Influence of dietary protein level and feed inputs on growth and feeding performance of the Nile tilapia under biofloc conditions

A. G., Amany,; Elnady, M.A.; Salem, M.A.I.; Metwally, N.E.

doi:10.21608/ejabf.2019.48627

Influence of dietary protein level and feed inputs on growth and feeding performance of the Nile tilapia under biofloc conditions

Document Type : Original Article

Authors

10.21608/ejabf.2019.48627

Abstract

The current experiment was designed to test the effect of crude protein content (25, 30 and 35% C.P.) as well as restricted feeding in biofloc culture on growth performance of Nile tilapia (Oreochromis niloticus) and water quality dynamics. The experiment included five treatments with duplicate tanks per treatment. Three normal feeding treatments and two restricted feeding treatments were adopted in the experiment. Two feed inputs were employed in the experiment: 1) The normal feeding rates which ranged 1.4 to 1.8% of fish biomass on daily basis according to season for the 25, 30 and 35% crude protein treatments, 2) The restricted feeding rate at 80% of the normal feeding rates (1.12 to 1.44% of fish biomass daily) according to season for the 30% and 35% crude protein treatments. Molasses were dissolved in water at dry feed to molasses ratio of 1:1 on a daily basis in order to develop biofloc and nourish heterotrophic bacteria. Starting with average initial weights of 13.5 to 20.3 grams/fish, Nile tilapia juveniles grew to harvest weight of 310.2 to 342.1 grams/fish. Increasing dietary protein from 30% to 35% within the biofloc treatments did not improve final body weight at harvest. Daily weight gains (0.82 g/fish/day) were slightly improved with the 30% crude protein diet compared to those of the 25% crude protein diet (p<0.05). Similar daily weight gains were obtained when fish were reared under the 30% restricted protein treatment (0.77 g/fish/day) compared to that of the 30% crude protein treatment. The higher crude protein content in the 35% crude protein treatment did not improve daily weight gain of Nile tilapia compared to the 30% crude protein treatment (p>0.05). It is recommended to feed Nile tilapia at crude protein level of 30% in order to obtain acceptable growth with economic returns. Nile tilapia reared under the 30% crude protein treatment had better PER ratio (1.96) and lower feed costs (15.11 L.E. /kilogram fish) at lower feeding rate compared to the 25% crude protein treatment.

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