| In present study, different levels of zinc were appended into diets of silver fox respectively in different growing phases. Based on feeding experiment,digestion metabolism experiment and slaughtering experiment, their effects on performance trait, digestion metabolism, fur quality and blood biochemical indexes of silver foxes who were in the growing period and furring period were discussed. Experimental methods and results were presented as follows:Exp.1: Single Factor design was adopted. 72 about 13-week-old healthy growing male silver foxes were randomly divided into six groups, each groups had 12 blue foxes. Zinc additive levels were 0, 30, 80, 130, 180, 500 mg/kg. Feeding experiment and digestion metabolism experiment were carried out, blood biochemical indexes were examined. The experiment was lasted for 75 days. The results indicated that:(1) Different zinc levels had significant influence on silver fox average daily gain (ADG) and feed conversion efficiencies, and the values in group 1 were significantly lower than that of the other groups which were supplemented with zinc (P<0.05), but the differences between the other zinc additive groups were not significant (P>0.05).(2) Different zinc levels had no significant influence on daily intake, DM digestibility, N metalbolism and fat digestibility of silver foxes (P>0.05).(3) The serum zinc concentration of group 1 was significantly lower than that of other zinc additive groups (P<0.05), with the increasing of dietary zinc, serum zinc level increased gradually.(4) The serum AKP enzyme activity of group 1 was significantly lower than that of the other zinc additive groups (P<0.05).It was enhanced with the elevation of dietary zinc additive levels in the range of 0 mg/kg to 180 mg/kg.(5) Different dietary zinc additive levels had no significant influence on the enzyme activity of serum CuZn-SOD, LDH and GPT (P>0.05).(6) All the experiment results indicated that the dietary zinc levels of 66.54 mg/kg (adding 30 mg/kg zinc in the basal diet) could be possible to meet the requirement for silver foxes during growing period, and it is suggested that the optimal supplement amount of zinc was from 30 mg/kg to 80 mg/kg in the growing period of silver fox.Exp.2: Single Factor design was adopted. 72 about 23-week-old healthy male silver foxes were randomly divided into six groups, each groups had 12 silver foxes. Zinc additive levels were 0, 30, 80, 130, 180, 500 mg/kg. Feeding experiment, slaughter experiment and digestion metabolism experiment were carried out, blood biochemical indexes were examined. The experiment was lasted for 91 days. The results indicated that:(1) The average daily gain (ADG) of group 1 was signficantly lower than that of the other groups which were supplemented with zinc (P<0.05), but the differences between the other zinc additive groups were not significant (P>0.05). (2) Different zinc levels had no significant influence on daily intake, feed conversion efficiencies, DM digestibility, N metalbolism and fat digestibility (P>0.05).(3) The serum zinc concentration of group 1 was signficantly lower than that of other zinc additive groups (P<0.05), with the increasing of dietary zinc, serum zinc level increased gradually.(4) The serum AKP enzyme activity of group 1 was significantly lower than that of the other zinc additive groups (P<0.05). It was enhanced with the elevation of dietary zinc additive levels in the range of 0 mg/kg to 180 mg/kg.(5) Different dietary zinc additive levels had no significant influence on the enzyme activity of serum CuZn-SOD, LDH and GPT(P>0.05).(6) The length of guard fur and underfur as well as the pelt classfication of group 1 was signficantly lower than that of the other groups (P<0.05), but the differences between zinc additive groups were not significant (P>0.05).(7) Different zinc levels had significant influence on the development of liver and pancreas, and had no significant influence on the development of the other tissues. The liver weight of zinc additive groups all increased in varing degree than group 1, the liver weight of group 6 was significantly higher than that of group 1(P<0.05). The pancreas weight of group 1 was significantly higher than that of the other zinc additive groups(P<0.05).(9) With the increasing of dietary zinc levels, zinc concentrations of liver, Pancreas and tibia increased significantly (p<0.05 or P<0.01). The correlations between dietary zinc levels and zinc concentrations in tissues were as follows: liver>pancreas>tibia. It was suggested that liver and pancreas zinc concentrations could be sensitively indicated of dietary zinc levels.(10) All the experiment results indicated that the dietary zinc levels of 67.67 mg/kg (adding 30 mg/kg zinc in the basal diet) could be possible to meet the requirement for silver foxes during furring period, and it is suggested that the optimal supplement amount of zinc was from 30 mg/kg to 80 mg/kg in the furring period of silver fox.
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