Effects Of L-carnitine On Growth Performance,Muscle Quality,Fat Metabolism And Ammonia Excretion Rate Of Paramisgurnus Dabryanus

In this study,the effects of L-carnitine on growth performance,muscle quality,fat metabolism and ammonia nitrogen excretion of Paramisgurnus dabryanus were studied.A total of 1680 healthy Paramisgurnus dabryanus with initial weight of(0.40±0.10)g were selected and randomly divided into 7 treatment groups(A~G),with3 replicates in each group and 80 duplicates in each group.Basic diet(group A)with crude fat content of 5.63% and high-fat diets with L-carnitine content of 0,100,200,300,400,500 mg/kg of crude fat content of 7.62% were fed to fish for 60 days.At the end of the feeding trial,growth performance,plasma biochemistry,lipolytic enzyme,muscle nutrition and ammonia excretion rate of the Paramisgurnus dabryanus were measured.There is a majority of results as follow:(1)Compared with the control group,the addition of 100 mg/kg L-carnitine to the high-fat feed increased the weight gain rate,specific growth rate,feed conversion rate of Paramisgurnus dabryanus,but no significant(P>0.05).However,with the increase of L-carnitine dose,the weight gain rate,specific growth rate,feed conversion rate were reduced.(2)The increase of feed fat content increased the content of TG,T-CHO,BUN(P<0.05)and ALB(P>0.05).L-carnitine in high-fat feed can reduce the content of triglyceride,total cholesterol and urea nitrogen in plasma and increase the level of albumin.When 500 mg/kg L-carnitine was added,the content of TG was the lowest,which was significantly different from the control group(P<0.05).When 300 mg/kg L-carnitine was added,T-CHO content was the lowest,compared with the control group,but no significant(P>0.05).With the increase of L-carnitine,BUN content decreased significantly and ALB content increased.When L-carnitine was added at 200 mg/kg,compared with the control group(P<0.05),BUN decreased by 38.89% and ALB increased by 49.15%.The increase of feed fat content increased the activity of LPL,HL and TL in hepatopancreas,but the difference was not significant(P>0.05).L-carnitine can increase LPL,HL and TL activities in high-fat diet.LPL and HL activities were the highest by feeding 500mg/kg L-carnitine,compared with the control group,but no significant(P>0.05)between other groups.With increased of L-carnitine,TL activity gradually increased.TL activity was the highest by feeding 500mg/kg L-carnitine,compared with the control group,increased significantly by 18.47%(P<0.05).(3)The increase of fat content in the feed increased the crude lipid content and decreased the crude protein content of the muscle of the Paramisgurnus dabryanus,but no significant(P>0.05).In high-fat feed,with the increase of L-carnitine content,crude protein content increased and crude lipid content in muscle decreased.Adding 200 and400mg/kg L-carnitine,compared with the control group,crude protein content increased significantly by 9.73% and 10.61%(P<0.05),respectively,but no significant difference(P>0.05)between other groups.Compared with the control group,adding 300,400 and500 mg/kg L-carnitine,crude lipid content decreased significantly(P<0.05)by 15.18%,17.9% and 15.95%,respectively,but no significant difference between other groups(P>0.05).Analysis on muscle amino acid components showed that 100mg/kg L-carnitine improved the TAA(total amino acid),EAA(essential amino acids),EAAI(essential amino acids)and DAA(flavor amino acid)contents,but no significant difference between control group and basal feed group(P>0.05).With the increase of L-carnitine content,Na,K,Mn and Mg contents in the muscle showed an incremental trend.But L-carnitine had no effect on the Fe and Zn contents.Compared the control group,Na contents was increased significantly(P<0.05)in 400 and 500 mg/kg dietary L-carnitine and Mn contents was increased significantly(P<0.05)in 100,400,500 mg/kg dietary L-carnitine.(5)Fat contents increased in the feed did not significantly affect ammonia excretion rate in Paramisgurnus dabryanus(P>0.05).However,after L-carnitine added in high-fat feed,firstly,the ammonia excretion rate decreased and then increased.Among them,ammonia excretion of 100 mg/kg L-carnitine group decreased significantly(P<0.05).In conclusion,Under experiment condition,adding appropriate L-carnitine in the diet can promote the growth performance and improve muscle quality and improve lipolytic enzyme activity in the hepatopancreas,reduce the content of plasma fat and urea nitrogen and ammonia excretion rate,and improve the level of albumin,so as to promote the growth of Paramisgurnus Dabryanus and improve its muscle quality.Considering muscle crude protein contents,it is suggested that the L-carnitine addition level is 224.5mg/kg.According to muscle crude fat contents,the effect of reducing fat was the best when the level of L-carnitine was 442.1 mg/kg.In terms of ammonia excretion rate,it is recommended to add 268.8 mg/kg.