Effect Of Dietary Iron On Mechanism Of Bone Development In Broilers

The experiment was conducted to investigate the effect of iron（Fe）level on growth performance,carcass traits,meat quality,blood relevant indices,tissue element contents and bone development indices of broilers from 22 to 42 days of age,so as to reveal the relationship between dietary iron level and bone development of broilers,as well as provide a scientific basis for further enrichment of existing knowledge of dietary iron nutrition for broilers and benefit of broiler breeding.In this experiment,a total of 240 commercial 1-day-old Arbor Acres（AA）male chicks were raised in two stages.All broilers were fed the same corn-soybean meal diet from 1 to 21 days of age.At 22 days of age,a total of 192 broilers were selected and randomly divided into 3 treatment groups according to body weight and housed in stainless steel cages.Each treatment group consisted of 8 replicate cages with 8chick per cage in a completely randomly design.These broilers aged 22 to 42 days were fed the corn-soybean meal basal diet with no iron as the control group and the basal diet supplemented with 100 and 500mg/kg of Fe as iron sulfate（Fe SO₄ 7H₂O）,composed of low iron group,normal iron group and high iron group（the measured dietary iron content of each group respectively was 60.43,180.96 and 712.56 mg/kg）.The trial lasted for 21 days.The results showed as follows:（1）broilers fed diet with Fe level had no effect on average daily gain,average daily feed intake and feed to gain ratio（P>0.51）.（2）Broilers fed diet with Fe level had no effect on percentages of dressing,eviscerated yield,abdominal fat,breast muscle,thigh muscle,organ indices of heart,liver and spleen（P>0.13）.Broilers fed diet with Fe level had no effect on percentages of pancreas（P<0.07）,broilers fed diet with low dietary Fe showed a trend of increasing pancreatic index（P<0.07）.Broilers fed diet with low dietary Fe had increased percentages of pancreas by 26.7%（P<0.07）.（3）Broilers fed diet with Fe level had effect on drip loss in breast muscle,a*values in breast muscle and b*values in thigh muscle（P<0.04）,and had no significant effect on other indices of meat quality（P>0.15）.Broilers fed diet with low dietary Fe had increased drip loss in both breast muscle by 78.8%（P<0.01）.Broilers fed diet with high dietary Fe had increased a*values in breast muscle by 43.1%（P<0.04）and b*values in thigh muscle by 34.2%（P<0.03）,respectively.（4）Broilers fed diet with Fe level had no effect on hematocrit,hemoglobin concentration and alkaline phosphatase activity,MDA,BGP and BALP（P>0.34）.（5）Broilers fed diet with Fe level had effect on P in tibia ash（P<0.06）.Broilers fed diet with low dietary Fe had increased P in tibia ash by 7%（P<0.06）.Broilers fed diet with Fe level had no effect on Fe,Mn,Zn,Ca in tibia ash（P>0.20）.Broilers fed diet with low dietary Fe had decreased Fe content in liver by 48.9%（P<0.05）,and had decreased by 55.5%than broilers fed diet with high dietary Fe（P<0.05）.（6）Broilers fed diet with high dietary Fe had decreased weight of tibia,bone density,the thickness of proliferating zone and hypertrophic zone by 11.9%,4.5%,4.6%and 30.2%（P<0.10）,respectively.Broilers fed diet with Fe level significant effect on alkaline phosphatase activity in bone（P<0.10）and the alkaline phosphatase activity in bone decreased with the increase of dietary Fe level（P<0.10）.Broilers fed diet with Fe level no significant effect on other bone development indexes（P>0.14）.（7）Broilers fed diet with high dietary Fe had increased the m RNA expression levels of COL1 and CX43 by 122.7%and 40.4%（P<0.01）,respectively.Broilers fed diet with low dietary Fe had decreased the m RNA expression levels of BGP by 55.3%（P<0.01）.Broilers fed diet with Fe level had no effect on the m RNA expression levels of ALP,BMP6,Bcl-1,P21,BMP2,OPG and FGF23 in tibia（P>0.11）.Broilers fed diet with Fe level had no effect on the m RNA expression levels of BMP6 and FPN1 in liver（P>0.87）.（8）Broilers fed diet with Fe level had no effect on the protein expression levels of BMP2,BMP6,COL1,OPG and P21 in tibia（P>0.27）.These results implied that broilers fed high Fe diet had decreased alkaline phosphatase activity,while broilers fed diet with high dietary Fe had increased the m RNA expression of Cx43 in tibia.Broilers fed low Fe diet had decreased m RNA expression of BGP in tibia,resulting to the inhibitory effect on the bone development of broilers.