Study On Relative Biom Ailabilitiy Of Iron Proceinate And An Optimal Dietary Iron Level For Broilers

Two experiments were conducted to investigate the relative bioavailability of organic Fe proteinatein broilers fed a casein-dextrose basal diet and the optimal Fe level of broilers fed a corn-soybean mealdiet from1～21days of age.Experiment1. Relative bioavailability of organic Fe proteinate in broilers fed a casein-dextrose basaldietAn experiment was carried out to determine the bioavailability of Fe proteinate with the moderatechelation strength （Bioplex Fe, Alltech, Nicholasville, KY） relative to inorganic source （FeSO₄7H₂O）in the broiler chicks fed a purified casein-dextrose basal diet. A total of4481-day-old Arbor Acrescommercial male broiler chicks were randomly allotted by body weight to one of eight replicate cages（eight chicks per cage） for each of seven treatments in a completely randomized design involving a2×3factorial arrangement of treatments with three levels of added Fe （10,20or40mg Fe/kg） and two Fesources （Fe proteinate with the moderate chelation strength and Fe sulfate） plus a control with no addedFe for an experimental phase of14d. The results showed that average daily gain （ADG）, average dailyfeed intake （ADFI）, blood hemoglobin, hematocrit and Fe concentrations in liver and kidney increasedlinearly （P<0.0001） and feed conversion ratio （F:G） and mortality decreased linearly （P<0.004） as dietaryFe level increased. However, only blood hemoglobin concentration differed （P=0.003） between the two Fesources. Based on slope ratios from the multiple linear regression of hemoglobin concentration on dailyintake of dietary analyzed Fe, the bioavailability of Fe proteinate relative to FeSO₄7H₂O （100%） was117%（P=0.008）. It was concluded that hemoglobin concentration was a sensitive index in reflectingdifferences in bioavailability among different Fe sources, and Fe proteinate with the moderate chelationstrength was significantly more available than inorganic Fe sulfate in enhancing hemoglobinconcentration of the broilers.Experiment2. An optimal dietary Fe level of broiler chicks fed a corn-soybean meal diet from1～21daysof ageA trial was carried out with a total of3361-day-old Arbor Acres commercial male broiler chicks toinvestigate the optimal dietary Fe level of the broiler chicks fed a corn-soybean meal diet from1-21daysof age. The birds were randomly assigned by body weight to one of six replicate cages （eight chicks percage） for each of seven treatments in a completely randomized design. Dietary treatments included thebasal diet （Control,66.6mg/kg Fe） supplemented with either0,20,40,60,80,100or120mg/kg Fe asFe sulfate. The experimental phase was21d. The results showed that average daily feed intake （ADFI）,feed conversion ratio （F:G）, total iron binding capacity （TIBC） in plasma, hemoglobin （Hb）concentration, hematocrit, Fe concentrations in pancreas and breast musle, succinate dehydrogenase（SDH） activity in kidney, Catalase （CAT） activity in kidney and heart, heart SDH mRNA level, liverCAT mRNA level and bone marrow Hb mRNA level were not significantly affected （P＞0.070） by the added Fe in dietary, while average daily gain （ADG）, transferrin saturation （TS）, plasma iron （PI）, Feconcentrations in liver, kidney, heart, spleen and tibia, SDH activity in liver and heart, CAT activity inliver and SDH mRNA level in liver were affected significantly （P<0.014）. ADG, TS, PI, Feconcentrations in liver, kidney, heart and tibia and liver SDH mRNA level increased linearly （P<0.029）as dietary Fe level increased. However, there were only ADG, Fe concentrations in liver and tibia, SDHactivity in liver and heart, CAT activity in liver and SDH mRNA level in liver displaying quadraticresponse （P<0.003）. Consequently,⑴ADG, Fe concentrations in liver and tibia, CAT activity in liver,SDH activity in liver and heart and SDH mRNA level in liver were suitable to estimating Ferequirement for broiler chicks of21d fed a corn-soybean meal diet, of which liver Fe and the latter threeindices were the new specific, sensitive functional criterions;⑵The optimal dietary Fe levels of broilerchicks fed a corn-soybean meal diet from1～21days of age were calculated to be97～136mg/kgbased on the above indices and the best regression model among the broken-line, asymptotic curve andquadratic curve. The final Fe requirement was suggested to be136mg/kg, which was1.70times morethan the recommendation （80mg/kg） of the NRC （1994）;⑶PI, TS and Fe concentrations in kidneyand heart were the sensitive criterions to estimate the bioavailabilitiy of Fe sources when the chickswere fed a corn-soybean meal diet.In summary, blood hemoglobin concentration was a sensitive index in reflecting the differentbioavailabilities among different Fe sources when the birds were fed the purified casein-dextrose basaldiet, and Fe proteinate with the moderate chelation strength was significantly more available thaninorganic Fe sulfate in enhancing hemoglobin concentration of the broilers; SDH activity in liver andheart and SDH mRNA level in liver were the specific and new sensitive functional indices for Ferequirement estimation, and the optimal dietary Fe level of the broiler chicks fed a practicalcorn-soybean meal diet from1～21days of age were estimated to be136mg/kg based on the aboveindices; PI, TS and Fe concentrations in kidney and heart were the sensitive criterions to estimate thebioavailabilitiy of Fe sources when the chicks were fed a corn-soybean meal diet.