Effect Of Dietary Copper Supplement On Growth Performance, Digestion, Blood Biochemical Parameters And Liver MT-â…  MRNA Expression Of Growing Meat Rabbits

Two experiments were designed to evaluate the effect of dietary Cu supplement levels on production performance, organ development, blood biochemical metabolites, serum hormone levels, microelement digestibility, tissue copper retention and liver MT-I mRNA expression of weaned~3 month old meat rabbits. One hundred weaned New Zealand rabbits were allocated to individual cages and randomly divided into five groups. Animals in each group were fed with the following copper additional levels: 0, 20, 40, 80, and 160 mg/kg in original matter basis respectively. The results were as follows.Experiment one: The dietary different amount of copper supplement affected significantly average daily gains (ADG) (P<0.05), and had no significant influence on feed/gain (F/G) and average daily intake (ADI) (P>0.05). The dietary copper supplement levels had no significant effect on organ weight, organ index, serum cuprozinc-superoxide dismutase (CuZn-SOD) and ceruloplasmin (Cp) (P>0.05). The dietary Cu levels affected significantly the contents of serum total protein (TP) and globulin (Glob) P<0.05), and it had no significant effect on serum albumin (Alb), the albumin/globulin ration (A/G), urea nitrogen (SUN) and total cholesterol (TC) ( P>0.05 ). The dietary different copper levels could improve serum insulin (Ins) concentration (P<0.01), and it had significant influence on serum growth hormone (GH) concentration (P<0.05), but it had no significant influence on serum insulin-like growth factor-I (IGF-I) concentration (P>0.05). The dietary copper levels affected significantly the fecal Cu, Zn (P<0.01) and digestible copper, digestible zinc and liver Cu content (P<0.01); When the dietary copper level increased, the content of fecal copper and liver copper multiple increased. But no significant effect on the fecal Fe, the digestible Fe, the rate of digestible Fe and Cu. Different dietary copper levels affected significantly the MT-I mRNA expression (P<0.01). In conclusion, the appropriate dietary copper supplement level of weaned~2 month-old meat rabbits was 40~80 mg/kg (The content of copper in feed is 50～90 mg/kg).Experiment two: When the initial body weight was no significant difference (P=1.000), dietary copper level affected significantly ADG, ADI and F/G; and could improve living body before slaughter, eviscerated carcass weight and semi-eviscerated carcass weight; and the liver weight of rabbits (P<0.01). But no significant effect on eviscerated percentage, semi-eviscerated percentage, other organ weight and organ indexes (P>0.05). The dietary copper supplement levels had significant effect on the activity of serum CuZn-SOD, Cp (P=0.006, P=0.0008), serum TP, Alb, Glob, A/G, SUN and TC of rabbits (P<0.05). The activities of two enzymes increased then decrease when dietary Cu levels rise. The different amount of dietary copper had significantly effected the content of Cu in liver and plasma, the fecal Cu, Fe, Zn, digestible copper and the digestibility of copper of 2~3month-old meat rabbits (P<0.01) . But had no significant influence on serum Ins, GH and IGF-I, the content of copper in muscle, the content of Zn, Ca, Mg in plasma, the digestible Fe, rate of digestible Fe, digestible Zn and rate of digestible Zn of 3 month-old meat rabbits (P>0.05). When the dietary copper level increased, the content of fecal copper and liver copper multiple increased. The dietary copper levels had no significant influence on the expression of MT-I mRNA in liver of 2~3 month-old rabbits (P>0.05). In conclusion, the appropriate dietary copper level to 2~3 month-old rabbits was 40~80 mg/kg (The content of copper in feed is 50～90 mg/kg).