| Evaluating the bioavailability of various trace element supplements in a effectively, rapidly, objectively way has a great meaning, no matter for regulating health food (preparation) production, consumption or supervision. A case study of zinc preparations, the market has experienced inorganic zinc (Zinc Sulfate as the representative) and organic zinc such as Zinc Gluconate, Licorzinc, Amino Acid Chelated Zinc and Zinc Protein. However, not only the evaluation methods, but the results for their bioavailability assessment are very confused. Such as the evaluate methods in vivo include balance test method, isotope tracing method, ligated intestinal segments method and situ intestinal perfusion method; in-vitro methods which include in vitro perfused intestinal segments method, everted gut sac method, intestinal brush border membrane particle method and cell culture method. In this paper, we choice several commercially available zinc supplements as the research objects. Use the broilers’ileum to build everted gut sac model. According to the absorption efficiency which is cultured at different times and concentrations of different zinc preparations in the model, we explore the feasibility and specific applications of everted intestinal sacs as trace element nutrition supplement bioavailability evaluation model. With a view to providing experimental basis for other related research.The main results of the research as follows:1Build the everted gut sacs model based on broilers’ileum. Neck slaughtered45broilers, dissected out of the ileum, then handling and everting, finish90everted gut sacs models (one broiler’s ileum made two everted intestinal). Select the inorganic zinc (Zinc Sulfate), organic zinc (Amino Acid Chelated Zinc) to assess the model. Results showed that:(1) the end volumes of serosal fluid have no significant difference (P>0.05) between the control group and experimental groups, and have obvious linear relationship with time’s change, the correlation coefficient R2=0.909.(2) The absorption rates by cultured Zinc Sulfate for5,15,30,45,60min increased significantly (P<0.01), then do the linear fitting between absorption rates and times R2=0.990. At15min the absorption rate of Zinc Sulfate in gut sac reaches the maximum. Changes in the first30min of Amino Acid Chelated Zinc’s absorption rates increased significantly (P<0.01), then the rate of increase leveled off, but significantly increase trend appears again at60min. The linear fitting result shows that R2=0.947. The gut sac has the most sensitive absorption to Amino Acid Chelated Zinc in30min. According to this experiment, everted gut sac model has good repeatability and accuracy, can be used to evaluate the bioavailability of different zinc preparations.2The absorption regularity of different zinc preparations which were incubated gut sac with different concentrations at different times. According the different preparations’single recommended intake doses to set four level concentrations to culture gut sacs each for10,20,30,40min, zinc concentrations are as follow:5.28,14.12,20,32.4(μg/ml).Zinc Sulfate: the rates of absorption were increased with time and concentrations increasing. Regard the absorption rate under the zinc concentration of32.4μg/ml (recommendation dose) as100%. At the zinc concentration of5.28μg/ml, cultured for4time’s absorption reached8.74%-19.13%; at14.12μg/ml, absorption rate was27.01%-45.52%; when the zinc concentration was20μg/ml, the absorption rate was63.61%-71.10%. It can be seen that in the recommended dose zinc sulfate absorbed best. At10min, the gut sac diffusion coefficient P of zinc reaches its maximum, was1.936±0.292cm2/min, it means gut sacs were most sensitive to Zinc Sulfate’s uptake at this time.Zinc Gluconate: under the four concentration levels, the absorption rates were increased with time. Culturing gut sacs exceeded20min at the zinc concentration of32.4μg/ml; the absorption rates were lower than other two concentrations’level. Regard the absorption rate under the zinc concentration of14.12μg/ml (recommendation dose) as 100%. At the zinc concentration of5.28μg/ml, cultured for4time’s absorption reached18.30%-22.21%; at20μg/ml, absorption rate was115.20%-121.11%; when the zinc concentration was32.4μg/ml, the absorption rate was from138.23%down to92.93%. It can be seen that in the recommended dose or zinc concentration of20μg/ml zinc gluconate all showed a better absorption effect. At10min, the gut sac diffusion coefficient P of zinc reaches its maximum, was3.867±0.248cm2/min, it means gut sacs were most sensitive to Zinc Gluconate at this time.Ca, Fe, Zn:the absorption rate between the higher three concentration levels did not change significantly (P>0.01), both of them showed decreased after increasing trend, and then increase again. Regard the absorption rate under the zinc concentration of5.28μg/ml (recommendation dose) as100%. At the zinc concentration of14.12μg/ml, cultured for4time’s absorption rates were89.84%,115.10%,75.38%,122.60%; at20μg/ml, absorption rates were122.85%,129.18%,97.74%,60.58%; when the zinc concentration was32.4μg/ml, the absorption rates reached94.78%,127.44%,65.60%,101.92%. Therefore, with the increasing of zinc concentration, the Calcium, Iron, Zinc preparation absorption effect in the intestinal sac was not stable. At20min, the gut sac diffusion coefficient P of zinc reaches its maximum, was1.063±0.212cm2/min, it means that at20min the gut sacs could absorb Calcium, Iron, Zinc preparation in the most sensitive way. Licorzince:when the zinc concentration was32.4μg/ml, the absorption rate over time showed increased at first and then decreased. Regard the absorption rate under the zinc concentration of14.12μg/ml (recommendation dose) as100%. At the zinc concentration of5.28μg/ml, cultured for4time’s absorption rates got34.66%-47.35%; at20μg/ml, absorption rates were reduced from119.82%to100.97%; when the zinc concentration was32.4μg/ml, the absorption rates were104.21%,101.40%,79.14%,76.21%. From these results we know that in the recommended dose or at zinc concentration of20μg/ml, Licorzince had a better absorption. At10min, the gut sac diffusion coefficient P of zinc reaches its maximum was3.447±0.230cm2/min, at which point gut sacs were most sensitive for licorzince absorption.Amino Acid Chelated Zinc:when the zinc concentration was32.4μg/ml, absorption rate with time performance was increased at first, then from smooth to increase again and finally decrease. Regard the absorption rate under the zinc concentration of20μg/ml (recommendation dose) as100%. At the zinc concentration of5.28μg/ml, cultured for4time’s absorption rates were reached27.77%-36.17%; at14.12μg/ml, absorption rates of up to52.57%-62.64%; when the zinc concentration was32.4μg/ml, the absorption rates were131.27%,85.57%,106.36%,97.84%. Seen, Amino Acid Chelated Zinc preparations in their recommended doses were more stable and had a better absorbed. At 10min, the gut sac diffusion coefficient P of zinc reaches its maximum was3.256±0.420cm2/min, at this time gut sacs were most sensitive to amino acid Chelated Zinc absorption.In summary, Zinc gluconate and Licorzince’s bioavailability in broiler ileum are higher than Amino acid chelated zinc; Zinc sulfate and Ca, Fe, Zn have poor bioavailability. |
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