Studies of the influence of nutritional factors on the ruminal mucosa. 1. Structure and functional state of the ruminal mucosa after feeding of extreme rations and abrupt change in nutrition

Abstract

Different rations were used in successive experimental periods (Dried green feeds (I), fresh green feed from sugar beet tops (II), concentrates (III, IV), and maize silage (V), to test the effect they have on the structure and oxidative functions of the ruminal mucosa in cattle. Rations I, II, IV, and V were both energy and protein equivalent. Biopsy specimens from ruminal papillae were taken on the day when rations were suddenly changed and on the 21st and 22nd day of the feeding period; they were then investigated histologically and manometrically. It was found that some characteristics, (viz. the type and thickness of the stratum corneum, the thickness of epithelia, the size of cell nuclei in the stratum basale of the epitheliumas well as the state of the lamina propria and the oxygen uptake were subject to alterations depending on nutrition. Nutrition with energy-equivalent, but otherwise extremely different diets representing particular types of rations led to the development of different and quite specific functional states of the ruminal mucosa. All these functional states of the mucosa were found to be within the limits of normality but seemed to have a definitely more favourable functional effect in the case of rations I and IV than in the case of rations II and V. The feeding of concentrates (III, V) increased the energy intake to an amount of 6.6 kEFr, i.e. double that of the other rations, and brought about changes in quantitative parameters. These, in turn, indicated that proliferative and oxidative processes had been stimulated. Changes of this kind were accompanied by increases in the concentration of volatile fatty acids in the ruminal fluid which rose from a maximum of 9 mMol per 100 ml (ration IV) to 12.5 mMol per 100 ml (ration III). Immediately after any change in nutrition brought about by a change of rations, processes of adaptation occurred in the ruminal mucosa. A balanced state of the mucosa was again achieved after a period of not more than 3 weeks.