Analysis Of The Difference In Nucleotide Ontent Between Goat And Cow Milk At Different Lactation Stages Based On LC-MS/MS

Due to the apical secretion of goat’s milk and the local secretion of cow’s milk,there are significant differences in active substances and functional components between sheep’s milk and cow’s milk.Nucleotide,as an important bioactive substance in milk,has unique physiological functions,and there are many forms of nucleotides in fresh milk.In addition to free form nucleotides,there are also many forms of nucleosides,such as nucleoside polymers and adduct.At this stage,research on nucleotides in milk mainly focuses on the determination of free nucleotides,and there is no systematic comparative study on the total amount of nucleotides in goat milk and cow milk.For this purpose,this study selected 9Guanzhong milk goats,9 milk sheep,and 9 Holstein cows with similar body weight and milk production in their second pregnancy.Goat milk,sheep milk,and cow milk were collected from three lactation stages: colostrum,full lactation,and final lactation.Targeted detection of 5 nucleotides and 4 nucleosides was performed using liquid chromatography tandem mass spectrometry(LC-MS/MS)method,and multivariate statistical analysis was conducted,To provide scientific basis for the differential utilization of functional dairy products.The research results are as follows:1.The content of 5 nucleotides(AMP,GMP,CMP,IMP,UMP)in goat milk and colostrum is the highest,especially the content of UMP and IMP in goat milk is 33% and28%,and the relative abundance of these 5 substances in goat milk is significantly higher than that in cow milk(P<0.01);The relative abundances of uridine,hypoxanthine and xanthine in goat milk at different lactation stages were significantly higher than those in cow milk(P<0.01)2.The content of five nucleotides(AMP,GMP,CMP,IMP,UMP)in sheep milk and cow milk during the colostrum stage accounts for 81%,and the relative abundance of these five substances in sheep milk is significantly higher than that in cow milk(P<0.01);The relative abundance of three nucleoside substances(Uridine,Hypoxantine,Xanthine)in sheep milk and cow milk during the early lactation stage was significantly higher than that in the peak and late lactation stages of cow milk(P<0.01),while the peak lactation stage was significantly higher than that in the late lactation stage(P<0.05).Especially,Uridine accounted for 68% and 78% of the content during the peak and late lactation stages of sheep milk,The relative abundance of Orotic acid in bovine milk during the entire lactation period was significantly higher than that in sheep milk(P<0.01).3.The relative abundance of five nucleotides(AMP,GMP,CMP,IMP,UMP)in goat milk and sheep milk was significantly higher in the early lactation stage than in the peak and late lactation stage(P<0.05),and the relative abundance in the late lactation stage was significantly higher than in the peak lactation stage(P<0.01).Moreover,the content of five nucleotides in goat milk was higher than that in sheep milk at different lactation stages,especially in colostrum,with a content of 80%;Uridine and Orotic acid,two nucleoside substances,account for a significant proportion in the peak and late lactation stages of sheep,and their abundance is significantly higher than that of goat milk at different lactation stages(P<0.05);The proportion of nucleoside substances,Hypoxantine and Xanthine,in different lactation stages is relatively low.In summary,the variation patterns of nucleotide substances in goat milk,sheep milk,and cow milk at different lactation stages can be obtained.In the early lactation stage,the abundance of five nucleotides(AMP,GMP,CMP,IMP,UMP)is highest in goat milk,followed by sheep milk and cow milk;During the peak and late stages of lactation,the abundance of uridine in sheep milk is the highest,followed by goat milk and cow milk;The abundance of whey acid in milk during the peak and late stages of lactation is significantly higher than that in goat and sheep milk,and it is a relatively high substance in milk.The above results show that the nucleotide substances in goat milk,sheep milk and cow milk have their own advantages,which can be regarded as a good natural source of these bioactive substances,and can become the basic reference basis for the differential utilization of milk product differentiation.