| Through detecting the content of lead, copper, zinc, cadmium, chromium and arsenic in the samples of feeding environment (soil and drinking water), feed and the different tissues in beef cattle which were come from different beef cattle feeding patterns in rural area, the existence situation of heavy metals in feeding environment and feed, as well as the accumulation content of heavy metals in different tissues of beef cattle were studied. And the relationship of the heavy metal content between the feeding environment (soil and drinking water) and the different tissues in beef cattle, the relationship of the heavy metal content between the feed and the different tissues in beef cattle, as well as the rules of heavy metals migrated in the beef cattle food chain were discussed. The results showed that:1.The content of lead, copper, zinc, cadmium, chromium and arsenic in the soil sample which come from the pattern 2 beef cattle farm(exogenous additives were used in these farm) were both slightly higher than the pattern 1 beef cattle farm(non feed additives were used in these farm), but the difference was not significant (P> 0.05); in the two patterns, the single pollution index of cadmium in soil were both greater than 1.0, indicated that the soil in the beef cattle farm of these two patterns were both exist the cadmium pollution. For the pattern 1 beef cattle farm (non feed additives were used in these farm), the integrated pollution rank of the lead, copper, zinc, cadmium, chromium, arsenic in soil was warning limits, and for the pattern 2 beef cattle farm (exogenous additives were used in these farm), the integrated pollution rank of the lead, copper, zinc, cadmium, chromium, arsenic in soil was light pollution. The significant positive correlation between soil lead and soil cadmium, as well as soil copper and soil arsenic were observed. And the correlation coefficient of soil lead and soil cadmium as well as soil copper and soil arsenic were 0.914 and 0.667, respectively. And the correlation also suggested the soil exist the compound pollution of copper, arsenic, lead, cadmium. For the single potential ecological risk parameters of lead, copper, zinc, chromium, arsenic in soil, the pattern 2 beef cattle farm(exogenous additives were used in these farm) were both greater than pattern 1 beef cattle farm(non feed additives were used in these farm), but both of them showed a low potential ecological risk. The single potential ecological risk parameter of cadmium in soil in these two patterns were both in the range of 80≤E ri<160, showing a high potential ecological risk. In these two feeding patterns, the multi-metal potential ecological risk index RI of the soil in the pattern 2 beef cattle farm (exogenous additives were used in these farm) is higher than the pattern 1 beef cattle farm (non feed additives were used in these farm), but both them were below 150, showed a low potential ecological risk.2. For the lead, copper, zinc, cadmium, chromium and arsenic levels in drinking water, the pattern 2 beef cattle farm(exogenous additives were used in these farm) were slightly higher than the pattern 1 beef cattle farm(non feed additives were used in these farm), but the difference was not significant (P>0.05 ). For the two feeding patterns, the single pollution index of copper, zinc, cadmium, chromium, arsenic in drinking water were both less than 1.0, and the single pollution index of lead in drinking water are both greater than 1.0, showing that the drinking water of both of them are exist lead pollution. For the pattern 1 beef cattle farm (non feed additives were used in these farm), the integrated pollution index of six metals was 1.58, and its water pollution level is light pollution; for the pattern 2 beef cattle farm(exogenous additives were used in these farm), the integrated pollution index of six metals was 2.39, and its water pollution level is pollution. The extremely significant positive correlation were observed between copper and lead, copper and copper and cadmium, arsenic and lead, cadmium and lead in drinking water, respectively, which were suggested that the water exist the compound pollution of copper, arsenic, lead, cadmium.3. There were no significant differences of the content of lead, copper, zinc, cadmium and arsenic in concentrated feed, roughage between the two feed patterns. But the differences of the content of chromium in beef cattle feed between these different feed types were significant (P<0.05), the content of chromium in pattern1 roughage were extremely significant higher than that of pattern 2 coarse feed and pattern 1 concentrates (P<0.01), and the content of chromium in pattern2 roughage were significant higher than that of pattern 2 concentrates (P<0.05), but there was no significant difference was observed between the content of chromium in pattern1 roughage and that of pattern 2 concentrates(P>0.05), and the content of chromium in beef cattle