Department of Animal Sciences, University of Florida, Gainesville 32611.
Arm & Hammer Animal Nutrition, Princeton, NJ 08543.
J Dairy Sci. 2018 Sep;101(9):7907-7929. doi: 10.3168/jds.2018-14580. Epub 2018 Jun 7.
The objectives were to evaluate the effects of feeding diets with 2 levels of negative dietary cation-anion differences (DCAD) during the last 42 or 21 d of gestation on performance and metabolism in dairy cows. The hypothesis was that extending feeding from 21 to 42 d and reducing the DCAD from -70 to -180 mEq/kg of dry matter (DM) would not be detrimental to performance. Holstein cows at 230 d of gestation were blocked by parity prepartum (48 entering their second lactation and 66 entering their third or greater lactation) and 305-d milk yield, and randomly assigned to 1 of 4 treatments arranged as a 2 × 2 factorial. The 2 levels of DCAD, -70 or -180 mEq/kg of DM, and 2 feeding durations, the last 21 d (short) or the last 42 d (long) prepartum resulted in 4 treatments, short -70 (n = 29), short -180 (n = 29), long -70 (n = 28) and long -180 (n = 28). Cows in the short treatments were fed a diet with DCAD of +110 mEq/kg of DM from -42 to -22 d relative to calving. After calving, cows were fed the same diet and production and disease incidence were evaluated for 42 d in milk, whereas reproduction and survival was evaluated for 305 d in milk. Blood was sampled pre- and postpartum for quantification of metabolites and minerals. Reducing the DCAD linearly decreased prepartum DM intake between -42 and -22 d relative to calving (+110 mEq/kg of DM = 11.5 vs. -70 mEq/kg of DM = 10.7 vs. -180 mEq/kg of DM = 10.2 ± 0.4), and a more acidogenic diet in the last 21 d of the dry period reduced intake by 1.1 kg/d (-70 mEq/kg of DM = 10.8 vs. -180 mEq/kg of DM = 9.7 ± 0.5 kg/d). Cows fed the -180 mEq/kg of DM diet had increased concentrations of ionized Ca in blood on the day of calving (-70 mEq/kg of DM = 1.063 vs. -180 mEq/kg of DM = 1.128 ± 0.020 mM). Extending the duration of feeding the diets with negative DCAD from 21 to 42 d reduced gestation length by 2 d (short = 277.2 vs. long = 275.3 d), milk yield by 2.5 kg/d (short = 40.4 vs. long = 37.9 ± 1.0 kg/d) and tended to increase days open because of reduced pregnancy per artificial insemination (short = 35.0 vs. long = 22.6%). Results suggest that increasing the duration of feeding diets with negative DCAD from 21 to 42 d prepartum might influence milk yield and reproduction of cows in the subsequent lactation, although yields of 3.5% fat- and energy-corrected milk did not differ with treatments. Reducing the DCAD from -70 to -180 mEq/kg of DM induced a more severe metabolic acidosis, increased ionized Ca concentrations prepartum and on the day of calving, and decreased colostrum yield in the first milking, but had no effects on performance in the subsequent lactation. Collectively, these data suggest that extending the feeding of an acidogenic diet beyond 21 d is unnecessary and might be detrimental to dairy cows, and a reduction in the DCAD from -70 to -180 mEq/kg of DM is not needed.
本研究旨在评估在妊娠最后 42 或 21 d 期间,采用 2 种不同负阴离子差异(DCAD)水平的饲粮对奶牛生产性能和代谢的影响。假设延长饲粮饲喂时间从 21 d 延长至 42 d,并将 DCAD 从-70 降低至-180 mEq/kg 干物质(DM)不会对生产性能产生不利影响。在妊娠 230 d 时,奶牛根据产次(48 头奶牛进入第 2 泌乳期,66 头奶牛进入第 3 泌乳期或更高泌乳期)和 305-d 产奶量进行分组,然后随机分配至 4 种处理组,处理组按 2×2 因子设计,2 个 DCAD 水平(-70 或-180 mEq/kg DM)和 2 个饲粮饲喂时间(最后 21 d 饲喂的短饲期和最后 42 d 饲喂的长饲期),共 4 种处理,短饲期-70(n = 29)、短饲期-180(n = 29)、长饲期-70(n = 28)和长饲期-180(n = 28)。短饲期的奶牛从-42 至-22 d 预产前饲喂 DCAD 为+110 mEq/kg DM 的饲粮。产后,奶牛饲喂相同的饲粮,并在泌乳期内评估 42 d 的生产性能和疾病发生率,而在泌乳期内评估 305 d 的繁殖和存活情况。产后和产前采集血液样本来定量分析代谢物和矿物质。线性降低产前 DCAD 从-42 至-22 d 相对于产犊时的 DM 采食量(-70 mEq/kg DM = 10.7 与+110 mEq/kg DM = 11.5 相比;-180 mEq/kg DM = 10.2 ± 0.4),干奶期最后 21 d 饲粮的产酸力增加使采食量减少 1.1 kg/d(-70 mEq/kg DM = 10.8 与-180 mEq/kg DM = 9.7 ± 0.5 kg/d)。饲喂-180 mEq/kg DM 饲粮的奶牛在产犊当天血液中离子化 Ca 浓度增加(-70 mEq/kg DM = 1.063 与-180 mEq/kg DM = 1.128 ± 0.020 mM)。将负 DCAD 饲粮的饲喂时间从 21 d 延长至 42 d,会使妊娠期缩短 2 d(短饲期 = 277.2 d,长饲期 = 275.3 d),产奶量减少 2.5 kg/d(短饲期 = 40.4 kg/d,长饲期 = 37.9 ± 1.0 kg/d),并由于配种受胎率降低而增加空怀天数(短饲期 = 35.0,长饲期 = 22.6)。结果表明,延长产前饲喂负 DCAD 饲粮的时间从 21 d 延长至 42 d 可能会影响奶牛在随后泌乳期的产奶量和繁殖性能,尽管 3.5%脂肪校正和能量校正奶产量不受处理影响。将 DCAD 从-70 降低至-180 mEq/kg DM 会引起更严重的代谢性酸中毒,增加产前和产犊当天的离子化 Ca 浓度,降低第 1 次挤奶的初乳产量,但对随后泌乳期的生产性能没有影响。总之,这些数据表明,延长饲喂产酸饲粮的时间超过 21 d 是不必要的,并且可能对奶牛有害,而且将 DCAD 从-70 降低至-180 mEq/kg DM 是不需要的。