The Adsorption And Detoxification Of Heavy Metals In Feeds

Lead,cadmium and mercury were widespread in environment.Heavy metals in feeds could be harmful to animals on performance,nervous system,immune system, reproductive system and residue in animal products.Consequently,how to alleviate the potential harm of heavy metals in feeds had become a highlight.The objective of this study were to investigate the isothermal adsorption and desorption experiment of lead, cadmium and mercury on glucomannan,combination of glucomannan and bentonite, phosphorylative glucomannan and bentonite,and the most effective adsorbent was selected.The detoxify effects of the adsorbent were studied by breeding experiment with broilers.1 The isothermal adsorption experimentGlucomannan,combination of glucomannan and bentonite(Proportions were 4:1, 2:1 and 1:1),phosphorylative glucomannan and bentonite were selected as adsorbents.The solution of lead,cadmium,mercury with different concentrations(pH=2) were added into 10mL centrifuge tubes which 10 mg adsorbent had been added initiatly.The tubes were placed into homeothermia waterbath oscillator at the condition of 37℃, 150r/min for 1.5h.At the end of the adsorption reaction,the tubes were centrifugated at the condition of 3000r/min for 10min.The heavy metals concentrations in supernatant were determined for each tube in order to calculate adsorption quantity of lead or cadmium or mercury on adsorbents.The adsorption quantity of lead or cadmium or mercury on all adsorbents were determined as the method mentioned above.The results showed that the isothermal adsorption of heavy metals on all adsorbents in the study were fitted to Langmuir equation.The adsorptive effects of the combination of glucomannan and bentonite(the proportion of combination were 4:1 and 2:1) were better than the other adsorbents.The maxium adsorption amount of Pb²⁺,Cd²⁺ and Hg²⁺ on the combination of glucomannan and bentonite(the proportion of combination was 2:1)were 1034.6μg/g,670.6μg/g and 87.5μg/g,respectively.The maxium adsorption amount of Pb²⁺,Cd²⁺ and Hg²⁺ on the combination of glucomannan and bentonite(the proportion of combination was 4:1)were 820.3μg/g,609.6μg/g and 83.6μg/g.2 Desorption experimentAt the end of the isothermal adsorption experiment,supernatant in the centrifuge tubes with origination concentration of lead with 2.8μg/mL,cadmium with 2.6μg/mL,and mercury with 0.28μg/mL was poured out.Then,10mL buffer solution(pH=5.7) was added into each centrifuge tube.The tubes were placed into homeothermia waterbath oscillator at the condition of 37℃,150r/min for 1.5h.At the end of the reaction,the tubes were centrifugated at the condition of 3000r/min for 10min.The heavy metals concentrations in supernatant were determined for each centrifuge tube,and the rate of desorption of heavy metals were calculated.The results showed that the desorption rate of the combination of glucomannan and bentonite(the proportion of combination were 4:1 and 2:1) were lower than the other adsorbents.The desorption rate of Pb²⁺,Cd²⁺ and Hg²⁺ on the combination of glucomannan and bentonite in the proportion of 2:1 were 2.4%,2.7%,2.3%,respectively.The desorption rate of Pb²⁺,Cd²⁺ and Hg²⁺ on the combination of glucomannan and bentonite in the proportion of 4:1 were 3.2%,3.2%,2.4%,respectively.According to the results of the isothermal adsorption experiment and desorption experiment,the combination of glucomannan and bentonite in the proportion of 4:1 was used for detoxified agentâ… and the combination of glucomannan and bentonite in the proportion of 2:1 was used for detoxified agentâ…¡for breeding experiment with broilers in order to further study both practical detoxify effects.3 Animal experimentThe detoxify effects of detoxified agentâ… and detoxified agentâ…¡were studied on growth performance,antioxidative capability,immune function,the residue levels in different tissues.180 4-day-old Avian broilers were randomly allotted into 6 treatment groups with 6 replicates of 5 each from age of day 4 to 45 with two-phase trial(day 4-28 and day 29-45).The diets of the 6 groups were(1) control group,basal diet;(2) the polluted group,basal diet +10mg/kg lead +5mg/kg cadmium +0.3mg/kg mercury;(3) treatment group 1,basal diet +10mg/kg lead +5mg/kg cadmium +0.3mg/kg mercury+0.05%detoxified agentâ… ;(4) treatment group 2,basal diet +10mg/kg lead + 5mg/kg cadmium +0.3mg/kg mercury+0.1%detoxified agentâ… ;(5) treatment