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):3559-3575. doi: 10.3168/jds.2022-22684. Epub 2023 Mar 10.
Huge differences exist between cow yields and body sizes during their first and second lactations. The transition period is the most critical and investigated phase of the lactation cycle. We compared metabolic and endocrine responses between cows at different parities during the transition period and early lactation. Eight Holstein dairy cows were monitored at their first and second calving during which they were reared under the same conditions. Milk yield, dry matter intake (DMI), and body weight (BW) were regularly measured, and energy balance, efficiency, and lactation curves were calculated. Blood samples were collected on scheduled days from -21 d relative to calving (DRC) to 120 DRC for the assessment of metabolic and hormonal profiles (biomarkers of metabolism, mineral status, inflammation, and liver function). Large variations in the period in question for almost all variables investigated were observed. Compared with their first lactation, cows during their second lactation had higher DMI (+15%) and BW (+13%), their milk yield was greater (+26%), lactation peak was higher and earlier (36.6 kg/d at 48.8 DRC vs. 45.0 kg/d at 62.9 DRC), but persistency was reduced. Milk fat, protein, and lactose contents were higher during the first lactation and coagulation properties were better (higher titratable acidity, faster and firmer curd formation). Postpartum negative energy balance was more severe the during the second lactation (1.4-fold at 7 DRC) and plasma glucose was lower. Circulating insulin and insulin-like growth factor-1 were lower in second-calving cows during the transition period. At the same time, markers of body reserve mobilization (β-hydroxybutyrate and urea) increased. Moreover, albumin, cholesterol, and γ-glutamyl transferase were higher during second lactation, whereas bilirubin and alkaline phosphatase were lower. The inflammatory response after calving was not different, as suggested by the similar haptoglobin concentrations and only transient differences in ceruloplasmin. Blood growth hormone did not differ during the transition period but was lower during the second lactation at 90 DRC, whereas circulating glucagon was higher. These results agree with the differences in milk yield and confirmed the hypothesis of a different metabolic and hormonal status between the first and second lactation partly related to different degrees of maturity.
奶牛在第一和第二泌乳期的产奶量和体型存在巨大差异。过渡期是泌乳周期中最关键和研究最多的阶段。我们比较了处于不同胎次的奶牛在过渡期和早期泌乳期的代谢和内分泌反应。8 头荷斯坦奶牛在第一次和第二次产犊期间进行监测，期间在相同条件下饲养。定期测量产奶量、干物质摄入量（DMI）和体重（BW），并计算能量平衡、效率和泌乳曲线。在预产期前-21 天（DRC）至 120 DRC 期间，按计划采集血液样本，以评估代谢和激素谱（代谢标志物、矿物质状态、炎症和肝功能）。几乎所有研究变量的时期都有很大的变化。与第一泌乳期相比，第二泌乳期的奶牛 DMI 更高（+15%），BW 更高（+13%），产奶量更大（+26%），泌乳高峰更高更早（48.8 DRC 时 36.6 kg/d，62.9 DRC 时 45.0 kg/d），但持续性降低。第一泌乳期的牛奶脂肪、蛋白质和乳糖含量较高，凝固特性较好（滴定酸度较高，更快、更坚固的凝乳形成）。第二泌乳期产后负能平衡更为严重（DRC 时 7 天 1.4 倍），血糖较低。在过渡期，第二胎奶牛的循环胰岛素和胰岛素样生长因子-1 水平较低。与此同时，体储备动员标志物（β-羟丁酸和尿素）增加。此外，第二泌乳期白蛋白、胆固醇和γ-谷氨酰转移酶较高，而胆红素和碱性磷酸酶较低。产后炎症反应无差异，如触珠蛋白浓度相似，铜蓝蛋白仅短暂差异所示。过渡期间血液生长激素无差异，但第二次泌乳期 90 DRC 时较低，而循环胰高血糖素较高。这些结果与产奶量的差异一致，并证实了第一和第二泌乳期之间存在不同的代谢和激素状态的假设，部分原因是成熟度不同。
