Feed and feeding are among the most important factors influencing growth, feed utilization and tissue composition of the fish in intensive culture (Okumuş and Mazlum, 2002). Probiotics are harmless bacteria that help the well being of the host animal and contribute, directly or indirectly to protect the host animal against harmful bacterial pathogens (Ali A., 2000). ) There are many studies on positive effects of probiotics on growth, survival and improving immune status of fish and shrimp (Naik et al., 1999; Phianphak et al. 1999; Queiroz and Boyd 1998). The use of plants as medicines dates from the earliest years of man’s evolution (Dattner, 2003). Nigella sativa Linn. (family Ranunculaceae), commonly known as black seed or black cumin, is an annual plant that has been traditionally used in the Indian subcontinent (Nadkarni, 1976), Arabian countries (Sayed, 1980) and Europe (Lautenbacher, 1997) for culinary and medicinal purposes as a natural remedy for a number of illnesses and conditions that include asthma, hypertension, diabetes, inflammation, cough, bronchitis, headache, eczema, fever, dizziness and influenza (Ali and Blunden 2003). The aim of the present study was to assess the effect of Lactobacillus rhamnosus and Nigella sativa on growth performance and feed utilization of Rainbow trout.
