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

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Abstract
To determine if energy and P status would affect postpartum health and lactational performance, 1st-calf heifers were assigned at parturition, 12 per group, to high (135% of requirement) or low (85% of requirement) energy, high (138% of requirement) or adequate (98% of requirement) P in a 2 .times. 2 factorial design. Treatments were extended 84 days postpartum after which standard rations were fed. Milk yield were similar until wk 5 of lactation. From wk 5-12, cows fed adequate P (98% of requirement) yielded 1.8 kg/day more milk than high P 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 the expected during the 1st mo. of lactation. Excess energy should be avoided for the 1st mo. of lactation and then gradually increased. P should be fed as recommended and no more.