In milk and blood plasma samples of 6 German Simmental and 12 German Black and White heifers it was investigated, whether purine and pyrimidine compounds are suitable indicators of the microbial protein synthesis in the rumen. Therefore the secreted quantities in milk and the concentration in blood plasma are correlated with energy intake. The results indicated significant correlation coefficients for both the secretion quantity of allantoin in milk (r = 0.942) and the concentration of allantoin in blood plasma (r = 0.694). Other investigated compounds appeared more suitable for evaluating the mammary gland metabolism (uridine-lactose synthesis, pseudouridine-protein synthesis). In an experiment with 7 male castrated pigmy goats subjected to a four-day fasting period the decrease of plasma allantoin, which was already apparent after 12 hours of fasting, was closely correlated with the increase of plasma free fatty acids.

No abstract

During pregnancy the rat liver shows alterations in metabolism which apparently do not to occur in the non-pregnant animal. In our study, the following metabolite concentrations and enzyme activities in the liver of pregnant and non-pregnant rats were measured after fasting periods of 6 and 12 h: malate, fumarate, isocitrate, alpha-keto-glutarate, glutamate, malate-dehydrogenase, fumarate-hydratase, glutamate-dehydrogenase, isocitrate-dehydrogenase, aspartate-aminotransferase and after 12 h fast, the concentrations of acetyl coenzyme A and citrate. These results are discussed with regard to their possible importance for the maternal and fetal energy supply.

Summary Investigations in cows on the influence of energy intake on rumen metabolism by means of allantoin excretion in the milk With two groups of dairy cows (A: 12 German Black and White‐ and 6 German Simmental Cows; B: 16 German Black and White‐ and 11 German Simmental Cows) allantoin concentrations of blood plasma (A) and milk (A and B) were analysed by HPLC. There exists a close correlation (r = 0.758) between allantoin concentration in blood plasma (370.6 ± 79.1 μmol/l) and milk (474.1 ± 78.9μmol/l). The relation between milk yield and allantoin excretion with milk seems to be non‐linear (r = 0.936). On the other hand there is a close correlation between energy intake with feed and allantoin excretion via milk (r = 0.885). In a further experiment the allantoin concentrations in blood plasma of 5 Angler steers were monitored for 24 h every second hour with feeding twice daily. There were remarkable fluctuations in the allantoin concentration from nearly 156 to 129 μmol/l. After that the rumen of the steers was emptied, while plasma concentrations were still monitored the same way as before. Concentrations of allantoin declined for about 55% to 65 μmol/l. Zusammenfassung An zwei Gruppen von Milchkühen (A: 12 DSB‐ und 6 DFV‐Kühe; B: 16 DSB‐ und 11 DFV‐Kühe) wurden die Allantoinkonzentrationen in Blutplasma (A) und Milch (A und B) mittels HPLC‐Analysen untersucht. Zwischen den Allantoinkonzentrationen im Blutplasma (370,6 ± 79,1 μmol/l) und in der Milch (474,1 ± 78,9 μmol/l) besteht eine enge Korrelation (r = 0,758). Der Zusammenhang zwischen Milchleistung und Allantoinausscheidung über die Milch erscheint als nicht‐lineare Beziehung (r = 0,936). Die Energieaufnahme über das Futter und die Allantoinausscheidung über die Milch sind eng korreliert (r = 0,885). In einem weiteren Versuch wurden bei 5 Angler‐Ochsen die Allantoinkonzentrationen im Blutplasma bei zweimaliger Fütterung pro Tag im 2stündigem Rhythmus über 24 Stunden aufgezeichnet. Dabei traten nennenswerte Schwankungen von erwa 156 bis 129 μmol/l auf. Anschließend wurde der Panseninhalt entfernt und die Allantoinkonzentration weiter verfolgt. Das Konzentrationsniveau sank um etwa 55 % auf etwa 65 μmol/l ab.