Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, QC, J1M 0C8, Canada; Département de Biologie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada.
Sherbrooke Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, QC, J1M 0C8, Canada.
J Dairy Sci. 2017 Jul;100(7):5782-5791. doi: 10.3168/jds.2017-12570. Epub 2017 May 10.
During the periparturient period, the abrupt increase in energy demand for milk production often induces metabolic and immunological disturbances in dairy cows. Our previous work has shown that reducing milk output by milking once a day or incompletely in the first few days of lactation reduces these disturbances. The aim of this study was to reduce metabolic and immunological disturbances by limiting milk production during the first week of lactation by inhibiting the lactogenic signal driven by prolactin. Twenty-two fresh cows received 8 i.m. injections of the prolactin-release inhibitor quinagolide (QUIN; 2 mg) or water as a control (CTL). The first injection was given just after calving, and the subsequent 7 injections were given every 12 h. Milk production was measured until d 28 after calving. Blood samples were taken from d 1 (calving) to d 5 and then on d 7, 10, 14, 21, and 28 to measure concentrations of urea, phosphorus, calcium, glucose, nonesterified fatty acids (NEFA), β-hydroxybutyrate, and prolactin. Other blood samples were taken on d 2, 5, 10, and 28 to analyze oxidative burst, phagocytosis, and the effect of the serum on the lymphoproliferation of peripheral blood mononuclear cells from donor cows. Blood prolactin concentration was lower from d 2 to 5 but higher from d 10 to 28 in the QUIN cows than in the CTL cows. Milk production was lower from d 2 to 6 in the QUIN cows than in the CTL cows (24.3 ± 6.4 and 34.8 ± 4.1 kg/d on average, respectively). We observed no residual effect of quinagolide on milk production after d 6. During the first week of lactation, blood glucose and calcium concentrations were higher and β-hydroxybutyrate concentration was lower in the QUIN cows than in the CTL cows. Blood NEFA, urea, and phosphorus concentrations were not affected by the treatment. At d 2 and 5, the phagocytosis ability of polymorphonuclear leukocytes was not affected by treatment; however, quinagolide injection enhanced the proportion of cells that entered oxidative burst, The mitogen-induced proliferation of peripheral blood mononuclear cells was greater when they were incubated with serum harvested from the CTL cows and was negatively correlated with the NEFA concentration in the serum. Reducing the prolactin peak at calving was effective in reducing milk production during the first week of lactation without compromising the dairy cow's overall productivity. Slowing the increase in milk production allowed a more gradual transition from pregnancy to lactation and led to a reduction in metabolic stress and an improvement in some immune system aspects during this period.
在围产期，奶牛产奶的能量需求急剧增加，这通常会导致代谢和免疫紊乱。我们之前的研究表明，通过每天挤奶一次或在泌乳初期不完全挤奶，可以减少这些紊乱。本研究的目的是通过抑制由催乳素驱动的泌乳信号来减少泌乳初期的产奶量，从而减少代谢和免疫紊乱。22 头新产奶牛接受了 8 次肌肉注射催乳素释放抑制剂喹那高利（QUIN；2mg）或作为对照的水（CTL）。第一次注射是在分娩后立即进行的，随后的 7 次注射每 12 小时进行一次。直到产后第 28 天测量产奶量。从第 1 天（分娩）到第 5 天，然后在第 7、10、14、21 和 28 天采血，以测量尿素、磷、钙、葡萄糖、非酯化脂肪酸（NEFA）、β-羟丁酸和催乳素的浓度。在第 2、5、10 和 28 天还采集其他血液样本，以分析氧化爆发、吞噬作用以及血清对供体奶牛外周血单个核细胞的淋巴细胞增殖的影响。在 QUIN 奶牛中，从第 2 天到第 5 天的催乳素浓度较低，但从第 10 天到第 28 天的催乳素浓度较高。与 CTL 奶牛相比，QUIN 奶牛的产奶量从第 2 天到第 6 天降低（分别为 24.3±6.4 和 34.8±4.1kg/d）。我们观察到 QUIN 对产奶量的影响在第 6 天后没有残留。在泌乳的第一周，与 CTL 奶牛相比，QUIN 奶牛的血糖和钙浓度较高，β-羟丁酸浓度较低。血液 NEFA、尿素和磷浓度不受处理影响。在第 2 天和第 5 天，中性粒细胞的吞噬能力不受处理影响；然而，喹那高利注射增强了进入氧化爆发的细胞比例。当用从 CTL 奶牛采集的血清孵育时，外周血单个核细胞的有丝分裂原诱导增殖更大，并且与血清中的 NEFA 浓度呈负相关。在产犊时降低催乳素峰值可有效减少泌乳初期的产奶量，而不会降低奶牛的整体生产力。减缓产奶量的增加可以使奶牛从妊娠到泌乳的过渡更加平缓，并在这段时间内减少代谢应激和改善某些免疫系统方面。
