Energy and Phosphorus Status as Factors Affecting Postpartum Performance and Health of Dairy Cows

To determine if energy and phosphorus status would affect postpartum health and lactational performance, first-calf heifers were assigned at parturition, 12 per group, to either high (135% of requirement) or low (85% of requirement) energy, high (138% of requirement) or adequate (98% of requirement) phosphorus in a 2 X 2 factorial design. Treatments extended 84 days postpartum after which standard rations were fed. Milk yields were similar until wk 5 of lactation. From wk 5 to 12, cows fed adequate phosphorus (98% of requirement) yielded 1.8 kg/day more milk than high phosphorus groups. Energy did not affect milk yield until wk 9 when persistency of low energy groups declined. High energy groups had almost twice as much disease and higher rectal temperatures than low energy groups in the first 3 mo of lactation. All heifers had temperatures above expected during the 1st mo of lactation. Excess energy should be avoided for the 1st mo of lactation and then gradually increased. Phosphorus should be fed as recommended and no more.