Apparent digestibility coefficient of duckweed (Lemna minor), fresh and dry for Nile tilapia (Oreochromis niloticus)

126 Dry matter (DMD), protein (PD), ash (AD), fat (FD), gross energy (ED) and phosphorus (PhD) digestibility coefficients were determined for five different iso-N fish diets fed to Nile tilapia (Oreochromis niloticus). Control diet contained, fish meal (35%), corn (29%), wheat (20%), wheat bran (10%), fish oil (3%), diamol (2%) and premix (1%). Partial replacement of dry matter of fishmeal, corn grain, wheat grain, wheat bran and fish oil by 20% and 40% of dry matter of duckweed, dry and fresh was performed. Diets of the treatment 1 and 2 included 20%) and 40% of duckweed, respectively in a dry form. In treatment 3 and 4, tilapia received formulated diets 4 and 5 in addition to 20% and 40%> fresh duckweed providing the same amount of dry matter and protein as in control. Specific growth rates of tilapia were https://www.w3.org/1998/Math/MathML" display="inline"> 1 . 51 ± 0 . 07 , https://www.w3.org/1998/Math/MathML" display="inline"> 1 . 38 ± 0 . 03 , https://www.w3.org/1998/Math/MathML" display="inline"> 1 . 31 ± 0 . 06 , https://www.w3.org/1998/Math/MathML" display="inline"> 1 . 44 ± 0 . 02 and https://www.w3.org/1998/Math/MathML" display="inline"> 1 . 33 ± 0 . 05 , in control and treatments 1 to 4. There was no significant difference between SGR for control diet and diet with 20% fresh duckweed while the other treatment groups had significantly lower SGR. All of the treatment diets provide good values for feed conversion ratios (FCR) and protein efficiency ratio (PER). The average values of FCR were 0.91, 0.98, 1.10, 0.98 and 1.10 for control and treatments 1 to 4 respectively. The average values of PER were 3.0, 2.8, 2.5, 2.9 and 2.6 in control and treatments 1 to 4, respectively. Except for treatment 2, which has higher significant faeces recovery (collected -faeces to total faeces excreted) percentage https://www.w3.org/1998/Math/MathML" display="inline"> ( p < 0 . 05 ) there was no significant differences between control and treatments. Faeces recovery in treatment 1 was significantly lower https://www.w3.org/1998/Math/MathML" display="inline"> ( p < 0 . 05 ) than the other treatments but not control. There was no significant difference between the dry matter content of faeces except in treatment 4, which had lower significant value in comparison to control and treatment 2. DMD ranged from 61.8% in treatment 4 to 85.2% in control. All the diets have high protein digestibility (88.4%o-93.9%o) and high-energy digestibility (78.1%-90.7%). Digestibility coefficients were determined for dry and fresh duckweed. DMD of duckweed were 66.8, 63.3, 45.8 and 28.3 in treatments 1 to 4, respectively. PD values were 78.4, 79.9, 77.6 and 75.9 while ED values were 59.8, 60.9, 64.5 and 58.4 in treatments 1 to 4, respectively. Body composition showed that tilapia fed diets with duckweed contain significantly https://www.w3.org/1998/Math/MathML" display="inline"> ( p < 0 . 05 ) higher phosphorus and protein content and significantly https://www.w3.org/1998/Math/MathML" display="inline"> ( p < 0 . 05 ) lower lipid content. Contrary, tilapia fed control diet has significant higher https://www.w3.org/1998/Math/MathML" display="inline"> ( p < 0 . 05 ) dry matter content and lower ash content.