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.

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.

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. 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.

Effects of intraruminal infusions of urea, sucrose or urea plus sucrose on plasma urea and glucose kinetics in sheep fed chopped lucerne hay

1993 ◽  
Vol 121 (1) ◽  
pp. 125-130 ◽  
Author(s):  
Y. Obara ◽  
D. W. Dellow
Keyword(s):  
Plasma Glucose ◽  
Rumen Fluid ◽  
Glucose Production ◽  
Ammonia Concentration ◽  
Irreversible Loss ◽  
Glucose Kinetics ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Urea Kinetics ◽  
Plasma Urea Concentration

SUMMARYThe effect of rumen fermentation on the relationship between urea and glucose kinetics was examined in sheep fed chopped lucerne hay with intraruminal infusions of water, urea, sucrose, or urea plus sucrose at Palmerston North, New Zealand in 1986. Sheep were fed hourly and infused intraruminally with water (1200 m1/day), or a similar volume containing either urea alone (13·7g/day), sucrose alone (178·2 g/day) or urea (14·6 g/day) plus sucrose (175·0 g/day). The added sucrose resulted in a lower rumen ammonia concentration (P< 0·05), lower plasma urea concentration (P< 0·05) and reduced urinary urea excretion (P< 0·05). Urea recycled to the gut tended to increase with the sucrose, urea or sucrose plus urea treatments compared with the water treatment. The fermentation of sucrose in the rumen resulted in decreases in ruminal pH (P< 0·05) and in the ratio of acetate to propionate (A:P) (P< 0·05). The infusion of sucrose also increased the concentration of propionate in rumen fluid (P< 0·05), tended to increase the plasma glucose level and increased plasma glucose irreversible loss (P< 0·05). The infusion of urea resulted in an increase in the plasma urea level (P< 0·05), urea pool size (P< 0·05) and urea irreversible loss (P< 0·01). However, urea infusion did not affect glucose metabolism or volatile fatty acid (VFA) fermentation. The effects of sucrose infusion on glucose and urea kinetics were broadly similar when given alone or with urea, apart from changes in the urea degradation rate. It was concluded that the additional fermentative activity resulting from sucrose increased propionate production which, in turn, was available for glucose production, thus ‘sparing’ amino acids for tissue protein utilization and reducing urea excretion.

Effects of Trichostrongylus colubriformis (Nematoda) on the nutrition and metabolism of sheep. II.* Metabolism of urea

1974 ◽  
Vol 25 (2) ◽  
pp. 363 ◽  
Author(s):  
FB Roseby ◽  
RA Leng
Keyword(s):  
Amino Acids ◽  
Urinary Excretion ◽  
Production Rate ◽  
Feed Intake ◽  
Loss Rate ◽  
Single Injection ◽  
Irreversible Loss ◽  
Trichostrongylus Colubriformis ◽  
Plasma Urea ◽  
Plasma Urea Concentration

The effect of infection with Trichostrongylus colubriformis on the rates of production, excrehon and recycling of urea was studied in 24 Merino lambs. The production rate of urea was estimated as the irreversible loss rate of [14C]urea given as a single injection. The feed intake of all sheep was maintained at 540 g/day throughout the experiment. Parasitized sheep had a higher plasma urea concentration than their paired controls 15–35 days after they were infected. This was associated with an increase in the rate of irreversible loss and the rate of urinary excretion of urea. The additional urea lost in urine is apparently produced from ammonia released from amino acids in the tissues or in the digestive tract. ______________________ *Part I, Aust. J. Agric. Res., 24: 947 (1973).

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.

Renal Response to Changes in Nitrogen Metabolism in Sheep

1958 ◽  
Vol 193 (3) ◽  
pp. 657-661 ◽  
Author(s):  
Bodil Schmidt-Nielsen ◽  
Humio Osaki
Keyword(s):  
Nitrogen Metabolism ◽  
Acute Effect ◽  
Regulatory State ◽  
Prolonged Administration ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Low Protein ◽  
Renal Tubular ◽  
Protein Free Diet ◽  
Urea Infusion

The camel has been found to be able to regulate the urea excretion on the renal tubular level. The same was demonstrated in sheep. Lactating or growing sheep, when placed on a low protein diet, decreased the fraction of filtered urea appearing in the urine to very low values. The low urea excretion was characterized by a urea U/P ratio not exceeding 5–7 even at low urine flows. The degree to which urea is concentrated in the urine over the plasma at low urine flows was found to be a good indicator of the regulatory state of the kidney. Changes in this regulatory state could be brought about within approximately one hour. A sudden lowering of the maximum urea U/P was found after a deficient protein-free diet was supplemented with grain. Conversely, a urea infusion raised the maximum urea U/P ratio abruptly in a sheep maintained on a low protein intake. The effect of administration of hydrocortisone or ACTH was studied to determine if these hormones could have a direct effect upon the regulatory state of the kidney. No acute effect was observed. Prolonged administration had in some instances a renal effect. The effect, however, was probably secondary to changes in nitrogen metabolism. The main results are that the excretion of urea is regulated by the renal tubule, that changes in the regulation can take place rapidly following a suitable stimulus, and that these changes are independent of plasma urea level.

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.

Renal Regulation of Urea Excretion in Sheep

1958 ◽  
Vol 194 (2) ◽  
pp. 221-228 ◽  
Author(s):  
Bodil Schmidt-Nielsen ◽  
Humio Osaki ◽  
H. V. Murdaugh ◽  
Roberta O'Dell
Keyword(s):  
Protein Intake ◽  
Urine Flow ◽  
Inulin Clearance ◽  
Urea Clearance ◽  
Clearance Ratio ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Low Protein ◽  
Abrupt Changes ◽  
Sudden Decrease

In order to elucidate the renal mechanism for the regulation of urea excretion the urea clearance and the GFR were studied in sheep during normal and low protein intake in a range of urine flows from extreme osmotic diuresis to minimal flows. Differences in the effects of osmotic and water diureses and the effects of abrupt changes in rate of urine flow were also studied. In sheep on normal protein intake the urea/inulin clearance ratio was constant in the range of urine flows corresponding to inulin U/P ratios from 10 to 500. On low protein intake the urea/inulin clearance ratio decreased markedly with decreasing urine flow. At extremely high urine flows no difference was found between the urea/inulin clearance ratios on different diets. Regulation was found to be independent of GFR, plasma urea concentration and osmotic load and must therefore be on the tubular level. Observations during abrupt changes in urine flow showed that the urea clearance is not only abnormally high during increasing flows but also abnormally low during a sudden decrease in flow. The first phenomenon is known as ‘exaltation,’ and we have termed the latter phenomenon ‘abatement.’ The data on exaltation and abatement and on the effects of urine flow are consistent with a previously suggested hypothesis that the excretion of urea in the mammalian kidney is brought about through a regulated active transport of urea, accentuated by a countercurrent multiplier system represented by Henle's loops and vasa recta.

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