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Feed dependent changes of the ruminal mucosa of high producing dairy cows during the dry period and first eight weeks post partumRumen mucosa samples were obtained from the ventral sack of the rumen (via rumen fistula) from two groups of Israeli-Holstein-Friesian cows (group A, n = 6 ; B, n = 5) during the time period from 9 weeks before to 8 weeks after parturition. Both morphometric and histological examinations were performed. Group A cows were switched from a low energy dry period ration to a production ration 14 days prepartum, whereas the ration change for group B occurred at calving.All animals experienced a continuous reduction in rumen mucosa after transition to a dry period ration. The mucosa of group A cows began to proliferate again after the prepartum ration change, but the mucosal degeneration in group B continued until parturition. At the end of the control period (eight weeks post partum) mucosal development in both groups surpassed quantitatively and qualitatively the initial level at the end of lactation. The importance of ration-dependent transformation processes in the rumen for pH-regulation of the forestomach contents and for energy balance (reparatory feeding, postpartum energy deficit) is discussed.Die Pansenschleimhaut der Wiederkauer ist kein ausdifferenziertes Gewebe mit konstanter Struktur, sondern an ihr laufen zeitlebens morphologische Veranderungen ab (1, 3, 12, 13, 15, 29). Sie werden jedoch weniger von endogenen Einflussen als von exogenen Faktoren, namlich vom Energiegehalt des aufgenommenen Futters, genauer gesagt von der darin enthaltenen Menge an (leicht-und schwerloslichen) Kohlenhydraten, bestimmt (3,4,8,9, lo). Als Induktoren der Schleimhautproliferation wirken nach derzeitiger Kenntnis Butter-und Propionsaure (17, 21, 22, 23, 24), die in den Vormagen beim bakteriellen Aufschlufi der verzehrten Kohlenhydrate gebildet werden. Das jeweilige Schleimhautniveau hangtsoweit es sich bislang iibersehen 1a13tvon den im Zeitraum 'i Die Untersuchungen wurden in dankenswerter Weise aus Mitteln der Deutschen Forschungsgemeinschaft und der H. W. Schaumann-Stiftung zur Forderung der Agrarwissenschaften unterstiitzt. U. S.

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SUMMARYA solution methodology has been developed for incompressible ow in general curvilinear co-ordinates. Two staggered grids are used to discretize the physical domain. The ÿrst grid is a MAC quadrilateral mesh with pressure arranged at the centre and the Cartesian velocity components located at the middle of the sides of the mesh. The second grid is so displaced that its corners correspond to the centre of the ÿrst grid. In the second grid the pressure is placed at the corner of the ÿrst grid. The discretized mass and momentum conservation equations are derived on a control volume. The two pressure grid functions are coupled explicitly through the boundary conditions and implicitly through the velocity of the ÿeld. The introduction of these two grid functions avoids an averaging of pressure and velocity components when calculating terms that are generated in general curvilinear co-ordinates. The SIMPLE calculation procedure is extended to the present curvilinear co-ordinates with double grids. Application of the methodology is illustrated by calculation of well-known external and internal problems: viscous ow over a circular cylinder, with Reynolds numbers ranging from 10 to 40, and lid-driven ow in a cavity with inclined walls are examined. The numerical results are in close agreement with experimental results and other numerical data.