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Biomedical subjects

J M Godeau

Publications and source records attributed to J M Godeau.

At least 19 recordsLinked to original sources
PubMed1997

Continuous profiles and within-day variations of metabolites and hormones in cows fed diets varying in alimentary supplies before short-term feed deprivation.

We investigated continuous profiles and within-day variations of some metabolites and hormones in four nonpregnant, nonlactating cows fed hay-based diets in two equal meals. Diets supplied either too much or too little N (approximately 1.3 or .8 times the maintenance requirements) and NE1 (approximately 1.2 or .8 times). Continuous collection of ruminal liquor, blood, and urine samples was performed for 42 consecutive hours, the last 16 h covering a period without feed. For twice-daily feeding, nitrogenous and energetic underfeeding decreased average ruminal propionate and the insulin:growth hormone ratio. However, only the energetic underfeeding increased plasma 3-methylhistidine and urinary excretion of 3-methylhistidine, and decreased body weight and ruminal acetate, butyrate, and total VFA. Conversely, only the nitrogenous underfeeding decreased glycemia. Whatever the dietary level, the 42-h patterns of metabolites and hormones were mainly affected by the time from the last meal. An energy deficit progressively took place during feed deprivation and the nocturnal interprandial period but not during the diurnal interprandial period. During the feed deprivation and nocturnal periods, glycemia was maintained despite a shortage in ruminal propionate. We conclude that in twice-daily fed cattle 1) the dietary supply of energy is the main trigger for an energy deficit and the subsequent muscle protein mobilization; 2) the nocturnal interprandial period may be considered as short-term feed deprivation; 3) the diurnal patterns of metabolites and hormones are not affected by the nitrogenous and(or) energetic supplies of the diet.

Acetates↗
PubMed1995

Experimental production of hypocalcemia by EDTA infusion in calves: a critical appraisal assessed from the profile of blood chemicals and enzymes.

Physiological studies of the effects of Ca2+ withdrawal using Na2EDTA have been conducted with the prior basic assumption that Na2EDTA-specific direct or indirect effects on the functions under study were negligible. The present study aimed at providing unequivocal confirmation of such assumption by establishing the pattern of response of blood constituents to intravenous infusions of Na2EDTA in calves. Na2EDTA infusion in calves allowed effective chelation of blood Ca2+, leading to a progressive hypocalcemia. Magnesium levels remained constant and concentrations of other ions (Na+, K+, Pi, H+, HCO3-), although significantly altered (P < or = 0.0001), remained within the normal range. Comparison of enzymes, urea, and creatinine changes precluded renal, hepatic, or muscular parenchymatous damages as being the cause of dysfunctions in the context of Na2EDTA-induced hypocalcemia. It was not possible, however, to standardize the Na2EDTA infusion characteristics (flow, volume) to obtain previsible Ca2+ decay in different animals. Conversely, monitoring of systemic arterial pressure (SAP) offered a precious tool to estimate the degree of hypocalcemia reached. Infusion rate must, therefore, be manipulated using careful on-line monitoring of SAP to obtain an experimental range of Ca2+ as large as possible. It was concluded that physiological data collected during Na2EDTA perfusions can be reliably discussed in terms of Ca2+ dependence rather than in terms of either Na2EDTA toxicity, electrolytes maladjustment, acid-base imbalance, impaired blood oxygenation, or hepatic, renal, myocardic, or skeletal muscle damages.

Acid-Base Equilibrium↗
PubMed1995

Response of milk yield, plasma cortisol, amino acids, urea and glucose to a single low-dose administration of adrenocorticotrophic hormone in lactating cows.

