| Summary: | 碩士 === 國立中興大學 === 動物科學系所 === 97 === The purpose of this study was conducted to compare the effects of dietary organic and inorganic zinc supplementation on performance, zinc retention and excretion in broilers and laying hens. Experiment I, Ninety one-day-old broilers were randomly assigned to five dietary treatments with three replications of six birds each and fed on corn-soybean diets supplemented with 0, 20 or 60 mg/kg of Zn oxide (ZnO) or Zn proteinate (ZnPro) respectively, until 5 weeks. Feed and water were supplied ad libitum. The results indicated that feed consumption was significantly (P < 0.001) higher in birds fed diet supplemented with inorganic Zn than those fed with diet supplemented with organic Zn. No significant differences were discovered on body weight gain, feed conversion, Zn contents in kidney, heart, liver, spleen, breast muscle, leg muscle, tibia strength, tibia ash, weights of organs and alkaline phosphatase (ALP) activity (P > 0.05). Compared with the birds fed on ZnPro had significantly (P < 0.001) higher content of Zn in plasma than those fed on ZnO. However, the content of Zn in tibia was increased, with increasing the dietary Zn level (P < 0.01). and chicks fed the supplemented ZnO at level of 60 mg/kg diet was significantly higher in the superoxide dismutase (SOD) activity, Zn intake and Zn excretion, lower in Zn retention rate than the ZnPro fed group. Experiment II, thirty-six force molted White Leghorn layers, 30-wk-old, were assigned to three dietary treatments with three replicates of four birds each and fed diets supplemented with 0 or 200 mg/kg of ZnO or ZnPro respectively. Feed and water were supplied ad libitum. The results indicated that there were not significant differences between Zn sources and Zn levels on feed intake, hen-day egg production, hen-day egg mass, feed conversion ratio, egg weight, yolk weight, percentage of yolk, albumin weight, eggshell strength, eggshell thickness, eggshell weight and percentage of eggshell, egg yolk, egg white, and Zn content in plasma. However, compared with the birds fed on ZnO has significantly higher feed intake and haugh unit than those fed on ZnPro. Moreover, when dietary Zn level was increase, a decrease (P < 0.001) in the haugh unit was observed. Zn excretion was not significantly (P > 0.05) affected by dietary Zn sources in the all experiment but the highest Zn retention rate was assigned to birds given diets supplemented with ZnPro than those given diets supplemented with ZnO. And Zn excretion was increased and Zn retention rate was decreased, with increasing the dietary Zn level (P < 0.001). Moreover, Zn supplementation at 200 mg/kg levels of ZnPro showed a significantly greater the Zn retention rate than ZnO (P < 0.001). The data suggest that the dietary supplementation of ZnPro can improve Zn retention and excretion in broilers and laying hens.
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