| This experiment was conducted to investigate the effects of supplemental feeding of Guanidineaceticacid(GAA)and methyl donors on concentration of GAA-related metabolites in plasma,digestion and metabolism,production performance and slaughter performance of Kazakh lambs,This study provides a scientific basis for the application of GAA and GAA combined with methyl donors in the diet of Kazakh lambs.Twenty-four healthy Kazakh lambs aged 4-5 months with an average body weight of(25.95±1.43)kg were randomly divided into 4 groups with 6 lambs in each group.They are the control group,test group I,test group II,and test group III.All lambs were fed basal diet with the same nutrient level.The control group was fed the basal diet only.Group I was supplemented with 1500 mg/kg GAA,Test group II was supplemented with 1500 mg/kg GAA+4 g/d Rumen Bypass Betaine(RPB),Test group III was supplemented with 1500 mg/kg GAA+9 g/d Rumen Bypass Methionine(RPM).The feeding experiment lasted for 80 days.Blood samples were collected 0 h before feeding and 1,2,3 and 4 h after feeding on the 30 th day of the experiment;The feces and urine of lambs were collected on the 25 th and 55 d of the experiment for four consecutive days;Lambs were weighed before morning feeding on day 1,31,61 and 81 of the experiment;Lambs were slaughtered on the 81 d of the experiment.The results showed that: 1)2 h after feeding,the plasma GAA concentrations of experimental group I,experimental group II and experimental group III increased by 48.12%,32.24% and 51.85% respectively compared with the control group(P<0.01);0h before feeding,plasma creatine concentration in test III group was increased by 20.37%compared with control group(P<0.05);2h after feeding,Compared with the control group,the plasma creatine concentration of test group Ⅰ and test group Ⅲ increased by 68.45% and 82.62% respectively(P<0.01);3h after feeding,plasma creatine concentration in test group I was increased by 25.58%compared with control group(P<0.01);2h after feeding,The plasma creatinine concentration of test groupⅠ and test group Ⅲ increased by 37.05% and 20.51% respectively compared with the control group(P<0.05).2)On the 25 th day of the experiment,P digestibility and apparent digestibility of test group II were increased by 22.22% and 21.81% compared with control group,respectively(P<0.05);P retention tended to increase(P=0.062).3)From 1 to 30 days of experiment,the daily gain of lambs in test II group and test III group was increased by 11.95% and 10.34% compared with control group,respectively(P<0.05);Compared with the control group,the feed weight decreased by 11.50% and 7.79% respectively(P>0.05).4)There were no significant differences in carcass weight,slaughter percentage,lean meat weight,lean meat percentage,fat meat weight,fat meat percentage,bone weight,bone ratio and bone-meat ratio among all treatment groups(P>0.05).Under the conditions of this experiment,Both GAA and methyl donors(RPB or RPM)could increase the concentrations of GAA,creatine and creatinine in plasma,GAA combined with RPB increased phosphorus digestibility and apparent digestibility,GAA combined with RPB or RPM can increase the daily gain of lambs at the early stage of experiment,However,it had no effect on the slaughter performance of lambs.As a result,It is better to supplement 4 g/d RPB when feeding1500 mg/kg GAA to lambs. |
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