| As the quick development of dairy industry, consumers need high quality of the dairy products . Subclinical mastitis is the important factor to affect the quality of milk. Therefore, the detection of mastitis should be set up for Holstein cows in order to improve the hygienic quality of milk, thus also improving the quality of products offered on the market. The concentrations of trace element Zn and Se in cow diet are associated with the udder health.The objective to research the condition of cow diet and positive rate of subclinical mastitis in Harbin area and the correlation between trace element and mammary immunity by survey the cow diet and the test of mastitis and the assay of milk composition and the test of immunity. At the same, find a useful method of preventing the subclinincal mastitis in nutritional angle.Eight cow diets from Harbin and suburb were surveyed, and 289 Holstein cows and 1134 quarters of cows were detected. The composition of 111 milk samples were analyzed.1. The concentrations of rude protein, Ca, P, Zn, Se and Mn in the dairy cow diet from 8 farms in Harbin city and suburb were surveyed 18.18±3.58%, 0.69±0.27%, 0.14±0.06%, 17.62±10.34mg/kg, 0.19±0.17mg/kg, 15.49±5.71mg/kg respectively.2. With the survey of 289 Holstein, the results indicated that test rate of subclinical mastitis is 75.09%. The positive rate of mammary area in the back is significantly higher than that in the front. The positive rate of the left and the right mammary area is not significantly different.3. The regression equation of the concentration of Se in cow diet with subclinical mastitis is y=-67.40x+74.15, (R2=0.85) .4. The regression equation of the concentration of Zn in cow diet with IgG in milk is y=0.01x+0.34 (R2=0.514) .5. The concentration of Se cow diet could significantly enhance the performance of PMN in milk. The regression equation of the concentration of Se in cow diet with performance of PMN in milkisy=31.68x+30.6 (R2=0.96) .6.The concentrations of Zn (P0.01), Se(P0.0l )and Ca(P<0.05) in Subclinical mastitis cow hair were significantly lower than that in healthy cow. The concentrations of P and Mn are not significantly different.7. Subclinical mastitis results in a highly significant reduction in fat (P0.05) and casein (P0.01) and lactose (P0.01) content and an increase in IgG (P0.01) content of milk. Butthe contents of dry matter, nonfat solids, total protein, density and freezing point of milk are not significantly different from those in heslthy cow. (P>0.05) .8. The concentrations of Ca (P0.01) and Se (P<0.01) and P (P0.05) in Subclinical mastitis milk are significantly lower than that in healthy cow. But the concentration of Zn is not significantly different (P>0.05) .ConclusionsThe cow diet in Harbin city and in the suburb vary very much. The regression coefficients of transformed Se on positive rate subclinical mastitis and the performance of PMN were plus and significant. The regression coefficients of zinc on IgG in milk was plus. The results obtained permitted us to infer that subclinical mastitis has a negative effect on milk yield in Holstein cows, causing losses to producers due to reduced milk production and quality.
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