Background. Linseed and its by-products constitute a major source of dietary protein, but due to amino-acid imbalance and presence of anti-nutritional factors their use in fish feed is limited. Therefore, fermentation of linseed by lactic acid bacteria and/or fermented diets increases the level of linseed inclusion into the diet of rohu fingerlings by up to 40 percentage points. Materials and methods. Six experimental diets (RL20, RL30, RL40, FL20, FL30, and FL40) for rohu fingerlings (Labeo rohita) were formulated using raw and fermented linseed meals. Finely powdered (400 µm) diet ingredients were incorporated at 3 different levels (20, 30, and 40%) into each diet, replacing equal proportions of all the ingredients from the reference diet. Two types of de-oiled linseed, Linum usitatissimum, meals were used as test ingredients: raw (RL) and fermented (FL). Prior to incorporation, a portion of the linseed meal was fermented by inoculating it with lactic acid bacteria, Lactobacillus acidophilus. The reference diet was prepared with fish meal as the chief protein source. Results. Fermentation of the oilseed meal resulted in reduction of tannin content from 2.45% to 1.32%. The total digestibility of the reference and test diets was significantly higher (P < 0.01) at all levels of fermented linseed addition. In particular, it was observed that the fermented samples showed comparatively better digestibility than the raw samples. Conclusion. Fermentation of oilseed meals which leads to the reduction of anti-nutritional factors may be applied as an efficient tool in formulation of feeds for rohu fingerlings.

anti-nutritional factors, fish feed, diets, fermentation, linseed meal, digestibility, fingerlings, rohu, Labeo rohita, fish