Factors affecting the urinary excretion of urea nitrogen in cattle. II. The plasma urea nitrogen concentration

1970 ◽  
Vol 21 (1) ◽  
pp. 145 ◽  
Author(s):  
RF Thornton
Keyword(s):  
Nitrogen Concentration ◽  
Urine Flow ◽  
Urea Concentration ◽  
Urea Clearance ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Factors Affecting ◽  
Urea Excretion ◽  
Plasma Urea Concentration ◽  
Filtered Load

The relationships between the plasma urea concentration and clearance variables associated with urinary urea excretion were investigated in urea-supplemented cattle. The plasma urea concentration was related to the urinary urea output, and thus to the urea clearance and the fraction of filtered urea excreted. It is suggested that the urine flow rate was influenced by urinary urea excretion, which in turn was influenced by the plasma urea concentration and therefore by the filtered load of urea. The probable influence of the recycling of urea to the rumen on the excretion of urinary urea is discussed.

Factors affecting the urinary excretion of urea nitrogen in cattle. I. Sodium chloride and water loads

1970 ◽  
Vol 21 (1) ◽  
pp. 131 ◽  
Author(s):  
RF Thornton
Keyword(s):  
Sodium Chloride ◽  
Flow Rate ◽  
Free Water ◽  
Urine Flow ◽  
Urea Concentration ◽  
Urine Flow Rate ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Plasma Urea Concentration

Urea metabolism in cattle was studied under conditions of different nitrogen, sodium chloride, and water intakes. Urea supplementation increased the concentrations of ammonia and trichloroacetic acid-insoluble nitrogen in ventral rumen fluid, raised the plasma urea concentration, and increased the excretion of faecal nitrogen and urinary urea and non-urea nitrogen. Sodium chloride loading increased the free water intake and urine flow rate, and the added sodium was quantitatively recovered in the urine. Plasma urea concentration was linearly related to urinary urea excretion but the slope of this relationship was influenced by the urine flow rate. Urea clearance and the fraction of filtered urea excreted were both related to the urine flow rate and to the urine-concentrating ability of the kidney, but not to the urinary urea output. During low nitrogen intakes, urinary urea excretion was influenced more by urine flow than by solute load.

Urea Excretion in the Camel

1957 ◽  
Vol 188 (3) ◽  
pp. 477-484 ◽  
Author(s):  
Bodil Schmidt-Nielsen ◽  
Knut Schmidt-Nielsen ◽  
T. R. Houpt ◽  
S. A. Jarnum
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Urea Concentration ◽  
Nitrogen Excretion ◽  
Renal Tubules ◽  
Urea Clearance ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Plasma Urea Concentration

The nitrogen excretion was studied in the one-humped camel, Camelus dromedarius. When a growing camel was maintained on a low N intake (dates and hay) the amount of N excreted in the form of urea, NH3 and creatinine decreased to 2–3 gm/day. This decrease was caused by a drop in urea excretion from 13 gm to 0.2–0.5 gm/day. Urea given intravenously during low N intake was not excreted but was retained. (The camel like other ruminants can utilize urea for microbial synthesis of protein.) The renal mechanism for urea excretion was investigated by measuring urea clearance and glomerular filtration rate during a period of 7 months. During normal N intake about 40% of the urea filtered in the glomeruli were excreted in the urine while during low N intake only 1–2% were excreted. The variations in urea clearance were independent of the plasma urea concentration and of glomerular filtration rate, but were related to N intake and rate of growth. No evidence of active tubular reabsorption of urea was found since the urine urea concentration at all times remained higher than the simultaneous plasma urea concentration. The findings are not in agreement with the current concept for the mechanism of urea excretion in mammals. It is concluded that the renal tubules must either vary their permeability to urea in a highly selective manner or secrete urea actively.

