The applicability of body composition as estimated by the bioimpedance method to predict energy expenditure (EE) was studied. Ten healthy subjects underwent measurement of body composition and 24-h energy expenditure (24-h EE) twice in a respiration chamber on a fixed program. The 24-h EE and its components, sleeping EE (SEE), basal EE (BEE), and daytime EE, for an individual were very reproducible (coefficient of variation 2.3%, 1.4%, 5.0%, & 3.1%, respectively). The variability of 24-h EE among subjects was 11.4% but only 4.1% when adjusted for differences in lean body mass (LBM). LBM was the best determinant of 24-h EE, BEE, and SEE and accounted for 91-93% of the interindividual variance of EE. The prediction equations were 24EE (kcal/d) = 390 + 33.3 LBM (r2 = 0.93, P = 0.000001), SEE (kcal/h) = 9.8 + 1.1 LBM (r2 = 0.92, P = 0.000001), and BEE (kcal/h) = -3.1 + 1.35 LBM (r2 = 0.91, P = 0.000002). In conclusion, 24EE, BEE, and SEE can be predicted with a high degree of precision from LBM as estimated by bioimpedance in normal-weight subjects.

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Zusammenfassung Die Oxidation von Nährstoffen und Retention von Kohlenhydraten, Protein und Fett hei wachsenden Schweinen Die Oxidation von Nährstoffen sowie deren Beitrag zur Fettretention wurde an Hand von 185 individuellen Bilanzstudien mit wachsenden Schweinen (40–100 kg Lebendgewicht) beurteilt. Der Respirationskoeffizient ohne Berücksichtigung des Proteins (RQnp) lag entweder unter oder über 1. Die beschriebene Methode basierend auf Gasaustausch sowie Kohlenstoff‐Stickstoffbilanz zur Berechnung der Oxidation von Nährstoffen und Lipogenese ist in beiden Fällen gültig (RQnp > 1 und RQnp < 1). Bei einer den Wachstumsbedarf deckenden Energiezufuhr (ME ≥ 1,2 MJ/kg0.75) ist die Oxidation von Nährstoffen im Bezug auf die Proteinretention abhängig von der Menge und Qualität des verdauten Proteins. Weiterhin besteht eine Abhängigkeit von der Menge an verdaulichen Kohlenhydraten. Die Versorgung mit Fett spielt dagegen keine Rolle. Die Oxidation von Kohlenhydraten trägt mit 85%, die von Protein mit 15% zur anfallenden Wärmeenergie bei. Eine Fettoxidation findet auch bei hohem Fettgehalt der Nahrung nicht statt. Die Lipogenese aus Kohlenhydraten stellt die Hauptquelle für die Körperfettretention dar. Da keine Fettoxidation stattfindet, wird das gesamte Nahrungsfett im Körper reteniert. Bei einer für das Wachstum zu geringen Energiezufuhr werden Nahrungsfett und Körperfett oxidiert. Um Protein für die Retention zu erhalten, ist die Oxidation von Protein vermindert. Selbst bei Mobilisierung von Körperfett und Oxidation von Nahrungsfett wird ein Teil der Kohlenhydrate und des Proteins für die Lipogenese vermutlich zum Aufbau von Strukturfett verwendet.

Energy metabolism and substrate oxidation was measured in 12 growing pigs by means of indirect calorimetry and nutrient balances. The measurements were carried out during 5 days of feeding followed by 4 days of starvation and 5 days of re-feeding. During the feeding period, dietary carbohydrates were the main energy source, sufficient to cover energy requirements without oxidation of fat. Starvation reduced the total heat production and affected the oxidation pattern by reducing protein oxidation and shifting from carbohydrate to fat oxidation. On the second day of starvation, the main energy source was body fat and there was no oxidation of carbohydrate. On the second day of re-feeding, the heat production reached the same level as during the feeding period. Also, during the second day of re-feeding, the pattern of nutrient oxidation was similar to the feeding period with oxidation of carbohydrate providing 90% and oxidation of protein providing 10% of the total heat production. There was no fat oxidation. The results demonstrated that the growing pigs were able to re-establish oxidative patterns already 2 days after re-alimentation.

Oxidation of protein (OXP), carbohydrate (OXCHO) and fat (OXF) was investigated with 12 growing bulls treated with beta-agonist (L-644, 969) during two 6 weeks trials (Section A and B) at a mean live weight of 195 and 335 kg. Heat production and nutrient oxidation was calculated from gas exchange, with CO2 reduced for CO2 from fermentation processes, and nitrogen excretion in urine. The beta-agonist had no effect on the level of rumen fermentation as indicated by the same methane production for control and treated animals. Heat Production (HE, RQx) increased by the treatment of beta-agonist corresponding to the increment in the protein retention. OXP/HE,RQx was reduced to about 10% in treated animals, indicating that in order to supply amino acids for an increased protein deposition oxidation of protein is decreased. OXF/HE,RQx were markedly higher in treated animals, but as indicated by the same CH4 production the level of the short chain fatty acids (SCFA) production was the same. Therefore, it was concluded that the increase in OXF was not caused by an increase in SCFA but by a direct influence of beta-agonist on mobilization and oxidation of body fat.

