The nitrogen metabolism of sheep consuming Flinders grass (Iseilema spp.), Mitchell grass (Astrebla spp.) and mixed native pasture

1978 ◽  
Vol 29 (3) ◽  
pp. 595 ◽  
Author(s):  
BW Norton ◽  
RM Murray ◽  
KW Entwistle ◽  
JV Nolan ◽  
FM Ball ◽  
...  
Keyword(s):  
Digestive Tract ◽  
Nitrogen Metabolism ◽  
Nutritive Value ◽  
The Body ◽  
Urea Synthesis ◽  
Plasma Urea ◽  
Native Pasture ◽  
Nitrogen Conservation ◽  
Plasma Urea Concentration ◽  
Energy Balances

Some aspects of nitrogen metabolism of sheep given Mitchell grass (Astrebla spp.), Flinders grass (Iseilema spp.) and mixed native pasture were investigated. All diets were of low nutritive value as demonstrated by negative nitrogen and energy balances in sheep on these diets. Studies of urea metabolism demonstrated a significant relationship between plasma urea concentration, the rate of irreversible loss of urea from plasma and the rate of urea degradation in the digestive tract. On average, 81% of the urea synthesized in the body was transferred to the digestive tract and degraded to ammonia and carbon dioxide. The proportion of urea degradation occurring intraruminally was estimated during an intravenous infusion of 14C urea by measuring the rate of appearance of 14CO2 in ruminal fluid, the proportion degraded post-ruminally being obtained by difference. Urea degraded in the rumen accounted for 7–13% of the total quantity degraded in the digestive tract, and the rate of urea transfer (0.55 ± 0.13 g nitrogen/day) was not related to the rate of urea synthesis in the body. The lower digestive tract was the major site of urea degradation in sheep given these low protein diets, and the rate of urea transfer to this part of the digestive tract was linearly related to the rate of urea synthesis in the body. The implications of these findings are discussed in relation to nitrogen conservation in sheep given low quality diets.

Digestion and nitrogen conservation in cattle and buffaloes given rice straw with or without molasses

1992 ◽  
Vol 119 (2) ◽  
pp. 255-263 ◽  
Author(s):  
N. Abdullah ◽  
J. V. Nolan ◽  
M. Mahyuddin ◽  
S. Jalaludin
Keyword(s):  
Rice Straw ◽  
The Body ◽  
Synthesis Rate ◽  
Urea Synthesis ◽  
Total Volatile ◽  
Plasma Urea ◽  
Rumen Ph ◽  
Swamp Buffaloes ◽  
Nitrogen Conservation ◽  
Plasma Urea Concentration

SUMMARYUsing [14C]urea, the rates of urea synthesis in the body, excretion in the urine and degradation in the rumen and gut were compared in 20-month-old Kedah-Kelantan cattle and swamp buffaloes at the Universiti Pertanian Malaysia, Malaysia in 1987. The animals were fed rice straw or straw plus molasses.The buffaloes were heavier than the cattle and had higher straw and nitrogen intakes, although these intakes did not differ significantly when compared on the basis of metabolic liveweight (W0·75).Rumen pH in the buffaloes was lower, whereas ammonia and total volatile fatty acid (VFA) concentrations were higher than in the cattle. Total VFA concentration was lower when the diet contained molasses. Rumen bicarbonate kinetics did not differ significantly between species or diets.There were no significant differences between species in plasma urea concentration, or urea synthesis rate per W0·75, or endogenous urea movement into the rumen per W0·75.The buffaloes consumed more water and discharged twice as much urine as the cattle, but nevertheless excreted less urea per W0·75, and a larger fraction of their endogenously produced urea entered the gut. Movement of urea into the rumen per W0·75 was lower when the diet contained molasses.

