Effects of twin pregnancy and dry period feeding strategy on milk production, energy balance, and metabolic profiles in dairy cows.

The present study evaluated the interaction of pregnancy type [PT; single (S) vs. twin (T)] and dry period feeding management [D; close-up (CU) diet (NE(l) = 1.54 Mcal/kg of DM)] throughout the entire dry period (8W) vs. far-off (FO) diet (NE(l) = 1.32 Mcal/kg of DM) from 60 to 21 d before expected calving date (ECD) followed by CU diet until calving (3W). Treatments were arranged in a 2 x 2 factorial with a randomized block design with primiparous (n = 8) and multiparous (n = 39) Holstein cows. We hypothesized that increasing the duration of feeding a CU diet would improve metabolic status and lactation performance for cows with T, but not for cows with S. All cows were fed similarly in late lactation (90 to 60 d before ECD; diet NE(l) = 1.58 Mcal/kg of DM) and in early lactation (calving to 105 DIM; diet NE(l) = 1.71 Mcal/kg of DM). Prepartum DMI as percentage of BW did not differ (P > 0.10) with D but tended to be greater (P = 0.10) for cows with S than with T. Cows with T tended to have greater (P = 0.08) BW than cows with S, but conceptus-free BW was less (P = 0.001) for cows with T than for cows with S. No differences (P > 0.10) were detected in prepartum BCS or BCS change with PT or D. Energy balance (EB) was greater for cows with S than with T (P < 0.001) and for cows fed 8W vs. 3W (P = 0.01). Cows with T had greater (P < 0.001) NEFA and a tendency for greater liver triglycerides (TG; P = 0.07) and plasma beta-hydroxybutyrate (BHBA; P = 0.06) than cows with S. Prepartum cows fed 3W had greater (P = 0.01) liver TG and greater (P = 0.02) plasma NEFA, but less (P = 0.02) plasma BHBA than cows fed 8W. Plasma glucose (P < 0.004) and liver glycogen (P = 0.02) were less for cows with T but were not affected (P > 0.10) by D. Postpartum, there was no effect (P > 0.1) of PT or D on mean DMI as percentage of BW, BW, and BCS, but there was an interaction (P = 0.02) of PT x D for mean BCS. Cows that calved T were in a more positive (P = 0.004) EB than cows that calved S. Milk production was 5.2 kg/d greater (P = 0.04) for cows fed 8W; however, they were in less (P = 0.01) EB than cows that received 3W. Postpartum cows that calved T had decreased concentrations of plasma NEFA (P = 0.02) and liver TG (P = 0.04) but greater concentrations of plasma glucose (P = 0.03) than cows that calved S. Plasma BHBA (P = 0.07) and NEFA tended (P = 0.06) to be greater for cows that received 8W than 3W. Neither PT nor D affected (P > 0.1) plasma glucose and liver glycogen. There was a tendency for an interaction of PT x D for plasma NEFA and liver TG. In contrast to our hypothesis, response to D was independent of PT. Based on milk production data from the present experiment, 8W is a more desirable feeding strategy than 3W.