Digestive enzymes in embryogenesis of Nile Tilapia, Oreochromis niloticus, GIFT strain

Abstract

Digestive enzymes reflect the characteristics digestive of the fish and influence the digestion and absorption of food. This study aimed to evaluate the activity of digestive enzymes (trypsin, pepsin, amylase and alanine phosphatase) in embryonic stages (eggs) and larvae originating from breeding of Nile Tilapia, GIFT strain, fed practical diets containing different levels of crude protein. The experiment will consist of 16 hapas, 9 females and 3 males in each, chipped, weighed and measured. The design is completely randomized design with four treatments and four replicates, and control, Tr1 (32 % CP) and other three treatments Tr2 (38 % CP), Tr3 (44 % CP) and Tr4 (50 % CP). The experiment is divided into three steps: 1) preparatory: receive the experimental diets 30 days before the implementation of the project and during the experiment (Jan., Feb. and March, 2014); 2) mating: biweekly during the three months, the eggs of only one female from each treatment (1 fêmea x 4 tratamentos x 6 coletas = 24 fishes) will be collected directly from the mouth, quantified (mL) and heavy. At time 0 (T0- cleavage), three subsamples of eggs shall be kept in liquid nitrogen to analyze the digestive enzymes, in a subsample Gilson to measure the diameter and the other subjected to histological techniques. The rest of the eggs will be divided in triplicate, incubated to monitor embryonic development (T1 - blastula; T2 - gastrula and T3 - hatching) and larval (T4 and T5 - 7 and 10th days of life) and 3) rest: by seven days remain separate females from males. The values of the activities of digestive enzymes and the average diameter of the eggs will be compared by treatment and subjected to ANOVA and the means were compared by Tukey test (5 %) (SAS, version 9.0). (AU)