Nitrogen metabolism in Brahman cross, buffalo, banteng and Shorthorn steers fed on low-quality roughage

1979 ◽  
Vol 30 (2) ◽  
pp. 341 ◽  
Author(s):  
BW Norton ◽  
JB Moran ◽  
JV Nolan
Keyword(s):  
Digestive Tract ◽  
The Other ◽  
Urea Synthesis ◽  
Irreversible Loss ◽  
Lower Efficiency ◽  
Plasma Urea ◽  
Intravenous Injections ◽  
Glomerular Filtrate ◽  
51Cr Edta ◽  
Nitrogen Conservation

Urea metabolism was studied in Brahman cross, buffalo, banteng and Shorthorn cattle offered a low quality hay. Intravenous injections of [14C]urea and 51Cr-EDTA were used to determine the irreversible loss of urea from the plasma, the degradation of urea in the rumen and lower digestive tract, and the glomerular filtration rate. When species were compared at equal liveweights and nitrogen intakes, buffaloes had significantly higher (P < 0.05) plasma urea concentrations and rates of irreversible loss of urea carbon from plasma than the other species. There were no significant differences between species in urinary urea excretion. Urea degradation in the digestive tract was linearly related to the irreversible loss of urea, and the proportion of irreversible urea loss degraded was significantly (P < 0.05) lower in Shorthorn cattle (48%) than in the other species (73–91%). Shorthorn cattle reabsorbed urea from the glomerular filtrate with a lower efficiency (60%) than did the other species (85–94%). In Brahman cross, buffalo and banteng, plasma urea recycled to the rumen was a relatively constant amount (4.3 g nitrogen/d) and represented on average 39% of the urea degraded in all parts of the digestive tract. Urea degraded in the digestive tract increased linearly with increasing irreversible loss of urea from plasma. It was concluded that, despite significant differences between species in urea synthesis and degradation, there was little indication that these differences constituted a significant nitrogen conservation mechanism in any one species.

scholarly journals Dynamic aspects of ammonia and urea metabolism in sheep

1972 ◽  
Vol 27 (1) ◽  
pp. 177-194 ◽  
Author(s):  
J. V. Nolan ◽  
R. A. Leng
Keyword(s):  
Amino Acids ◽  
Digestive Tract ◽  
Isotope Dilution ◽  
Quantitative Model ◽  
The Body ◽  
Plasma Urea ◽  
Nitrogenous Compounds ◽  
Urea Metabolism ◽  
Turn Over ◽  
Lower Digestive Tract

1. To obtain a quantitative model for nitrogen pathways in sheep, a study of ammonia and urea metabolism was made by using isotope dilution techniques with [15N]ammonium sulphate and [15N]urea and [14C]urea.2. Single injection and continuous infusion techniques of isotope dilution were used for measuring ammonia and urea entry rates.3. Sheep were given 33 g of chaffed lucerne hay every hour; the mean dietary N intake was 23.4 g/d.4. It was estimated that 59% of the dietary N was digested in the reticulo-rumen; 29% of the digested N was utilized as amino acids by the micro-organisms, and 71% was degraded to ammonia.5. Of the 14.2 g N/d entering the ruminal ammonia pool, 9.9 g N/d left and did not return to the pool, the difference of 4.3 g N/d represented recycling, largely within the rumen itself (through the pathways: ruminal ammonia → microbial protein → amino acids → ammonia).6. Urea was synthesized in the body at a rate of 18.4 g N/d from 2.0 g N/d of ammonia absorbed through the rumen wall and 16.4 g N/d apparently arising from deamination of amino acids and ammonia absorbed from the lower digestive tract.7. In the 24 h after intraruminal injection of [15N]ammonium salt, 40–50% of the N entering the plasma urea pool arose from ruminal ammonia; 26% of the15N injected was excreted in urinary N.8. Although 5.1g N/d as urea was degraded apparently in the digestive tract, only 1.2g N/d appeared in ruminal ammonia; it is suggested that the remainder may have been degraded in the lower digestive tract.9. A large proportion of the urea N entering the digestive tract is apparently degraded and absorbed and the ammonia incorporated in the pools of nitrogenous compounds that turn over only slowly. This may be a mechanism for the continuous supply to the liver of ammonia for these syntheses.10. There was incorporation of15N into bacterial fractions isolated from rumen contents after intraruminal and intravenous administration of [15N]ammonium salts and [15N]urea respectively.11. A model for N pathways in sheep is proposed and, for this diet, many of the pool sizes and turn-over rates have been either deduced or estimated directly.

