PSII-B-12 - Association of Glucose Metabolism with Feed Intake, Growth, and Efficiency of Beef Steers

Abstract: The objective of this experiment was to determine the association of glucose metabolism and insulin sensitivity with dry matter intake (DMI), average daily gain (ADG), and feed efficiency (G:F) of steers fed a finishing diet. Steers (n = 55; initial body weight 518 ± 26.7 kg) were subjected to an intravenous glucose tolerance test (IVGTT) where glucose was dosed through a jugular catheter and serial blood samples were collected. Three days after the final IVGTT, steers began a 63-d DMI and ADG test. Body weight was measured on d 0, 1, 21, 42, 62, and 63, and DMI was measured using an Insentec Roughage Intake Control system (Insentec, Markenesse, The Netherlands). Peak insulin concentration in response to the IVGTT tended to be correlated with ADG (r = 0.25; P = 0.07) and DMI (r = 0.23; P = 0.09), indicating cattle with greater ADG and DMI tend to require a greater insulin release in response to glucose. Glucose nadir concentrations were correlated with ADG (r = 0.27; P = 0.044) and G:F (r = 0.37; P = 0.005). Additionally, when steers within 0.5 standard deviations of the mean for DMI are classed as displaying high- or low-ADG, glucose nadir was greater in high-ADG steers (P = 0.042). The association of greater glucose nadir with high-ADG could indicate that high-ADG steers do not clear glucose as efficiently as low-ADG steers, potentially indicating reduced insulin sensitivity. Carcass marbling score was negatively correlated with area under the glucose curve (r = -0.38; P = 0.006), glucose clearance rate (r = -0.33; P = 0.016), and glucose nadir concentration (r = -0.40; P = 0.004). These results indicate that glucose metabolism and insulin signaling are associated with growth, efficiency, and carcass quality, but the molecular mechanisms that drive these effects need to be elucidated.