SHORT COMMUNICATION Evaluation of Fermented Mixture Containing Fish Offal Meal in Compound Diets for the Freshwater Catfish Mystus vittatus (Bloch) Ayan Samaddar • Kausik Mondal • Anilava Kaviraj Received: 17 February 2011 / Revised: 3 July 2011 / Accepted: 6 July 2011 / Published online: 27 September 2011 Ó Zoological Society, Kolkata 2011 Abstract Fermented mixture containing fish-offal meal (FOM) was used to partially replace fish meal (FM) in the formulation of diets for the freshwater catfish Mystus vitt- atus. The two supplementary diets, one containing 25% FM and 25% FOM (T2) and the other containing 20% FM and 30% FOM (T3) showed significantly higher (P \ 0.05) digestibility, growth and protein deposition than the ref- erence diet without FOM supplementation (T1, 40% FM). Digestive enzyme activities were correlated with the pro- tein, carbohydrate and lipid levels in the diet. The fish fed diets containing FOM showed better lipid digestion effi- ciency than the reference group. It was concluded that fermented mixture containing FOM could be effectively used to partially replace fishmeal in the diet of M. vittatus. Keywords Fish-offal meal Á Fermentation Á Diet Á Catfish Á Digestive enzymes Á Growth Introduction Use of fish wastes as alternative feedstuffs in fish and other animal diets is gaining importance because it produces environmental benefits and reduces the cost of animal production (Hammoumi et al. 1998; Esteban et al. 2007). However, one drawback of using meals produced from by-products or wastes is the high variability in their bio- chemical composition and low digestibility (Cruz-Saurez et al. 2007). Fermentation has been proved to be a most suitable technique to improve nutritional quality of animal by-products and to make them suitable for inclusion in fish diet formulation (Fagbenro and Jauncey 1995; Nwanna 2003; Rangacharyulu et al. 2003; Bertsch and Coello 2005). The fish-offal, containing mainly the viscera of Indian major carps (Mondal et al. 2006), tuna muscle by- product powder (TMP), obtained from residues of tuna muscle (Uyan et al. 2006) and various other fish wastes (Hammoumi et al. 1998) have been found as viable alter- native feedstuffs for inclusion in fish diet. Fermented fish- offal meal has been successfully used to partially replace fishmeal in the formulation of diet for Indian major carp Labeo rohita (Mondal et al. 2007) and the catfish Hete- ropneustes fossilis (Mondal et al. 2008). However, acceptability of a formulated diet (Hasan et al. 1997) and digestibility of the nutrients contained in it (Cho and Kaushik 1990) are crucial factors besides sources and quality of the nutrients (Kaushik et al. 1995; Guillou et al. 1995; Bjerkeng et al. 1997) that can have profound influ- ence on the growth and flesh quality of fish. Mystus vittatus is a freshwater catfish and survives on diverse food of animal origin in the nature (Weliange and Amarasinghe 2007). Under culture condition optimum dietary protein requirement of most catfish has been found to vary between 26 and 37% (Akand et al. 1989; Brown and Robinson 1989; Gaylord and Gatlin III 2001; Salhi et al. 2004). Apart from crude protein level of the diet, growth of a fish is influenced by feed intake rate, ratios between different nutrients in the diet and digestive enzyme activities of the fish (Garling and Wilson 1977; Ali and Jauncey 2005). While feeding on Tubifex worm M. vittatus showed maximum feeding rate of 26.00 mg dry A. Samaddar Á A. Kaviraj (&) Department of Zoology, University of Kalyani, Kalyani 741235, West Bengal, India e-mail: akaviraj@gmail.com K. Mondal Department of Zoology, Tamralipta Mahavidyalaya, Tamluk 721636, West Bengal, India 123 Proc Zool Soc (July-Dec 2011) 64(2):117–123 DOI 10.1007/s12595-011-0011-2 T H E Z O O L O G I C A L S O C I E T Y K O L K A T A