The Israeli Journal of Aquaculture - Bamidgeh 55(4), 2003
The 7th Annual Dan Popper Symposium


David Sklan*

Faculty of Agriculture, Hebrew University, Rehovot 76100, Israel


The major purpose of fish cultivation is the production of high quality protein for human consumption. The predominant expense is feed,therefore improvements in uptake and efficiency of utilization will decrease production costs.It is important to know the proportion of the feed that is indigestible. This cannot be conveniently determined by simple input-output measurements but generally requires the use of markers to determine the availability of individual ingredients. Digestion commences with luminal hydrolysis, mainly by pancreatic enzymes in the gastrointestinal tract, and digestion of macromolecules at uptake sites, processes that are often rate-limiting steps in intestinal absorption. Synthesis, secretion and activation of pancreatic enzymes cannot be determined directly in the intestinal contents since the latter are not static. These factors have been addressed by determining mRNA expression for enzymes in the pancreas and by luminal marker studies. Further digestion and uptake occur on and within the brush border by membrane anchored enzymes and transporters which were examined by determining the expression of mRNA for the specific proteins and by measuring the digestion and uptake of labeled substrates.