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

Crescimento e estruturas do sistema digestório de larvas de pacu alimentadas com dieta microencapsulada produzida experimentalmente

Foram comparados os efeitos de diferentes dietas e da transição alimentar sobre o desempenho zootécnico e a morfologia do trato digestório de larvas de pacu alimentadas com duas dietas comerciais e uma dieta experimental microencapsulada produzida por gelificação interna. Larvas com quatro dias de vida receberam os seguintes protocolos alimentares: somente náuplios de artêmia em quantidades crescentes (controle positivo); larvas mantidas em jejum (controle negativo); três tipos de alimento formulado durante todo o experimento (dieta experimental microencapsulada, dieta comercial NRD1.2/2.0, Inve, USA, e dieta Poli-Peixe 450F, PoliNutri, Brasil); e três protocolos de transição alimentar com náuplios de artêmia durante os seis primeiros dias, seis dias de coalimentação, e somente as respectivas dietas formuladas após esse período. O experimento foi conduzido por 23 dias em delineamento inteiramente casualizado, com avaliações periódicas do crescimento e do sistema digestório. A taxa de sobrevivência foi determinada ao final do experimento. Os melhores desempenhos de crescimento e sobrevivência, assim como mais acelerada organogênese do sistema digestório, foram verificados entre os animais que receberam alimento vivo. As larvas que passaram pela transição alimentar apresentaram médias intermediárias de crescimento e sobrevivência e não diferiram entre si. Entre os grupos que receberam apenas dieta inerte, somente naquele alimentado com a dieta nacional houve sobrevivência até o final do experimento. Nenhuma das dietas formuladas é adequada para uso como alimento exclusivo para larvas de pacu. Na fase de transição alimentar, a dieta experimental microencapsulada proporciona resultados de sobrevivência e crescimento semelhantes aos obtidos com dietas comerciais.The effects of different diets and dietary transition on the performance and morphology of the digestive tract of pacu larvae fed two commercial formulated diets and an experimental microencapsulated diet produced by internal gelation were evaluated. Four-day old pacu larvae received the following treatments: only artemia nauplii in increasing amount during the experiment (positive control); larvae maintained at fasting (negative control); three types of formulated diets throughout the experiment (experimental microencapsulated diet, commercial diet NRD1.2/2.0, Inve, USA, and diet Poli-Peixe 450F, PoliNutri, Brazil); and three weaning protocols in which artemia nauplii were given from the 1st to 6th days, six days of co-feeding (artemia nauplii + the respective formulated diet), and only respective diets formulated after this period. The experiment was conducted for 23 days in a completely randomized design, with periodical evaluations of growth and digestive system. Survival rate was determined at the end of the experiment.The best performances of growth and survival, as well as the organogenesis of the digestive tract, were verified for the animals which received live feed. The larvae at weaning treatments induced intermediate growth and survival, which did not differ statistically between them. Considering the treatments that received only formulated diets as first feed, the PoliNutri diet was the unique that showed alive larvae at the end of experiment. None of the formulated diets are adequate as initial exogenous food for pacu larvae. During the weaning, the microencapsulated experimental diet provides growth and survival performances similar to those obtained with the commercial diets

Early weaning of sea bass (Dicentrarchus labrax) larvae with a compound diet: Effect on digestive enzymes

International audienc

Ontogeny of the gastrointestinal tract of marine fish larvae

International audienc

Influence of diet on pepsin and some pancreatic enzymes in sea bass (Dicentrarchus labrax) larvae

International audienc

Dietary modulation of some digestive enzymes and Metabolic processes in developing marine fish: Applications to diet formulation

International audienc