[The effect of the energy intake of cows on the rumen metabolism studied using the excretion of allantoin in milk]. / Untersuchungen an Kühen über den Einfluss der Energieaufnahme auf den Pansenstoffwechsel mittels der Allantoinausscheidung in der Milch.

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 mumol/l) and milk (474.1 +/- 78.9 mumol/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 mumol/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 mumol/l.

[Purine and pyrimidine metabolites for the estimation of rumen metabolism: HPLC analysis in milk and blood plasma]. / Purin- und Pyrimidinmetaboliten zur Beurteilung des Pansenstoffwechsels: HPLC-Analysen in Milch und Blutplasma.

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.

Postnatal development of hepatic xanthine oxidase in baby pigs and turnover of purine catabolites at reduced ambient temperature.

1. The activity of xanthine oxidase in liver samples of baby pigs up to 4 weeks of age was investigated. On the 3rd day of life the turnover of hypoxanthine and of uric acid were measured after intravenous injection of 3H- and 14C-labelled tracers into animals kept at normal (32 degrees C) and reduced (20 degrees C) ambient temperature. 2. Hepatic xanthine oxidase activity increased progressively from 2 to 28 days of age (r = 0.689; P < 0.001). The increase of Vmax and of KM within 3-4 weeks was about 4.5-fold. 3. In 3-day-old baby pigs kept at normal temperature, pool size and turnover was about 10-fold higher for hypoxanthine than for uric acid. 4. At reduced ambient temperature, the pool size of uric acid increased 3.9-fold (P < 0.01) and turnover 1.6-fold (P < 0.05). For hypoxanthine the increases were insignificant.

Metabolic changes in the rat liver during pregnancy. II. Tricarboxylic acid cycle.

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.