Dynamics of Selected Milk Quality Parameters and Expression Patterns of miR-26a, miR-27a, and miR-148a During Transition From Colostrum to Mature Milk in Awassi Sheep.

This study investigated expressions of microRNA (miR)-26a, miR-27a, and miR-148a in plasma, colostrum and milk collected on different days (0th, 4th, 7th, 14th, and 28th days) during transition from colostrum to milk in Awassi sheep. Relationships between miRNAs and quality parameters were also explored. During transition, Somatic Cell Count, Fat-free dry matter, protein, lactose decreased, pH, freezing point (FP), electrical conductivity (EC) increased. Malondialdehydes (MDA) were tended to decrease in plasma and milk. Compared to 0th day, miR-26a was upregulated approximately 27-folds and 17-folds in 14th and 28th days, in milk. On 14th day, miR-27a showed almost 18-folds upregulation, while miR-148a was downregulated more than fivefolds on 7th and 14th days. In plasma, miR-26a was upregulated almost 40-folds and sevenfolds on 7th and 14th days. Additionally, miR-27a was upregulated by approximately fivefolds on 4th day, around 20-folds on 7th day, and about fourfolds on 14th day. miR-148a was upregulated approximately 11-folds on 7th day. While miR-26a positively correlated with miR-27a, pH, fat, and EC, it was negatively correlated with MDA in plasma. miR-27a was positively correlated with miR-148a and pH. Plasma miR-148a and milk miR-148a were negatively correlated. miR-26a and miR-27a were positively correlated in milk. Milk miR-26a was positively correlated with pH, FP, and EC, while it was negatively correlated with fat, milk and plasma MDA. Milk miR-27a was negatively correlated with fat and MDA, but positively with EC. The results obtained for the first-time during transition indicate potentials of miR-26a and miR-27a to act as biomarkers for sheep milk quality.