Growth and energy metabolism of Nile tilapia juveniles fed glycerol

Diego Vicente Da Costa,Marinez Moraes De Oliveira,Daniel Okamura,Renan Rosa Paulino,Priscila Vieira E Rosa

doi:10.1590/s0100-204x2015000500001

Diego Vicente Da Costa, Marinez Moraes De Oliveira + Show 3 more

Open Access

https://doi.org/10.1590/s0100-204x2015000500001

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Abstract

The objective of this work was to evaluate the effect of inclusion of dietary glycerol in replacement to starch on the growth and energy metabolism of Nile tilapia juveniles. The experiment was carried out in a completely randomized design with four treatments (0, 5, 10, and 15% purified glycerol) and six replicates. Pelleted, isonitrogenous, and isocaloric diets were provided for 60 days. Growth performance parameters and muscle glucose and protein concentrations were not affected by dietary glycerol levels. The treatment with 15% glycerol presented higher levels of muscle and liver triglycerides. A quadratic effect of treatments on muscle and liver triglyceride concentrations was observed. The treatment with 0% glycerol presented higher hepatic glucose levels than the one with 15%. Treatments did not differ for concentrations of liver protein, as well as of plasma glucose, triglycerides, and protein. Treatments with 10 and 15% glycerol showed higher activity of the glucose-6-phosphate-dehydrogenase enzyme than the treatment with 5%; however, there were no significant differences in the hepatic activities of the malic and glycerol kinase enzymes. A linear positive effect of treatments was observed on the activity of the glycerol kinase enzyme in liver. Levels of glycerol inclusion above 10% in the diet of Nile tilapia juveniles characterize it as a lipogenic nutrient.

Highlights

Aquaculture, as opposed to stagnating extractive fish production, has greatly developed worldwide in recent years
The objective of this work was to evaluate inclusion levels of dietary glycerol in replacement to starch on the growth and energy metabolism of Nile tilapia juveniles
These results corroborate those of Neu et al (2013), who did not find any difference in the growth performance of Nile tilapia fed different levels of dietary glycerol

Summary

Introduction

Aquaculture, as opposed to stagnating extractive fish production, has greatly developed worldwide in recent years. World production of food‐fish aquaculture expanded at an average annual rate of 6.2% in the period of 2000–2012, and Brazil has improved its global ranking significantly (Food and Agriculture Organization of the United Nations, 2014). In massive research to identify alternative ingredient sources (Olsen & Hasan, 2012), in order to replace finite or expensive feeds, without affecting fish growth performance and healthiness. One of the alternative ingredients that may be applied in fish feeding is glycerol, due to its current excess in the market as a result of the recent increase in worldwide biodiesel production. The biodiesel production process generates large amounts of crude glycerol or glycerin, which is the main coproduct and represents approximately 10% of the total production of biodiesel. The percentage of glycerol in glycerin ranges from 65 to 85% (w/w), and most of the impurities, such as free fatty acids, esters, salt, and residual alcohol, are formed by the reaction of lipids with alcohol in the presence of a catalyst

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