Effect of feeding with soaked and fermented Iranian acorn (Quercus brantii) on the growth, feed utilization and carcass composition of common carp (Cyprinus carpio)

Peeled oak acorn was soaked in tap water for 24 or 48 h. The 24 h soaked acorn was fermented by baking yeast for 24 h. The effect of four diets including treatments 1: diet without acorn, 2: diet containing not soaked and fermented acorn, 3: diet containing 48 h soaked acorn, and 4: diet containing 24 h soaked and 24 h fermented acorn was determined on common carp with an initial weight of 8 g for 61 days. The phenolic compounds in the acorn were significantly reduced by soaking and fermentation (P<0.05). Diet had no significant effect on total length, feed intake, carcass moisture and survival rate (P>0.05). Treatment 3 significantly increased weight and specific growth rate in comparison with treatments 2 and 4. The condition factor in treatment 3 was significantly higher than treatment 4. The best feed conversion ratio and protein and lipid efficiency rates were observed in treatment 3, which were significantly different from treatment 2. There was no significant difference in protein retention between the treatments fed with acorn, but treatment 4 compared to treatment 1 had significantly less protein retention. The highest lipid retention was observed in treatment 1, which had a significant difference with treatments 3 and 4. Acorn led to a significant reduction in carcass crude protein, crude fat and ash. There was no significant difference in terms of carcass ash between treatments fed with acorn. The negative effects of treatments 3 and 4 were higher on the percentage of carcass lipid and carcass protein, respectively. Soaked acorn for 48 h did not have a negative effect on growth and feed consumption and can be used up to 5% of diet, but the study of other soaking and fermentation methods is recommended to improve the carcass quality.