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. 2023 May;106(5):3576-3585. doi: 10.3168/jds.2022-22685. Epub 2023 Mar 10.
Dairy cows during their first and second lactation have different milk yield, body development, feed intake, and metabolic and endocrine statuses. However, large diurnal variations can also exist in terms of biomarkers and hormones related to feeding behavior and energy metabolism. Thus, we investigated the diurnal patterns of the main metabolic plasma analytes and hormones in the same cows during their first and second lactations in different stages of the lactation cycle. Eight Holstein dairy cows were monitored during their first and second lactation, during which they were reared under the same conditions. Blood samples were collected before the morning feeding (0 h) and after 1, 2, 3, 4.5, 6, 9, and 12 h on scheduled days between -21 d relative to calving (DRC) and 120 DRC for the assessment of some metabolic biomarkers and hormones. Data were analyzed using the GLIMMIX procedure of SAS (SAS Institute Inc.). Regardless of parity and stage of lactation, glucose, urea, β-hydroxybutyrate, and insulin peaked a few hours after the morning feeding, whereas nonesterified fatty acids decreased. The insulin peak was attenuated during the first month of lactation, whereas postpartum growth hormone spiked on average 1 h after the first meal in cows during their first lactation. This peak occurred earlier than during the second lactation. Most of the differences in diurnal trends between lactations were observed in the postpartum period (and in some cases even in early lactation). Glucose and insulin were higher during the first lactation throughout the day, and the differences increased 9 h after feeding. Conversely, nonesterified fatty acids and β-hydroxybutyrate showed the opposite trend, and their plasma concentrations at 9 and 12 h after feeding differed between lactations. These results confirmed the differences observed between the first 2 lactations in prefeeding metabolic marker concentrations. Furthermore, plasma concentrations of investigated analytes showed high variability during the day, and thus we advise caution when interpreting metabolic biomarker data in dairy cows, especially during the periods close to calving.
奶牛在其第一次和第二次泌乳期间具有不同的产奶量、身体发育、采食量以及代谢和内分泌状态。然而，与采食行为和能量代谢相关的生物标志物和激素也存在较大的日间变化。因此，我们研究了同一头奶牛在第一次和第二次泌乳期间不同泌乳阶段的主要代谢血浆分析物和激素的日间变化模式。对 8 头荷斯坦奶牛在第一次和第二次泌乳期间进行了监测，期间它们在相同条件下饲养。在预定的日子里，在接近产犊的前 21 天（DRC）到 120 DRC 之间，于 0 h（早晨喂养前）以及 1、2、3、4.5、6、9 和 12 h 后采集血液样本，以评估一些代谢生物标志物和激素。使用 SAS（SAS 研究所）的 GLIMMIX 程序对数据进行分析。无论胎次和泌乳阶段如何，葡萄糖、尿素、β-羟丁酸和胰岛素在早晨喂养后几个小时内达到峰值，而非酯化脂肪酸则减少。在泌乳的第一个月，胰岛素峰值减弱，而在第一次泌乳的奶牛中，产后生长激素在第一次进餐后平均 1 小时出现峰值。该峰值早于第二次泌乳期间出现。在产后期间观察到了两次泌乳之间的日间趋势差异（在某些情况下甚至在泌乳早期）。在整个白天，第一次泌乳时葡萄糖和胰岛素更高，且在喂食后 9 小时，两者的差异增大。相反，非酯化脂肪酸和β-羟丁酸则呈现相反的趋势，且在喂食后 9 和 12 小时，两者在两次泌乳之间的血浆浓度不同。这些结果证实了在预喂食代谢标志物浓度方面，前两次泌乳之间的差异。此外，所研究分析物的血浆浓度在白天表现出高度变异性，因此，我们建议在解释奶牛代谢生物标志物数据时要谨慎，尤其是在接近产犊的时期。
