Recent years have seen rapid progress in dairy cattle genomics with many achievements having been made up to now. For the synthesis of protein and fat, the key positive regulatory genes STAT5, mTOR and SREBP and the key negative genes SOCS3 and GSK3Beta have been established; however, their mechanisms of action need further research. Additional regulatory genes for milk secretion are needed to elucidate the mechanism responsible for controlling milk quality.

Objective: To explore the changing pattern of lactose content during mammary gland development of Holstein cows. Methods: High-performance liquid chromatography was used to determine lactose content. Results: Lactose was detectable in the mammary gland during the perinatal period, and showed an increasing trend during the lactation period, reaching a peak after 140 d of lactation, and then a dramatic decrease during the involution period, reaching a very low level after 30 d of involution. In conclusion, lactose content exhibits different levels in the mammary gland of Holstein cows during different physiological periods.