| The purpose of this experiment was to investigate the effects of different levels of iron（FeSO4）in diet on growth performance,slaughter performance,muscle quality,serum biochemistry,nutrient digestion and metabolism,iron metabolism-related genes and protein expression in rex rabbits from 3 to 5 months of age.In order to determine the optimal amount of iron,it provides a theoretical basis for the reasonable addition of iron in actual production.Two hundred three-month-old rex rabbits were randomly divided into five groups,with 40 replicates in each group and one rabbit in each experiment.The control group was basal diet（no iron source was added）,and the experimental group was fed with 4experimental diets supplemented with different levels of iron（FeSO4）.The iron levels were:20,40,80,160 mg/kg.The single factor test design method was adopted,with a prefeeding period of 7 days and a positive feeding period of 45 days.The main test results are as follows:（1）In terms of production performance,the dietary iron level has a significant effect on the terminal weight,average daily weight gain,and average daily feed intake of rex rabbits（P（27）0.01）,and when the iron addition is 40 mg/kg The average daily weight gain is the largest.The effect on the weight-to-weight ratio was not significant（P（29）0.05）.When the dietary iron content is 40 mg/kg,it has a significant effect on the brightness and redness in the flesh color（P（27）0.01）.The effects of drip loss and yellowness were not significant（P（29）0.05）.In addition,dietary iron levels had a significant effect on fur area（P（27）0.05）,with a maximum in the 80 mg/kg group.The effect of dietary iron level on fur thickness and fur length was not significant（P（29）0.05）.（2）In digestive metabolism,dietary iron had significant effects on UN,DN and NAD（P（27）0.05）,but not on IN,FN,RN,NUR,NBV（P（29）0.05）.compared with the control group,dietary iron added significantly increased crude protein digestibility.dietary iron levels significantly affected crude fat digestibility（p（27）0.05）,and the 160mg/kg group was significantly lower than the others.The dietary iron level significantly affected the intake of iron and fecal iron content（P（27）0.05）,and increased with the increase of dietary iron content.The apparent digestibility of iron increased first and then decreased with the increase of dietary iron content,reaching the maximum in the40 mg/kg group.Iron content in muscle also increases with increasing iron levels.But there was no significant difference in liver iron content between different groups（P（29）0.05）.（3）Compared with the control group,dietary iron could significantly affect the expression of liver transferrin,ferritin,divalent metal transporter and cytochrome b gene（P（27）0.01）,dietary iron could significantly increase the expression of duodenal transferrin and divalent metal transporter gene（P（27）0.01）,and dietary iron could significantly affect rabbit jejunin,ferritin,divalent metal transporter and transferrin receptor gene（P（27）0.05）.（4）In terms of serum-related indexes,dietary iron had no significant effect on serum related indexes such as ALT,AST,ALP,BUN and TP,but had a very significant effect on serum Glu content（P（27）0.01）,which increased with the increase of dietary iron content.Dietary iron level had no significant effect on IgA,IgM and IgG contents of rex rabbit serum immunoglobulin（P（29）0.05）,but very significant effect on HB and TIBC（P（27）0.01）,and no significant effect on serum Fn and TF contents（P（29）0.05）.Compared with the control group,dietary iron significantly increased serum iron,zinc and copper content（P（27）0.05）.The effect on serum manganese content was not significant.In conclusion,the basic diet supplemented with appropriate concentration of iron can significantly improve the production performance of 3-5 month old otter rabbits.The optimum amount of iron in the diet is recommended to be 40 mg/kg.HAMP,TF and SLC11A2 genes in the liver,duodenum and jejunum of rex rabbits are involved in the regulation of iron metabolism in vivo. |
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