Insect meal inclusion and nutritional programming affect the digestive process and growth performance of Nile tilapia (Oreochromis niloticus)

Abstract

The present thesis concerns issues with a high demand for knowledge, in four manuscripts. In the first manuscript, two trials evaluated the effects of feeding tilapia fry with Z. morio meal on (i) fry survival, growth performance, feed utilization, and carcass composition; and on juveniles (ii) growth performance, feed utilization, carcass and fillet composition, after fed increasing Z. morio meal (ZM) diets. Feeding fry with ZM increased survival, weight gain, feed utilization and carcass protein, energy and lipids. Juveniles fed with ZM during fry stage had better feed intake, feed conversion ratio and carcass weight when fed with a diet containing 300g/kg of ZM. In the second manuscript, three trials evaluated the influence of nutritional programming on the ability of tilapia juveniles to use diets containing an increasing concentration of Z. morio meal. The activity of digestive enzymes and chitinase, histomorphology of the intestine and apparent digestibility of the diets were evaluated. Increasing levels of ZM positively affect chitinase activity. The introduction of ZM during the fry phase improved the activities of trypsin and chymotrypsin, in addition to the digestibility of dry matter of juveniles fed with a diet containing 300 g/kg of ZM. Feeding fish continuously, from fry to juveniles, with Z. morio meal at high levels of inclusion improves the digestive capacity of fish and the use of insect meal, allowing inclusions of up to 300g/kg. The third study deals with the adequacy of the chitinase activity determination protocol for Nile tilapia. After a series of evaluations, a methodology was proposed to obtain adequate chitinase activity values for tilapia with reduced costs, time and with greater applicability. The fourth study discussed the ideal sampling procedure to capture the activity of the digestive enzymes: amylase, lipase, trypsin, and chymotrypsin at their best. Plasmatic glucose, cholesterol, and triglycerides were also evaluated. Overall, to sample the anterior portion of the intestine into the interval between 10- and 12-hours post-feeding is an adequate sampling procedure to be used in digestive enzymatic assays for Nile tilapia.