Diet components as internal indicators in the determination of the apparent digestibility coefficients for Nile tilapia

Rafael Lopes Da Silva,Luiz Edivaldo Pezzato,Flavia Mota Damasceno,Margarida Maria Barros,Paulo Roberto De Lima Meirelles,Jakeline Marcela Azambuja De Freitas,Maria Márcia Pereira Sartori,Eric Portilho De Araújo,Mariucha Karina Honório Ribeiro Rocha

doi:10.1590/s0100-204x2017000600003

Abstract

Abstract: The objective of this work was to evaluate the diet components - crude fiber, neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, and lignin - as internal indicators in the determination of the apparent digestibility coefficients of dry matter, gross energy, and of the nutrients - crude protein, phosphorus, and amino acids - in Nile tilapia (Oreochromis niloticus). Groups of ten juveniles (80.3±1 g) were randomly distributed in six tanks of 250 L and fed two practical diets, either of a plant-origin diet or of a plant- and animal-origin diet. Both diets were supplemented with 0.1% chromium (III) oxide (Cr2O3). Faeces were collected by the modified Guelph system. The apparent digestibility coefficients were determined by the content difference of the internal indicators, present in the diets and faeces, and compared by Dunnett’s test to those obtained by the use of Cr2O3. Cellulose was effective in the determination of the apparent digestibility of dry matter, energy, and nutrients of both experimental diets; and the acid detergent fiber was effective only for the diet composed exclusively of plant-origin ingredients. The use of crude fiber, neutral detergent fiber, hemicellulose, and lignin as digestibility indicators was inefficient for the analyzed nutrients of both diets. Therefore, cellulose is the most suitable indicator for digestibility evaluation in Nile tilapia.

Highlights

In intensive animal farming, feed is the main or exclusive source of nutrients for fish, accounting for 50–70% of production costs (Guimarães et al, 2008a)
The diet with animal- and plant-origin ingredients showed a higher percentage of crude fiber (CF), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, and cellulose than the diet containing exclusively plant-origin ingredients (Table 2)
There is a result reported on a study on tambaqui (Colossoma macropomum) whose ADF provided values which differed from those obtained with Cr2O3, when the digestibility coefficients of dry matter (DM) and crude protein (CP) of finely ground corn and soybean meal were evaluated (Vidal Junior et al, 2004)

Summary

Introduction

In intensive animal farming, feed is the main or exclusive source of nutrients for fish, accounting for 50–70% of production costs (Guimarães et al, 2008a). The use of feeds that are not properly balanced reduces the absorption of nutrients by fish, which results in excess organic. Under tropical conditions, this excess is rapidly mineralized and becomes readily available for phytoplankton growth, with a consequent decrease of water transparency and change of water quality. A decrease occurs in the concentration of dissolved oxygen, especially at night, leading to respiratory and biochemical stresses that induce to serious fish health risks, and to possible production losses (Cyrino et al, 2010). The apparent digestibility coefficient of the nutrients is not determinant in the choice of feeds, whether due to the absence of these values as a rule, or to the difficulty of obtaining them, without reprocessing the feeds, for the inclusion of an external indicator of digestibility

Objectives

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Conclusion