Effects of dietary fish oil replacement by poppy seed oil on growth performance and fillet quality of rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) were fed replacement of fish oil with diets including poppy seed oil (PSO; 0%, 50% and 100%). At the end of the 90-day feeding period, the water holding capacity of the fillets decreased when the storage time increased. The colour and pH values were affected by both storage and diets. The hardness, springiness, gumminess and chewiness index of the fillet samples decreased as a consequence of increasing storage time, whereas the cohesiveness values of the fillets increased. The addition of PSO increased unsaturated fatty acids and reduced saturated fatty acids in the fatty acid composition of the fillets. These results demonstrated that the fatty acid (FA) composition of the rainbow trout fillets was reflecting the FA composition of dietary treatments and oils sources. The total mesophilic and psychrophilic bacteria count of the fish oil (FO), poppy seed oil/fish oil (PSO/FO) and poppy seed oil (PSO) samples was found within the legal limit on the third day of storage; however, it was found above the legal limits on the fifth day of storage. The sensory evaluation results showed that the fish fed with PSO diet were found to be non-desirable. The results of the study suggested that the blend of 50% fish oil and 50% poppy seed oil could be used as a replacer of fish oil in diets for rainbow trout to obtained the best growth performance, fillet quality and storage conditions.