Effect Of Feeding Systems On Antioxidative Capacity And Mitochondrial Function Of Lamb During Post-mortem Aging

Due to the grazing prohibition in grassland and the pursuit of breeding benefits,the sheep were usually finished with high concent rat e diets.Long-term feeding of high concentrate diet led to the oxidative stress of sheep,which may cause changes in meat quali ty after slaughter.In this thesis,the effect of grazing or high-concentrat e diet finishing on the antioxidative capacity and mitochondrial functi on of l amb during post-mortem aging（0h,6h,24h,72h,120h）was investigat ed.Meanwhil e,the physical and ch emical properties,proteome of lamb after sl aughter were detect ed.10 Mongoli an sheep were select ed with 5 in pasture group（PF）and 5 in high concentrat e group（HC）respectively.The lam bs i n two groups had a similar average live weight of 50±5 kg at slaughter.After slaughter,the left longissimus dorsi muscle was sampled and used for further det ection.The res ults were as foll ows:1.The ultimate pH value,ash content,a*value and essent ial amino acid content in PF group were signifi cantly hi gher than those in HC group（P<0.05）,while the crude fat cont ent was significantly lower than that in HC group,indicated that the lamb finished at pasture had higher nutritional components than those of high-concentrate di et finished lamb.2.The carbonyl cont ent and TBARs value in HC group were significantl y higher than thos e in PF group（P<0.05）during aging,whil e the sulfhydryl content and SOD activity,T-AOC value,CAT and GSH-Px activity w ere significantly lower t han those in PF group（P<0.05）.The re sults indicated that high-concentrat e diet finishing led to the decrease of antioxidat ive capacity and cell oxidative stability of lamb during post-mortem aging.3.During the m aturation period,the intracellular ROS content,mitochondrial m embrane perm eab ility and lipid peroxidation in HC group were significantly higher than those in PF group（P<0.05）.The ROS content,mitochondrial membrane permeability and lipid peroxidation l evel in HC g roup were higher than thos e in P F group by 25.27%,8.75%and 14.7 5%（0h）and by10.06%,70.37%and 16.81%（120h）res pectively.The reduction level of cytochrome c in HC group was significantl y lower than that in PF group during whole aging period.The mitochondri al Ca²⁺content in HC group and PF group reached the highes t value at post-mortem 6h and 72h respectively.The above results suggested that the mitochondrial function dam age of lam b fed with high concentrat e diet was more serious at post mortem m aturity,wtich may due to earli er occurre nce of Ca²⁺overload and lowe r reduction l evel of cytochrom e C.4.Based on TMT technology,the proteomics in the longissi mus dorsi muscle in PF group and HC group at 0h after slaughter were analyzed,and a total of 2029 protei ns containing quanti tative information were identifi ed.There were 156 prot eins with signifi cant differences in expression,among which 102 proteins were up-regulat ed,including CRYAB,HSPB1,TNNT1,TNNI1,TNNC1,MYL2,MYL4,MYH7,MCU and ACSL4.In addition,there were 54 down-regulat ed prot eins,including GSTM3,SOD1,CAT,HBB,PDK2,PDK4 and PGM 1.The results from GO function enrichment analysis toward differential proteins showed that the up-regulated differential proteins were mainly enri ched in the functional area of s triated muscl e cont raction process,mitochondrial transm embrane transport process and heat shock bi nding protein.The down-regul ated differential prot eins were mainly concentrated in the functional areas of lipid metabolism reg ulation,catal ase and antioxidant activity,indicat ed that high-concent rate diet finishing had rem arkable effects on protein st ructure,antioxidat ive capacit y,mitochondri al function and lipid metabolism of sheep muscle.In conclusion,oxidat ive stress in sheep caused by high concent rate di et finishing significantl y decreased the oxidative stability of lamb after slaughter,lead to the damage m itochondrial.Those changes also had rem arkable impact on muscle protein expression and antioxidat ive enzym e activities in longissimus dorsi muscle,may finally result in the decline of m eat quality.