Effect of rumen degradable protein and lactation on nitrogen metabolism in dairy goats

1991 ◽  
Vol 71 (4) ◽  
pp. 1111-1124 ◽  
Author(s):  
J. Brun-Bellut ◽  
J. M. Kelly ◽  
G. W. Mathison ◽  
R. J. Christopherson
Keyword(s):  
Amino Acids ◽  
Digestive Tract ◽  
Urea Concentration ◽  
Dairy Goats ◽  
Rumen Microorganisms ◽  
Plasma Urea ◽  
Available N ◽  
Lactation Stage ◽  
Plasma Urea Concentration ◽  
Degradable Protein

Nitrogen flow and exchanges in the digestive tract were measured in three goats during a dry stage and a subsequent hormonally induced lactation stage. Two diets, formulated with and without urea to contain either a high or low level of crude protein and rumen-degradable protein (RDP), were tested in a crossover experimental design within each stage. The amount of urea nitrogen (N) recycled to the ruminoreticulum was higher (P < 0.05) during lactation (3.5 g d−1) than in the dry stage (0.9 g d−1), as was plasma urea concentration. However, the mean amount of urea recycled was lower (P < 0.05) when the high-RDP diet was fed (1.4 g N d−1) than when the low-RDP diet was fed (3.0 g N d−1), even though the plasma urea concentration tended to be higher in goats fed the high-RDP diet. Of the estimated ruminally available N, 90–110% was incorporated into microbial cells. The proportion of bacterial N derived from rumen ammonia (0.77–0.89) was not influenced by protein source or lactation. Of the amino acids flowing into the duodenum, 69–75% were apparently absorbed in the small intestine, whereas total digestive tract apparent digestibility ranged from 81 to 83%. No more than 60% of the fecal N was derived from undigested bacteria from the rumen. It was concluded that the amount of urea which is recycled to the rumen is under metabolic control and that there is efficient use of ruminally available N by rumen microorganisms. Key words: Goats, lactation, rumen-degradable protein, 15N, urea recycling, amino acids

scholarly journals Nitrogen digestion and metabolism in sheep consuming diets containing contrasting forms and levels of N

1985 ◽  
Vol 54 (1) ◽  
pp. 175-187 ◽  
Author(s):  
R. C. Siddons ◽  
J. V. Nolan ◽  
D. E. Beever ◽  
J. C. Macrae
Keyword(s):  
Absorption Coefficient ◽  
Digestive Tract ◽  
Rumen Fluid ◽  
Ammonia Concentration ◽  
The Body ◽  
Urea Synthesis ◽  
Total N ◽  
Apparent Absorption ◽  
Molar Proportion ◽  
Rate Of Absorption