1. Total methane excretion (CH, in breath+flatus) was measured in two experiments with thirty-six castrated male pigs (Danish Landrace) during the growth period from 20 to 120 kg live weight (LW). In Expt A, twenty-eight pigs were fed on a commercial diet alternately at high (HFL; metabolizable energy (ME) 1234 (SE 41) kJ/kg LW0'75) or low (LFL; ME 784 (SE 31) kJ/kg LW0'75) feed levels in different weight classes. In Expt B, eight pigs were constantly fed on a semi-purified diet at HFL without (-oil) or with 90 g soya-bean oiI/kg diet (foil) corresponding to daily intakes of ME of 1339 (SE 11) and 1413 (SE 8) kJ/kg LW0"5 respectively.2. CH, excretion was measured during 24 h respiration trials in open-air-circulation chambers. 3. About 1 litre CH, was excreted per day at 2&25 kg LW increasing to a maximum of 12 litres at 120 kg LW, which corresponded to no more than 1.2% of dietary gross energy.4. In Expt A, CH, excretion increased linearly with LW, while in Expt B the increase was linear until about 70 kg LW, when it reached a plateau. On average LFL reduced CH, excretion by 23% compared with HFL. When related to dry matter (DM) intake, however, the pigs on LFL excreted 3.1 litres CH,/kg dietary DM and those on HFL 2.5 litres CH,/kg dietary DM, the difference being significant (P < 0.05). In Expt B the inclusion of soya-bean oil in the basal diet (+oil) reduced CH, excretion by 26% compared with the diet without oil (-oil). The pigs receiving the basal diet excreted 5.2 litres CH,/kg DM and the pigs receiving soya-bean oil 4.3 litres CH,/kg DM, the difference being highly significant (P < 0.001). All differences between Expt A and B in CH, excretion based on DM intake were highly significant (P < 0.001). 5.The results are discussed in relation to gas production in ruminants, rats and humans. It is suggested that flatus production may not only be reduced by changing the composition of the dietary carbohydrates, but also by inclusion of a polyunsaturated oil in the diet of simple-stomached animals and humans.Fermentation of carbohydrates in the hind-gut results in the formation of gases including hydrogen, carbon dioxide and methane. The main part is excreted in flatus, while a smaller part is absorbed into the bloodstream and excreted in expired air. CH, production has been studied extensively in ruminants and in vitro, but to a lesser extent in the hind-gut in simple-stomached animals and in man.In the rumen, CH, is formed by reduction of CO, and, to some extent, from formate (Hungate, 1968). CH, excretion represents a loss of dietary energy as it contains 39.55 kJ/1 (Brouwer, 1965). In growing calves the total loss of CH, amounts to 50-100 litres daily depending on the size of the animal, feed composition, feed level and digestibility of the feed, and it constitutes a loss of energy corresponding to 4-1 1 % of dietary gross energy (GE) (Thorbek, 1980). CH, production in the hind-gut of growing pigs amounts to only a few litres daily and represents an energy loss of about 0.2-1.0% of GE (Verstegen, 1971 ;Hoffma...

1. Balance trials with respiration measurements were performed with twelve rats and twelve pigs given either low-or high-crude-fibre diets. There were six collection periods with the rats over a live-weight range of 86264 g and three collection periods with the pigs over a live-weight range of 30-55 kg. Measurements were made on the influence of microbial activity in the digestive tract on digestibility and nitrogen and energy metabolism. Dietary inclusion of the antibiotic Nebacitin was the method used to reduce the microbial population.2. The microbial activity in the hind-gut (pmol AT€'/$ air-dry contents) of antibiotic-treated rats was reduced to approximately one-tenth of that of untreated rats.3. Live-weight gain was not significantly affected in either species by a reduction in the microbial activity, in spite of a reduction in dry matter digestibility in animals with reduced microflora. 4.For rats on low-crude-fibre diets, a reduction in microflora reduced digestibility of all nutrients and energy and metabolizability of digestible energy by approximately 5.4%. All differences were highly significant. On high-crude-fibre diets the decrease was approximately 5.9%. In pigs on both crude fibre levels, the digestibility was also influenced by the level of microflora, but the pattern was somewhat different from that obtained with rats, with the Nebacitin treatment increasing the digestibility of N slightly, and the digestibility of fat markedly.5. Retained N in rats reached a maximum when the rats were approximately 60 d old and thereafter decreased with increasing age. However, for pigs daily N retention increased with age. The retained N:digested N value decreased linearly with age in the rats, but varied little with age over the range (104146 d) studied in the pigs.6. The metabolizability of gross energy (metabolizable energy (ME): gross energy) was significantly reduced with an increase in crude fibre level and by the addition of Nebacitin.7. Retained energy (RE) in relation to ME (RE:ME), was not significantly affected either by level of microbial activity or by crude fibre. 8.The ratio, RE as fat (RF):RE as protein (RP) increased as the animals grew. In the rat experiment there was a tendency for RP to be higher for animals with normal microflora than for animals with r e d u d microflora for both crude fibre levels.9. With rats, the regression analyses indicated that the energy requirement for maintenance could be influenced by both the level of microbial activity in the digestive tract and by the level of fibre in the diet. The net availability of ME for maintenance and growth by rats averaged 0.72 for all treatments.10. The net availability of ME for growth in the pigs averaged 0.65 for all treatments.

The present paper deals with the possibility of using measurements of CH4 production in growing calves to estimate the amount of CO2 produced by fermentative processes and to calculate the oxidation of nutrients. Twenty bull calves were fed diets with varying proportions of corn grain and forage. The protein and energy metabolism was measured in 118 individual balance trials in the live weight range of 120-350 kg by means of indirect calorimetry and carbon-nitrogen balances. The values of oxidized carbohydrate (OXCHO) and fat (OXF) were directly dependent on the fermentation level. With increasing fermentation, less glucose was absorbed and oxidized as OXCHO, while more carbohydrate was converted to short chain fatty acids and oxidized as OXF.