Peris C, Díaz J R, Balasch S, Beltrán M C, Molina M P, Fernández N
Department of Animal Science, Universitat Politècnica de València, 46071 València, Spain.
J Dairy Sci. 2003 Dec;86(12):3891-8. doi: 10.3168/jds.S0022-0302(03)73997-6.
The effects of vacuum level and overmilking on udder health were studied in ewes. Vacuum levels of 36 and 42 kPa were assigned to two groups of 23 Manchega ewes in a crossover study design with two experimental periods of 5 wk for each. Moreover, for each ewe, one teat was overmilked 1.5 to 2 min at all milkings during these 10 wk. The milking machine used had a midlevel milkline and pulsation was fixed at 180 cycles per min and a pulsation ratio of 50:50. Bacterial exposure of all teats was increased by dipping them in a suspension of Staphylococcus simulans at eight milkings of each period. New intramammary infections (IMI) were not significantly affected by the vacuum level used (18 and 23% of ewes infected, at 36 and 42 kPa, respectively) or application of overmilking (9 and 11% of half udders infected without and with overmilking, respectively). Likewise, neither factor significantly affected the somatic cell count (SCC) of the milk. Teat thickness changes after milking varied significantly due to the presence of overmilking (-13.6 and -7.4%, in teats not overmilked and overmilked, respectively) but were not affected by vacuum level. At no time were any lesions or variations visibly noted in the teat walls or orifice. So, in this work we were unable to demonstrate that the vacuum and overmilking levels assayed, both used with a pulsation rate of 180 cycles/min, have an important effect on the state of udder health in the short term. Furthermore, it was also observed that, in absence of IMI, the two factors studied did not cause irritation of any kind in the gland that might influence the SCC of the milk.
在母羊中研究了真空度和过度挤奶对乳房健康的影响。在交叉研究设计中，将36 kPa和42 kPa的真空度分别分配给两组23只曼彻格母羊，每个实验期为5周，共两个实验期。此外，在这10周内，每只母羊的一个乳头在每次挤奶时都过度挤奶1.5至2分钟。所用的挤奶机有一个中等高度的奶线，脉动固定为每分钟180次循环，脉动率为50:50。在每个时期的八次挤奶时，将所有乳头浸入模拟葡萄球菌悬液中，以增加细菌暴露。新的乳房内感染（IMI）不受所用真空度（分别在36 kPa和42 kPa时，感染母羊的比例为18%和23%）或过度挤奶的影响（未过度挤奶和过度挤奶的半侧乳房感染比例分别为9%和11%）。同样，这两个因素均未显著影响牛奶的体细胞计数（SCC）。由于存在过度挤奶，挤奶后乳头厚度变化差异显著（未过度挤奶和过度挤奶的乳头分别为-13.6%和-7.4%），但不受真空度影响。在乳头壁或乳头口未观察到任何明显的病变或变化。因此，在这项研究中，我们未能证明所测定的真空度和过度挤奶水平（均以每分钟180次循环的脉动率使用）在短期内对乳房健康状况有重要影响。此外，还观察到，在没有IMI的情况下，所研究的两个因素不会对乳腺造成任何可能影响牛奶SCC的刺激。
