Fish silage was prepared by fermentation of fish by-products with Lactobacillus plantarum, molasses and rice bran. The ensilage process completed after 30 days and the fermented fish silage (FFS) was sun-dried for 3 days and incorporated into the experimental diets.
Two growth trials were conducted to investigate the effect of partial or complete replacement of fish meal (FM) by dried fermented fish silage (FFS) in diets of Nile tilapia, Oreochromis niloticus and African catfish, Clarias gariepinus. Five dry pelleted diets containing 0, 10, 20, 30 and 40% FFS to replace 0, 25, 50, 75 and 100% of FM (on protein content basis) were prepared to be isonitrogenous (30% CP) and isocaloric (2600 kcal ME/kg diet) and tested in 3 months feeding separate two trials. Nile tilapia fry (2.57- 2.71 g) and catfish (3.98 - 4.03 g) fed the tested diets twice daily for six days a week in triplicate (Nile tilapia) and duplicate (African catfish) groups experiments. Results indicated that, dried FFS can successfully replace up to 25 and 50% of FM in tilapia and catfish diets, respectively without any significant loss in growth performance and feed utilization. The higher levels of replacement of FM by FFS (50, 75 or 100% in tilapia diets and 75 or 100% in catfish diets) significantly reduced growth performance, feed utilization parameters as well as significant effect on fish body composition of tilapia and catfish. Apparently, FFS can be used efficiently as a protein source in Nile tilapia and catfish diets to reduce feed costs for the two fish species.
From economic view, it was observed that replacing 25% (tilapia) or 50% (catfish) of FM by FFS in diets did not significantly adversed growth or feed utilization parameters of Nile tilapia and catfish and this replacement reduced feed costs/kg diet and feed costs/kg weight gain by 7.35 and 11.30%, for tilapia and by 15.59 and 19.39% for catfish, respectively.
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