Effect of sources and levels of protein in diets of tilapia (sarotherodon gaulaeus) fingerlings on the digestibility of nutrients [electronic resource].

Includes references.

This study was planned to investigate the effect of three sources and levels of protein in fish diets on the digestibility coefficients on Tilapia galilae ( average bcdy weight 4.7g ) reared in aquarium under laboratory condition. Nine diets representing three protein sources, anima', plant and mixture of animal and plant protein sources at three protein levels 22, 27 and 32% within each source were tested. The obtained results revealed that: 1- Fish fed on plant protein source as a sole source resulted in the significant (P<0.05) higher value of digestion coefficient of dry matter ( 91.93% ) , nitrogen free extract ( 75.12% ) and energy (75.88%), while, fish fed on animal plus plant protein source showed the best significant (p< 0.05) values of digestibility of crude protein ( 87.18%) and ether extract ( 90.55% ). 2-Level of 22% crude protein resulted in the best significant (p<0.05) values of digestion coefficient of dry matter ( 91.12%), ether extract ( 90.75% ), nitrogen free extract (71.64%), energy (76.67%), and resulted in significant lower (p< 0.05) values of crude protein digestion (81.14%), comparative to 32% protein level, while, a level of 27% crude protein improved significantly (p< 0.05) the digestion coefficient of dry matter (90.05%), ether extract (87.28%), nitrogen free extract (75.12%) and energy (75.19%) comparative to 32% dietary protein . 3-Within any dietary protein source, tested increasing the level of protein from 22 to 27 or 32% lowered significantly the digestion coefficient of dry matter, nitrogen free extract, energy and (p< 0.05) the digestion coefficient of ether extract, while, the digestion of crude protein increased insignificantly. Fish fed on plant protein source at level of 22% showed higher insignificant value of digestion coefficient of dry matter ( 92.85% ),nitrogen free extract ( 75.74% ) and energy (77.54%), While, 22% protein level from animal plus plant protein source showed significantly the highest value (p< 0.05) of digestion coefficient of ether extract ( 92.88% ) .

Summary in Arabic.

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