Effects Of Feeding Regimens On Apoptosis And Meat Quality In Mongolian Lambs During Postmortem Aging

Intensive feeding system is the development trend of China’s mutton sheep industry.It has been clear that feeding regimens affect meat quality of sheep,but it is not clear whether this influence will continue to the postmortem aging process.Postmortem aging is an important process to complete muscle tenderization and improve meat quality.At the same time,apoptosis involved in muscle tenderization also occurs during this process.The present study was conducted to explore the effects of feeding regimens(intensive and extensive system)on postmortem muscle biochemical metabolism and meat quality of lambs based on the apoptosis pathway.In this study,Mongolian lambs were selected as the experimental objects,longissimus thoracis were collected and stored at 4 °C for 0,1,2,3,4 days.These samples were used to compare the differences in meat quality,analyze the changes in muscle cell structure and internal environment,clarify the effects of feeding regimens on apoptosis during postmortem aging in Mongolian lambs.Metabolomics and proteomic techniques were used to explore the mechanism of feeding regimens affecting apoptosis in Mongolian lambs during postmortem aging.Finally,we studied the methods for regulating apoptosis in postmortem muscle.The main findings are as follows:The effect of feeding regimens on the meat quality of Mongolian lambs during postmortem aging was analyzed.The results showed that the p H value of extensive group lambs was significantly lower than that of lambs reared in the intensive system at 1 d postmortem(P < 0.05).The cooking loss was significantly lower in the extensive group than the intensive group(P < 0.05),with the only exception of 2 d postmortem(P > 0.05).Importantly,the MFI was higher in extensive than in intensive-reared lambs during postmortem aging(P < 0.05),and the shear force was significantly lower in extensive-reared lambs than that in intensive-reared lambs within 3 d postmortem(P <0.05).The results showed that the tenderness of extensive-reared lambs was higher than that in intensive-reared lambs.The apoptosis-related morphological changes were observed,that is increased extracellular spaces and cell shrinkage.Compared to the intensive-reared lambs,the extensive-reared lambs presented significantly higher mean extracellular spaces from 1-3d postmortem(P < 0.05).The AMPK activity in extensive-reared lambs was significantly higher than that in intensive-reared lambs at each aging time(P < 0.05).The glycogen content of the extensive group was significantly lower intensive group during postmortem aging,while the lactic acid concentration and glycolytic enzyme activity were significantly higher than the intensive group(P < 0.05).The activities of CAT,GSH-Px,and T-AOC were significantly higher in extensive-reared lambs than that in intensive-reared lambs during postmortem aging(P < 0.05).The MDA content in extensive-reared lambs was significantly lower than intensive-reared lambs(P < 0.05).These data suggested that compared to the intensive system,the extensive feeding system increased AMPK activity and accelerated glycolysis,which created a low p H environment that is conducive to apoptosis,while the enhancement of muscle antioxidant capacity by extensive feeding system may be detrimental to oxidative stress-induced apoptosis.The effect of feeding regimens on apoptosis of Mongolian lambs during postmortem aging was clarified.The expression level of caspase-3 in extensive-reared lambs was significantly higher than that in intensive-reared lambs during postmortem aging,and enzyme activity of caspase-3 was also significantly higher than that in intensive-reared lambs within 3 d postmortem(P < 0.05).Overall,according to the results of expression level and enzyme activity,the activities of caspase-8 and caspase-9 in extensive-reared lambs were significantly higher than those in intensive-reared lambs(P < 0.05).The Bax/Bcl-2 ratio in extensive-reared lambs was significantly higher than that in intensive-reared lambs at 2 d and 3 d(P < 0.05).The above results showed that compared to the intensive system,the extensive system was conducive to promoting apoptosis of Mongolian lambs during postmortem aging,which was induced by the extrinsic pathway mediated by caspase-8 and the intrinsic pathway mediated by caspase-9.Exploring the mechanism of feeding regimens affecting apoptosis in Mongolian lambs during postmortem aging through metabolomics and proteomics.Ten significantly different metabolites found related to apoptosis were identified by untargeted metabolomics,of which L-alanine,glutathione,succinate,pantothenate,and oleic acid may be beneficial to promote apoptosis in extensive-reared lambs.In addition,eight metabolic pathways,including arginine biosynthesis,lysine degradation,glutathione metabolism,were closely related to apoptosis.A total of 13 differentially expressed proteins related to apoptosis were identified by TMT proteomics.Among these proteins,eight pro-apoptotic proteins such as S100A8,MFN2,BNIP3 were significantly up-regulated in extensive-reared lambs,while anti-apoptotic proteins,including CRYAB,DBNL,CD44,and BAG3 were significantly down-regulated in extensive-reared lambs.Differentially expressed proteins involved in oxidative phosphorylation,glycolysis,and ubiquitination pathways may cause the differences in apoptosis between two feeding groups,which further affected the degradation of proteins related to cytoskeleton and muscle contraction,and ultimately led to differences in meat tenderness.Dietary arginine and probiotics supplementation were used to regulate postmortem apoptosis in Mongolian lambs.Results showed that arginine and probiotics significantly reduced the enzyme activities of caspase-3,caspase-8,and caspase-9,and further affected muscle tenderization.These results indicated the feasibility of regulating postmortem apoptosis by pre-slaughter feeding technology.In conclusion,compared to the intensive system,the extensive system is beneficial to promoting apoptosis,thereby improving meat tenderness of Mongolia lambs during postmortem aging.It is feasible to regulate postmortem apoptosis by feeding technology,which provides a new thought for regulating apoptosis and muscle tenderness.