Comparative Study On The Effects Of Breeding Time On The Quality Of Yak Beef And Muscle Metabolites

In this experiment,six adult healthy male yaks in three different breeding times,traditional grazing,short-term fattening(3 months)and medium-long-term fattening(6 months),were used as research objects.Quality,edible quality,volatile flavor composition and muscle metabolic group differences.It aims to clarify the effect of breeding times on the distribution of yak carcass meat and muscle metabolism and provide data support for precise nutrition control of yak fattening production,and provide theoretical basis for yak meat fine processing.The test results are as follows:1.The difference in breeding time has obvious influence on the eating quality and nutritional quality of yak beef.(1)Shearing force: Short-term,medium-and long-term fattening significantly reduced the shearing force of the longest back muscle,psoas major muscle,and semitendinosus muscle(P<0.05);(2)Cooking loss: Short-term,medium-and long-term fattening significantly reduces the cooking loss of the triceps brachii(P<0.05).(3)Protein: Short-term,medium-and long-term fattening significantly increases the protein content of the triceps brachii(P<0.05).Medium-and long-term fattening significantly increases the protein content of the biceps femoris(P<0.05).(4)Fat: Short-term,medium-and long-term fattening significantly increased the fat content of the dorsal longus,semitendinosus,and biceps femoris(P<0.05);medium-and long-term fattening significantly increases the triceps and psoas fat content(P<0.05);(5)Amino acids: Short-term fattening significantly reduces the serine content of the biceps femoris,semitendinosus and dorsal longus muscles,and significantly increases the serine content of the triceps brachii(P<0.05).(6)Fatty acids: Short-term,medium-and long-term fattening significantly reduces the content of n-3PUFA and n-6PUFA in the longest back muscle,psoas major muscle,semitendon and biceps femoris(P<0.05);The PUFA content of muscles and psoas major muscles tends to decrease with increasing fattening time.The n-6/n-3 of the longissimus dorsi,biceps femoris,and semitendinosus tends to increase significantly with the extension of fattening time.It increases from 2.55,2.64 and 2.52 in the natural grazing state to 3.63,3.93 and3.64 in the short-term fattening state and 5.97,5.2 and 5.54 in the mid-long-term fattening state.2.The effect of farming times on the volatile flavors of the longest muscle of the yak.The SPME-GC-MS method was used to detect the volatile flavors of the longest muscles of the yak's back in 2 feeding modes: 26 substances;31 substances were detected in the short-term fattening group;30 substances were detected in the medium-and long-term fattening group.The detected substances can be divided into 7 categories,which are ketones,aldehydes,acids,esters,alcohols,alkenes and aromatics.The results of principal component analysis showed that compared with traditional grazing,short-term fattening and medium-long-term fattening caused a significant change in the composition of the volatile flavor compounds of the longest muscle of the yak.PCA analysis can distinguish the three.3.The effect of medium-and long-term fattening on the metabolic group of the longest muscleof the yak's back After PCA,PLS-DA and OPLS-DA analysis of the data,a total of 104 significantly different metabolites were screened out for mid-and long-term fattening compared with grazing.There are 23 significant metabolites involved in the main enriched metabolic pathways.There are 14 types of up-regulation,namely stearic acid,GMP,IMP,AMP,ADP,UMP,cytidine,uracil,palmitoleic acid,betaine,glutathione,glycolic acid,pyridoxal and D-ribose-5-Phosphate;there are 9 different metabolites down-regulated,including 3-phosphoglycerol,pyruvate,L-isoleucine,glycine,3-phospho-D-glycerol,eicosapentaenoic acid,and linoleic acid,Caprylic acid and dodecanoic acid.