1. Nitrogen kinetics were studied in six sheep (45–55 kg live weight) consuming either a high-N grass silage or a low-N dried grass made from swards of perennial ryegrass (Lolium perenne). The diets were fed hourly at a level of 600 g dry matter/d and supplied 19.5 and 11.0 g N/d respectively.2. The amounts of organic matter (OM) consumed and flowing at the duodenum and ileum and excreted in the faeces were similar (P < 0.05) with both diets. Each diet supplied 23 g digestible OM/d per kg live eight0.75, which was sufficient to maintain body-weight.3. There were no differences (P < 0.05) between diets in rumen fluid volume, fractional outflow rate of fluid from the rumen, total concentration of volatile fatty acids or molar proportion of acetate in the rumen. The pH and molar proportion of propionate in rumen fluid were higher (P < 0.01), and molar proportion of butyrate lower (P < 0.001) when the silage was given.4. There was a net loss of N (4.0 g/d) between mouth and duodenum when the silage was consumed but a net gain (5.5 g/d) when the dried grass was consumed. As a result, total non-ammonia-N (NAN) flow at the duodenum did not differ (P / 0.05) between diets. Rumen microbial NAN flow at the duodenum, based on 15N as the marker, also did not differ (P < 0.05) between diets but the efficiency of microbial N synthesis in the rumen (g/kg OM apparently digested) was higher (P < 0.05) with the dried grass.5. When the sheep were consuming silage they had a higher concentration of ammonia in rumen fluid (P < 0.01), a higher rate of irreversible loss of ammonia from the rumen (P < 0.05) and a higher rate of absorption of ammonia across the rumen wall (P < 0.01). The rate of absorption was found to be more closely related to the unionized ammonia concentration in rumen fluid (r2 0.85) than to the total ammonia concentration (r2 0.36).6. Endogenous N entry into the forestomachs was calculated to be 5.5 g/d when the silage was given and 9.4 g/d when the dried grass was given, of which 1.7 and 3.5 g/d respectively were in the form of urea. Thus, approximately 4–6 g N/d were derived from non-urea materials.7. Within the small intestine the apparent absorption coefficient of rumen microbial NAN (0.72) did not differ (P < 0.05) between diets but the apparent absorption coefficient of total NAN was lower (P < 0.05) when the I silage was given, owing to a lower (P < 0.01) absorption coefficient of the non-microbial NAN fraction (undegraded feed and endogenous).8. Within the large intestine, diet had no effect (P < 0 05) on the apparent absorption coefficients of total N (0.22) and rumen microbial NAN (0.63).9. Plasma urea concentration, the rate of urea synthesis in the body and urinary urea excretion were higher (P < 0.001) when the silage was consumed. However, the transfer of urea to the whole digestive tract and to the post-ruminal part of the tract did not differ (P < 0.05) between diets; urea transfer to the rumen was higher (P < 0.01) when the dried grass was given.10. The results were used to construct a whole-animal model of N flows between the digestive tract and the tissues.

The effect of diethylstilbestrol on nitrogen excretion in sheep

1970 ◽  
Vol 48 (8) ◽  
pp. 573-574 ◽  
Author(s):  
T. L. Huber
Keyword(s):  
Nitrogen Metabolism ◽  
Direct Effect ◽  
Tubular Reabsorption ◽  
Arginase Activity ◽  
Nitrogen Excretion ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Nitrogen Conservation ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Administration of 2 mg of diethylstilbestrol (DES) daily to lambs reduced total urinary nitrogen excretion, urea excretion, plasma urea concentrations, and liver arginase activity. The percent of filtered urea reabsorbed was greater in untreated lambs, thus suggesting that the increased nitrogen conservation observed following DES administration to ruminants is not the result of a direct effect of DES on tubular reabsorption of urea but on nitrogen metabolism.

scholarly journals Fermentation and nitrogen dynamics in Merino sheep given a low-quality-roughage diet

1979 ◽  
Vol 42 (1) ◽  
pp. 63-80 ◽  
Author(s):  
J. V. Nolan ◽  
S. Stachiw
Keyword(s):  
Digestive Tract ◽  
Nitrogen Dynamics ◽  
The Body ◽  
Metabolizable Energy ◽  
Total Production ◽  
Urea Synthesis ◽  
Total N ◽  
Nitrogenous Compounds ◽  
Merino Sheep ◽  
Isotope Tracer

