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The aim of this study was to examine the changes of the daily energy amount of lactose, protein and fat throughout the lactations, and compare them to each other. A total of 309 Israeli Holstein-Friesian cows from one kibbutz were investigated in three lactations, and information was given for a period of five years from 1996 to the end of 2000. The distribution of milk components and milk yield during lactation, and changes of the absolute and relative energy amount in the different milk components were calculated and evaluated. The results showed changes in the energy content of milk and its different components throughout the lactation. Each component (fat, lactose and protein) is dominant in different periods during the lactation. The energy amount from fat reaches a peak first, between days 40 and 50. Lactose has a peak at about day 66 of lactation, and protein reaches the peak last, approximately at day 104 of lactation. It seems that this peak sequence is constant and it is considered to be physiological. It might be suggested that there is a regulation governing the secretion of the different components at different times, and only one component is dominant in a given period. Each component exerts negative and positive influences on the secretion of the other components, which interact with each other and are not fully independent.

Lectins of different carbohydrate specificities (GNA (Galanthus nivalis), con A (Canavalia ensiformis), VFL (Vicia faba), PSL (Pisum sativum), LCA (Lens culinaris), PNA (Arachis hypogaea; with or without prior neuraminidase treatment), WGA (Triticum vulgare), SBA (Glycine max), UEA-I (Ulex europaeus), LPA (Limulus polyphemus), BS-I B4 (Bandeiraea simplicifolia, isolectin B4)) were explored for use as differentiation markers of rumen epithelial cells in vivo and in vitro. Lectins specific for mannose (GNA), mannose/glucose (con A, VFL, PSL and LCA), N-acetylglucosamine (WGA) or for N-acetylneuraminic acid (LPA) reacted generally with all types of rumen epithelial cell from both rumen tissue and cell culture. They were, therefore, not suitable markers of epithelial differentiation. SBA was unsuitable because, although it reacted with both tissue and cultured rumen epithelial cells, it was also bound to non-stratified areas of primary rumen epithelial cell cultures. Both BS-I B4 and PNA (after neuraminidase treatment) had to be ruled out because they did not react with differentiated rumen tissue epithelial cells, although they did bind to both stratified and non-stratified cultured cells. In contrast, UEA-I reacted strongly with differentiated rumen epithelial cells both from rumen tissue and cell cultures and therefore appears to be a good general marker for rumen epithelial cell differentiation.

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Summary Incorporation of 3H‐thymidine was followed up in primary ruminal epithelial cell cultures during 24‐hr treatment with sodium n‐butyrate at concentrations of 2 and 10 mM/L. Depression of the incorporation of the label by 64.5 and 92.2 %, respectively, indicated a concentration‐dependent inhibition of cell growth by sodium n‐butyrate. Zusammenfassung Wirkung von Natrium‐n‐Butyrat auf primäre Pansenepithel‐Zellkulturen Die Inkorporation von 3H‐Thymidin in primäre Pansenepithel‐Zellkulturen wurde während eines 24stündigen Einwirkens von Natrium‐n‐Butyrat in Konzentrationen von 2 und 10 mM/L untersucht. Die Unterdrückung des Markers um 64,5 bzw. 92,2 % zeigt, daß Natrium‐n‐Butyrat auf das Wachstum von primären Pansenepithel‐Zellkulturen eine konzentrationsabhängige Hemmwirkung hat. Résumé Effet du n‐butyrate de sodium sur une culture cellulaire primaire d'épithélium de la panse L'incorporation de 3H‐thymidine dans une culture cellulaire primaire d'épithélium de la panse a été examinee durant l'action pendant 24 heures de n‐butyrate de sodium à la concentration de 2 et 10 mM/l. La suppression du marqueur de 64,5 et 92,2 % montre que le n‐butyrate de sodium a une influence inhibitrice dépendante de la concentration sur la croissance d'une culture cellulaire primaire d'épithélium de la panse. Resumen El efecto de n‐butirato sódico sobre los cultivos celulares primarios del epitelio ruminal Se estudió la incorporación de 3H‐timidina en los cultivos celulares primarios del epitelio ruminal durante el tratamiento durante 24 horas con n‐butirato sódico en concentraciones de 2 y 10 mM/l. La depresión de la incorporación del marcador en un 64.5 y 92,2 %, resp., muestra que el n‐butirato sódico verifica una acción inhibidora, dependiente de la concentración, sobre el crecimiento de los cultivos celulares primarios del epitelio de la panza.