The effect of dietary protein
and total energy content on digestive enzyme activities, growth and survival
of Litopenaeus setiferus (Linnaeus 1767) postlarvae
C.
The
effect of dietary protein and energy content on the activity of digestive
enzymes (total proteinases, trypsin, chymotrypsin a-amylase and lipase), and
growth and survival of Litopenaeus setiferus postlarvae was
investigated under controlled conditions. There was a clear relationship
between the diet fed to the postlarvae, growth and survival. Highest weight
gain (2110 ± 96.7%) was obtained with a 400 g kg-1
protein and low energy diet (13.9 kJ g-1) (P < 0.05).
The optimal protein to energy ratio (P/E) estimated was 28.8 mg of
protein kJ-1. Good survival was obtained with low energy diets
containing between 200 and 400 g kg-1 protein and with
high energy diets containing 300–500 g kg-1 protein.
Higher values for total proteinases, trypsin and a-amylase were obtained
with the low energy, 400 g kg-1 protein diet.
Chymotryptic activity was considerably lower than that of other proteinases
and lipase activity was too low to be reliably measured with the
turbidimetric method employed. Total proteinase activity was significantly
lower than in experimentally grown postlarvae. The a-amylase activity was at
least two orders of magnitude higher in wild postlarvae than in animals fed
with the best experimental diet. Protein requirement was related to total
energy content of the diet: best growth and digestive enzyme activity
coincide with the low energy, 400 g kg-1 protein diet.
These results suggest that dietary carbohydrates cannot spare protein
because growth rates obtained with diets containing 200–300 g kg-1
protein (337 and 226 g kg-1 dextrin content,
respectively) were significantly lowered.
(Laboratorio
de Ecofisiología, Fac. de Ciencias, UNAM, Sede Cd. del Carmen, Campeche,
Mexico)