CONICET | Buscador de Institutos y Recursos Humanos

The transition period (last 3 weeks of prepartum until 3 weeks postpartum) is the most critical stage in the lactation of a dairy cow, characterized by lipid mobilization, proinflammatory state and insulin resistance during peripartum. The aim of this study was to evaluate the insulin-signaling pathway and certain proinflammatory factors in the liver and metabolic biomarkers in plasma during the transition period in cows with different body condition score (BCS). Sixteen grazing dairy cows from a commercial dairy farm were classified according to BCS using the 5-point scale as high BCS (HBCS, ≥ 3.5, n = 8) and low BCS (LBCS, < 3.5, n = 8). Blood and liver biopsies were sampled at -14, 4, 14 and 28 days relative to parturition. The concentrations of non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), glucose, triglycerides, insulin and liver triglycerides content were spectrophotometrically measured. Also, liver protein expression of relevant insulin signaling components: insulin receptor (IR), insulin receptor substrate 1 (IRS-1), total and phosphorylated protein kinase B (Akt and p-Akt); along with tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and nuclear factor-κB (NF-κB) were measured by Western blot. Results obtained shown that cows with HBCS had greater BHB concentration than LBCS (p < 0.05); an interaction effect (BCS x time, p < 0.05) for TNF-alpha was determined; protein abundance of TNF-alpha was greater at day 4 postpartum in HBCS group (p < 0.05). In addition, cows with HBCS had a tendency to have a greater p-Akt/Akt than those with LBCS (p = 0.08). These results suggest that the proinflammatory state in liver of dairy cows with HBCS during postpartum could affect the insulin signaling in agreement with reports of other researchers. This knowledge could help to understand the metabolic behavior and to optimize the health and milk production of dairy cattle during this period.