The Study Of Characterization Of Organic Zinc Sources And Their Bioactivities And Modes Of Action In Cows

Four experiments for this thesis were conducted to characterize organic Zn sources chemically, and study their bioactivities for dairy cows and modes of action. Experiment 1. Studies on chemical characteristic of organic Zinc sourcesMineral concentrations, amino acid contents, structural characteristics, solubilities, complexed Zn percentages in soluble fractions of Zn sources in pH2, 0.2M HC1-KC1 buffer, pH5, 0.1M KH₂PO₄-K₂HPO₄ buffer and deionized water, and complex quotients (Q_f) of seven Zn sources and reagent Zn Sulfate were measured by IRIS Intrepid II emission spectrophotometry, HPLC, infrared spectroscopy, gel filtration chromatography and polarographic method, respectively. The results showed that: Zn concentrations and amino acid composition of organic Zn sources varied greatly;Organic Zn sources (ZnProB and ZnAAB) had characteristic peaks of complexed Zn. The solubility of all Zn products was more than 90% in the buffer of HC1, citric acid and meutral ammonium citrate, and the solubility of Zn sources in pH2 buffer was ranged from 53.92 to 98.54%, and the solubility in water and pH5 buffer was changed from 6.04 to 98.54%;No complexed Zn was found for these organic Zn sources filtrates from pH2, 0.2M HC1-KC1, pH5, 0.1M KH₂PO₄- K₂HPO₄ buffer, or deionized water;Four organic Zn sources showed weak complex strength, and one organic Zn source showed moderate complex strength, and two organic Zn sources showed strong complex strength. Experiment 2. The effects of organic Zn sources with different complex strength on the milk production, milk quality, immune function and relative enzyme activities of dairy cowsIn this study, a completely randomized design was used, and 30 healthy Holstein cows were randomly allotted to one of five treatments. The results showed that: The addition of organic Zn source with weak or strong complex strength improved the milk production of dairy cattle;The addition of Zn sources decreased somatic cell count, and Zn source with strong complex strength was the most effective, and Zn source with weak or moderate complex strength was more effective;The Zn content in plasma from cattle supplemented with organic Zn sources was higher than that from cattle on the Zn Sulfate treatment. Cattle supplemented with the Zn source showing the strong complex strength had the highest Zn content in plasma;The activity of alkaline phosphatase in serum from cattle supplemented with Zn source showing the weak or strong complex strength was higher than that from cattle on the control treatment or Zn Sulfate treatment. The addition of Zn sources with moderate or strong complex strength increased activities of total superoxide dismutase and CuZn superoxide dismutase in serum;The addition of Zn sources with weak or strong complex strength increased the antibody titer of mouth-hoof disease, and the antibody was more effective on 21d than on 42. Experiment 3. A study on the stability of organic Zn sources with different complexstrength in rumen by in vitro rumen fermentation methodA completely randomized design involving a 6×4 factorial arrangement of treatments was used in this study. Four Zn sources were reagent Zn Sulfate, the Zn source with weak complex strength (ZnAAC), moderate complex strength (ZnProB) or strong complex strength (ZnProA), and there were also a control treatment with urea and a Zn Sulfate plus urea andcasein treatment. The content of NH3-N and Zn solution were measured on each of four fermentation time (hO, 6, 12 and 24), The results showed that: The organic Zn sources with different complex strength were stable in the rumen in vitro, and the rumen by-pass ratio of them were more than 90%. The rumen by-pass ratio of Organic Zn source with strong complex strength was the highest (99.55%), and that of Organic Zn source with weak complex strength was in the middle (94.85%), and that of Organic Zn source with moderate complex strength was the lowest (92.16%). Experiment 4. The effects of organic Zn sources with different complex strength on therumen fermentation in vitroA completely randomized design involving a 4x3 factorial arrangement of treatments was used in this in vitro trial. Four Zn sources were the organic Zn source with weak complex strength ( ZnAAC ) , the Zn source with moderate complex strength (ZnProB) , the Zn source with strong complexed strength (ZnProA) and Zn Sulfate. Three supplemental Zn levels were 0, 10 and 20pg/ml.The results showed that: The pH in artificial rumen was in the normal range in vitro;The added Zn source, Zn level or the interaction of Zn source and Zn level had an effect on the degradability of DM, Zn content in bacterium, the VFA and bacteria content, and the protein in bacterium of artificial rumen.In conclusion, these organic Zn sources varied considerably in chemical characteristics, and there was a close correlativity between complex strengths of these organic Zn sources and their relative bioactrvities for cows, in which the availability of Zn source with the strong complex strength was the highest, and the Zn source with the weak complex strength was less available than the former one, while the Zn source with the moderate complex strength was the lowest one. Organic Zn sources with proper complex strength enhanced milk performance of dairy cows by improving the characteristics of fermentation and by-pass of rumen, increasing Zn content in plasma, relative enzyme activities in serum, or ability of immune, and reducing somatic cell count in milk.