Association of postabsorptive glucose and acetate metabolism with feed intake, growth, and efficiency in finishing beef heifers

The objective of this experiment was to determine whether acetate and glucose metabolism and insulin response to glucose are associated with the growth, feed intake, and feed efficiency of finishing heifers. Charolais heifers (n = 18; initial body weight = 415.7 +/- 45.17 kg) were acclimated to restraint with a halter and fed a finishing diet ad libitum using an Insentec feeding system. Following a 12 h fast, a jugular catheter was inserted, and an acetate clearance test was performed followed by a glucose clearance test. Four days after the metabolic tests, heifers began an 84-day DMI and ADG test period. Heifers gained 1.69 +/- 0.03 kg/day and consumed 10.4 +/- 0.19 kg/day. Acetate and glucose clearance rates were not associated with any production trait (P >= 0.40). Insulin time to peak concentration after the glucose challenge was associated (r = 0.69; P = 0.003) with G:F, but not peak concentration (P = 0.45). The increased time to insulin peak could indicate that efficient heifers have pancreatic fl-cell dysfunction, which is a contributor to insulin resistance. These data indicate that insulin resistance early in the finishing period could be related to improved feed efficiency in finishing heifers.