Effect of 25-hydroxyvitamin D3 during prepartum transition and lactation on production, reproduction, and health of lactating dairy cows

We hypothesized that feeding 25-hydroxyvitamin D3 [25-(OH)D3] during lactation and prepartum in conjunction with negative dietary cation-anion difference diets would improve milk production, increase the probability of pregnancy, reduce incidence postcalving diseases. Cows from 4 dairies transition were used 2 randomized cohort experiments. In Experiment 1 (Exp. 1), cows assigned to control [CON; n = 645; no 25-(OH)D3] or treatment [TRT; 537; mg/d 25-(OH)D3 ∼21 d parturition lactation] groups at prepartum. monitored for weekly yield, composition every 60 d, health reproductive measures. 2), (n 2,064; median 147 milk) same measures as Exp. end (L1), subsequent (∼21 parturition), next (L2). Groups follows, amount fed (mg/d) indicated parentheses L1, transition, L2, respectively: (A) control-control (CON-CON; 0–0–0), (B) treatment-treatment (TRT-TRT; 1–2–1), (C) control-treatment (CON-TRT; 0–2–1), (D) treatment-control (TRT-CON; 1–0–0). For a total 1,032 entered A C B D. The number D L2 was 521, 523, 273, 248, respectively. Blood calcium, phosphorus, concentrations measured 17 cows/group 5 times. 1, TRT had 0.2 lower log somatic cell count than CON (4.21 ± 0.045 vs. 4.01 0.050, respectively) multiparous 41 23% higher pregnancy/day cows, resulting 22-d decrease time pregnancy. Primiparous 1.67 0.40 times greater odds mastitis/day primiparous cows. TRT-TRT between 16 29% be bred/day other groups. Multiparous CON-CON TRT-CON 20 8% 30 17% respectively, Serum calcium not affected by group, but phosphorus highest study provides further insights into use 25(OH)D3 lactation.