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

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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Metabolism of urea in sheep

British Journal Of Nutrition ◽

10.1079/bjn19670037 ◽

1967 ◽

Vol 21 (2) ◽

pp. 353-371 ◽

Cited By ~ 113

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.

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The effects of dietary sucrose and the concentrations of plasma urea and rumen ammonia on the degradation of urea in the gastrointestinal tract of cattle

British Journal Of Nutrition ◽

10.1079/bjn19800072 ◽

1980 ◽

Vol 43 (1) ◽

pp. 125-140 ◽

Cited By ~ 45

Author(s):

P. M. Kennedy

Keyword(s):

Gastrointestinal Tract ◽

Medicago Sativa ◽

Multiple Regression ◽

Ammonia Concentration ◽

Urea Concentration ◽

Entry Rate ◽

Plasma Urea ◽

Plasma Urea Concentration ◽

The Relationship ◽

Microbial N

1. The rates of entry of urea into plasma, of urea degradation in the gastrointestinal tract, and the partition of that degradation between the rumen and post-ruminal tract were determined by use of [14C]urea and NaH14CO3 in Hereford steers receiving hay diets with or without sucrose. The concentrations of plasma urea and rumen ammonia were varied by infusions of urea into the rumen or abomasum.2. For all diets, plasma urea concentration was related to urea entry rate, to degradation of urea in the whole gastrointestinal tract, and to its degradation in the post-ruminal tract, but the relationship with its degradation in the rumen was poor.3. Degradation of urea in the rumen was related in a multiple regression in a curvilinear manner in three groups of diets (pasture-hay alone, pasture-hay–lucerne (Medicago sativa) mixtures, diets with sucrose), and negatively to rumen ammonia concentration for pasture-hay diets, and diets with sucrose.4. Ruminal clearance of urea (rate of urea degradation per plasma urea concentration) was negatively related to the rumen ammonia concentration for steers given diets with sucrose, of pasture-hay with or without urea infusions. Provision of sucrose in the diet significantly increased clearance.5. Enhanced urea degradation in the rumen associated with dietary sucrose supplements accounted for 0.4 of additional microbial N synthesis in the rumen.6. The partition of transfer of urea to the rumen via saliva and through the rumen wall is discussed.

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UREA DEGRADATION IN THE CAMEL

Canadian Journal of Animal Science ◽

10.4141/cjas76-072 ◽

1976 ◽

Vol 56 (3) ◽

pp. 595-601 ◽

Cited By ~ 11

Author(s):

B. EMMANUEL ◽

B. R. HOWARD ◽

M. EMADY

Keyword(s):

Crude Protein ◽

Urea Concentration ◽

Pool Size ◽

Entry Rate ◽

Plasma Urea ◽

Dietary Nitrogen ◽

Urea Metabolism ◽

Plasma Urea Concentration ◽

Kinetics Of ◽

General Plasma

Following a single injection of 14C-urea, the kinetics of urea metabolism have been studied in two female Arabian camels (Camelus dromedarius) fed roughage diets containing 6.1 (diet A), 9.6 (diet B), and 13.6% (diet C) crude protein. In general, plasma urea concentration, urea pool size, urea entry rate and urinary urea excretion rate increased as the dietary nitrogen intake increased. The mean extents of urea degradation were approximately 86, 74 and 47% for diets A, B, and C, respectively, as calculated from the ratio of urea degradation rate to urea entry rate, or from the fraction of 14C-urea recovered in the urine. The following parameters were linearly related: urea entry rate and urea pool size, urea pool size and plasma urea concentration, percentage urea degraded and urea entry rate, and percentage urea degraded and crude protein intake.

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Urea Excretion in the Camel

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1957.188.3.477 ◽

1957 ◽

Vol 188 (3) ◽

pp. 477-484 ◽

Cited By ~ 81

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.

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

Australian Journal of Agricultural Research ◽

10.1071/ar9700145 ◽

1970 ◽

Vol 21 (1) ◽

pp. 145 ◽

Cited By ~ 24

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.

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

Australian Journal of Agricultural Research ◽

10.1071/ar9700337 ◽

1970 ◽

Vol 21 (2) ◽

pp. 337 ◽

Cited By ~ 2

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.

