Effects of dietary methionine levels and sources on performance, blood lipid profile and histopathology in Nile tilapia (Oreochromis niloticus)

Abstract

The present study was aimed to evaluate the effects of feeding different levels and sources of methionine (DL-Methionine and methionine hydroxy analogue, MHA) on growth performance and histopathological changes in Nile tilapia. The experiment was carried out over 60 days divided into 7 groups as follow: One group was fed a basic level of Met in the diet (5 g/kg diet) without any supplementation. The other groups were fed with different Met levels (+1/ +2/ +3 g/kg diet) as DL-Met or as MHA. Transmission electron microscopy and immunological index were also performed. Fish fed +1 g Met/kg as DL-Met had significantly higher body weight (58.1 g ± 3.85) than those fed +2 or +3 g Met/kg as DL-Met. No significant effects were found in body weight for fish fed +1 or +2 g Met/kg as MHA. All treatments induced significant reduction in the muscle thickness of the anterior segment of the intestine.