| In this paper, the oxytetracyline residues in the feeds and manures of pig in scale farms in Zhejiang province were investigated to find the correlationship between the content of oxytetracyline of pig feeds and manures. The effect of oxytetracyline on pig manure composting was found, and then the highly effective technology of aerobic compost of pig manure with high oxytetracycline was discussed in this paper. Main conclutions were draw as following:(1)The oxytetracycline residues of the feeds and manures of pig in scale farms of11citys in Zhejiang province were analyzed, and the results showed the detection rates of oxytetracycline in pig feeds and manures sampled from scale farms in Zhejiang province were all100%.The average content of feeds was8.76mg/kg, while the content of pig manures was2.98mg/kg averaged, the scale of oxytetracycline content of Zhejiang province was significantly higher than that of Germany, Turkey and other European countries. The content of oxytetracycline in feeds of piglet was significantly positive correlated with the residues in its manure, the correlation coefficient was0.604, but the similar correlationship was not founded in sow and fattening pig. According to the correlationship of piglet, the addition of oxytetracycline in the feeds of piglet must be less than38.04mg/kg was suggested.(2)The composting results of five different initial oxytetracycline residues treatments which was0(CK),10mg/kg,50mg/kg,100mg/kg,150mg/kg showed that oxytetracycline residues restricted the activity of microorganisms during the composting process, oxytetracycline residues accelerated the decline of temperature and gone against the rise of temperature,50mg/kg,100mg/kg,150mg/kg oxytetracycline treatment just had4days temperature risen duration.100mg/kg and150mg/kg oxytetracycline treatment had negative influence on the loss of water during composting and would result in the high water content after composting.Oxytetracycline restricted the activity of microbial in manure, including the utilization of organic carbon and nitrogen and the nitrification of nitrifying bacteria. Different oxytetracycline residues had different effects, the150mg/kg oxytetracycline treatment had the most significantly inhibition.The high temperature was the key factor of the degradation of oxytetracycline, the degradation of oxytetracycline occurred mainly in the temperature-rise and high temperature period. The changes of the concentration of OTC in pig manure with time had a trend of kinetic equation, and different concentration of oxytetracycline residues had different dynamics equation, the half-life of the10mg/kg,50mg/kg,100mg/kg,150mg/kg oxytetracycline treatment were8.97d,5.12d,3.09d and6.18d. The10mg/kg,50mg/kg,100mg/kg,150mg/kg oxytetracycline treatment had the degradation rate of27.22%,81.06%,88.3%,82.64%after30d composting.(3)A strain TJ-1, that could utilize oxytetracycline as the sole carbon source, was isolated from pig manure compost and identified as Staphylococcus sp. The oxytetracycline degrading rate was80.7%within5.5d with the inoculum concentration3%, temperature30℃, pH7.0and the shake bed130r/min, and was significantly higher than that of Oxy2which was reported ever. The prome condition for OTC-degradation of TJ-1was the inoculum concentration5%, pH7.0, temperature30℃. The highest concentration of oxytetracycline that the strain could tolerate was300mg/1.(4)The results of optimising the pratical parameters in aerobic composting such as moisture content, C/N, bacterium inoculation and turning frequency showed that with the increase of moisture content, C/N, bacterium inoculation increased, the oxytetracycline degrading rate also increased, the oxytetracycline degrading rate was significantly effected by the moisture content and C/N(p<0.01) and was effected by the bacterium inoculation(p<0.05).While the turning frequency increased, the oxytetracycline degrading rate decreased adversely, the turning frequency could effect the oxytetracycline degrading rate(p<0.05). The optimal environment factor conditions for oxytetracycline degradation of pig manure was initial moisture content70%, C/N30,1%of bacterium agent TJ-1inoculation amount, turning frequency1.5d/time.(5)The highly effective technology of aerobic compost of pig manure could significantly improve the degradation rate of oxytetracycline (p<0.05), the degradation rate was82.0%after21d composting, while the degradation rate of ordinary composting process was only62.7%. The change of the concentration of OTC in pig manure with time had a trend of kinetic equation, the half-life of150mg/kg oxytetracycline in ordinary compost and the highly effective technology of aerobic compost were2.75d and0.78d seperately. Oxytetracycline residues restricted the activity of microorganisms including the utilization of nitrogen and the nitrification of nitrifying bacteria during the composting process, but the highly effective technology of aerobic compost of pig manure could reduse the negative influence of oxytetracycline, and could significantly increase the utilization of nitrogen of microorganisms in high temperature period. The effects of oxytetracycline on the diversity of microbial community in composting materials were explored using Biolog method. The results showed that microbial activities of the highly effective technology of aerobic compost was higher than ordinary compost, conductive to communities richness and functional diversity. Correlation analysis showed that the difference was significant between the highly effective technology of aerobic compost and ordinary compost (p<0.05). |