group3, basal diet +10mg/kg lead +5mg/kg cadmium +0.3mg/kg mercury+0.05%detoxified agentâ…¡;(6) treatment group 4,basal diet +10mg/kg lead +5mg/kg cadmium +0.3mg/kg mercury+0.1%detoxified agentâ…¡.Broilers were monitored daily and then body weight and feed consumption were recorded at the first day of experiment,end of each week and 45 days of experiment.On last day of the experiment,1 broiler chicken from each replicate were taken out randomly,lugular bloodletting then slaughtered,blood samples were collected to determine the antioxidative and immune indexes.The results were as follows: The growth performance:The average daily feeds intake,average daily body gain and feed conversion ratio of broilers had no significant difference(p＞0.05),which indicated that the growth performance of broilers were not affected by adding lead(10mg/kg)+cadmium(5mg/kg)+mercury(0.3mg/kg) in feeds.But feed conversion ratio of treatment group 4 was the highest and feed conversion ratio and feed conversion ratio of the polluted group was the lowest by numerical value.The immune function:T-lymphocyte transformation rate and ND antibody value in the polluted group were significantly decreased comparing to control groups(p＜0.05),which showed that the immune function of broilers was damaged by adding heavy metals in feeds.The immune function of broilers could be improved with detoxified agents.ND antibody value in the treatment group 1 was significantly increased comparing to the polluted group(p＜0.05).T-lymphocyte transformation rate and ND antibody value in the treatment group 2,treatment group 3 and treatment group 4 were significantly increased comparing to the polluted group(p＜0.05).The antioxidative function:SOD and GSH-Px activity in blood serum and liver in the polluted group were significantly decreased comparing to control groups(p＜0.05),and the content of MDA in blood serum in the polluted group was significantly increased comparing to control groups(p＜0.05),which showed that the antioxidative function was damaged by adding heavy metals in feeds.The antioxidative function of broilers was improved with detoxified agents.Treatment group 1,Treatment group 2, Treatment group 3 compared to the polluted group,SOD and GSH-Px activity in blood serum and SOD activity in liver were significantly increased(p＜0.05),MDA content was significantly decreased(p＜0.05) in blood serum.Treatment group 4 compared to the polluted group,SOD and GSH-Px activity in blood serum and in liver were significantly increased(p＜0.05),MDA content was significantly decreased(p＜0.05)in blood serum, but the effect of Treatment group 4 had the best by numerical value,and compeared to control groups,it had no significant difference(p＞0.05).The heavy metals residue level:Heavy metals residue leve lin the polluted groupwas significantly increased comparing to control groups(p＜0.05) in cerebrum,leg muscle, breast muscle,liver,kidney and tibia.Heavy metals residue level in different tissues was decreased with detoxified agents.The content of cadmium in liver and the content of mercury in leg muscle and cerebrum in the treatment group 1 were decreased with no significant difference comparing to the polluted group(p＞0.05),the residue level of heavy metals in the treatment group 1 were significantly decreased comparing to the polluted group(p＜0.05) in other tissues.The residue level of heavy metals in the treatment group 2 and Treatment group 3 were significantly decreased comparing to the polluted group(p＜0.05) in all tissues,except for the residue level of cadmium in liver. The residue level of heavy metals in the treatment group 4 were significantly decreased comparing to the polluted group(p＜0.05) in all tissues.The distribution of trace element:The distributions of trace element copper,iron and zinc in leg muscle,breast muscle,liver and kidney were changed by adding lead (10mg/kg)+cadmium(5mg/kg),mercury(0.mg/kg).The effect of the distributions of trace element copper,iron and zinc in leg muscle,breast muscle,liver and kidney could be lessened with detoxified agents.The results of animal experiment showed that the harmfulness of the immune function and the antioxidative function of broilers with heavy metals to animals could be lessened,and heavy metals residue level was decreased with detoxified agents added in feeds.The detoxified effect of the combination of glucomannan and bentonite(2:1) at 0.1%in feeds was the best in all treatment groups.