PSVII-18 - Association of post-absorptive glucose and acetate metabolism with feed intake, growth, and efficiency in finishing beef heifers

Glucose and acetate are important nutrients for muscle and fat accretion in beef cattle. The objective of this experiment was to determine if the demand for acetate and glucose, as well as insulin response to glucose, are associated with dry matter intake (DMI), average daily gain (ADG), residual feed intake (RFI), and gain:feed (G:F). Charolais heifers (n = 16; initial BW = 412 ± 10 kg) were trained to close human contact and fed a finishing diet ad libitum in an Insentec feeding system. Following a 12-hour fast, a jugular catheter was inserted, and an acetate clearance test was performed by infusing acetate (2.18 mmol/kg BW^0.75) and collecting blood samples over a 30-minute period. One hour after the conclusion of the acetate test, a glucose clearance test was performed by infusing glucose (7.57 mmol/kg BW^0.75) and collecting samples over a two-hour period. Four days after the metabolic tests, heifers began an 84-d DMI and ADG test period. The area under the acetate, glucose, and insulin curves were calculated as were the clearance rate, peaks, nadir, and insulin time to peak. Pearson correlations were calculated for the metabolic parameters and production traits using SAS 9.4. Heifers gained 1.69 ± 0.03 kg/d and consumed 10.4 ± 0.19 kg/d. 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 peak concentration was not (P = 0.45). Additionally, there was a trend (r = 0.40; P = 0.13) for area under the insulin curve to be associated with G:F. Given the small sample size in this experiment, it is possible that decreased insulin sensitivity early in the finishing period is related to improved feed efficiency in finishing heifers.