Effects Of Feeding Regimen On Myofibrillar Protein And Meat Quality After Sunit Sheep Slaughter

The longissimus dorsi muscle and biceps femoris muscle of Sunit sheep under different feeding regimen after maturation for 0,1,2,and 3 days were used as experimental materials to determine meat quality and myofibrillar function characteristics(hydration characteristics,emulsification characteristics and gel characteristics)and protein degradation related indicators,and the calpain system(CAPN1,CAPN2,CAST)and MyHC gene expression levels were determined by q-PCR technology,in order to determine the best aging time of Sunite sheep and explore the effects of feeding regimen on post-mortem aging and its mechanism.The results showed:The slaughter weight,total gain,carcass depth,carcass weight and slaughter rate of concentrated group were significantly higher than those of grazing group(P<0.05),which showed excellent slaughter performance and carcass quality.Before aging,the cooking loss of the both parts in the grazing group was significantly lower than that in the concentrated group(P<0.05),the pH value,protein solubility and EAI of the longissimus dorsi muscle were significantly higher than that in the concentrated group(P<0.05),and the b*value,protein hydrophobicity and gel elasticity were significantly lower than those in the concentrated group(P<0.05).The protein gel water retention,L*and a*values of biceps femoris muscle in the grazing group were significantly higher than those in the concentrated group(P<0.05).During the aging process,the tenderization rate of the longissimus dorsi muscle in the grazing group was significantly higher than that in the concentrated group(P<0.05),and the MFI values of the two parts in the grazing group at 2 and 3 days of aging were significantly higher than that in the concentrated group(P<0.05).And all the main indicators indicated that the muscle enters the mature stage when it was aged for 2 days.CAPN2 expression quantity of longissimus dorsi muscle in the grazing group was significantly higher than that in the concentrated group(P<0.05),CAPN1,MyHCIand MyHCIIb expression quantity of biceps femoris muscle in the grazing group was significantly higher than those in the concentrated group(P<0.05),which caused the difference of protein degradation,meat tenderizer rate,meat quality and processing performance after slaughter between two group.Correlation analysis results show that pH,solubility and MFI have significant correlations with multiple indicators.During post-mortem aging,shear force has a significant positive correlation with MyHCIIb(P<0.05),MFI has a very significant positive correlation with CAPN1,MyHCⅡb(P<0.01),EAI and MyHCI have a very significant negative correlation(P<0.01);CAPN1 and MyHCⅡb has a significant positive correlation(P<0.05).In summary,the higher expression levels of CAPN1 and MyHCⅡb in grazing group promoted the degradation of myofibrillar protein after slaughter,which in turn promoted the tenderization after slaughter.