Abstract: Metabolic imbalance in early lactation dairy cows often leads to abnormal oestrus or lack of oestrus,which seriously affects reproductive efficiency. This study compared the metabolic and reproductive function differences between cows in estrus and anestrus through literature analysis. The results showed that cows in estrus had enhanced blood glucose（4.2~5.6 mmol/L）,lipid （triglyceride elevation of 12%~18%）and protein metabolism,and active ovarian activity（LH peak 15~20 IU/L）,and the conception rate reached 55%~60%,while cows in anestrus had a negative energy balance （glucose<3.8 mmol/L,NEFA>1.2 mmol/L） and mineral deficiency （blood calcium<1.2 mmol/L）,which resulted in abnormal estrus. Mineral deficiencies （blood calcium<2.2 mmol/L） resulted in ovarian quiescence （follicle diameter <10 mm） and reduced hormone levels （FSH<5 IU/L）. Reproductive performance was significantly improved by dietary addition of per rumen fat （7%~8%） and GnRH combined with PGF2α treatment. This study provides a theoretical basis for nutritional and reproductive management of early lactation cows.

Key words: early lactation, negative energy balance, reproductive hormones, nutritional regulation, ovarian quiescence