Changes in feeding behavior, milk yield, serum indexes, and metabolites of dairy cows in three weeks postpartum

Parturition and lactation stress greatly affect physiological and metabolic status of postpartum cows. Monitoring feeding behavior can help assess the health status of postpartum cows. This study aimed to explore the changes in feeding behavior, milk yield (MY), serum indexes, and metabolites of dairy cows during three weeks postpartum. Furthermore, the relationships between feeding behavior, milk yield and serum metabolites were investigated. One hundred seventy-eight healthy multiparous Holstein dairy cows were enrolled to continuously record feeding behavior variables, including feeding time (FT), frequency of feeding (FF), and average feeding time (AFT), using the Nedap neck collar devices, wherein the milk yield was recorded. Out of 178 Holstein dairy cows, 20 cows with the same parity number (2 parities), body condition score (3.0 ± 0.25, recorded in 7 days before parturition), and with eutocic calvings, were selected to explore the serum indexes changes on week 1, 2, and 3 postpartum. Then, 7 cows were further selected based on similar calving date (± 7 d) for metabolic transition detection. Compared to week 1 postpartum, the FT and AFT normalized values on week 2 and 3 postpartum were significantly increased (P < 0.001). The normalized values of FT and AFT were significantly and positively correlated with MY (P < 0.01). Furthermore, the serum total protein (TP), total cholesterol (T-Chol) and IgA contents on week 2 and 3 postpartum were significantly increased compared to week 1 postpartum, while the β-hydroxybutyric acid (BHBA) concentration was significantly decreased. Serum malondialdehyde (MDA), interleukin-6 (IL-6), and leptin (LEP) contents of the 2nd week postpartum, were significantly declined compared to the 1st week postpartum. The normalized values of FT was negatively correlated with serum BHBA level, while positively correlated with the contents of TP and T-Chol (P < 0.05). According to UPLC-MS/MS and pathway analysis results, the serum levels of glycerophospholipids changed most in first three weeks postpartum, which were mainly related to glycerophospholipid metabolism. Finally, the correlation analysis showed that 29 glycerophospholipids (GPs) and 3 fatty acyls (FAs) were significantly and positively correlated with the FT and AFT normalized values (P < 0.05). Together, the findings suggest that the feeding behavior variables, such as FT and AFT, could serve as reliable indicators of energy metabolism in dairy cows during the first three weeks postpartum.