effects of diet supplementing onion (allium cepa) powder on growth, survival, fillet composition and hematological parameters of oncorhynchus mykiss

abstract in order to investigation the effect of different levels of onion powdr (allium cepa) on growth performance, survival, fillet composition and hematological parameters of  rainbow trout, a completly randomize design with six treatments and three replicates (15 fish in each replicate) were conducted for eight weeks. experimental dietary included 0, 0.5, 1, 2, 3 and 5% onion powder. all the rainbow trout fishes that have 60± 1 weight adobeted with enviromental condition for two weeks. all of the data was analyze with spss software. the results of this experiment showed that onion powder significantly increase weight gain at 1 percent level  in comparison with control treatment (p<0.05) but no significant differences was observed in other growth parameters such as feed conversion ratio, specefic growth rate and survival (p>0.05). results showed that the highest level of white blood cells was observed in 5% level of onion powder and lower level was observed in control (p<0.05). but no significant differences was observed in red blood cells, hematocrite, hemoglobin and rbc indices (mcv, mch, mchc) (p>0.05). body coposition (protein, fat, moisture and ash) also showed no significant differences among treatments (p>0.05).  indeed, these results showed that onion powder at higher levels did not any adverse effect on other parameters.