The relationship of negative energy balance (NEB) and energy metabolism, milk production and reproductive performance during early lactation in dairy cows in Heilongjiang, China

Negative energy balance (NEB) causes economic losses to dairy farms around the globe. The aim of this study was to investigate the effect of NEB on energy metabolism, reproduction, etc. during early lactation in dairy cows on intensive farms in Heilongjiang, China. According to ??-hydroxybutyric acid (BHBA), glucose (GLU), Non-esterified fatty acid (NEFA) levels, and clinical manifestations 14-21 days postpartum, 118 cows were divided into a positive energy balance (PEB) group (BHBA 1.2, GLU 0.7 mmol/L, n=67) and an NEB group (BHBA 2.8, NEFA 0.7 mmol/L, n=51). These indicators were analyzed by cross-sectional research methods combined with Pearson correlation analysis and a prospective cohort study. The results showed that at 14-21 days postpartum, compared with the PEB, the body condition score, body condition loss (BCL), milk urea nitrogen, BHBA, NEFA, the interval from calving to first estrus (ICFE), pregnancy per artificial insemination (P/AI), and calving interval were higher (P<0.05), and daily lactation (DL), milk protein and GLU, estrus rate and conception rate were lower in NEB cows. BCL was positively correlated with ICFE and P/AI (P<0.05), and negatively correlated with estrus and conception rate (P<0.05). DL was negatively correlated with the P/AI (P<0.05). There was a positive association between NEB and anestrus (2M-H=12.63, P=0.0004), the risk of anestrus caused by NEB rose by 3.67 times that of PEB. The conclusion showed that NEB is closely related to BCL, which is a factor in the decline of lactation and reproductive performance in dairy cows. NEB is a risk factor for anestrus in dairy cows.