| The purpose of this trail was to study the effect of different methionine levels on the production performance, nitrogen metabolism performance,immunity performance, blood metabolites in serum, hormone levels in serum and IGF-ImRNA expression in liver of weaned～2 month and 2～3months old 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 a diet with the following methionine additional levels: 0, 2, 4, 6, and 8 g/kg in original matter basis respectively. The results were as follows.Experiment one: Different amount of dietary methionine had significant influence on growth performance of weaned～2 month old rabbits (P<0.05). When the crude protein was suitable, in isoprotein diets, the additional methionine level was 0.4%, the average daily gain (ADG) was 30.8 g/d, and the ADG first increased and then decreased, when the methionine was 0.4%, F/G was the lowest and was 3.29:1, F/G first decreased and then increased. In isoprotein diets, the main factor which influenced the nitrogen balance was the nitrogen level in the diets but was not the methionine level. Methionine level in diets only influenced the Albumin levels in serum. Immunity performance was affected by methionine levels, the weight of thymus and thymus index was the highest when the methionine was 0.4%, at the same time, when the methionine level was 0.2%～0.4%, immunoglobulin A (IgA) levels in serum was the highest. Methionine can affect the release of hormone in some degree, when the methionine level was 0.8%, growth hormone (GH) levels in serum was the highest, insuline like growth factor -I (IGF-I) in serum had a trend that first increased and then decreased (P=0.086), IGF-I level in serum was the highest when the methionine levels was 0.4%. IGF-I level in serum had a close relationship with growth performance. In conclusion, the appropriate methionine level was 0.4% to weaned～2 month old rabbits.Experiment two: Methionine levels had significant influence on the ADG of 2～3 month old rabbits, when the additional level of methionine was 0.2%, 0.4%, it had a significantly difference compared with other groups (P<0.05), when the methionine level was 0.2%, ADG was the highest, and was 34.72 g/d, methionine had no significant influence on F/G and ADI. Methionine had no significant influence on nitrogen metabolism, when the additional methionine level was 0.2%, retained nitrogen was the highest, serum urine nitrogen (SUN) was the lowest. Methionine can improve immunity performance of rabbits, when the additional level was 0.4%, liver weight and liver index was the highest, methionine had no effect on immunoglobulin. Methionine can improve hormone in serum of rabbits, the concentration of IGF-I in serum was the lowest in control group, and had a significant differences with the other groups. The concentration of insuline increased and then decreased, methionine had no effect on GH concentration. Methionine had no influence on the carcass percentage and internal organs growth index. In conclusion, the appropriate methionine for 2～3 month old rabbits was 0.2%～0.4%.Experiment three: Dietary methionine levels had significant effect on the expression of IGF-ImRNA of weaned～2 month rabbits(P<0.05) and had extreme significantly influence on the 2～3 month old rabbits(P<0.01), but the expression of IGF-ImRNA of weaned～2 month was higer than that of 2～3 month old rabbits.
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