| Two experiments were conducted to evaluate the effect of feeding 70mg/kg,105mg/kg,140mg/kg,175mg/kg,210mg/kg zinc (Zn), from zinc methionine (Met-Zn) and zinc sulfate (ZnSO4), on growth performance, carcass rate, purtenance index, tissue zinc concentration of 1.5-month-old and 2.5-month-old Brittany Rabbits. It can provide scientific basis for the determination of suitable zinc level in practical diet of commercial rabbit in different stages, and it also provide base references to explore the role of zinc on animals and the application of organic and inorganic zinc.Experiment 1. 132 rabbits at 1.5-month-old were selected and randomly divided into 11 treatments (4 duplicates per treatment and each duplicate had 3 rabbits). The control group was fed basic diet, test groups were fed diets added zinc with different sources and levels on the base of basic diet. The trial lasted for 37d, including 7d for adaptation. The result showed that: The average daily gain (ADG) of Met-Zn groups were significantly higher than the groups which added ZnSO4 (P<0.01),the feed gain ratio (F/G) of Met-Zn groups were significantly lower than the groups which added ZnSO4 (P<0.01),the carcass rate (CR) of ZnSO4 groups were higher than the groups whith added Met-Zn (P<0.05). There was no sighificant difference of the average daily intake (ADI), purtenance index, tissue zinc concentration among zinc sources groups(P>0.05).Zinc levels affected spleen index significantly (P<0.05), the spleen index of 170mg/kg and 210mg/kg levels were lower than 105mg/kg and 140mg/kg levels (P<0.05). The interaction of the zinc source with levels affected spleen index (P<0.05), and it significantly affected liver index, liver zinc content and spleen zinc content (P<0.01). It showed that adding the two zinc sources in diet can improve production performance of rabbits, and the effect of Met-Zn was superior to ZnSO4. There were interaction among zinc source and zinc levels in diet, and there were difference mechanisms of action between Met-Zn and ZnSO4. Comprehensively considerate, the optimal zinc level in 1.5-month-old rabbit was between 70mg/kg and 140mg/kg.Experiment 2. 132 rabbits at 2.5-month-old were selected. Experiment design refered to experiment 1. The result showed that the average daily intake (ADI), spleen zinc content, kidney zinc content of ZnSO4 were higher than the groups which added Met-Zn (P<0.05), There was no sighificant difference of the average daily gain (ADG), feed gain ratio (F/G), carcass rate, purtenance index, liver zinc content, longissimus muscle zinc content among zinc sources groups (P>0.05). Zinc levels affected the average daily intake (ADI) highly significantly (P<0.01), and affected the carcass rate (CR) significantly (P<0.05),the average daily intake (ADI) and the carcass rate (CR) increased with increasing in the amounts of zinc in diets. Zinc levels affected the kidney zinc content highly significantly (P<0.01), and it affected the liver zinc content significantly (P<0.05). As the amounts of zinc in diets increased, kidney and liver zinc content increased and then decreased with the peak in 140mg/kg . The interaction of the zinc source with levels significantly affected the average daily gain (ADG), liver and kidney zinc content (P<0.01), and it affected spleen zinc content (P<0.05). It showed that adding zinc in diet can improve production performance of 2.5-month-old rabbits, but there was no difference between Met-Zn and ZnSO4. There were interaction among zinc source and zinc levels in diet, and there were difference mechanisms of action between Met-Zn and ZnSO4. Comprehensively considerate, the optimal zinc level in 2.5-month-old rabbit was about 70mg/kg.To sum up, adding zinc in diet can improve production performance of rabbits, With the development procedure, the difference between two kinds of zinc source become indistinct. there were difference mechanisms of action between Met-Zn and ZnSO4. The change trend of purtenance index and tissue zinc concentration were different. Zinc sources and levels in diet had no effect on muscle zinc content. |
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