Utilization of carbohydrates by shrimp

Resumen

Glucose metabolism was extensively studied in Crustacea during the 60's and 70's with an
emphasis on decapods. In decapods juveniles can be described precisely at each step of intermolt cycle which
last longer than penaeid ones (Aquacop, 1972) and qualified as diecdysis. Consequently metabolic pathways
for glucose can be described accurately. This basic approach in decapods can help understand metabolism in
shrimp. Comprehension of metabolic pathways lead to draw the outlines for carbohydrate utilization by
shrimp: after going through main carbohydrates (CBH) sources, digestibility, glucose tolerance test, utilization
by whole animal, hepatopancreas glycogen, pathways of CBH breakdown such as glycogenolysis, glucolysis,
substrate cycle, minor pathways, aerobic breakdown, CBH synthesis and glucose utilisation. The diabetic like
shrimp is under the pervasive influence of the molting process. Shrimp derives energy from CBH. Even
though protein can easily supply energy too through gluconeogenesis. Related to the balance between protein
and calories, shrimp sustain optimal growth even at high dietary protein. Maximal growth rate of juveniles can
be achieved with high dietary protein level (50-60%) but CBH can play a role in sparing protein for optimal
growth in practice. CBH under starch form will represent up to 20-30%. A good comprehension of CBH
metabolism will lead to a greater supply of plant protein sources (soybean meal, pea meal, lupin, canola, wheat
gluten, rice bran, distillers) in shrimp feed. A recycling of chitin is done with the re-ingestion of exuviae, which
tend to underline the capability for chitin hydrolysis. Can ponds natural productivity help to maintain constant
food supply leading to a high glycemia level compared to tank experiments where a zero food supply during 12
hours makes a difference? Keeping that in mind, the formulator will propose diet with as much CBH as
possible, taking into account the potential to digest it, whether under native or pre-cooked form, the structure of
CBH (ratio amylose / amylopectin), the possibility to stimulate enzymes of intermediary metabolism. To a
certain extent it will lead to a great respect of the environment when reducing phosphorous output (wastes). Up
to which extent CBH can fit with immune response in regular grower feed for shrimp is worth to be addressed.
Complex CBH could represent a potential source of stimulants for immune response.