Development of phytase transgenic Nile tilapia (Oreochromis niloticus)
Abstract
The feeding of plant proteins to fish results in generation of a high amount of phytate because fish cannot effectively digest it. The hydrolysis of phytate by microbes in the environment release P which can stimulate eutrophication. This study was conducted to express phytase gene from fungi, Aspergillus niger in the gastrointestinal tract of tilapia and to conduct feeding trials with the transgenic fish produced. The DNA construct used consist of CMV promoter, secretion signal, phy A gene and a terminator. Transgenic tilapia was produced with the construct, and germ line males were backcrossed (BC) with wild type females to generate BC1, and transgenic male from the cross was backcrossed to generate BC2 which were used for the feeding trial. Western blot analysis showed that 60 kDa phytase protein bands were present in the stomach, small and large intestines of transgenic tilapia and the stomach had additional 85 kDa band. The proteins had varying levels of glycosylation. Integration of phytase gene did not affect survival. It takes more than 10 weeks for P deficiency related mortality to significantly impact survival (%) in tilapia. Fish fed with basal diet supplemented with P had a significantly higher weight gain. Calcium to P ratio was constant no matter the genotype or diet. Fecal Ca was higher than dietary Ca which suggests that the fish were absorbing the element from water. High level of dietary Ca lowered the efficacy of both exogenous and endogenous phytase.
Degree
Ph.D.
Advisors
Muir, Purdue University.
Subject Area
Livestock|Molecular biology|Aquaculture|Fish production|Genetics
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