Abstract Ten pregnant heifers and 26 dry multiparous cows, 4 weeks before their expected parturitions, were blocked according to parity, BCS (body condition score) and BW (body weight) into two treatments: (1) control – cows fed until parturition with free choice of oat hay and 3 kg DM (dry matter) per day of a lactating cow diet, and (2) treatment – cows were fed as the control plus 0.75 kg (as fed, 860 g/kg DM) of a supplement containing 410 g/kg of non-structural carbohydrates (NSC) and 760 g/kg total carbohydrates. Post-partum, both groups were fed the same lactation diet (168 g/kg CP and 7.27 MJ L/kg DM). The mean live-weight of the treatment cows 2 days post-partum was 22.0 ± 9.2 kg higher than control cows ( P < 0.01). Mean daily milk and milk fat production during the first 120 days of the subsequent lactation were 38.5 and 36.9 kg ( P < 0.0003) and 33.1 and 30.4 g/kg ( P < 0.0004) for the treatment and control cows, respectively. Feeding a supplement containing a high proportion of NSC to dry cows reduced plasma glucose concentrations both pre-partum ( P < 0.06) and post-partum ( P < 0.01), and increased plasma insulin pre-partum ( P < 0.04) and decreased it post-partum ( P < 0.03) as compared with control cows. Pre-partum plasma β-hydroxybutyrate concentrations were enhanced ( P < 0.04), and triglycerides reduced ( P < 0.04), in the treatment cows with no post-partum differences. Pre-partum feeding with a supplement containing a high proportion of NSC can produce long term changes in metabolism with enhanced BW at parturition and increased milk and milk fat production through 120 days of the subsequent lactation.