Effects Of Dietary Methionine On Growth Performance, Blood Metabolites In Serum And Ghr Mrna Expression Of Growing Rex Rabbits

The purpose of this trail was to study the effect of different methionine levels on theproduction performance, nitrogen metablosim performance, immunity performance, bloodmetabolites in serum, hormone levels in serum and GHR mRNA expression in liver ofweaned to3months-old and3to5months-old rabbits. Two hundred weaned Rex rabbits wrerallocated to individual cages and randomly divided into five groups. Animals in each groupwere fed with a diet with the following methionine additional levels:0,1.5,3.0,4.5and6.0g/kg in original matter basis respectively. The results were as follows.Different amount of dietary methionine had no significant influence on average dailyintake (ADI) of weaner to3months old Rex rabbits (P>0.05) but significantly affect averagedaily gain (ADG)(P<0.05), in0.45%methionine treatment was the highest16.76(g/d), anddid extremely significant affect feed/gain (F/G)(P<0.01), in0.45%methionine treatment hasthe minimum (3.55). Different dietary methionine levels had no significant influence onintake nitrogen(IN)，fecal nitrogen(FN)，urinary nitrogen(UN)，digestible nitrogen(DN)，Nitrogen retention(RN)， nitrogen apparent digestibility(DN/IN)， nitrogen utilizationrate(RN/IN) and biological value of nitrogen (RN/DN)(P>0.05). Dietary threonine levels hadsignificantly influence on isoleuci, lysine(P<0.05) and extreme significantly influence on thedigestibility of serine, glutamicacid, alanine, cystine, valine, methionine, leucine andtyrosine(P<0.01).With the increase of methionine level， IgA， IgM and IgG concentration inserum had no significant changes (P>0.05）. Different dietary methionine levels also had nosignificant influence on TP and TG（P>0.05）but had extremely significant influence on serumurea nitrogen (SUN) in serum （P<0.01）.The SUN in the groups with the dietary containing0.30%,0.45%was extremely lower than those groups which containing0,0.15%and0.60%,in0.45%methionine treatment has the minimum5.70（mmol/L）. Dietary methionine levelshad no significance on InS and GH, but had extremely sinnifcance on IGF-I. Dietarymethionine levels also had no significance on the expression of GHR-ImRNA. In conclusion,the appropriate supplementation of methionine in diet of weaner to3-month-old growing Rexrabbit was0.45%(the actual content of threonine in diet was0.61%). Methionine levels had no significant influence on the ADG of3~5months old Rexrabbits(P>0.05), ADG had a trend that first increased and then decreased, when themethionine level was0.15%, ADG was the highest, and was16.60g/d, methionine hadsignificant influence on the ADI(P<0.05), in0.30%methionine treatment was the highest.,methionine levels had no significant influence on the F/G bue F/G had a trend that firstdecreased and then increased, when the methionine level was0.30%, F/G was the lowest, andwat6.69. Different dietary methionine levels had no significant influence on intakenitrogen(IN)，fecal nitrogen(FN)，urinary nitrogen(UN)，digestible nitrogen(DN)，Nitrogenretention(RN)，nitrogen apparent digestibility(DN/IN)，nitrogen utilization rate(RN/IN) andbiological value of nitrogen (RN/DN)(P>0.05). Dietary methionine levels had extremesignificantly influence on the digestibility of methionine and histidine（P<0.05）and extremesignificantly influence the digestibility of threonine, serine,glutamicacid and cystine. With theincrease of methionine level， IgA and IgM concentration in serum had no significantchanges (P>0.05）but IgG had extreme significantly influence(P<0.01). Different dietarymethionine levels had no significant influence on TP and TG and SUN in serum（P>0.05）,when the additional level of methionine was0.15%, SUN was the lowest.Methionine can effect the relase of hormone in some degree, when the methionine wa0.15%,growth hormone (GH) levels in serum was the highest. Dietary methionine levels hadsignificant dffect on the expression of GHRmRNA. In conclusion, the appropriate methioninefor3to5months old rabbit was0.15%～0.30%(the actual content of threonine in dietwas0.31%～0.46%).