Department of Animal Science, Food and Nutrition (DIANA), Faculty of Agricultural, Food and Environmental Sciences, Università Cattolica del Sacro Cuore, 29122 Piacenza, Italy.
Department of Animal Science, Food and Nutrition (DIANA), Faculty of Agricultural, Food and Environmental Sciences, Università Cattolica del Sacro Cuore, 29122 Piacenza, Italy; Romeo and Enrica Invernizzi Research Center for Sustainable Dairy Production of the Università Cattolica del Sacro Cuore (CREI), 29122 Piacenza, Italy.
J Dairy Sci. 2021 Jul;104(7):8228-8242. doi: 10.3168/jds.2020-19944. Epub 2021 Apr 15.
The dry-off of dairy cows represents an important phase of the lactation cycle, influencing the outcome of the next lactation. Among the physiological changes, the severity of the inflammatory response can vary after the dry-off, and this response might have consequences on cow adaptation in the transition period. The plasma protein profile is a diagnostic tool widely used in humans and animals to assess the inflammatory status and predict the outcome of severe diseases. The albumin-to-globulin ratio (AG) can represent a simple and useful proxy for the inflammatory condition. In this study, we investigated the relationship between AG before dry-off and inflammation, metabolic profile, and performance of 75 Holstein dairy cows. Blood samples were collected from -62 (7 d before dry-off) to 28 d relative to calving (DFC) to measure metabolic profile biomarkers, inflammatory variables, and liver function. Daily milk yield in the first month of lactation was recorded. Milk composition, body condition score, fertility, and health status were also assessed. The AG calculated 1 wk before dry-off (-62 DFC) was used to retrospectively group cows into tertiles (1.06 ± 0.09 for HI, 0.88 ± 0.04 for IN, and 0.72 ± 0.08 for LO). Data were subjected to ANOVA using the PROC MIXED program in SAS software. Differences among groups observed at -62 DFC were almost maintained throughout the period of interest, but AG peaked before calving. According to the level of acute-phase proteins (haptoglobin, ceruloplasmin, albumin, cholesterol, retinol-binding protein), bilirubin, and paraoxonase, a generally overall lower inflammatory condition was found in HI and IN than in the LO group immediately after the dry-off but also after calving. The HI cows had greater milk yield than LO cows, but no differences were observed in milk composition. The somatic cell count reflected the AG ratio trend, with higher values in LO than IN and HI either before dry-off or after calving. Fertility was better in HI cows, with fewer days open and services per pregnancy than IN and LO cows. Overall, cows with high AG before dry-off showed an improved adaptation to the new lactation, as demonstrated by a reduced systemic inflammatory response and increased milk yield than cows with low AG. In conclusion, the AG ratio before dry-off might represent a rapid and useful proxy to evaluate the innate immune status and likely the ability to adapt while switching from the late lactation to the nonlactating phase and during the transition period with emphasis on early lactation.
奶牛干奶期是泌乳周期的一个重要阶段，影响着下一泌乳期的结果。在生理变化中，干奶后炎症反应的严重程度可能有所不同，而这种反应可能对奶牛在过渡期的适应产生影响。血浆蛋白谱是一种在人类和动物中广泛用于评估炎症状态和预测严重疾病结果的诊断工具。白蛋白与球蛋白比值（AG）可以作为炎症状态的简单而有用的替代指标。在这项研究中，我们研究了 75 头荷斯坦奶牛在干奶前 AG 与炎症、代谢谱和性能之间的关系。从干奶前 62 天（-62 DFC）到产后 28 天（DFC）采集血液样本，以测量代谢谱生物标志物、炎症变量和肝功能。记录产后第一个月的日产量。还评估了牛奶成分、体况评分、繁殖力和健康状况。使用在干奶前 1 周（-62 DFC）计算的 AG 将奶牛回溯性地分为 3 组（HI 组为 1.06 ± 0.09，IN 组为 0.88 ± 0.04，LO 组为 0.72 ± 0.08）。使用 SAS 软件中的 PROC MIXED 程序进行方差分析。在-62 DFC 时观察到的组间差异几乎在整个研究期间都保持不变，但 AG 在产犊前达到峰值。根据急性期蛋白（触珠蛋白、铜蓝蛋白、白蛋白、胆固醇、视黄醇结合蛋白）、胆红素和对氧磷酶的水平，HI 和 IN 组在干奶后和产犊后立即的炎症状态普遍低于 LO 组。HI 奶牛的产奶量高于 LO 奶牛，但在干奶前后牛奶成分没有差异。体细胞计数反映了 AG 比值的趋势，LO 奶牛的体细胞计数高于 IN 和 HI 奶牛。HI 奶牛的繁殖力更好，发情天数和配种次数少于 IN 和 LO 奶牛。总的来说，干奶前 AG 较高的奶牛对新泌乳的适应性更好，表现为全身性炎症反应降低，产奶量增加，而 AG 较低的奶牛则相反。综上所述，干奶前的 AG 比值可能是评估先天免疫状态和适应能力的快速而有用的替代指标，这种适应能力在从泌乳后期向非泌乳期转变以及过渡期（特别是泌乳早期）的过程中尤为重要。
