Protein to energy ratios and cost, performance, and ammonia excretion in juvenile jundiá (Rhamdia quelen), South American catfish

Luiz Eduardo Lima De Freitas,Débora Machado Fracalossi,Tarcila Souza De Castro Silva

doi:10.1590/1678-992x-2020-0288

Luiz Eduardo Lima De Freitas, Débora Machado Fracalossi + Show 1 more

Open Access

https://doi.org/10.1590/1678-992x-2020-0288

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Abstract

ABSTRACT: The determination of nutritional requirements, based on diets administered in practice, considers physiological specificities and sustainability are essential to the development of suitable aquaculture technologies for novel fish species. The growth of jundia (Rhamdia quelen Quoy and Gaimard) juveniles (31.54 ± 4.92 g) fed five diets comprising increasing levels of digestible protein (DP: 24, 29, 34, 39, and 44 %) and digestible energy (DE: 12.13, 13.39, 13.81, 14.64, and 15.06 MJ kg−1) with DP:DE ratios: 20, 22, 25, 27, and 29 g MJ−1, respectively, was evaluated. Each diet was fed to three groups of 25 fish for 75 days. Regression analysis showed that the different DP:DE ratios affected both growth and economic performance as well as excretion of total ammonia nitrogen. Fish fed diets with DP:DE ratios between 22 and 27 g MJ−1 achieved a higher daily weight gain, superior apparent net protein utilization, feed conversion rates, and lower feed costs. For the economically viable and environmentally friendly farming of jundia juveniles in the initial grow–out stage (30 to 80 g average weight), the best DP:DE ratio was 25 g MJ−1 DP:DE (34.05 % DP and 13.81 MJ kg−1 DE).

Highlights

Protein, a high–cost nutrient in aquafeeds, is a key determinant of fish growth and, of the profitability of aquaculture systems (Guy et al, 2018)
DWG, SGR, and DDI increased, while FCR improved with the digestible protein (DP):digestible energy (DE) ratio increasing up to and including 27 g MJ–1
Regression analysis showed that the best daily weight gain was achieved with a ratio of 26.62 g MJ–1 DP:DE in the diet (38.64 % DP and 14.86 MJ kg–1 DE)

Summary

Introduction

A high–cost nutrient in aquafeeds, is a key determinant of fish growth and, of the profitability of aquaculture systems (Guy et al, 2018). A delicate balance between the amounts of protein and energy (P:E) in aquafeeds is needed, considering that feed consumption is largely determined by the energy content provided in the diet (NRC, 2011). Jundiá farming lacks species–specific technologies and the species is being commercially farmed using aquafeeds developed for other omnivorous fish, such as the Nile tilapia (Oreochromis niloticus L.). Jundiá is not a typical omnivore, presenting a short intestine (Gominho–Rosa et al, 2015; Rodrigues et al, 2012) and having less ability to utilize dietary carbohydrates than Nile tilapia has (Moro et al, 2010; Oliveira Filho and Fracalossi, 2006; Rodrigues et al, 2012)

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