Urea excretion in ruminants. II. Studies in sheep whose rumen contents were replaced with physiological saline

1970 ◽  
Vol 21 (2) ◽  
pp. 337 ◽  
Author(s):  
RF Thornton
Keyword(s):  
Maximum Concentration ◽  
Close Association ◽  
Physiological Saline ◽  
Urine Flow ◽  
Urea Concentration ◽  
Nitrogen Accumulation ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Plasma Urea Concentration

Urea was infused intravenously into sheep whose rumen contents were removed and replaced with physiological saline. Despite large differences in plasma urea concentration the rate of nitrogen accumulation in the rumen, as urea plus ammonia, was similar at 6-7 mmoles/hr. The maximum concentration of nitrogen, as urea plus ammonia, was not influenced by plasma urea concentrations higher than 15-17 mg N/100 ml. Urinary urea excretion was positively related to plasma urea concentration but within any level of plasma urea concentration there was a close association between urine flow and urinary urea excretion.

Factors affecting the urinary excretion of urea nitrogen in cattle. III.* High plasma urea nitrogen concentrations

1972 ◽  
Vol 23 (4) ◽  
pp. 727 ◽  
Author(s):  
RF Thornton ◽  
BW Wilson
Keyword(s):  
Nitrogen Concentration ◽  
High Plasma ◽  
Nitrogen Excretion ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Factors Affecting ◽  
Linear Relationships ◽  
Nitrogen Concentrations ◽  
51Cr Edta ◽  
Filtered Load

The relationship between urinary urea nitrogen excretion, the filtered load of urea nitrogen, and the plasma urea nitrogen concentration were studied in cows intravenously infused with 0.5–10 g urea nitrogen per hour. These levels of infusion resulted in ranges of plasma urea nitrogen concentration of 12–63 mg/100 ml, of filtered urea nitrogen of 3–19 g/hr, and of urinary urea nitrogen excretion of 2.5–12.7 g/hr. There were linear relationships between the filtered load of urea nitrogen and the plasma urea nitrogen concentration (r = 0.91), between urinary urea nitrogen excretion and the filtered load of urea nitrogen (r = 0.92), and between urinary urea nitrogen excretion and the plasma urea nitrogen concentration (r = 0.97). It was concluded that the amount of urea excreted in the urine was regulated more by the plasma urea concentration than by renal processes such as glomerular filtration rate (GFR), the concentrating ability of the kidneys, or urine flow rate. The capacity of the bovine kidneys to excrete urea and mechanisms involved in the renal excretion of urea are discussed. The successful use of 51Cr-EDTA for the estimation of GFR in cattle is reported in an appendix. __________________ *Part II, Aust. J. Agric. Res., 21: 145 (1970).

Salvage of blood urea nitrogen in sheep is highly dependent on plasma urea concentration and the efficiency of capture within the digestive tract1,2

2007 ◽  
Vol 85 (4) ◽  
pp. 1006-1013 ◽  
Author(s):  
N. E. Sunny ◽  
S. L. Owens ◽  
R. L. Baldwin ◽  
S. W. El-Kadi ◽  
R. A. Kohn ◽  
...  
Keyword(s):  
Blood Urea Nitrogen ◽  
Urea Concentration ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Plasma Urea Concentration

scholarly journals Metabolism of urea in sheep

1967 ◽  
Vol 21 (2) ◽  
pp. 353-371 ◽  
Author(s):  
M. R. Cocimano ◽  
R. A. Leng
Keyword(s):  
Flow Rate ◽  
Crude Protein ◽  
Excretion Rate ◽  
Urine Flow ◽  
The Body ◽  
Urea Concentration ◽  
Urine Flow Rate ◽  
Entry Rate ◽  
Plasma Urea ◽  
Plasma Urea Concentration

