Stress and inflammatory gene networks in bovine liver are altered by plane of dietary energy during late pregnancy

The prepartal dietary energy level is tightly correlated with the degree of tissue mobilization that the animal experiences around parturition (giving birth). To better understand the link between the dry period dietary energy management and the inflammatory status around parturition, 12 multiparous Holstein cows were fed for the entire dry period either a high-wheat straw/lower-energy diet to supply at least 100 % of the calculated net energy for lactation (NEL) (control, CON) or a higher-energy diet to supply >140 % of NEL (overfed, OVE). The blood was sampled throughout the transition period for biomarker analyses. Liver tissue samples were taken on days −14, 7, 14, and 30 relative to parturition for triacylglycerol (TAG) composition and gene expression analysis. Fifty genes involved in inflammation, endoplasmic reticulum (ER), and oxidative stress, and cell cycle and growth were evaluated. Although blood biomarkers did not reveal signs of a greater inflammatory status compared with OVE, CON cows had a greater activation of the intrahepatic unfolded protein response prepartum. However, postpartum mRNA profiling indicated that the OVE group experienced a mild but sustained level of ER stress, with higher oxidative stress and impairment of antioxidant mechanisms. After parturition, inflammation-related genes were upregulated in OVE cows compared with CON. However, CON cows experienced a gradual increase in expression of key inflammatory transcription regulators up to 30 days postpartum which agreed with the lower plasma albumin and cholesterol, suggesting an inflammatory state. Data underscored that ER stress is not necessarily linked with inflammation during the peripartal period. Gene expression data also suggest that prepartum overnutrition could have negative effects on normal cell cycle activity. Overall, allowing cows to overconsume energy prepartum increased the hepatic pro-inflammatory response prepartum and up to the point of parturition. Subsequently, cows fed the lower-energy diet experienced a gradual increase in the inflammatory response. The lack of differences between groups in voluntary feed intake and lactation capacity suggests that nutritional management prepartum triggers different mechanisms that affect ER and oxidative stress along with inflammation. Although no clinical disorders were detected, these alterations expose animals to the development of immuno-metabolic disorders.