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There is a constant need to increase productivity in aquaculture, particularly to improve growth rate, feed utilization as well as stress resistance of fish. Because of consumer concerns and strict regulations in many countries, the use of synthetic chemicals, hormones and antibiotics is becoming unviable and natural compounds are more acceptable to the public. A wide variety of chemical compounds are found in plants, and many of them have been shown to have beneficial effects on appetite, growth and the immune status of fish acting through different mechanisms. Phytochemicals contained in herbs may enhance the innate immune system, possess antimicrobial capabilities, and are redox active molecules with antioxidant characteristics that may help to improve the general physiological condition of fish. Many studies have discussed the values of phytochemicals as feed additives. Another paramount concern related to phytochemicals is their endocrine modulator effect that can be applied both in aquaculture targeting the production of table fish and the growing sector of ornamental fish production. Different mechanisms such as the effects at the steroid receptor level, effects on steroid synthesis, distribution and excretion, actions on the hypothalamus-pituitary-gonad axis, as well as indirect mechanisms including thyroid and growth hormone disruption have been postulated for the reproductive endocrine disruption in fish populations by phytochemicals. This paper reviews the results of a great number of studies focusing on phytochemicals such as essential oils, saponins, flavonoids and phytosterols discussing their effects on productive traits and the putative mechanism of action. [ABSTRACT FROM AUTHOR]

Selenium (Se) supplementation in animal feeds for producing feasible foods was successfully experimented with in different meat-producing animals including fish. In the present study, Nile tilapia were fed Se-fortified diets (0.5, 2.0, or 4.0 mg/kg) ad lib for six weeks. In addition to traditional production traits, the antioxidant parameters glutathione (GSH), glutathione peroxidase (GPx), and malondialdehyde (MDA) in the blood, liver, and muscle of the tilapia, Se accumulation in the fillet, and body composition were determined. The highest Se value in the fillet was obtained with the diet containing 2 mg/kg supplementation, where the actual Se content of 2.47 mg/kg Se induced 128 µg/kg Se in the fillet. Selenium incorporation had a cubic relationship with the dietary Se content. [ABSTRACT FROM AUTHOR]

In the 21th century the more and more intense industrial activity of human civilization is based on the utilization of chemicals. A significant part of these chemicals gets into the environment and pollute it. Toxic elements - like heavy metals - from anthropogenic sources take part in biochemical cycles and can accumulate in plants and animals. This way they mean a significant risk to the living environment. In the last few years it is more and more accepted that the detection and tracking of heavy metal pollutants is based on their detection in living organisms. The detection and the tracking of fate of pollutants e.g. in water can be realized by the analysis of the accumulated heavy metals in fish and water plants. This method has a growing importance nowadays. In our experiments the fish was fed with a special fish food of copper. These feeding experiments were performed in the Fish Laboratory of the Faculty of Animal Science of Kaposvár University. The elemental analysis of the fish samples was performed by PIXE (Proton Induced X-ray Emission) and by ED-XRF (Energy Dispersive X-ray Fluorescence) methods in the Institute for Nuclear Research of the Hungarian Academy of Sciences in Debrecen. [ABSTRACT FROM AUTHOR]