1. The entry rates of urea into the urea pool of the body fluids have been measured in sheep given rations varying in crude protein percentage from 3.5 to 27.3.2. Results obtained with a single injection and with continuous infusions of [14C]urea were essentially the same.3. The difference between the entry rate and the rate of excretion of urea in the urine was taken to indicate the quantity of urea degraded in the alimentary tract.4. Plasma concentrations and urea entry rates were significantly and linearly related.5. The relationship between excretion rate and plasma urea concentration was best described by a cubic equation.6. Degradation of urea in sheep was found to be extensive in all the animals studied; as the protein intake increased, the quantity of urea degraded also increased but the percentage of urea entering the body pool that was degraded was decreased. Animals given a ration containing 3.5% crude protein degraded 76–92% of the urea entering the body pool.7. A rectilinear relationship was found between pool size and plasma urea concentration. The urea space in animals given low-protein rations was significantly less than in animals on high-protein rations.8. The effects of starvation for 2, 4 and 6 days on urea metabolism in sheep were investi-gated. In a11 the sheep starved for 2 days there was a significant increase in urea pool size, but the entry rate was markedly depressed indicating a retention of urea in the body pool on starvation.9. A significant amount of nitrogen was found to go through the system: rumen ammonia → portal blood ammonia→blood urea→rumen ammonia.10.Urea excretion rate, urea clearance by the kidney, urine flow rate and the ratio of the concentration of urea in urine to that in plasma (urea U:P ratio) were also examined.11. There were significant correlations between urine flow rate and urea excretion and between plasma urea concentration and urine flow rate.

The Origin and Fate of Salivary Urea and Ammonia in Man

1977 ◽  
Vol 52 (1) ◽  
pp. 9-17 ◽  
Author(s):  
J. Kopstein ◽  
O. M. Wrong
Keyword(s):  
Plasma Concentration ◽  
Nitrogen Concentration ◽  
Urea Concentration ◽  
Ionic Diffusion ◽  
Parotid Saliva ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Parotid Duct ◽  
Hydrolysis Of ◽  
Hydrolysis Of Urea

1. Saliva obtained from the parotid duct of normal and uraemic subjects had an average urea concentration of 86% of the plasma concentration whereas in mixed saliva obtained from the mouth the urea concentration was only 31% of the plasma concentration. Ammonia concentrations were low or unmeasurable in parotid saliva but varied between 0·6 and 26 mmol/kg in oral saliva, showing a positive correlation with the plasma urea concentration. 2. The urea in samples of mixed oral saliva incubated at 37°C disappeared by 290 min. Ammonia steadily increased during incubation; within the first 100 min, the increase could be largely accounted for by bacterial hydrolysis of urea, but later non-urea sources became relatively more important. 3. These findings suggest that the ammonia in mixed oral saliva is derived by bacterial hydrolysis of urea within the mouth. However, the concentration of ammonia plus urea nitrogen in oral saliva was only 76% of the urea nitrogen concentration of parotid saliva, which suggests that some ammonia is lost from the mouth by buccal absorption or by volatilization. 4. To assess the role of non-ionic diffusion of ammonia through the buccal mucosa, we studied the effect of pH on the disappearance of ammonia from buffered solutions retained in the mouth. Ammonia concentrations fell more rapidly at pH 9 than at pH 7, as also did those of hydrazine, a non-volatile analogue of ammonia which is known to be absorbed through other mucosae by non-ionic diffusion. These findings suggest that salivary ammonia is reabsorbed passively through the oral mucosa in the un-ionized phase.

Urea excretion in ruminants. I. Studies in sheep and cattle offered the same diet

1970 ◽  
Vol 21 (2) ◽  
pp. 323 ◽  
Author(s):  
RF Thornton
Keyword(s):  
Body Size ◽  
Urinary Excretion ◽  
Urine Flow ◽  
Lower Plasma ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Consequent Reduction ◽  
Renal Tubular ◽  
Plasma Urea Concentration ◽  
Cattle And Sheep

Cattle and sheep were offered the same diet in amounts according to the ratio of their metabolic body size, and were intravenously infused with urea in amounts according to the same ratio. An apparent limit to the transfer of urea from the blood to the rumen occurred at lower plasma urea and rumen ammonia concentrations in cattle than in sheep. Associated with ingestion of feed there was a decline in the concentrations of both rumen ammonia and plasma urea, and in urinary urea excretion. It is suggested that (a) the transfer of urea from the blood to the rumen and the urinary excretion of urea are reciprocally related, and (b) the transfer of urea from the blood to the rumen and the consequent reduction in plasma urea concentration associated with feed ingestion may account for the decline in urinary urea excretion after ingestion of feed, rather than changes in the urine flow rate and in renal tubular mechanisms.

