Effects Of Dietary Supple Mentation With Arginine And Glutamate On Meat Quality And Its Mechanism In Growing-finishing Pigs

The functional amino acids,arginine(Arg)and glutamate(Glu),not only serve as substrate for protein synthesis,but also represent several physiological functions in animals.Sixty Duroc × Large White × Landrace pigs with an average initial body weight(BW)of 77.1 ± 1.3 kg were used to investigate the effects of dietary supplementation with Arg and Glu on the meat quality in growing-finishing pigs.The animals were randomly assigned to one of five treatment groups(12 pigs/group,male: female 1:1).The pigs in the control group were fed a basal diet(basal diet group),and those in the experimental groups were fed a basal diet supplemented with 2.05% L-alanine(iso-nitrogenous control group),1.00% arginine(Arg group),1.00% glutamate + 1.44% L-alanine(Glu group),or 1.00% arginine + 1.00% glutamate(Arg + Glu group).After a 60-day period of supplementation,the growth performance,carcass traits,and meat quality were evaluated and the mechanism were investigated by determining the genes expression related to fat metabolism,amino acid transporters,and muscle growth factors.The results are as follows.(1)Compared with the basal diet,no significant differences(P > 0.05)in the growth performance were observed in the Arg group;however,a decrease(P < 0.05)in the percentage of SFA was observed of their longissimus dorsi(LD)muscle and backfat.In the Glu group,the final BW,1-30 d ADFI,31-60 d ADFI,average backfat thickness,and the percentage of SFA of LD muscle and backfat decreased(P < 0.05)by 7.14,23.43,8.03,33.88,6.26,and 7.87%,respectively,when compared with the basal diet group.Dietary 1.00% Arg + 1.00% Glu supplementation showed no effects(P > 0.05)on the final BW or average daily gain in pigs,but decreased(P < 0.05)their 1-30 d ADFI,average backfat thickness,percentage of SFA in the LD muscle and backfat,and the concentrations of cholesterol(CHO)and low density lipoprotein cholesterol(LDL-C)in the plasma,and increased(P < 0.05)the intramusclar fat(IMF)contents of LD and biceps femoris(BF)muscle s,when compared with the basal diet group.Furthermore,a decrease(P < 0.05)in the yellowness(b* value)in LD muscle and crude protein in BF muscle were observed in the Arg + Glu group,when compared with the iso-nitrogenous control group.(2)Dietary supplementation with 1.00% Arg + 1.00% Glu up-regulated(P < 0.05)the expression levels of PPAR? in BF muscle and HSL in backfat relative to the basal diet.Compared with the iso-nitrogenous control group,dietary supplementation with 1.00% Arg or 1.00% Glu up-regulated(P < 0.05)the expression level of LPL in LD muscle and down-regulated(P < 0.05)FATP-4 in backfat,while supplementation with 1.00% Arg + 1.00% Glu up-regulated(P < 0.05)the expression levels of FAS and LPL in LD muscle and PPAR? in BF muscle,but down-regulated(P < 0.05)the expression levels of FATP-4 and PPAR? in backfat.(3)A decrease in the free Glu and an increase in the Arg,Tau,and ?-AAA in LD muscle were observed in Arg + Glu group(P < 0.05),when compared with the basal diet.Dietary supplementation with 1.00% Arg + 1.00% Glu down-regulated(P < 0.05)the expression levels of TAT1 in LD muscle relative to the basal diet.Compared with the iso-nitrogenous control group,dietary supplementation with 1.00% Arg + 1.00% Glu down-regulated(P < 0.05)the expression levels of Mu RF1 in LD muscle.In summary,these findings suggest that dietary supplementation with 1.00% Arg showed no effect on the growth performance,but improved the meat quality by increasing the IMF content in muscle;supplementation 1.00% Glu decreased the growth performance of the pigs;supplementation with 1.00% Arg + 1.00% Glu beneficially increased the IMF deposition and improved the meat color without affecting growth performance in growing pigs,and differently regulated the expression of lipid metabolism-related genes in the adipose tissue and muscles.