Intravenous Glucose Tolerance Test Reveals Altered Glycemic Response in Dairy Cows with Metritis

Abstract

Immune activation redirects energy metabolism, increasing glucose uptake and utilization by activated leukocytes. This process is well demonstrated in lipopolysaccharide (LPS) challenge models, but evidence remains scarce in naturally occurring diseases such as metritis. This study compared the glycemic response of postpartum dairy cows with and without clinical metritis using an intravenous glucose tolerance test (IVGTT). Forty-five Holstein cows from the INIA La Estanzuela experimental dairy farm (Uruguay) were evaluated. Twenty cows had clinical metritis (scores 2 and 3), and 25 were classified as healthy (scores 0 and 1) based on Metricheck^® assessment. Animals were randomly assigned to receive a glucose infusion (GLU; 0.3 g/kg BW of 50% dextrose solution) or placebo (PLA), administered via jugular vein over ~5 minutes. Blood samples were collected at -15, -10, 5, 10, 15, 20, 30, 45, 60, 90, and 120 minutes. Data were analyzed using NAVURE^® software by repeated measures mixed linear models (MLM). No significant three-way interaction was found (group × treatment × time; p = 0.0950), but group × time (p = 0.0148) and treatment × time (p < 0.0001) interactions were significant, along with main effects of group, treatment, and time (p < 0.0001). Glucose-treated cows peaked at 5 minutes: MET_GLU reached ~160 mg/dL and SAU_GLU ~105 mg/dL. In both, values declined thereafter, with MET_GLU remaining elevated until 30 minutes. PLA-treated cows showed no distinct peak. MET_PLA stayed between ~55–65 mg/dL, and SAU_PLA remained lowest and most stable (~35–45 mg/dL). The IVGTT revealed differences in glucose clearance during early lactation. Cows with metritis showed higher and more sustained glycemic peaks, while healthy cows showed faster declines. These patterns indicate that clinical inflammation and glucose availability influence glycemic dynamics. Slower decline in metritic cows suggests altered peripheral glucose use, possibly reflecting increased immune demand and reduced metabolic efficiency.