy metals deposited in the body tissues of fish. This study aimed to analyze the potential of coconut cake and palm oil cake for Pb depuration of nirwana. The research result would be benefitial information for farmers and the community of tilapia fishery, especially on the use of local products as alternative feed ingredients to improve food security through depuration mechanism. The treatments in this study were 100% commercial feed (Pk), 30% coconut cake + 70% commercial feed (PBB) and 30% palm oil cake + 70% commercial feed (PBS). The nirwana tilapia used with a weight of 100 ± 15 g. 10 fish were put in each plastic drum container corresponding with the number of treatments (3 treatments and 3 replications). Test fish were injected with 1 mg/L Pb(NO3)2 intraperitoneally. Each test animal was fed at satiation twice a day for eight days. The sampling was done on days two, four, six and eight. Parameters observed were Pb content in flesh, feces and water used in the raising activity, proximate flesh to find out the content of fat and coarse fiber in the fish flesh, histochemistry in liver and kidney, survivability, growth rate and water quality. The data analysis used was ANOVA and descriptive. AAS analysis results on flesh and feces proved that most of the Pb was excreted through feces. The highest concentration of Pb excreted through feces was in PBS treatment (1.46 mg/kg), while on days two, four, six and eight, the Pb concentrations were less than 0.001 mg/kg. The highest content of dietary
Keyword: coconut cake, palm oil cake, depuration, feed, tilapia nirwana

Judul: Supplementation of humic acid in the diet of tilapia Oreochromis niloticus cultured at water contaminated with lead (Pb)
Abstrak: Cemaran logam berat seperti Pb banyak ditemukan di beberapa perairan, baik danau maupun sungai, di Indonesia.Oleh karena itu, penelitian ini bertujuan mengevaluasi pengaruh penambahan asam humat dalam pakan terhadap kinerja pertumbuhan, histologi, dan kualitas daging ikan nila yang dipelihara pada air tercemar Pb. Terdapat empat perlakuan, yaitu penambahan asam humat ke dalam pakan sebanyak 0,0, 0,8, 1,6, dan 2,4 g/kg. Pakan-pakan tersebut diberikan ke ikan nila yang dipelihara di dalam air yang mengandung Pb 0,023-0,037 mg/L. Ikan nila berukuran 17,36±0,01 g sebanyak 15 ekor dipelihara pada akuarium berukuran 90x45x45 cm selama 55 hari. Ikan diberi pakan tiga kali sehari secara at satiation. Pergantian air dilakukan setiap hari sebanyak 95%. Perlakuan penambahan asam humat memiliki nilai laju pertumbuhan spesifik, jumlah kebutuhan pakan, rasio konversi pakan, rasio efisiensi protein, serta bobot akhir yang lebih baik dibanding tanpa penambahan asam humat. Humat 1,6 g/kg memiliki nilai biomassa yang berbeda nyata hingga 28,5% lebih tinggi dibandingkan Humat 0,0 g/kg. Terjadi kerusakan jaringan insang, hati, dan ginjal di seluruh perlakuan dengan tingkat kerusakan hati dan ginjal terparah pada perlakuan humat 0,0 g/kg. Humat 1,6 g/kg merupakan dosis optimal untuk ikan nila. Tidak ditemukan akumulasi Pb di daging ikan nila. Kata kunci: Asam humat, Oreochromis niloticus, Timbal (Pb), Heavy metal contamination such as Pb is found in several waters, both lakes and rivers, in Indonesia. Therefore, this study aimed to evaluate the effect of the addition of humic acid in the feed on the growth performance, histology, and meat quality of tilapia reared in Pb polluted water. There were four treatments, namely the addition of humic acid to the feed either of 0.0, 0.8, 1.6, and 2.4 g/kg. The feeds were given to tilapia reared in water containing Pb 0.023-0.037 mg/L. Fifteen tilapia measuring 17.36±0.01 g were kept in an aquarium measuring 90x45x45 cm for 55 days. Fish were fed three times a day at satiation. Water changes were carried out every day as much as 95%. The addition of humic acid had a better specific growth rate, total feed requirement, feed conversion ratio, protein efficiency ratio, and final weight than without the addition of humic acid. Humic 1.6 g/kg has a significantly different biomass value up to 28.5% higher than Humic 0.0 g/kg. There was damage to gill, liver, and kidney tissue in all treatments with the worst level of liver and kidney damage in the humic treatment of 0.0 g/kg. Humic 1.6 g/kg is the optimal dose for tilapia. No accumulation of Pb was found in tilapia meat. Keywords: Humic acid, Oreochromis niloticus, Lead (Pb)
Keyword: Humic acid, Oreochromis niloticus, Lead (Pb)

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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