An experiment was conducted to determine the effects of a single low-dose administration of adrenocorticotrophic hormone (ACTH) on milk yield, plasma cortisol, free amino acids, urea and glucose in lactating cows. The animals were treated with either 6 IU synthetic ACTH or 5 ml physiological saline (control) administered intravenously via a jugular vein catheter. Blood was withdrawn 60 and 5 min pretreatment (baseline), and 10, 20, 30, 60, 120, 180, 240, 300, 360, and 420 min post-treatment. A rapid positive response (P < 0.05) in plasma cortisol occurred within 10 min of administration of 6 IU ACTH. The maximum increase in plasma cortisol concentration occurred at 1 h post-ACTH treatment and plasma cortisol returned to baseline 4 h later. Until 7 d after ACTH administration, no effect on milk yield was recorded. In comparison with the saline-treated group, the ACTH-treated group exhibited a significant (P < 0.05) increase in the plasma concentrations of 3-methylhistidine, glycine, histidine, isoleucine, leucine, lysine, valine, and glucose. In contrast, the concentrations of alanine, aspartate, glutamate, glutamine and proline decreased significantly (P < 0.05) after ACTH treatment. Hormone administration had no effect on the plasma arginine, asparagine, methionine, phenylalanine, serine, threonine, tyrosine, and urea. These results demonstrate that the bovine species behaves like other mammalians with respect to its metabolic response to stress. Thus, during stress, ACTH increases adrenal cortical activity which, in turn, stimulates protein catabolism in muscle and gluconeogenesis from some non-essential amino acids.

Adrenocorticotropic Hormone↗
PubMed1995

[Energetic and/or nitrogen underfeeding in the dry cow. Effects on volatile fatty acids in the rumen, some plasma metabolites and hormones and urinary excretion of 3-methylhistidine].

In order to study the effects of a nitrogenous and/or energetic underfeeding on some metabolites and hormones, 4 dry cows were fed in 2 equal daily meals with hay-based rations. Four rations were distributed. They supplied too much (HN) or too little (LN) digestible protein in the small intestine and too much (HE) or too little (LE) net energy, ie the diets were HN-HE, HN-LE, LN-HE, and LN-LE. Continuous collection of rumen liquor samples (volatile fatty acids or VFA determination), venous blood samples (amino acids (alanine Ala, glutamine Gln, glycine Gly and serine Ser), urea, glucose, insulin and growth hormone (GH) measurements) and urine samples (determination of the amount of 3-methylhistidine 3-MeHi excreted) was carried out for 24 consecutive hours. By comparison with the reference diet (HN-HE), underfeeding was accompanied by a reduction in ruminal VFA concentrations, an increase in those of plasma Gly and GH, and a maintenance of glycemia levels. Furthermore, nitrogenous and energetic underfeeding (LN-LE) was accompanied by a decrease in plasma Ala, Gln and insulin concentrations. Nitrogenous underfeeding (LN-HE) caused a decrease in uremia levels, an increment in those of serinemia and no variation in circulating insulin concentrations. The energetic underfeeding (HN-LE) was accompanied by a reduction in insulinemia levels and an increase in those of alaninemia and serinemia. Such changes suggest that dry cattle adapt to underfeeding by mobilizing endogenous proteins. However, only the 2 diets with reduced energetic supplies were accompanied by an increase (P < 0.05) in the amount of the urinary 3-MeHi excreted per 24 h, suggesting that the level of energy in the diet is the main trigger for protein mobilization. Finally, the study of the 24-h evolution of the parameters revealed the influence of the feeding time (morning or evening) and the level of the dietary nitrogen and energy supplied on the variation in their concentration.

Alanine↗
PubMed1991

Total protozoa counts and ammonia in the rumen of mature dry Friesian cows on hay-based rations.

The present work was an attempt to determine whether the variations in ruminal ammonia concentrations could be directly correlated to corresponding changes in total protozoa numbers of cattle. Four dry Friesian cows fed with hay-based rations were used through several experiments in which the twice daily feeding (6.15-15.30 h) as well as a 30 h-fasting period were studied. Simultaneously to a continuous or a regular collection of rumen liquor (for NH3), samples of rumen contents (for total protozoa numbers) were regularly withdrawn from the ventral sac. Any definite nycthemeral cycle of the protozoa numbers could not be related to feeding time. Moreover, no significant relationship could be found between the ruminal ammonia and the corresponding total protozoa numbers measured in the nocturnal interprandial period or during starvation. The data suggest that the nycthemeral ammonia profiles recorded in cattle are not directly related to protozoal activity.

