Effects Of Low Protein Level Diets Supplemented With Essential Amino Acids And Cysteamnie Supplementation On Meat Quality Of Pigs

In recent years,with the improvement of genetic breeding,nutrition and feeding environment,the growth performance of pigs was improved significantly,while the meat quality was deline.The studies have proved that low protein level diets supplemented with essential amino acids could improve meat quality,especially the tenderness of meat.However,the effect of the low protein level diets supplemented with essential amino acids and cysteamine(CS)supplementation on meat quality remain unknown,and whether the interaction between them is unclear.Therefore,the aim of the present study was to evaluate the effects of low protein level diets supplemented with essential amino acids and CS supplementation on the meat quality of growing and finishing pigs,and the interactions between them.1.Effects of low protein level diets supplemented with essential amino acids and CS supplementation on meat quality and related indices of growing pigsA total of 120 barrows(42.18±0.70 kg)were arranged in a 2×2 factorial arrangement with five replicates of six each.The main effects were crude protein levels(16%and 12%)and CS supplemental levels(0 and 100 mg/kg).The duration of the experiment was 31 days.The results showed that the low protein level diets supplemented with essential amino acids(LPD)decreased the shear force and increased the intramuscular fat content(P<0.05);CS supplementation increased the activity of catalase(CAT),Total superoxide dismutase(T-SOD),glutatione peroxidase(GSH-Px)and total antioxidant capacity(T-AOC)(P<0.05),increased the content of glutathione(GSH)(P<0.05),and decreased the content of malonaldehyde(MDA)(P<0.05);LPD increased monounsaturated fatty acids(MUFA)of Longissimus dorsi(P<0.05).LPD increased(P<0.05)the mRNA abundance of sterol regulatory element binding protein 1c(SREBP-lc),fatty acid synthase(FAS),acetyl-COA carboxylase(ACC);stearoyl-CoA desaturase(SCD);heart-fatty acid bingding protein(H-FABP)and μ-calpain,decreased(P<0.05)the mRNA abundance of hormone-sensitive lipase(HSL),carnitine palmitoyl transferase-1(CPT-1)and calpastatin.CS supplementation decreased(P<0.05)the mRNA abundance of calpastatin.These results indicated that LPD increased the intramuscular fat content,changed the proportion of unsaturated fatty acids and then improved meat tenderness of longissimus dorsi in growing pigs,possibly by up-regulating lipogenic genes and down-regulating lipolytic genes expression;CS supplementation increased the antioxidation enzyme activity,decreased the content of lipid peroxide,and enhanced the antioxidant capacity of longissimus dorsi.There were no interactions between dietary protein levels and CS supplementation for all variables.2.Effects of low protein level diets supplemented with essential amino acids and CS supplementation on meat quality and related indices of finishing pigsOne hundred and twenty barrows were randomly allocated to a 2×2 factorial arrangement with five replicates of six pigs each.The primary variations were crude protein levels(14%or 10%)and CS supplemental levels(0 or 140 mg/kg).The duration of the experiment was 41 days.The results showed that low protein level diets supplemented with essential amino acids(LPD)increased the L*and a*and the content of intramuscular fat(IMF)(P<0.05),decreased the shear force(P<0.05).CS supplementation increased the activity of CAT and T-AOC(P<0.05),increased the content of GSH and decreased the content of MDA(P<0.05).LPD increased palmitic acid,linoleic acid,eicosapentaenoic acid and docosahexenoic acid(P<0.05).LPD increased(P<0.05)the mRNA expressions of fatty acid synthase(FAS),acetyl-COA carboxylase(ACC);stearoyl-CoA desaturase(SCD);peroxisome proliferators-activated receptor y(PPARy),heart-fatty acid bingding protein(H-FABP)and μ-calpain,decreased(P<0.05)the mRNA abundance of hormone-sensitive lipase(HSL),carnitine palmitoyl transferase-1(CPT-1)and calpastatin.CS supplementation increased the mRNA expression of μ-calpain(P<0.01).In conclusion,LPD improved the L*,a*and tenderness,increased the IMF content,and changed the composition of fatty acids of longissimus dorsi in finishing pigs.It might be attributed to the maintenance of lipogenesis and lipolysis and the regulation of the proteolysis process in muscle.CS supplementation increased the antioxidation enzyme activity,decreased the content of lipid peroxide.There was an interaction between dietary protein levels and CS supplementation in a*and cooking loss of meat.