Effects of Transition Diets Varying in Dietary Energy Density on Lactation Performance and Ruminal Parameters of Dairy Cows

Abstract

Forty cows and twenty heifers were used to study the effects of dietary energy density during late gestation and early lactation on lactation performance and ruminal parameters. A 2 2 factorial arrangement of treatments was used. During prepartum (-28 d to calving), animals were fed a low energy density diet [DL; 1.58 Mcal of net energy for lactation (NE L )/kg, 40% neutral detergent fiber (NDF) and 38% nonfiber carbohydrate (NFC)] or a high energy diet (DH; 1.70 Mcal NE L /kg, 32% NDF and 44% NFC). After calving, half of the cows from each prepartum treatment group were assigned to a low energy density diet (L; 1.57 Mcal NE L /kg, 30% NDF and 41% NFC) or a high energy density diet (H; 1.63 Mcal NE L /kg, 25% NDF and 47% NFC) until d 20 postpartum. After d 20, all cows were fed H until d 70.