Ammonia↗
PubMed1989

Protein and energy relationships in dairy cattle. 1. Dry cows.

Nitrogen metabolism in ruminants is a dynamic process depending on level of intake and composition of dietary dry matter and on the physiological state of the animals. These parameters were analysed in a regression model for the requirements of nitrogen absorbed in the small intestine in relation to nitrogen balance of dry cows fed at maintenance level. The amount of total dietary nitrogen and the apparent nitrogen digestibility vary notably according to energy intake and energy concentration in dietary dry matter. On the contrary, the amount of nitrogen absorbed in the small intestine is only slightly affected by these parameters. The discrepancy between these statements lies mainly in differences in intestinal nitrogen absorption and in altered fermentation processes of the large intestine in response to changes in energy supply and ME concentration in dietary dry matter.

Animals↗
PubMed1989

Protein and energy relationships in dairy cattle. 2. Lactating cows.

Nitrogen requirements of lactating cows were calculated by means of statistical relationships established for nitrogen excretion in faeces and urine, for nitrogen balance, and for nitrogen flow in proximal duodenum and terminal ileum. The data used for elaboration of the relationships came from simultaneous measurements of nitrogen and energy balances. It appears that an increase in dietary nitrogen solubility augments total nitrogen and apparently digestible nitrogen requirements of the animals because of higher urinary nitrogen losses. This effect can be off-set by an increased metabolizable energy intake. High proportions of concentrates in the diets cause a shift in nitrogen excretion from faeces to urine. Requirements of intestinal absorbed nitrogen and its conversion into milk protein are dependant of dietary nitrogen solubility and metabolizable energy concentration, while they are favourably influenced by energy supply. Crude protein concentration is not an adequate way for expressing optimal protein supply in lactating cows because it may vary between 11.2% and 20.0% according to dietary characteristics for the same animal.

Animals↗
PubMed1986

Some attempts to improve the nutritive value of urea for dairy cows. 3. Its adjunction to fermentable carbohydrates: starea.

Starea, an intimate mixture of gelatinized wheat starch and urea, was tested again urea with regard to the ammonia release in the rumen, the amount and composition of the nitrogen fraction reaching the intestine, the nitrogen and energy balances, and the performance of lactating cows. Maize silage was the basal feed in all experiments. The ammonia concentration in the rumen liquor was measured in two cows fitted with a permanent rumen cannula. The curve of the ammonia concentration was about the same with both nitrogen supplements, and peaked at about 250 mg/l (14.7 mmol/l) two hours postfeeding. Two dry cows fitted with a re-entrant cannula at 10 cm from the pylorus were fed with maize silage supplemented with increasing amounts of either urea or starea. The duodenal nitrogen flow rapidly levelled off with both supplements and no significant difference between them could be detected. The amount of ammonia in the duodenal digesta remained very low. Nitrogen digestibility measured in lactating cows was not noticeably affected when starea instead of urea was added to maize silage. However, nitrogen excretion in the urine tended to decrease, while nitrogen secretion in milk was augmented with starea. The digestibility of the rations and their metabolizable energy supply were not significantly affected, and milk production was quite the same with both supplements, apart from the higher amount of milk protein obtained with starea compared with urea. As a general conclusion from the whole work conducted on the nutritive value of urea for lactating cows, it can be stated that the decline in performance of the animals after substitution of urea for conventional protein is mainly due to a decrease of the metabolizable energy concentration in the diets. None of the attempts tested in an effort to improve the nutritive value of urea was able to overcome this difficulty.

Ammonia↗
PubMed1984

The association of maize silage with urea: the effect on the ammonia content of the rumen fluid, the N flow in the duodenum, the nitrogen and energy balances and the milk production.

