Animal and Bioscience Research Department, Animal and Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, Co Meath, Ireland.
J Dairy Sci. 2012 Mar;95(3):1177-87. doi: 10.3168/jds.2011-4408.
Twice-daily milking is the most common milking regimen used globally. A reduction in milking frequency to once daily, combined with a reduced feed allowance (FA), could reduce the physiological stress associated with the transition to peak milk production, and hence improve immune function. This study investigated how milking frequency and FA affect dairy cow immune status. Cows (n = 48) were milked once a day (OAD) or twice a day (TAD) on 1 of 2 FA: high (HFA) or low (LFA), in a 2 × 2 factorial arrangement of treatments. After the mean calving date of March 11, HFA cows were offered ad libitum grass silage and 7 kg of concentrates/cow per day until March 22, then 4 kg of concentrates/cow per day until April 17, and thereafter allocated 31.3 kg of dry matter (DM) grass/cow per day. The LFA cows were offered 4 kg of concentrates/cow per day, 1 kg of concentrates/cow per day, and allocated 19 kg of DM grass/cow per day for the same respective periods. Milk yield was recorded daily and body condition score weekly, and somatic cell count was performed at approximately 2-wk intervals. Blood samples were collected prepartum (d -7 to -1) and at d 1 to 7, d 14 to 21, and d 42 to 49 postpartum. Total and differential leukocyte percentage, IFN-γ production in response to concanavalin A and phytohemagglutinin, and cortisol, haptoglobin (Hp), and serum amyloid A (SAA) concentrations were evaluated. Cows milked OAD had reduced milk yield and body reserve mobilization, but higher somatic cell counts. Milking frequency and diet had no effect on total leukocyte counts. Cows milked OAD had a higher lymphocyte percentage and lower monocyte percentage, and tended to have a lower neutrophil percentage than cows milked TAD. In addition, the LFA cows had a higher eosinophil percentage than cows fed the HFA. Milking frequency and diet had no effect on IFN-γ, Hp, SAA, or cortisol production. Utilization of strategies to reduce milk yield at the beginning of the lactation could not only reduce body reserve mobilization, but also help to maintain a functioning immune system, and thus improve cow welfare.
每日两次挤奶是全球最常见的挤奶方案。将挤奶频率降低到每天一次，并减少饲料供应（FA），可以减轻与产奶高峰期过渡相关的生理压力，从而改善免疫功能。本研究探讨了挤奶频率和 FA 如何影响奶牛的免疫状态。奶牛（n = 48）在两种 FA 中的 1 种上每天挤奶 1 次（OAD）或 2 次（TAD）：高（HFA）或低（LFA），以 2 × 2 因子处理安排。在 3 月 11 日的平均产犊日期之后，HFA 奶牛自由采食干草青贮饲料，并每天提供 7 公斤精料/头，直到 3 月 22 日，然后每天提供 4 公斤精料/头，直到 4 月 17 日，此后每天为每头奶牛分配 31.3 公斤干物质（DM）草。LFA 奶牛每天提供 4 公斤精料/头，每天提供 1 公斤精料/头，并在相应的时间内为每头奶牛分配 19 公斤 DM 草。每天记录产奶量，每周记录体况评分，并每隔大约 2 周进行一次体细胞计数。在产前（-7 至-1 天）和产后第 1 至 7 天、第 14 至 21 天以及第 42 至 49 天采集血液样本。评估总白细胞百分比、刀豆球蛋白 A 和植物血凝素刺激后的 IFN-γ 产生以及皮质醇、触珠蛋白（Hp）和血清淀粉样蛋白 A（SAA）浓度。每日挤奶 OAD 的奶牛产奶量和体储备动员减少，但体细胞计数较高。挤奶频率和饮食对总白细胞计数没有影响。每日挤奶 OAD 的奶牛淋巴细胞百分比较高，单核细胞百分比较低，中性粒细胞百分比低于每日挤奶 TAD 的奶牛。此外，低 FA 奶牛的嗜酸性粒细胞百分比高于高 FA 奶牛。挤奶频率和饮食对 IFN-γ、Hp、SAA 或皮质醇的产生没有影响。在泌乳初期采用减少产奶量的策略，不仅可以减少体储备动员，还可以帮助维持有效的免疫系统，从而改善奶牛福利。
