The objectives of the experiment were to evaluate the effects of feeding diets with distinct dietary cation-anion difference (DCAD) levels and supplemented with 2 sources of vitamin D during the prepartum transition period on postpartum health and reproduction in dairy cows. The hypotheses were that feeding acidogenic diets prepartum would reduce the risk of hypocalcemia and other diseases, and the benefits of a negative DCAD treatment on health would be potentiated by supplementing calcidiol compared with cholecalciferol. Cows at 252 d of gestation were blocked by parity (28 nulliparous and 52 parous cows) and milk yield within parous cows, and randomly assigned to 1 of 4 treatments arranged as a 2 × 2 factorial, with 2 levels of DCAD, positive (+130 mEq/kg) or negative (−130 mEq/kg), and 2 sources of vitamin D, cholecalciferol or calcidiol, fed at 3 mg for each 11 kg of diet dry matter. The resulting treatment combinations were positive DCAD with cholecalciferol (PCH), positive DCAD with calcidiol (PCA), negative DCAD with cholecalciferol (NCH), and negative DCAD with calcidiol (NCA), which were fed from 252 d of gestation to calving. After calving, cows were fed the same lactation diet supplemented with cholecalciferol at 0.70 mg for every 20 kg of dry matter. Blood was sampled 7 d before parturition, and at 2 and 7 d postpartum to evaluate cell counts and measures of neutrophil function. Postpartum clinical and subclinical diseases and reproductive responses were evaluated. Feeding a diet with negative DCAD eliminated clinical hypocalcemia (23.1 vs. 0%) and drastically reduced the incidence and daily risk of subclinical hypocalcemia, and these effects were observed in the first 48 to 72 h after calving. The diet with negative DCAD tended to improve the intensity of oxidative burst activity of neutrophils in all cows prepartum and increased the intensity of phagocytosis in parous cows prepartum and the proportion of neutrophils with killing activity in parous cows postpartum (58.5 vs. 67.6%). Feeding calcidiol improved the proportion of neutrophils with oxidative burst activity (60.0 vs. 68.7%), reduced the incidences of retained placenta (30.8 vs. 2.5%) and metritis (46.2 vs. 23.1%), and reduced the proportion of cows with multiple diseases in early lactation. Combining the negative DCAD diet with calcidiol reduced morbidity by at least 60% compared with any of the other treatments. Cows with morbidity had lower blood ionized Ca and serum total Ca concentrations than healthy cows. Treatments did not affect the daily risk of hyperketonemia in the first 30 d of lactation. Despite the changes in cow health, manipulating the prepartum DCAD did not influence reproduction, but feeding calcidiol tended to increase the rate of pregnancy by 55%, which reduced the median days open by 19. In conclusion, feeding prepartum cows with a diet containing a negative DCAD combined with 3 mg of calcidiol benefited health in early lactation.

该实验的目的是评估在产前过渡期喂养具有不同饮食阳离子-阴离子差异（DCAD）水平并补充2种维生素D的饮食对奶牛产后健康和生殖的影响。假设是产前饮食产酸饮食将降低低血钙症和其他疾病的风险，与胆钙化固醇相比，补充钙化二醇可增强DCAD阴性治疗对健康的益处。胎龄252天的母牛被胎次（28胎和52胎）和胎牛的产奶量所阻塞，并随机分配为4种处理方法中的1种，排列为2×2阶乘，DCAD的水平为2，阳性（+ 130 mEq / kg）或阴性（−130 mEq / kg），以及2种维生素D，胆钙化固醇或骨化二醇的来源，每11公斤饮食中的干物质以3毫克喂食。最终的治疗组合为妊娠252天至产犊后加胆钙化醇（PCH）的阳性DCAD，含钙化二醇（PCA）的阳性DCAD，含胆钙化醇（NCH）的阴性DCAD和含钙化二醇（NCA）的阴性DCAD。产犊后，以相同的哺乳期饲喂母牛，每20千克干物质添加0.70毫克胆钙化固醇。在分娩前7天，产后2天和7天对血液进行采样，以评估细胞计数和中性粒细胞功能的测量。评估了产后临床和亚临床疾病以及生殖反应。饲喂DCAD阴性的饮食可消除临床低血钙症（23.1比0％），并大大降低了亚临床低血钙症的发生率和每日风险，在产犊后的最初48至72小时内观察到了这些影响。DCAD阴性的饮食趋于提高所有奶牛产前中性粒细胞的氧化爆发活性强度，并增加产后同胎牛的吞噬作用强度和产后中性仔牛中具有杀伤活性的中性粒细胞比例（58.5比67.6％）。饲喂钙化二醇改善了具有氧化爆发活性的中性粒细胞比例（60.0对68.7％），减少了保留胎盘的发生率（30.8对2.5％）和子宫炎（46.2对23.1％），并降低了多发母牛的比例泌乳早期疾病。与其他任何治疗方法相比，将DCAD阴性饮食与降钙素相结合可使发病率降低至少60％。患病奶牛的血液离子钙和血清总钙浓度低于健康奶牛。在哺乳的前30天，治疗不影响高酮血症的每日风险。尽管奶牛的健康状况发生了变化，但操作产前DCAD并不会影响生殖，但是饲喂降钙素往往会使妊娠率提高55％，这使中位开放天数减少了19天。阴性DCAD结合3 mg降钙素可促进早期哺乳期的健康。