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This study aimed to investigate the changes in the blood metabolic profiles of grazing yaks during the cold season to reveal their physiological status and seek the nutrients needed to be supplemented. Six castrated yaks (3 years old) with 166.8 kg (standard deviation = 5.3) of liveweight grazed in the Qinghai-Tibetan Plateau were used as experimental animals without supplementary feeding. Blood samples of each animal were collected in October and December 2015, and March 2016 for the analysis of serum biochemicals and metabolome. Results showed serum indices involved in protein metabolism in grazing yaks showed greater differences during the cold season than the metabolisms of energy or minerals. Cold stress in December had minor effects on the serum metabolic profiles of yaks compared with those in October. Yaks in October and December shared seven differential serum metabolites and enrichments of the "arachidonic acid metabolism" and "glycine, serine, and threonine metabolism" pathways compared with those in March caused by the shortage of feeds. Summarily, the nutrient deficiency would be influential on the physiological status of grazing yaks during the cold season, especially on the protein metabolism, which could be improved by supplementary feeds. [ABSTRACT FROM AUTHOR]

Yak milk dreg (YMD) is a traditional homemade fermented daily food in Tibet. In this study, we characterized the amino acid profiles and bacterial community diversities of nine different YMD samples collected from Nyingchi region of Tibet. The results showed that Glu and Pro were the major amino acid, Proteobacteria and Firmicutes were the predominant phylum, Lactobacillus was the predominant genus. The taxonomic composition and abundance of bacterial community were distinct with the YMD samples of three regions (B, G, and M) based on the principal component analysis. Metagenomic prediction based on PICRUSt analysis revealed that amino acid metabolism, carbohydrate metabolism, membrane transport were the most abundant KEGG pathway. Moreover, we constructed a related relationship of heatmap to explain correlations among the bacterial community and amino acids. This study descripted the bacterial community diversity of the YMD and enable us to develop traditional daily products resources derived from YMD. • Amino acid profiles and bacterial community diversities of yak milk dreg (YMD) were profiled. • Glu and Pro were the major amino acid. • Lactobacillus was the predominant genus. • The relationships between bacteria genera and amino acid were evaluated. [ABSTRACT FROM AUTHOR]

The objective of the present study was to produce antioxidant hydrolysate from Tibetan egg white protein hydrolyzed with papain, and to investigate the effect of added papain egg white hydrolysate (PEWH) on the quality characteristics and amino acid profiles of yak milk yogurt. A response surface methodology (RSM) was utilized to analyze the effects of hydrolysis time (X1), the ratio of enzymes to substrates, and enzyme dosage (X3) on the superoxide anion radical (O2−) scavenging activity of hydrolysates. The predicted maximum value of O2− scavenging activity (89.06%) was obtained an X1 of 2.51 h, X2 of 4.13%, and X3 of 4500 U/g of substrate, almost approaching the experimental value (88.05 ± 1.2%). Furthermore, it was found that the addition of PEWH to yak milk can enhance acidification, sensory score, the number of lactic acid bacteria (LAB), and the amino acid content in yak milk yogurt. The results suggested that PEWH displayed an exceptional potential to be developed as a functional food ingredient that could be applied during the manufacturing process of yak milk yogurt. [ABSTRACT FROM AUTHOR]