A new method has been developed which permits the crude protein digestibility of feedstuffs in the intestine of cattle to be measured with little effort in terms of samples and experimental work. It consists of welding 0.4 ... 0.8 g of the feedstuff (particle size: 125 ... 1000 micron) into polyamide fabric bags (25 X 40 mm) which are inserted via cannulae into the digestive tracts of fistulated cows from the abomasum/duodenum to the ileum or from the abomasum/duodenum to the faeces. The mean retention time of the bags in the animal was 8.5 +/- 2.7 h from the abomasum to the end of the ileum and (13.3 +/- 1.9 h from the abomasum to the faeces. Up to 15 bags per day and cow may be used. The random error of the method is 1.3% (absolute) when the measurements are performed on two animals using two bags each. Intestinal digestibilities of over 90% were measured for concentrate proteins (except linseed meal) and of 72 ... 95% for forage proteins. Post-ruminal digestion was virtually finished at the end of the small intestine.

A total of 36 high-yielding cows were -- post partum -- divided into two analogous groups. During the following 90 days they received rations containing 14.5 resp. 19.1% crude protein. The daily milk yield ranged between 27.8 and 28.8 kg resp. 29.4 and 31 kg FCM. The urea content of the milk reached 16.8 and 33.8, that in the blood plasma 19.7 and 38.8 mg/100 ml. The correlation between urea content in milk and blood serum was r = 0.94, between milk and urea content in urine r = 0.69. The period between gravidities of 82 days (14.4%) in contrast to 127 days (19.1%) was distinctly improved, and so was the insemination index (2.0 resp. 2.8). We consider 14.5% crude protein meet the requirement for yields of 30 kg milk, which is approximately 15% below the norm.

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.

An extensive number of metabolic experiments have been carried out at the former Oskar-Kellner-Institute, now the ›Oskar Kellner‹ Research Unit of Nutritional Physiology at the Research Institute for the Biology of Farm Animals (FBN), Dummerstorf, on cattle, pigs and humans. Their expired amounts of CO2 having been compiled and stratified with regard to various performance and nutrition levels. The annual CO2 emission of a 700 kg cow with an annual milk yield of 10 000 kg has been estimated to be 4.7 t. With increasing food intake and performance, a concomitant increase of CO2 production per time unit has been observed. However, with increasing performance, we have determined a strong decrease of CO2 output per mass unit of animal-derived food (i.e. meat and milk). This decrease amounts to 40 % when comparing cows with 4 000 kg and 8 000 kg annual milk yields. The CO2 emission per kg dry matter (DM) intake amounts to 0.55 kg and is relatively constant, irrespective of live weight and performance. According to this, the world cattle livestock of 1.3 thousand million (UK)/billion (US) individuals produce 6 % of the total yearly CO2 emission of 30 thousand million (UK)/ billion (US) t. Similarly, in pigs, increasing daily weight gains of an additional 200 g result in a reduction of 10-15 % of CO2 emissions. Sows produce 1.5-1.7 kg CO2 daily; fattening pigs and humans each produce 1 kg CO2.Keywords: CO2 production, dairy cattle, bulls, swine, food intake, performance level, human Zusammenfassung Zusammenhang zwischen Kohlendioxidproduktion und Leistung bei Rind und SchweinAus dem umfangreichen Fundus der im Oskar-Kellner-Institut, seit 1992 ein Forschungsbereich des FBN Dummerstorf, durchgeführten Gesamtstoffwechselversuche wurden die mit den Atemgasen von Rind, Schwein und Mensch bei verschiedenen Leistungen und unterschiedlicher Ernährung abgegebenen CO2-Mengen zusammengestellt. Dabei wurde ein Anstieg der CO2-Produktion mit ansteigender Nahrungsaufnahme und zunehmender Leistung in der Zeiteinheit aufgezeigt. Es konnte aber auch ein starker Rückgang in der CO2-Abgabe je Masseeinheit erzeugtes Produkt mit ansteigender Leistung nachgewiesen werden. Dieser Rückgang betrug beim Vergleich der Jahresleistungen von 4 000 und 8 000 kg Milch 40 %. Unabhängig von der Lebendmasse und Leistung der Kühe blieb die CO2-Emission je kg verzehrter Trockensubstanz bei 0,55 kg relativ konstant. Danach sind die weltweit lebenden 1,3 Milliarden Rinder mit 6 % an der jährlich freigesetzten CO2-Menge von ca. 30 Milliarden t beteiligt. Auch bei Schweinen bestätigt sich der Trend, dass bei JENTSCH et al.: Relationship between carbon dioxide production and performance in cattle and pigs 486 200 g höheren Tageszunahmen die CO2-Abgabe um 10-15 % sinkt. Zuchtsauen gaben täglich 1,5-1,7 kg CO2 und Mastschweine ebenso wie der Mensch 1 kg CO2 ab.

The relationship between dry matter (DM) degradation and crude protein (CP) degradation in the dairy cow's rumen was determined with a view to defining the protein value of feeds for ruminants. The nylon bag technique was applied for these studies. For all the feeds investigate (green fodder and preserves from cocks-foot, ryegrass, alfalfa/grass and meadow grass, as well as alfalfa, extracted soybean meal) a significantly positive relationship was found to exist between the levels of DM and CP degradation (r = 0.73 to 1.0). The regression coefficient b1 (CP degradation as regressor) was found to average 0.87. The positive relationship between DM degradation and CP degradation implies that microbial protein amount and unfermented feed protein at the duodenum are negatively correlated. Model calculations show that, on account of the compensation between microbial protein and feed protein at the duodenum, in feeds with a CP concentration below 200 g/kg DM, the extent of ruminal protein degradation does not exert a marked influence on duodenal protein passage. The partial calculation of the duodenal protein supply on the basis of undegraded feed protein and microbial protein, as practiced in the new models of protein evaluation, leads to systematic errors unless the relationship between DM degradation and CP degradation is considered.

The objective of the present study was, to investigate the effect of varying conditions of differential centrifugation of duodenal content on the isolation of bacteria (B-fraction) and feed particles + protozoa (FP-fraction). The treatments at low-speed centrifugation were as follows: 100 x g/5 min, 400 x g/10 min, 1000 x g/10 min and 2000 x g/10 min, high speed conditions were 30,000 x g/30 min/4 degrees C. The results of three experiments are given. Analytical examination gave similar results for N-contents for all treatments, the mean values being 7.90 +/- 0.27% (n = 12) for B-fractions and 6.53 +/- 0.73% (n = 12) for FP-fractions. Increasing the low-speed from 100 x g to 2000 x g lead to increasing DAP-contents and decreasing N:DAP-ratios of the bacterial isolates, the values being 2.43, 3.02, 3.22 and 3.39 mg DAP/g DM and 32.0, 27.4, 25.0 and 23.0 N:DAP-ratio. Decreased isolation of bacterial material in the B-fraction in conjunction with increased incorporation in the FP-fraction resulted in rising the speed of the low speed centrifugation. The rates of loss of DAP, measured by comparison with the total amount were 10, 32, 48 and 70% respectively. It was concluded to prefer the isolation of bacteria from rumen fluid.

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