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The effect of digestible undergradable protein (DUP) content of concentrates on colostrum production and lamb performance of triplet-bearing ewes on grass-based diets during late pregnancy

Animal Science ◽

10.1079/asc40890101 ◽

2005 ◽

Vol 80 (1) ◽

pp. 101-110 ◽

Cited By ~ 10

Author(s):

R. W. Annett ◽

A. F. Carson ◽

L. E. R. Dawson

Keyword(s):

Crude Protein ◽

Late Pregnancy ◽

Metabolizable Energy ◽

Plasma Urea ◽

Esterified Fatty Acids ◽

Condition Score ◽

Gross Energy ◽

Plasma Urea Concentration ◽

And Control ◽

Degradable Protein

AbstractAn experiment was carried out to investigate the effects of increasing the digestible undegradable protein (DUP) concentration of concentrates on colostrum production and lamb output from prolific ewe breed types. Sixty triplet-bearing ewes with a mean condition score of 3.75 were allocated to one of five treatments (no. =; 12) for the final 6 weeks of pregnancy. Four of the treatments were offered a restricted grass diet (0.6 kg dry matter (DM) per day) plus one of four isoenergetic and isonitrogenous concentrates (0.56 kg DM per day) that were formulated to provide 25 (P25); 40 (P40); 75 (P75) and 95 (P95) g DUP/kg DM. Control ewes were offered a grass-only diet with the aim of achieving an equivalent total DM intake (1.16 kg DM per day). Concentrate composition had no effect on total diet DM, crude protein or metabolizable energy intakes, but the intake of DUP increased with increasing concentrate DUP level (P< 0.001). Supplementing grass with concentrates led to significant reductions in plasma β-hydroxybutyrate (P< 0.05) and non-esterified fatty acids(P< 0.001) concentrations. Plasma urea concentration tended to be negatively and linearly related to the concentrate DUP level (P< 0.1). Colostrum production and composition were not affected by concentrate type, except for the concentration of gross energy which was highest for P40 ewes. Concentrate feeding led to significant (P< 0.05) increases in colostrum yield 18 h post lambing and colostral outputs of ash, crude protein, total solids and gross energy but resulted in a lower (P< 0.05) colostral immunoglobulin G concentration. Lamb birth weight and total litter weight were not affected by late pregnancy feeding regime. However lamb survival to weaning was reduced significantly (P< 0.05) for P25 and control ewes, resulting in lower levels of lamb output at weaning. The results from this study indicate that offering rumen undegradable rather than rumen degradable protein has no effect on colostrum production and lamb performance when ewes are offered high quality grass-based diets in late pregnancy.

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Whole body Kt/V from dialysate urea measurements during hemodialysis.

Journal of the American Society of Nephrology ◽

10.1681/asn.v9112118 ◽

1998 ◽

Vol 9 (11) ◽

pp. 2118-2123

Author(s):

J Sternby

Keyword(s):

Removal Rate ◽

Plasma Concentrations ◽

The Body ◽

Urea Concentration ◽

Whole Body ◽

Water Volume ◽

Dialysis Dose ◽

Plasma Urea ◽

Urea Distribution Volume ◽

Plasma Urea Concentration

A new method for the calculation of dialysis dose from continuous measurements of dialysate urea concentrations has been developed. It is based on urea mass in the patient instead of plasma concentrations, and results in a measure of dialysis dose that has been named whole body Kt/V. The measured urea mass removal rate and the slope of the dialysate urea concentration curve are the key parameters needed for the calculations. No assumptions have to be made about urea distribution in the body (single or double pool, etc.). Blood sampling is not needed. This simplifies the logistics and eliminates the problems with rebound and timing in taking samples. The total urea mass present in the body before treatment is also obtained. It can be used directly, or in relation to body weight or water volume, as a measure of the level of urea in the body. This may serve as an alternative to pretreatment plasma concentration. If a pretreatment plasma urea concentration is available, the urea distribution volume can be calculated, which may be of separate clinical interest.

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

Australian Journal of Agricultural Research ◽

10.1071/ar9700131 ◽

1970 ◽

Vol 21 (1) ◽

pp. 131 ◽

Cited By ~ 11

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.

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