1. Fermentation in the rumen and nitrogen dynamics in the body were studied in mature Merino sheep given a maintenance ration of a low-quality-roughage diet containing mainly chopped wheat straw.2. Intake of metabolizable energy was 3.49 MJ/d and of total N 6.2 g/d.3. From measurements of volatile fatty acid (VFA) production rates and stoichiometric principles, it was calculated that 75% of the digestible organic matter intake was fermented in the rumen, making an estimated 44 g/68d microbial dry matter available to the animal.4. The total flux of ammonia through the rumen NH3 pool, estimated by 15NH3 dilution methods, was 8.2 g N/d of which 3.5 g N/d was irreversibly lost; thus 4.7 g N/d was recycled, partly within the rumen (approximately 3.8 g N/d) and partly via endogenous secretions (approximately 0.9 g N/d). The extensive recycling of NH3-N within the rumen indicated that turnover of microbial N was considerable, and the total production of micro-organisms was at least twice the net outflow.5. The proportion of the N in rumen bacteria derived from rumen ammonia was 62% and thus 38% was derived from other nitrogenous compounds such as peptides and amino acids.6. The rates of transfer of blood urea into the rumen, estimated from the appearance of 14CO2 or 15NH3 in the rumen after intravenous single injections of [14C]-and [15N]urea, did not differ significantly and the mean transfer was 2.3 urea-N/d.7. Estimates of the rate of irreversible loss of urea-C (i.e. urea synthesis in the body) were obtained by analysis of samples of either blood or urine obtained after a single, intravenous injection of [14C]urea. The two methods gave results that did not differ significantly. The estimated rate of urea synthesis in the body was 5.3 g N/d. Urea excretion rate was relatively low, i.e. 1.2 g N/d, and thus transfer of urea to the digestive tract was approximately 4.1 g N/d. Approximately 53% of the latter was transferred to the rumen, and 47% to the rest of the digestive tract. These results are discussed in relation to similar studies with sheep given other diets.8. Various aspects of isotope-tracer methods and the errors that could occur in this type of study are discussed.

scholarly journals The effects of intraruminal infusions of sodium bicarbonate, ammonium chloride and sodium butyrate on urea metabolism in sheep

1982 ◽  
Vol 48 (2) ◽  
pp. 265-274 ◽  
Author(s):  
B. W. Norton ◽  
A. N. Janes ◽  
D. G. Armstrong
Keyword(s):  
Sodium Bicarbonate ◽  
Digestive Tract ◽  
Ammonium Chloride ◽  
Sodium Butyrate ◽  
Rumen Fluid ◽  
Specific Radioactivity ◽  
Urea Synthesis ◽  
Plasma Urea ◽  
Carbon Transfer ◽  
Lower Digestive Tract

1. Three sheep fitted with rumen cannulas were fed hourly a daily ration of 1000 g pelleted-grass cubes, and during four successive 2-week periods were intraruminally infused (0·45 l/d) with solutions containing sodium chloride (0·47 mol/d), sodium bicarbonate (0·47 mol/d), ammonium chloride (0·47 mol/d) and sodium butyrate (0·47 mol/d). Each solution, except that for NaHCO3, was adjusted to pH 7 before infusion, and provided equal sodium intakes for sheep in all periods.2. In the final week of each infusion period, a balance trial was conducted and on separate days each sheep was continuously infused with [14C]urea and NaH14CO3 intravenously and NaH14CO3 intraruminally. Carbon transfer rates between blood urea, blood bicarbonate and rumen fluid bicarbonate were calculated from the specific radioactivity of urea and bicarbonate samples and isotope infusion rates during each experimental period.3. There was no significant effect of intraruminal infusions on N balance, and with the exception of sheep in fused with NH4Cl, all sheep utilized apparently digested N with similar efficiency for N retention. Sheep infused with NH4Cl (6·2 g N/d) excreted the equivalent of 93% of the infused N as urea in urine.4. Infusion of NaHCO3. NH4Cl and sodium butyrate significantly (P < 0·05) increased the rurnen fluid concentrations of bicarbonate, ammonia and butyric acid respectively, and all infusions significantly (P < 0·05) increased total volatile fatty acid concentrations. Both NaHCO3 and sodium, butyrate significantly (P < 0·05) increased the pH of rumen fluid There was no significant effect of infusion on the proportions of propionic acid or the osmolality of rumen fluid.5. Intraruminal infusions of NH4Cl significantly (P < 0·05) increased and infusion of sodium butyrate significantly (P < 0·05) decreased plasma urea concentrations. Sheep infused with NH4Cl had higher rates of urea synthesis and urinary urea excretion compared with sheep on the other treatments, and a significantly (P < 0·05) lower proportion of urea synthesized by these sheep was degraded in the digestive tract. Sheep infused with sodium butyrate degraded a significantly (P < 0·05) greater amount (3·2 g N/d) and proportion (0·24) of total urea synthesis in the rumen than did sheep infused with NaCl. Corresponding values for the control (NaCl) sheep were 1·5 g N/d and 0·13 respectively. There was no significant effect of other infusions on the amount of urea recycled to the rumen or on the distribution of total urea degradation between the rumen and lower digestive tract. Plasma urea clearance to the rumen was significantly (P < 0·05) increased during sodium butyrate infusion, and the clearance of urea to the lower digestive tract was significantly (P < 0·05) decreased during NH4Cl infusion.6. The mechanism by which urea entry into the rumen is regulated by rumen metabolite levels is discussed.

