Different expressions of trypsin and chymotrypsin in relation to growth in Atlantic salmon (Salmo salar L.)

The expressions of trypsin and chymotrypsin in the pyloric caeca of Atlantic salmon (Salmo salar L.) were studied in three experiments. Two internal (trypsin phenotypes, life stages) and three common external factors (starvation, feeding, temperatures) influencing growth rates were varied. Growth was stimulated by increased temperature and higher feeding rate, and it was depressed during starvation. The interaction between trypsin phenotype and start-feeding temperature affected specific activity of trypsin, but not of chymotrypsin. Trypsin specific activity and the activity ratio of trypsin to chymotrypsin (T/C ratio) increased when growth was promoted. Chymotrypsin specific activity, on the other hand, increased when there was a reduction in growth rate whereas fish with higher growth had higher chymotrypsin specific activity resulting in lower T/C ratio value. During a rapid growth phase, trypsin specific activity did not correlate with chymotrypsin specific activity. On the other hand, a relationship between specific activities of trypsin and chymotrypsin could be observed when growth declined, such as during food deprivation. Trypsin is the sensitive key protease under conditions favouring growth and genetically and environmentally affected, while chymotrypsin plays a major role when growth is limited or depressed. Trypsin specific activity and the T/C ratio value are shown to be important factors in the digestion process affecting growth rate, and could be applicable as indicators for growth studies of fish in captive cultures and in the wild, especially when food consumption rate cannot be measured

A piscicultura e o ambiente: o uso de alimentos ambientalmente corretos em piscicultura Fish farming and the environment: the use of environmental friendly feeds in fish culture

Embora a ciência da nutrição de peixes esteja longe de estabelecer um padrão geral de exigências nutricionais, a necessidade de desenvolvimento de alimentos de baixo impacto poluente há muito faz parte da agenda das comunidades científica e empresarial internacional da aqüicultura. Não só é absolutamente possível formular alimentos ambientalmente corretos, como é necessário modelar a formulação destes alimentos. Porém, é necessária absoluta acurácia para atender formulações espécie-específicas, considerando-se as interações da biologia e fisiologia nutricional das espécies com os alimentos e com as variações abióticas do meio. O conhecimento disponível sobre as mais de 200 espécies de peixe produzidas comercialmente no mundo é ainda incipiente e os sistemas de produção de peixe, nos diferentes regimes de exploração, estão implantados em todas as condições ecológicas possíveis. Neste cenário, produzir rações ambientalmente corretas é, senão impossível, pelo menos muito difícil e depende da ação coordenada e positiva de produtores, indústria da alimentação, agências regulatórias, e instituições de ensino e pesquisa para definir os parâmetros necessários à consecução deste objetivo.<br>Although fish nutrition science is far from establishing general standards of nutritional requirements, the need for developing low impact feeds has long been included in the agenda of aquaculture's international scientific and business communities of. Not only is absolutely possible to formulate environmental friendly feeds, as it is necessary modeling the formulation of these feeds. However, it is necessary higher accuracy to develop species-specific formulations, considering interactions of the biology and nutritional physiology of the species with the feedstuffs and variations of abiotic environment. The knowledge on more than 200 species of commercially farmed fish is still incipient and fish production systems, in their most varied farming conditions, are set up in every possible ecological conditions. In this scenario, producing environmental friendly feeds is if not impossible, at least very, very difficult, depending on coordinated and positive action of producers, industry, regulatory agencies, and institutions of higher education and research to define the parameters needed to achieve this goal