feed showed a basic law that is the roughage enrich higher levels of chromium than concentrate feed. From the aspect of heavy metals contained in feed in the two feeding patterns, the beef cattle from the pattern 1 may be more vulnerable to the hazards of chromium than the beef cattle from the pattern 2; and the beef cattle from the pattern 2 may be more vulnerable to the hazards of lead, arsenic, zinc than the beef cattle from pattern 1.4. The lead, copper, zinc, cadmium and chromium content in back muscles of the beef cattle which comes from pattern 2 were all higher than that in beef cattle which comes from pattern 1, but only the difference of lead content came to a significant level (P<0.01). The copper content in leg muscles of pattern 2 beef cattle was significantly higher than it in pattern 1 beef cattle (P<0.05), and the chromium content in leg muscles was extremely significantly higher than it in pattern 1 beef cattle (P<0.01),but the content of lead, zinc, cadmium, arsenic in leg muscles between the cattle come from these two feeding patterns were not significant. The relationship of the heavy metal content in liver between these two feeding patterns showed that: the lead, chromium content in pattern 2 beef cattle liver were significantly higher than that in pattern 1 beef cattle liver(P<0.05), and pattern 2 beef cattle liver copper content were extremely significantly higher than that in pattern 1 beef cattle liver(P<0.01), but there were no significant difference of the zinc, cadmium, arsenic content in liver in beef cattle between these two patterns were observed (P>0.05). The relationship of the heavy metal content in kidney between these two feeding patterns showed that: the lead, copper, zinc, chromium content in pattern 2 beef cattle kidneys were significantly higher than that in pattern 1 beef cattle kidneys (P<0.05); the cadmium and arsenic levels in pattern 1 beef cattle kidneys were higher than that in pattern 2 beef cattle kidneys, but the difference was not significant (P>0.05).5. The heavy metals in different tissues existed the following rules respectively: in the normal circumstances, the lead levels in liver and kidney were significantly higher than that in muscle tissue; the copper content in liver was extremely significantly higher than the copper content in other tissues; the zinc content in kidney was extremely significantly lower than other tissues, but the cadmium content in kidney was extremely significantly higher than other tissues; the accumulation of chromium in animal tissues was small, and the differences of chromium content among different tissues were no significant; the arsenic levels in liver was higher, but there was no significant difference of arsenic content between liver and other tissues.6. Heavy metal content in different tissues exist a complex correlation.7. Except the lead content in liver and kidney were negatively correlated with drinking water lead level, there were no significant correlation between lead content in beef cattle tissues and soil and drinking water, respectively, but the lead content in different beef cattle tissues and the lead content in beef cattle feed had extremely significant positive correlation relationship, and the muscle tissue were more susceptible contaminated by lead in feed than the liver and kidney. The copper content in feeding environment (soil, water) had a certain relationship with the copper content in different beef cattle tissues, but correlation is relatively weak, while the copper content in feed and copper content in tissue had a strong correlation. The zinc content in soil, water and dietary almost showed a positive correlation with the zinc in different beef cattle tissues (except from the correlation of the zinc content in soil and leg muscle), but the contribution rate of zinc in water and feed on tissue zinc were greater than the contribution of zinc in soil. There were no significant correlation between tissue cadmium content and cadmium content in soil, water and feed, respectively. The accumulation content of chromium in beef cattle tissues was small, and did not reflected the content of chromium in soil, water and feed. There was no significant correlation between the content of arsenic in tissues and the arsenic content of drinking water, and it also had no significant correlation with the content of arsenic in feed8. According to the contribution rate of independent variable on the dependent variable and the significance of standardized regression coefficient, and through the backward stepwise multiple regression analysis, the independent variables which had no significant influence to the dependent variable were excluded, and the best multiple linear regression equation which were measure the influence of heavy metal content in soil, water and feed to the heavy metal in beef cattle different tissues were established. |
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