scholarly journals Further studies of the dynamics of nitrogen metabolism in sheep

1976 ◽  
Vol 35 (1) ◽  
pp. 127-147 ◽  
Author(s):  
J. V. Nolan ◽  
B. W. Norton ◽  
R. A. Leng
Keyword(s):  
Digestive Tract ◽  
Rumen Fluid ◽  
The Body ◽  
Considerable Proportion ◽  
Plasma Urea ◽  
Nitrogenous Compounds ◽  
Normal Feeding ◽  
The Difference ◽  
Computer Simulation Studies ◽  
Microbial N

1. A study of ammonia and urea metabolism in sheep was made using isotope dilution techniques with (15NH4)2SO4, [15N]urea and [14C]urea in order to determine quantitatively the movements of urea-N and NH3-N throughout the body of normal, feeding sheep.2. Single injections of 15N-labelled compounds were made into the rumen fluid NH3, caecal fluid NH3 and the blood urea pools, in order to estimate the rates of flux through, and the transfer of N between, these and other nitrogenous pools in the body. 51Cr EDTA was injected into the rumen and caecum with (15NH4)2SO4 to allow estimation of fluid volumes and to provide an indication of mixing, and of times of transit of isotopes between different sampling sites in the digestive tract.3. The sheep ate approximately 22 g lucerne chaff/h and the mean dietary N intake was 16.3 g/d.4. The rate of flux of NH3 through the rumen NH3 pool was 15.0 g/d (i.e. 90% of the dietary N ingested; however, this amount also included N from plasma urea (1.1 g/d) and other endogenous sources including NH3 derived from caecal NH3 (0.4 g/d).5. Only 40% of the N in isolated rumen bacteria was derived from NH3, indicating that a considerable proportion of their N requirements were obtained from compounds other than NH3 (e.g. peptides and amino acids).6. There was evidence of recycling of N between nitrogenous pools in the rumen, probably through rumen NH3 → microbial N → NH3.7. It was estimated that 5.3 g blood urea-N/d entered the digestive tract: 20% of this urea was degraded in the rumen, 25% in the caecum and the remainder was apparently degraded elsewhere; there was evidence of urea degradation in the large intestine posterior to the caecum and it is suggested that urea degradation and absorption of the resultant NH3 may occur in the ileum.8. Of the 4.8 g N/d entering the caecal NH3 pool, 4.2 g N/d left and did not return and the difference (0.6 g N/d) was recycled, possibly through caecal NH3 → microbial N → NH3.9. A large proportion of the NH3 entering the caecal NH3 pool (70% or 3.2 g N/d) was apparently derived from degradation of nitrogenous products, other than urea, including rumen microbial N (1.0 g N/d) passing undigested from the small intestine.10. Less than half the NH3-N of caecal origin entering the rumen passed through the blood urea pool; the remainder was apparently transported as other nitrogenous compounds in the blood or body fluids.11. The results of the three experiments were combined in a general three-pool, opencompartment model which formally recognizes an unlimited number of other unspecified, interconnected pools together comprising the whole-animal system. Rates of flux through, and transfer of N between these and other nitrogenous pools in the body were calculated by solving this model and the information derived has been applied to whole-animal models with a view to subsequently using these models in computer simulation studies.

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.

Sign in / Sign up

Export Citation Format

Share Document