the effects of iron nanoparticles in combination with lactobacillus casei on growth parameters and probiotic counts in rainbow trout (oncorhynchus mykiss) intestine

background: today the use of natural substances plays a major role in improving the growth and immunity of aquatic organisms. objectives: the purpose of the present study was to evaluate the effects of iron nanoparticles with lactobacillus casei as a probiotic on growth parameters and probiotic counts in rainbow trout intestine. methods: seven hundred and twenty fish with 12±0.49 g initial weight were prepared and after acclimatized to the laboratory conditions divided randomly into six groups. first group was selected as control, other groups were fed with a commercial diet supplemented with 108 cfu/g lactobacillus casei (group 2), 50 µg/kg iron nanoparticles (group 3), 100 µg/kg iron nanoparticles (group 4), 50 µg/kg iron nanoparticles with 108 cfu/g lactobacillus casei (group 5) and 100 µg/kg iron nanoparticles with 108 cfu/g lactobacillus casei (group 6), respectively. biometry and intestine bacteriologic examination were carried out at days 0 and 60. results: results showed that growth parameters (weight gain, body weight gain, specific growth rate, daily growth rate, and condition factor and food conversion rate) were significantly higher in group 5 compared with the other groups. also, intestine bacterial counts increased by using iron nanoparticles in combination with lactobacillus casei. the fish that received 100 µg/kg iron nanoparticles and probiotic had significantly higher bacterial counts in their intestine compared with the other groups. conclussions: based on the obtained results we conclude that diet supplementation with iron nanoparticles and lactobacillus casei as a probiotic could significantly improve growth parameters in rainbow trout. however, these results would warrant further study on the clinical application of these agents.