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Introduction  Feedstuffs with elevated contents of bacterially fermentable substrates (BFS: GFE 1987) offered to pigs have intermediate metabolizable energy (ME) contents compared with feedstuffs mainly composed of starch or hardly fermentable fibre (H adorn et al. 1996a,b). Consequently, BFS‐elevated feeds could be used as major components enabling pig fattening rations to obtain the ME values required for feed calculation from tabulated values (DLG 1991) or equations based on nutrient composition (GFE 1996). The main field of application for BFS‐elevated feeds is, however, still the feeding of adult, non‐lactating sows, with the majority of investigations on fermentation characteristics also being conducted with sows. In fattening pigs a higher accuracy of estimated ME contents is required than in non‐lactating sows. Furthermore, the ME values of feeds with elevated BFS contents might be systematically different in sows and fattening pigs because a still incomplete evolution of the fermentative capacity of the hindgut of growing pigs cannot be totally excluded (J entsch et al. 1990). The efficiency of hindgut bacterial protein synthesis might also be different from that being assumed from sow data (e.g. K irchgessner et al. 1989, 1994). The objective of the present study was to determine the actual ME and BFS contents of rations varying widely in type and level of BFS in three experiments with growing pigs. By comparing these values with those calculated from equations or from tabulated values a re‐examination of the currently applied feed evaluation system should be carried out. Furthermore, interactions of BFS with dietary protein reduction were investigated, since in low‐protein rations fermentation efficiency might be limited by a lack of nitrogen in the hindgut (M osenthin 1987).

Knowledge is limited on the efficacy of hindgut-fermentable dietary fibre to reduce blood, bile and body tissue cholesterol levels. In three experiments with growing pigs the effects of different kinds and levels of bacterially fermentable fibre (BFS) on cholesterol metabolism were examined. Various diets calculated to have similar contents of metabolizable energy were supplied for complete fattening periods. In the first experiment, a stepwise increase from 12 to 20% BFS was performed by supplementing diets with fermentable fibre from sugar beet pulp (modelling hemicelluloses and pectin). Beet pulp, rye bran (modelling cellulose) and citrus pulp (pectin) were offered either independently or in a mixture in the second experiment. These diets were opposed to rations characterized in carbohydrate type by starch either mostly non-resistant (cassava) or partly resistant (maize) to small intestinal digestion. The third experiment was planned to explore the interactions of BFS from citrus pulp with fat either through additional coconut oil/palm kernel oil blend or full-fat soybeans. In all experiments the increase of the BFS content was associated with a constant (cellulose) or decreasing (hemicelluloses, pectin) dietary proportion of non-digestible fibre. In experiment 1 an inverse dose-response relationship between BFS content and cholesterol in blood serum and adipose tissue as well as bile acid concentration in bile was noted while muscle cholesterol did not respond. In experiment 2 the ingredients characterized by cellulose and hemicelluloses/pectin reduced cholesterol-related traits relative to the low-BFS-high-starch controls whereas, except in adipose tissue cholesterol content, the pectinous ingredient had the opposite effect. However, the changes in serum cholesterol mainly affected HDL and not LDL cholesterol. Adipose tissue cholesterol also was slightly lower with partly resistant starch compared to non-resistant starch in the diet. Experiment 3 showed that the use of citrus pulp increased serum cholesterol concentrations when levels were low in the corresponding low-BFS diets (low-fat and soy bean diets), but caused no further increase in the coconut-oil/palm kernel oil blend diet. From the present results it seems that fermentable hemicelluloses have a more favourable effect of decreasing metabolic cholesterol and related traits than hardly digestible fibre, fermentable cellulose or, particularly, pectin. Furthermore, some types of fibre expressed a certain potential to reduce cholesterol content of fat pork and pork products by up to 10% (experiment 1) and 25% (experiment 2).

The effects Of 4% fat either rich in medium-chain fatty acids (MCFA; saturated fat) or in polyenoic fatty acids (PUFA; unsaturated fat) isoenergetically exchanging carbohydrates of a low-fat diet (control) on performance and product quality were evaluated with 180 growing pigs. Growth, carcass and meat quality were not affected by the fat treatments. Although elevated in blood serum, cholesterol was not increased in belly meat when the MCFA-rich diet was fed. Fatty acid composition of backfat reflected dietary fat composition. The significantly lowest shelf life and melting temperatures were found with the unsaturated-fat diet. When compared with control, fat tissue PUFA contents were slightly higher in the saturated-fat diet, and fat melting temperatures were somewhat lower. In contrast, the use of this MCFA-enriched diet increased penetrometer firmness in pure 4°C temperated backfat by more than 50% as compared with control and to about the tenfold level of the firmness obtained in the unsaturated-fat diet. Impression of flavour and odor in lean and fatty meat were not systematically affected by the diets. The present results show a high potentiaLof MCFA-enriched diets to selectively increase fat firmness in pigs without greater undesired side effects on other traits of product quality. Selekive Verbesserung der Kbrperfetthlirte beim Schwein durch eine rnit mittellangkettigen Fettsliuren angereicherte Ration. An 180 Schweinen wurden die Auswirkungen von 4% Fett mit hohen Anteilen an mittellangkettigen Fettsauren (gesattigtes Fett) oder an Polyenfettsauren (ungesattigtes Fett) im isoenergetischen Austausch zu Kohlenhydraten aus einer Niedrigfettration (Kontrolle) auf die Leistung und Produktqualitat untersucht. Es ergab sich kein EinfluD auf Zuwachs, Schlachtkorper-und Fleischbeschaffenheit. Trotz der erhohten Blutserumwerte traten keine hoheren Cholesterolgehalte im Bauchfleisch auf, wenn das gesattigte Fett eingesetzt wurde. Das Fettsaurenmuster des Ruckenspecks spiegelte die Zusammensetzung der Futterfette wider. In der Ration mit dem ungesattigten Fett wurden die signifikant niedrigsten Fetthaltbarkeiten und Schmelztemperaturen gefunden. Im Vergleich zur Kontrolle lagen die Polyengehalte des Korperfetts rnit dem gesattigten Fett etwas hoher. und die Schmelztemperaturen gingen etwas zuruck. Dagegen steigerte die Verwendung dieser, mit mittellangkettigen Fettsauren angereicherten Ration die Fettharte des reinen, auf 4°C temperierten Rukkenspecks im Vergleich zur Kontrolle um mehr als 50% und auf den etwa IOfachen Wert der Harte, die rnit dem ungesattigten Fett erzielt wurde. Der Aroma-und Geruchseindruck von magerem und fettem Fleisch wurde durch die Rationen nicht systematisch beeinflufit. Die vorliegenden Ergebnisse belegen ein grol3es Potential von Rationen rnit erhohten Anteilen an mittellangkettigen Fettsauren zur selektiven Steigerung der Fettharte, ohne daD starkere ungunstige Nebenwirkungen auf andere qualitative Produktmerkmale auftreten.

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