The aim of the present study was to investigate the effect of feeding biological treated rice straw with Pleurotusostreatus or treated corn stalks with Trichodermareesei at different levels on carcass characteristics of rabbits. Dried treated rice straw (RS) or corn stalks (CS) were used to formulate the experimental pelleted diet by substituting of berseem hay with treated rice straw with medium only (without Pleurotusostreatus) and biological treated rice straw with Pleurotusostreatus (BTRS) or treated corn stalks with medium only (without Trichodermareesei) and biological treated corn stalks with Trichodermareesei (BTCS) at different levels. All diets were formulated to be iso-nitrogenous and iso-caloric, and to meet nutrients requirements for growing rabbits. A number of 78 weaned New-Zealand white rabbits about 6 weeks of age and weighed 500 g in average were randomly divided into 13 groups (R1 to R13) 6 rabbits in each. The experimental groups were fed as following the first group fed control diet (0% rice straw or corn stalks) and other 12 groups were fed on diets containing rice straw either with or without fungi or corn stalks either with or without fungi at 33, 66 and 100% as replacing of berseem hay (11, 22 and 33% of total diet). At the end of the experimental period (91 days), three rabbits from each group were slaughtered to evaluate carcass characteristics. The results showed that the values were significantly (P<0.05) higher with the slaughter weight (SW). The eviscerated body (EBW), carcass weight (CW1) and carcass weight and total giblets(CW2) with R13 (BTCS) ration and R6 ration were significantly (P<0.05) higher with CW1, CW2 and BTRS rations than other experimental rations. While SW, EBW, CW1 and CW2 were significantly lower with R2 (NBTRS) ration than other experimental rations. Values of the dressing percentage (DP1) showed that R6 (BTRS) ration was significantly higher while R3 (NBTRS) ration was significantly lower than other experimental rations. The values of the dressing percentage (DP3) showed that R10 (NBTCS) ration and R12 (BTCS) rations were significantly higher than other experimental rations. The average values of carcass cuts showed that R5 and R6 with (BTRS) rations were improved (P<0.05). The excellent carcass cuts weight (middle part than that of the control diet). It's worthy to recommend the treated rice straw or corn stalks with fungi to be used to  enhance carcass characteristics in rabbits' diet.
Conclusion : It was concluded that the treatment of rice straw with Pleurotusostreatus and corn stalks with Trichodermareesei (especially the replacement of berseem hay with 100% of the biological treated BTRS and BTCS) had beneficial returns on the carcass characteristics (traits) of the growing white New Zealand rabbits.