The effects of continuous intravenous and intraruminal infusions of urea on nitrogen metabolism in sheep

1971 ◽  
Vol 22 (3) ◽  
pp. 429 ◽  
Author(s):  
KH McIntyre
Keyword(s):  
Nitrogen Metabolism ◽  
Nitrogen Balance ◽  
Nitrogen Concentration ◽  
Route Of Administration ◽  
The Body ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Low Protein ◽  
Nitrogen Concentrations

Urea was infused into sheep both intravenously and intraruminally, and at several increasing rates. The infusions were continuous for at least 6 days for each quantity of urea infused. Three predominantly roughage rations were used. Two of these had the same roughage constituents; both had relatively low protein contents, but one contained starch. The amount of urea nitrogen retained in the body from the urea infused was greatest on the ration containing starch, when the nitrogen balance improved by as much as 4.3 g/day. The concentration of ammonia in the rumen increased linearly with the amount of urea infused by either route of administration, but was much higher in the sheep infused intraruminally. Plasma urea nitrogen concentrations increased linearly with each quantity of urea infused until they reached about 30 mg/100 ml. They increased above this concentration only in the sheep fed on the low protein roughage ration without starch. The results suggest that a renal mechanism for urea excretion may control the plasma urea nitrogen concentration at about 30 mg/100 ml under certain conditions.

scholarly journals Determination of nitrogen requirement for microbial growth from the effect of urea supplementation of a low N diet on abomasal N flow and N recycling in wethers and lambs

1976 ◽  
Vol 36 (3) ◽  
pp. 353-368 ◽  
Author(s):  
Sarah A. Allen ◽  
E. L. Miller
Keyword(s):  
Crude Protein ◽  
The Body ◽  
Urea Concentration ◽  
Metabolizable Energy ◽  
Entry Rate ◽  
Simple Diffusion ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Plasma Urea Concentration ◽  
Microbial N

1. Plasma urea entry rate, urinary urea excretion and, by difference, urea recycling in the body, together with the flow of non-ammonia N through the abomasum and digestion of dry matter (dm) before the abomasum were determined in both wethers and lambs receiving cereal-starch diets supplemented with urea to give 60–120 g crude protein (N × 6.25)/kgdm.2. Lambs excreted less urea in urine than wethers given the same diet.3. Relationships between plasma urea entry rate or urine urea excretion rate and plasma urea concentration were different for lambs compared to wethers suggesting greater conser vation of body N by renal control in lambs.4. Recycling of urea was not related to plasma urea concentration in wethers but was related exponentially in lambs, suggesting recycling is controlled rather than the result of simple diffusion from the blood to the gastro-intestinal tract.5. Abomasal non-ammonia-N flow was similar for wethers and lambs and increased linearly with urea supplementation.6.dmdigestion prior to the abomasum was not significantly altered, although there was a tendency for decreased digestion of the basal diet given to lambs.7. Maximum microbial N flow to the abomasum was estimated as 30 g N/kg organic matter (OM) fermented in the rumen.8. This work and the literature reviewed suggested maximum net microbial production can be obtained when the diet supplies an amount of fermentable N equal to the microbial N output. It is calculated the diet should supply approximately 26 g fermentable N/kg digestible OM or 1.8 g fermentable N/MJ metabolizable energy. This corresponds to a fermentable crude protein supply varying from 65 to 130 g/kg DM as digestible OM content increases from 400 to 800 g/kg DM.

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