Effects Of High Dietary Iron On Hepatic Lipid Metabolism And Abdominal Fat Deposition In Broilers

This study included two experiments.The objective of the experiment 1(Exp1)was to investigate the effects of high dietary iron on the abdominal adipose tissue development and hepatic lipogenesis in the starter broilers.The aim of Exp2 was to determine the effects of high dietary iron and lard level on abdominal fat deposition and hepatic lipid metabolism in the finisher broilers,determining the relationship of dietary iron and lard level on lipid metabolism.Exp1: effects of high dietary iron on hepatic lipogenesis and abdominal adipose tissue development in the starter broilersA total of 240 1-d-old male chicks(Ross 308)was allotted randomly two groups with six replicates(20 bird each replicate pen).The birds were fed basal diet(containing 109 mg Fe/kg by analysis)added with 30(adequate level,Control)or 500 mg Fe/kg(High-iron)for 21 days respectively.At end of trail,one bird from each replicate was selected to collect the serum,liver,and abdominal adipose tissue.The results were as following: 1)high dietary iron decreased the absolute and relative weight of abdominal adipose tissue(P < 0.001),and simultaneously reduced body weight gain and feed intake(P < 0.001)as compared to control;2)high dietary iron decreased(P < 0.001)adipocyte size mean and total DNA amount in abdominal adipose tissue;3)the concentrations of serum total cholesterol(TC)and highdensity lipoprotein(HDL)in serum and hepatic triglyceride were lower(P < 0.05)in Highiron group than in Control;4)high dietary iron decreased the activities of fatty acid synthetase(FAS),acetyl-CoA carboxylase(ACC),and stearoyl-coenzyme desaturase 1(SCD1)in the liver,and glyceraldehyde-3-phosphate dehydrogenase(G3PDH)in abdominal adipose tissue(P < 0.05);5)the mRNA abundance of FAS,SCD1,and sterol regulatory element-binding transcription factor(SREBP1)was lower(P < 0.05),whereas the mRNA transcription level of CCAAT/enhancer-binding protein(C/EBP)α and liver X rector alpha(LXRα)was higher(P <0.05)in the liver for High-iron treated broilers than for the control broilers;6)high dietary iron decreased(P <0.05)the mRNA abundance of C/EBPα and lipoprotein lipase(LPL)in abdominal adipose tissue of broilers when compared with the control.These results suggested that high dietary iron decreased the adipogenesis in abdominal adipose tissue and hepatic lipogenesis in the starter broilers.Exp2: effects of dietary iron and lard level on hepatic lipid metabolism and abdominal fat deposition in the finisher broilersA total of 480 1-day-old male broilers(Ross 308)were randomly divided into 4 treatments with 10 replicate cages each(12 birds per replicate),in 2(Lard level)× 2(added Fe level)completed factorial arrangement.The broilers were fed with the diet supplemented with 1.5(Low)or 4.0%(High)lard,and 30(Control)or 300 mg Fe/kg(Highiron)for 35 days.At end of trial,one bird of each replicate was selected to collect the blood,liver,abdominal adipose tissue for analyses.The results were as following: 1)high dietary iron decreased the feed consumption(P = 0.02);2)high dietary iron decreased the absolute weight of abdominal adipose tissue(P = 0.025)regardless of dietary lard level.However it only decreased(P = 0.043)the relative weight of abdominal adipose tissue of broilers in High lard group,not in Low lard group;3)high iron increased serum insulin concentration(P < 0.05)in High-lard treated broilers,not in Low-lard treated broilers;however,high iron increased serum glucagon concentration regardless of dietary lard level;4)high iron increased hepatic TG concentration and decreased hepatic TC concentration in High-lard treated broiler,not in Low-lard treated broilers,and it simultaneously increased the optical density value in hepatic tissue sections stained with oil red;5)high iron decreased(P < 0.03)the activities of hepatic ACC and SCD1 in Low-lard treated broilers,not in High-lard treated broilers;however it decreased(P < 0.02)hepatic FAS activity and G3 PDH activity in abdominal adipose tissue of broilers regardless of dietary lard level.The results suggested that high iron decreased hepatic lipogenesis and abdominal fat deposition in the finisher broilers fed High-lard diet,but these functions were not observed for the finisher broilers fed Low-lard diet.In summary,these results indicated that high iron decreased the hepatic lipogenesis and abdominal adipose tissue development in the starter broilers.High iron also decreased the hepatic lipogenesis and abdominal fat deposition in the finisher broilers fed High lard diet,however high iron had not these effects in the finisher broilers fed Low lard diet.