Counteractive effects of propionate or 1,2-propanediol against hypoglycemia and ketonemia of tributyrin-treated cows

Accumulation of 1,2-propanediol and enhancement of aerobic stability in whole crop maize silage inoculated with Lactobacillus buchneri

AIMS

To assess the effects of inoculation of Lactobacillus buchneri on the ensiling properties and aerobic stability of maize silage.

METHODS AND RESULTS

Chopped whole crop maize was ensiled in 0.5 litre airtight polyethylene bottles (0.4 kg per bottle) and in double-layered, thin polyethylene bags (15 kg per bag), with or without inoculation of Lact. buchneri. The silos were stored for two to four months and the chemical composition, microbial numbers and aerobic stability were determined. Inoculation lowered lactic acid and yeasts, and increased acetic acid and pH value, resulting in improved aerobic stability of the silages. Inoculated silages produced 1,2-propanediol, the content of which increased as ensiling was prolonged, and nearly 50 g kg-1 dry matter had accumulated after four months of storage. The effects of inoculation, however, were much less pronounced in silages prepared in bags. Mannitol was found in all silages; the production was lowered by Lact. buchneri treatment and appeared to be unrelated to the accumulation of 1,2-propanediol.

CONCLUSIONS

Inoculation of Lact. buchneri occasionally causes accumulation of 1,2-propanediol in silages without further degradation into propionic acid and 1-propanol.

SIGNIFICANCE AND IMPACT OF THE STUDY

Substantial amounts of 1,2-propanediol could be consumed by ruminants when fed on silages inoculated with Lact. buchneri. In addition to increasing acetic acid, attention needs to be paid to 1,2-propanediol because the two fermentation products might affect the intake and utilization of silage-based diets.

The role of propylene glycol metabolism in lactatemia in the rabbit

Propylene glycol (1,2-propanediol PD) has been reported to significantly alter the blood parameters when administered as a drug vehicle. In this study, experiments were performed to estimate the pH, levels of PD, and its metabolites to determine the acute effect of PD in blood. PD was administered to rabbits orally in a single dose of 1 ml 28.4% aqueous solution per 100 g body weight equivalent to 38.66 mmol/kg. Whole blood pH and the levels of PD and metabolites were estimated at fast (O.O h, before feeding PD) and at 0.25, 1, and 3 h after the dose. PD elevated the concentrations of blood PD to its maximum (41.04 +/- 9.98 mmol/liter, n = 4) at 1 h; whereas blood PD is normally absent during fasting. PD significantly increased (P less than 0.01) the concentration of L-lactate in blood, which reached its plateau (2.55 +/- 0.62 mmol/liter, n = 4) at 0.25 h and was 2.45-fold higher than the observed fasted values (1.04 +/- 0.22 mmol/liter, n = 4). Production of D-lactate in blood was similarly increased significantly from 5.1 +/- 5.0 mumols/liter at fast to 150.0 +/- 30.4 mumols/liter at 3 h after oral PD (P less than 0.001, n = 4). As was observed in the fasted blood of PD treated rabbits, D-lactate levels at fast and after saline ingestion in the control animals was found either absent or too low. Despite this increase in lactate, blood pH did not alter significantly when appropriate anticoagulant, i.e., heparin + 4-methylpyrazole, was employed.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of propane-diols on the intestinal uptake of nutrients and brush border membrane enzymes in the rat

The effect on rats of oral doses (38.66 mM/kg body wt) of propane-1,2-diol (PD) administered daily for 10 (Group 1), 20 (Group 2), and 30 days (Group 3) was investigated. Weight gain was initially retarded (P less than 0.05) in Group 1, but was later reversed and elevated significantly (P less than 0.05) in Groups 2 and 3 as compared with their respective controls receiving an equal volume of saline. PD showed a tendency toward enhancing the activities of various enzymes involved in terminal digestion, with the significant effect exerted in few groups on sucrase (P less than 0.05), lactase (P less than 0.05), and gamma-glutamyl transpeptidase (P less than 0.05) when compared with the respective controls. Absorption of D-glucose, glycine, L-aspartic acid, L-lysine, and calcium was elevated and was especially significant in Groups 2 and 3 (P less than 0.001). The structural integrity of the jejunal surface was retained for the most part. A similar examination of the effects of PD was also carried out in vitro to ascertain whether PD itself or its metabolites are involved in its action. The in vitro effects of propane-1,2-diol were compared with those of the more toxic compound propane-1,3-diol. The former exerted greater inhibitory action on the activities of the disaccharidases. The degree of inhibition was in the order sucrase much greater than lactase greater than maltase. The kinetic data revealed that inhibition by 1,2-diol in native and detergent solubilized sucrase is noncompetitive, with Ki values in the range of 0.35-0.41 M. The two diols did not alter the nutrient transport in the brush border membrane vesicles. The present work on rats indicates that PD may influence the intestinal digestive and absorptive functions in vivo and that this in vivo effect of PD is different from that observed in vitro suggesting that the nutritional and toxicological effect of PD may be mediated by different mechanisms.

Metabolic effects of intraruminal administration of 1,3-butanediol or tributyrin in lactating goats

Acute effects of dietary 1,3-butanediol and tributyrin on concentrations of glucose, beta-hydroxybutyrate, and insulin in plasma were compared in lactating goats. In Experiment 1, glucose was decreased by intraruminal administration of 75 or 150 g of 1,3-butanediol or by 84 or 168 g of tributyrin. Tributyrin caused transient hyperglycemia immediately after administration. beta-Hydroxybutyrate was increased in a dose-dependent manner by tributyrin and increased independently of dose by 1,3-butanediol. Tributyrin, but not 1,3-butanediol. Tributyrin, but not 1,3-butanediol, caused large increases of insulin in plasma. In Experiment 2, 75 g of 1,3-butanediol or 84 g of tributyrin administered intraruminally decreased glucose, whereas 73 g of butyric acid (pH 5.6) increased glucose compared with water or 25.6 g of glycerol. All treatments produced transient hyperglycemia immediately after administration. Tributyrin, butyric acid, or 1,3-butanediol greatly increased beta-hydroxybutyrate compared with administration of water or glycerol. Concentrations of beta-hydroxybutyrate in both experiments increased more slowly for 1,3-butanediol than for tributyrin. Both 1,3-butanediol and tributyrin decreased glucose and increased beta-hydroxybutyrate. Because 1,3-butanediol does not stimulate increases of insulin in plasma, it may be more desirable than tributyrin for inducing metabolic changes characteristic of lactation ketosis.