In different experiments, the nutritive value of maize silage associated with urea was compared with that of the same forage without any N supplement. The ammonia concentration in the rumen liquor was measured with two dry cows fitted with a permanent rumen cannula. Urea was rapidly hydrolysed in the rumen and gave rise to high ammonia concentrations. The control diet did not supply enough fermentable nitrogen to the ruminal flora. The duodenal N flow was measured with two dry cows fitted with a re-entrant cannula at 10 cm from the pylorus. When increasing amounts of urea were fed, the duodenal N flow initially increased to a maximum, but it leveled off with higher amounts of urea in the diet. With 13 cows in the second part of lactation, the feeding of urea increased the nitrogen balance of the animals and the metabolizable energy density of the rations. However, the milk production and the milk protein secretion were only slightly enhanced.

Ammonia↗
PubMed1984

The substitution of soybean meal for urea: the effect on the ammonia content of the rumen fluid, the N flow in the duodenum, the nitrogen and energy balances and the milk production.

In different experiments, the nutritive value of maize silage associated with urea was compared with that of the same forage associated with soybean meal. The ammonia concentration in the rumen fluid was measured with two dry cows fitted with a permanent rumen cannula. Urea gave rise to much higher NH3 concentrations compared with soybean meal. The duodenal N flow was measured with two dry cows fitted with a re-entrant cannula at 10 cm from the pylorus. Adding increasing amounts of either of the two N supplements to the maize silage showed that they were equivalent with low N intakes. However, clearly more N reached the intestine with soybean meal than with urea when the N intake increased. With 33 cows in the second part of lactation, the substitution of soybean meal for urea decreased the urinary N loss. At the same time, it significantly increased the mammary protein secretion and the milk production. The increase of the dietary metabolizable energy density noted under these feeding conditions corresponded to about two thirds of the increase of the milk production. Milk composition was only slightly affected.

Ammonia↗
PubMed1980

Arginyl-transfer ribonucleic acid synthetase of Bacillus stearothermophilus. Purification and kinetic analysis.

Arginyl-tRNA synthetase from Bacillus stearothermophilus (NCA 1518) has been purified 880-fold to apparent homogeneity as demonstrated by electrophoresis in the presence of sodium dodecyl sulphate. The molecular weight is 59 000 as confirmed by Sephadex G-100 and by sucrose gradient ultracentrifugation. The enzyme is monomeric, no subunits were detected. Its cognate tRNA induces an apparent increase in molecular weight suggesting the dimerisation of the enzyme. Nevertheless, it is not obvious that the enzyme dimer forms prior to the aminoacylation reaction catalysed by the enzyme. An ATPase activity was found associated to the synthetase but can be neglected because the ATP consumption is too low for hampering the arginyl-tRNA synthetase activity. The order of addition of substrates and release of products has been studied by measurements of initial velocity, product inhibition and dead-end inhibition. The nature of the kinetic patterns indicates that the aminoacylation reaction conforms to the classical concept of the mechanism which includes the formation of an enzyme-bound aminoacyl-adenylate as an intermediate in the first step followed by transfer of the amino acid to tRNA. The first partial reaction, measured by the ATP-32PPi exchange or AMP synthesis in the presence of ATP and arginine, requires tRNA, which is consistent with the model in which tRNAArg is an activator of the arginyladenylate synthesis.

Adenosine Triphosphate↗
PubMed1979

Adenosine triphosphate consumption by bacterial arginyl-transfer ribonucleic acid synthetases.

ATP consumption by arginyl-tRNA synthetases from Escherichia coli and Bacillus stearothermophilus has been investigated by the firefly luciferin--luciferase assay. Arginyl-tRNA synthetase from E. coli utilizes ATP only for aminocylation of tRNA with a 1:1 stoicheiometry. In contrast, we have shown an adenosine triphosphatase activity of arginyl-tRNA synthetase from B. stearothermophilus in the absence of tRNAArg. Dowex chromatography revealed the formation of ADP by the thermophile enzyme; under aminoacylation conditions, AMP was also formed in amounts stoicheiometric with arginyl-tRNA formation.

Adenosine Triphosphate↗