Effect Of Dietary Iron Levels On Growth,iron Concentration In Tissues,Transferrin And Hepcidin In Bighead Carp(Aristichthys Nobilis)

To research the appropriate iron requirement of bighead carp（Aristichthys nobilis）,a60 days growth trial was conducted in the indoor recirculating aquaculture system to study the effects of iron levels on the growth,body and muscle composition,tissue iron content,blood biochemical parameters,fatty acid composition of muscle,intestinal epithelial cell,digestive enzyme activity,transferrin and hepcidin concentrations in the blood of bighead carp.The trial 1 was single-factor gradient design.The six experimental diets were formulated to contain different Fe levels（0,43.1,84.2,123.3,162.2,and 203.1 mg/kg of dry diet）using ferrous sulfate（Fe SO₄）as the source.The test subject was bighead carp with average initial body weight 6.18g,divided into six groups,with three replicates of 30fish in each replicate.The results were summarized as follows:1.Fe level of 123.3 mg/kg were significantly higher than that of the 0 mg/kg Fe group（p<0.05）.The results indicated that the growth was affected by dietary Fe levels.Regression analysis of WG and SGR at different levels of dietary Fe suggests that the appropriate dietary requirement of Fe for the bighead carp larvae is 120–134.36 mg/kg.2.With the increase of dietary iron level,the crude ash and water contents in the whole fish were significantly decreased thereafter increased（P<0.05）.The crude ash and water contents in the whole fish of the 123.3 mg/kg Fe group were the lowest in all groups（P<0.05）.Approriate dietary iron level could make crude ash and water contents increased.No significant differences were revealed in the crude protein and lipid concentrations in the whole body among all groups（p>0.05）.3.With the increase of dietary iron level,the crude ash and water contents in the muscle were significantly decreased thereafter increased（P<0.05）.The crude ash content in the muscle of the 84.2 mg/kg Fe group was the lowest in all groups（P<0.05）.The water content in the muscle were significantly increased thereafter decreased,with the increase of dietary iron content.The water content in the muscle of the 162.2 mg/kg Fe group was the highest in all groups（P<0.05）.The crude protein content in the muscle were significantly increased thereafter decreased（P<0.05）,with the increase of dietary iron content.The crude protein content in the muscle of the 84.2 mg/kg Fe group was the highest in all groups（P<0.05）.Approriate dietary iron level could make crude ash and water contents increased and make crude ash content decreased.No significant differences were revealed in the crude lipid concentrations in the muscle among all groups（p>0.05）.4.No significant differences were revealed in the iron concentrations in the whole body among all groups（p>0.05）.With the increase of dietary iron level,the iron contents in the muscle and vetebra were significantly increased（P<0.05）.The iron content in the muscle and vetebra of the 203.1 mg/kg Fe group was the highest in all groups（P<0.05）.The iron content in the intestine was significantly increased thereafter decreased,with the increase of dietary iron content.The iron content in the intestine of the 84.2 mg/kg Fe group was the highest in all groups（P<0.05）.The iron content in the liver and spleen were significantly increased thereafter decreased,with the increase of dietary iron content.The iron content in the intestine of the 84.2 mg/kg Fe group was the highest in all groups（P<0.05）.Approriate dietary iron level could make whole fish,intestine,muscle,vetebra,liver and spleen contents increased（P<0.05）.5.The trypsin activity was significantly increased with increasing dietary Fe levels up to 43.1 mg/kg diet and thereafter declined（P<0.05）.The almylse and lipase activities were significantly increased with increasing dietary Fe levels up to 162.2 mg/kg diet and thereafter declined（P<0.05）.6.The transferrin content was significantly increased with increasing dietary Fe levels up to 162.2 mg/kg diet and thereafter declined in the blood（P<0.05）.The Fe content was significantly decreased with increasing dietary Fe levels up to 162.2 mg/kg diet and thereafter increased in the blood（P<0.05）.These results indicate that the transferrin content was increased with decreasing Fe content up to 229.41μg/m L and thereafter declined with increasing Fe content in the blood.The transferrin content was significantly increased with decreasing hepcidin up to 264.63μg/m L content and thereafter decreased in the blood.It could be concluded from these results that,after transferrin saturation,hepcidin may function to raise iron content in the blood of A.nobilis by decreasing transferrin content.7.With the increase of dietary iron level,the AKP activity in the blood was significantly decreased thereafter increased and then decreased（P<0.05）.The AKP activity in the blood of the 123.3 mg/kg Fe group was the highest in all groups（P<0.05）.The TG and TC activities in the blood were significantly decreased thereafter increased and then decreased,with the increase of dietary iron content.The TG activity in the blood of the84.2 mg/kg Fe group was the lowest in all groups（P<0.05）.The TC activity in the blood of the 162.2 mg/kg Fe group was the lowest in all groups（P<0.05）.The GLU content in the blood was significantly decreased thereafter increased,with the increase of dietary iron content.The GLU contenty in the blood of the 162.2 mg/kg Fe group was the highest in all groups（P<0.05）.There was not significant difference between dietary iron level and TP,ALB and CLB（p>0.05）.8.Excessive iron level could make hepcidin content and AKP activity decreased（P<0.05）and inhibition of cell differentiation.Approriate iron level could make hepcidin content increased（P<0.05）and improving the antibacterial ability of cells and improving cell survival rate.