Population Medicine, University of Guelph, Guelph, ON, Canada, N1G 2W1.
Population Medicine, University of Guelph, Guelph, ON, Canada, N1G 2W1.
J Dairy Sci. 2020 Jul;103(7):6200-6208. doi: 10.3168/jds.2019-18012. Epub 2020 May 14.
Our objectives were to assess the effects of a diet with a negative dietary cation-anion difference (DCAD) before calving on phagocytosis (Pc) and oxidative burst (OB) function of circulating neutrophils, and to determine the associations of serum ionized (iCa) and total calcium (tCa) concentrations with Pc and OB in transition dairy cows. We hypothesized that multiparous cows fed a negative DCAD diet prepartum would have greater iCa and tCa, and thus improved Pc and OB. From 3 wk before expected parturition until calving, 38 healthy multiparous cows from 3 farms were assigned to negative DCAD treatment (TRT; -100 mEq/kg of diet dry matter; n = 21) or a control (CON; 95 mEq/kg of dry matter; n = 17) diet. Each farm was on one treatment or the other at a time, but all farms contributed cows to both groups. Urine pH was measured weekly and in TRT was 6.1 ± 0.8 with 80% of 50 samples <7 and 74% ≤ 6.5. Phagocytosis, OB, iCa, and tCa were measured at d -7, 1, and 4 relative to calving. Median fluorescence intensity for Pc (MFIP) and OB (MFIOB), and the shift of percentage of cells active for Pc (PPc) and OB (POB) were measured in isolated, stimulated neutrophils via flow cytometry. Outcomes were assessed with mixed linear regression models accounting for repeated measures. There were no differences between treatments in the 4 neutrophil function outcomes. Although MFIOB varied over time, there were no interactions of treatment with time for any outcome. Serum ionized and tCa did not differ between TRT and CON. The least squares means ± standard deviation for iCa were: d -7, 1.23 ± 0.12 vs. 1.21 ± 0.12; d 1, 1.07 ± 0.12 vs. 1.02 ± 0.12; d 4, 1.16 ± 0.12 vs. 1.17 ± 0.12 mmol/L for TRT and CON, respectively; and for tCa: d -7 2.39 ± 0.25 vs 2.44 ± 0.31; d 1, 2.01 ± 0.25 vs 1.97 ± 0.31; d 4, 2.33 ± 0.25 vs 2.32 ± 0.31 mmol/L, respectively. The proportion of blood samples with tCa <2.15mmol/L at d -7, 1 and 4 was 5, 76, and 13%, respectively, with no differences between TRT and CON. Correlations of iCa or tCa with each of the 4 polymorphonuclear leukocyte (PMN) function outcomes were weak (r < |0.3|). We did not observe the hypothesized differences in aspects of innate immunity in clinically healthy multiparous cows fed a negative DCAD. We underline that cows that experienced clinical disease were excluded from this study, which is important for interpretation of the results.
我们的目的是评估产前负日粮阳离子-阴离子差（DCAD）对循环中性粒细胞吞噬作用（Pc）和氧化爆发（OB）功能的影响，并确定血清离子化（iCa）和总钙（tCa）浓度与过渡奶牛 Pc 和 OB 的关系。我们假设产前接受负 DCAD 饮食的经产奶牛会有更高的 iCa 和 tCa，从而提高 Pc 和 OB。从预期分娩前 3 周到分娩，38 头来自 3 个农场的健康经产奶牛被分配到负 DCAD 处理（TRT；-100 mEq/kg 日粮干物质；n = 21）或对照（CON；95 mEq/kg 干物质；n = 17）饮食。每个农场一次只采用一种处理方式，但所有农场都为两组提供了奶牛。每周测量尿液 pH 值，TRT 组为 6.1 ± 0.8，80%的 50 个样本<7，74%≤6.5。在分娩前 7、1 和 4 天测量吞噬作用、OB、iCa 和 tCa。通过流式细胞术测量分离刺激的中性粒细胞中的吞噬作用（MFIP）和 OB（MFIOB）的中值荧光强度，以及吞噬作用（PPc）和 OB（POB）活性细胞的百分比变化。结果采用混合线性回归模型进行评估，考虑了重复测量。在 4 个中性粒细胞功能结果方面，处理之间没有差异。尽管 OB 随时间变化，但任何结果都没有处理与时间的相互作用。TRT 和 CON 之间的血清离子化和 tCa 没有差异。iCa 的最小二乘均值±标准偏差为：d-7，1.23 ± 0.12 vs. 1.21 ± 0.12；d1，1.07 ± 0.12 vs. 1.02 ± 0.12；d4，1.16 ± 0.12 vs. 1.17 ± 0.12mmol/L 分别为 TRT 和 CON；tCa 为：d-7，2.39 ± 0.25 vs 2.44 ± 0.31；d1，2.01 ± 0.25 vs 1.97 ± 0.31；d4，2.33 ± 0.25 vs 2.32 ± 0.31mmol/L。d-7、1 和 4 时 tCa<2.15mmol/L 的血样比例分别为 5%、76%和 13%，TRT 和 CON 之间没有差异。iCa 或 tCa 与 4 个中性粒细胞（PMN）功能结果中的每一个的相关性都很弱（r<|0.3|）。我们没有观察到在产前接受负 DCAD 的临床健康经产奶牛中对先天免疫方面的预期差异。我们强调，患有临床疾病的奶牛被排除在本研究之外，这对于解释结果很重要。
