Effects Of Dietary Iron Levels On Growth Performance,Carcass Indices,Plasma Biochemical Parameters And Bone Development Of Broilers

The purpose of this experiment was to investigate the effects of dietary iron levels on growth performance,blood biochemical index,carcass parameters,meat quality,tissue element contents,tibial development related indices,so as to determine the relation of iron metabolism and bone development in broilers.A total of 360 1-d old AA broilers were divided into 4 groups with six replicates in each group and 12 chickens in each replicate.The 4 treatment diet were the non-iron basal diet（control group）and basal diet supplemented Fe as iron sulfate（FeSO₄ 7H₂O）with 100,250 or 500 mg/kg.The results showed that:（1）Dietary iron level had significant effect（P<0.10）on growth performance during 1 to 21 and22 to 42 days of age in broilers Chicks fed diet supplemented with 500 mg Fe/kg had the lowest（P<0.10）average daily gain and average daily feed intake.（2）Plasma iron linearly increased（P<0.01）and transferrin saturation linearly decreased（P<0.01）as the dietary iron supplemental level increased.（3）Dietary iron level significantly affected abdominal fat rate and heart index（P<0.04）.The heart index in chicks fed diet supplemented with 500 mg Fe/kg was significantly higher than those of other three groups（P<0.10）.（4）Dietary iron level significantly affected the b*value of breast muscle and leg muscle（P<0.01）,the drip loss of breast muscle（P<0.01）and the a value of leg muscle（P<0.06）.The b*value and a*value of leg muscle in chicks fed diet supplemented with 500 mg Fe/kg iron were significantly higher than those of chicks in the control group（P<0.02）.（5）Dietary iron level significantly affected the contents of Fe and Mn in tibia ash of 21-day-old broilers（P<0.05）,in which the Fe content increased（P<0.10）andthe Mn content decreased（P<0.05）with the increase of dietary iron level.（6）Dietary iron level had significant effect on tibia development indices of broilers at 21 days of age（P<0.09）.The tubia width,bone mineral density,bone strength,thickness of proliferating and hypertrophic zone,and alkaline phosphatase activity in chicks fed diet supplemented with 500 mg Fe/kg were significantly lower（P<0.10）than those of chick in other three groups,but osteocalcin content was higher（P<0.08）than those of chicks fed diets supplemented with 100 or 250 mg Fe/kg.The tibia development indices of broilers at 42 days of age had similar trend with with those of broilers at 21 days of age,but only the thickness of hypertrophic zone,osteocalcin content and alkaline phosphatase were significantly affected（P<0.06）by dietary iron level.The thickness of hypertrophic zone in chicks fed diet supplemented with 500 mg Fe/kg was significantly lower（P<0.03）than that of chicks fed diet supplemented with 100 mg Fe/kg,and the alkaline phosphatase activity was significantly lower（P<0.10）than that of chicks fed diet supplemented with 250 mg Fe/kg,while the osteocalcin content was higher（P<0.09）than that of chicks in the other three groups.These results indicated that dietary high iron level could reduce growth performance,quality of breast and leg muscle.Dietary high iron level reduce bone mineral density and bone strength by regulating osteocalcin content and alkaline phosphatase activity in tibia,thus inhibiting tibial development.These results were important for making rational use of iron resources,reducing the pollution of iron emissions to the environment,and improving the breeding efficiency of broilers.