Glucose challenge in early lactating dairy cows selected for high or low milk-fat concentration

Responses to intravenous glucose challenge (no. = 26) and basal metabolite and hormone concentrations (no. = 68) were determined in dairy cows selecte d for high (HFI) or low (LFI) milk-fat concentration hut with similar 40 g/ kg fat-corrected milk (FCM) yields. All cows were given a mired diet ad lib itum. Following a glucose challenge the insulin release was higher (P < 0.0 5) and the glucose clearance rate faster (P < 0.05) in the HFI cotes compar ed with the LFI cows. Basal plasma concentrations of the metabolites alanin e, beta-hydroxybutyrate, glucose, non-esterified fatty acids and urea and t he hormones insulin-like growth factor-1 (IGF-1), insulin and leptin were n ot influenced by selection line.