Effects of dietary Iranian acorn on the growth performance, feed utilization and carcass composition of common carp

Oak acorn is widely used as animal feed due to its low price. Oak acorns (Quercus brantii) were processed by de-hulling, drying and milling. In acorn flour, the total phenolic compounds, non-tannin phenols and condensed tannins were 14.71, 0.35 and 6.60 g/100g on the basis of dry matter respectively. Five isonitrogenous and isoenergetic diets with different levels of acorn at 0 (control), 25, 50, 75 and 100 g/kg, were prepared. A total of 435 fish (average weight 0.3 g) were randomly distributed in 15 tanks with three replicates and fed for 10 weeks. Polynomial orthogonal contrast analysis revealed that there were no significant differences in terms of feed intake, feed conversion ratio, protein retention, carcass ash and survival rate between treatments (p>0.05). Dietary intake of acorn significantly affected the weight after four weeks, final weight after 10 weeks, total length, head depth, specific growth rate, condition factor, protein efficiency ratio, lipid retention and carcass lipid and moisture contents, which represented linear order polynomial (LOP) models, but crude protein content of carcass displayed a cubic order polynomial (COP) model, using optimal acorn flour levels of 25.00 – 64.28 g/kg. Acorn flour improved the protein level of carcass, but deteriorated the growth performance and carcass lipid and moisture levels. Therefore, even if the amount of de-hulled acorn flour in the diet is low (2.5 % of diet), it is not allowed to use it without further processing.