| The experiment was conducted to study the effects of dietary lysine levels on growthperformance, nitrogen metabolism, serum immunoglobulin, biochemical indices, serumhormone concentration and liver and musle GHR mRNA expression of weaner to3monthsold and3～5months old growing rex rabbits. Two hundred weanling rex rabbits with anaverage body weight of (665±123) g were randomly assigned to5groups with40replicates ineach group and each replicate contained1rabbit. Rabbits in5groups were fed withexperimental diet with the following lysine levels:0.55%,0.7%,0.85%,1.0%and1.15%. Theresults were as follows..Dietary lysine levels did not affected significantly average daily intake (ADI), averagedaily gain (ADG) and feed/gain (F/G)(P>0.05) of weaned to3months old rex rabbits.Dietary lysine levels had significant influence on intake nitrogen (IN)(P=0.0065), retentionnitrogen (RN)(P=0.0459), nitrogen biological utilization (RN/DN)(P=0.0226) and the serumIgA, IgM, IgG (P<0.0001) and cholesterol (CHO)(P=0.0167). The dietary lysine levels hadextreme influence on, Lys, Met, Try, Glu, Arg (P<0.01) and Cys digestibility (P<0.05), GH(P<0.01) and IGF-I (P<0.01), and musle GHR mRNA expression (P<0.05). In conclusion, theappropriate lysine concentration in the diet of weaner to3months old growing rex rabbit was0.55～0.70%.Dietary lysine levels had very significant differences on average daily gain (ADG),feed/gain (F/G)(P<0.01) and fecal nitrogen (FN)(P<0.05) of3～5month old rex rabbits,expect for average daily intake (ADI)(P>0.05). Meanwhile, Dietary lysine levels had extremesignificantly influence on Arg, Cys (P<0.01) and Lys digestibility (P<0.05), and hadsignificantly influence on GH (P<0.05), IGF-I (P<0.01), musle GHR mRNA expression(P<0.01), liver GHR mRNA expression (P<0.05) and pH, L, a*, b*of meat quality (P<0.01).In conclusion, the appropria-te lysine concentration in the diet of3～5months old growingrex rabbit was0.70～0.85%. |
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