Comparative metabolomics analysis of Small-Tailed Han and DairyMeade ovine milk

As health improvement is paid increased attention, the research on small ruminant milk is becoming more prevalent. Studies have shown that the nutrient content in sheep milk is higher than goat and cow milk. This study aimed to explain the difference of Small-Tailed Han (STH) and DairyMeade (DM) milk through the untargeted metabolomics analyze with ultra-high-performance liquid tandem chromatography quadrupole time-of-flight mass spectrometry (UPLC–Q-TOF–MS). The results showed that fat, protein, casein, solids of STH milk were higher than DM, but the lactose of it was lower than DM. The metabolomics analysis showed that 4904 annotated metabolites were identified and 68 significantly different metabolites between milks were detected. 47 metabolites in the STH were significantly higher than the DM and 21 metabolites were significantly lower than the DM. The significantly different metabolites were mainly enriched in glycerophospholipid metabolism, glycosyl phosphatidyl inositol (GPI)-anchor biosynthesis, regulation of autophagy, and purine metabolism. We hypothesized that the high level of phospholipids in STH milk may lead to higher fat content than DM milk; the high level of L-Carnitine would enhance the lipid metabolism and further lead to lower milk fat of DM milk. The high level of nucleotides and their derivatives in DM milk may be related with its high milk production performance. It demonstrated that the composition of the sheep milk changed with breeds. Furthermore, the interactions and metabolic pathways were analyzed to explore the mechanisms related to different lactation traits between two breeds. This study would provide theoretical basis for later dairy sheep breeding.