Urea excretion in ruminants. III. The role of the hind-gut (caecum and colon)

1970 ◽  
Vol 21 (2) ◽  
pp. 345 ◽  
Author(s):  
RF Thornton ◽  
PR Bird ◽  
M Somers ◽  
RJ Moir
Keyword(s):  
Terminal Ileum ◽  
Nitrogen Excretion ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Dry Matter Digestibility ◽  
Nitrogen Concentrations ◽  
Faecal Nitrogen ◽  
Hind Gut

The transfer of endogenous nitrogen to the hind-gut digesta of sheep and its relationship with urinary nitrogen excretion were studied concurrently with the estimation of nitrogen balance and of dry matter digestibility in sheep fitted with a re-entrant ileal cannula. Infusion of glucose into the terminal ileum increased the excretion of faecal nitrogen by 1 g/day, while the urinary urea nitrogen excretion decreased by 1 g/day, relative to the respective control levels. Plasma urea nitrogen concentrations remained unchanged. When glucose was infused, the excretion of nitrogen in the faeces was higher than the amount of nitrogen passing the terminal ileum. It is suggested that endogenous urea nitrogen was transferred to the digesta of the hind-gut, where it was incorporated into microbial protein and subsequently excreted in the faeces. The transfer of urea from the blood to either of the fermentative areas of the gut tract is apparently the preferential pathway of urea excretion in ruminants.

The effects of increased nitrogen intakes on plasma urea nitrogen and rumen ammonia levels in sheep

1970 ◽  
Vol 21 (3) ◽  
pp. 501 ◽  
Author(s):  
KH McIntyre
Keyword(s):  
Dry Matter ◽  
Nitrogen Excretion ◽  
Kidney Tubules ◽  
Urea Clearance ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Nitrogen Intake ◽  
Ad Libitum ◽  
Excretion Rates

A series of five roughage rations providing increasing amounts of nitrogen (6.8, 16.8, 23.5, 37.3, and 46.3 g/day) and some changes in dry matter intakes (720, 710, 704, 1056, and 1408 g/day) was offered to sheep. The first four rations were given hourly and the fifth ad libitum. Urine outputs, urine total nitrogen, urine urea nitrogen, and urea clearance values increased with nitrogen intakes. Water intakes were linearly related to dry matter intakes. Plasma urea nitrogen and rumen ammonia levels both increased linearly to about 30 mg/100 ml, but did not increase further on higher levels of nitrogen intake. At these levels of intake both plasma urea nitrogen and rumen ammonia levels were no longer related to urine nitrogen excretion rates. The results are discussed in relation to the role of the kidney tubules in nitrogen excretion in the sheep.

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).

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.

Some effects of water restriction on nitrogen metabolism of cattle

1969 ◽  
Vol 20 (1) ◽  
pp. 185 ◽  
Author(s):  
RF Thornton ◽  
NG Yates
Keyword(s):  
Nitrogen Metabolism ◽  
Energy Intake ◽  
Water Intake ◽  
Nitrogen Concentration ◽  
Nitrogen Retention ◽  
Nitrogen Excretion ◽  
Water Restriction ◽  
Urea Nitrogen ◽  
Plasma Urea ◽  
Faecal Nitrogen

Water restriction was found to decrease nitrogen retention in cattle when compared with periods of similar digestible energy intake but unrestricted water intake. The decreased nitrogen retention was associated with increases in both faecal nitrogen output and urinary urea excretion. The rise in urinary urea nitrogen excretion appeared to be mediated through increased plasma urea nitrogen concentration.

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.

scholarly journals Biochemical indicators of condition, nutrition and nitrogen excretion in caribou

Rangifer ◽  
1996 ◽  
Vol 16 (4) ◽  
pp. 201 ◽  
Author(s):  
Ray Case
Keyword(s):  
Body Composition ◽  
Adult Female ◽  
Rangifer Tarandus ◽  
Nitrogen Excretion ◽  
Late Winter ◽  
Marrow Fat ◽  
Urea Nitrogen ◽  
Biochemical Indicators ◽  
Fat Reserves ◽  
Nitrogen Concentrations

Urinary urea nitrogen to creatinine ratios, urinary Nt-methylhistidine to creatinine ratios, serum urea nitrogen concentrations (SUN mg/dl), and serum Nt-methylhistidine concentrations were compared with physical measures of body composition in adult female barren-ground caribou (Rangifer tarandus groenlandicus) from the Bathurst and Southampton Island herds during late winter. Body weight and UUC were used to estimate urinary urea nitrogen (urea-N) excretion in free ranging caribou. Only mean UUC reflected differences in fat reserves between populations. None of the biochemical indicators were directly related to body composition. However, elevated UUC were only observed in caribou with depleted fat reserves as demonstrated by low kidney fat index (KFK40) and/or reduced femur marrow fat (FMF<80). UUC greater than 0.25 were indicative of undernourished animals with depleted fat reserves. SUN and UN -MHC showed no clear relationship with fat reserves. The mean estimated daily urea-N excretion for adult female caribou in late winter was extremely low (0.11+0.01SE g urea-N/day, n=76, range=0.011-0.510). The results of my study suggest that UUC can be used to detect nutritionally stressed caribou with depleted fat reserves on lichen winter ranges.

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.

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