New Nitrogen Feed Compounds for Ruminants—A Laboratory Evaluation

Belasco, I. J.

doi:10.2527/jas1954.133601x

Cited by 82 publications

(24 citation statements)

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“…Both urea and allantoin are recycled in the rumen via saliva [4,9] and, at least for urea, through the rumen wall [14], enhancing the availability of N for microbial protein synthesis. Allantoin and other purine derivatives are degraded by rumen bacteria [13,17] and N could be used for microbial synthesis [3].…”

Section: Discussionmentioning

confidence: 99%

Microbial protein production determined by urinary allantoin and renal urea sparing in normal and low protein fed Corriedale sheep

et al. 2002

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-The aim of the present study was to compare the amount of microbial N entering the duodenum and the efficiency of N utilisation for microbial protein synthesis in normal (NP, 17.4 g N/d) and low protein (LP, 7.5 g N/d) fed Corriedale sheep. Renal functional tests for urea handling studies, and determination of urinary allantoin as an indirect method to estimate the microbial protein production were used. Although the N intake was 57% lower in LP sheep, the microbial N production was not very different between both diets (NP: 3.99 ± 0.01 vs. LP: 3.79 ± 0.02 g/d, P < 0.05). The efficiency of the microbial protein synthesis in the rumen, expressed as grams of microbial N per kg of digestible organic matter apparently digested in the rumen, was not statistically different for both diets. The urinary elimination of urea was reduced by 84% in LP sheep, essentially due to an important decrease in both renal plasma flow (-63%) and glomerular filtration rate (-71%). These haemodynamic changes would also reduce the filtered load and the urinary elimination of allantoin, thereby leading to an underestimation of the amount of microbial protein entering in the duodenum. Since the renal urea spared by the kidneys remains in the blood, it limits the drop of the available urea for ruminal recycling consecutive to a low nitrogen diet. (NP,17,4 g N/j) ou hypoprotéique (LP, 7,5 g N/j). Des tests de fonctionnement rénal pour étudier les transferts d'urée, et le dosage de l'allantoïne pour estimer la production de protéine microbienne ont été utilisés. Malgré une ingestion d'azote réduite de 57% chez les moutons LP, la production d'azote microbien n'a pas été très différente entre les deux régimes (NP: 3,99 ± 0,01 vs. LP: 3,79 ± 0,02 g/j, P < 0,05). L'efficacité de la synthèse protéique microbienne dans le rumen, exprimée en grammes d'azote microbien par kg de matière organique apparemment digérée dans le rumen, n'a pas été statistiquement différente dans les deux régimes. L'élimination urinaire d'urée a été réduite de 84% chez les moutons LP, grâce essentiellement à une importante diminution du débit plasmatique rénal (-63%) et de la filtration glomérulaire (-71%). Ces modifications hémodynamiques réduisant également la charge filtrée et la quantité d'allantoïne éliminée, peuvent être responsables d'une sous estimation de la quantité de protéine microbienne entrant dans le duodénum. L'urée épargnée au niveau rénal restant dans le sang, limite la baisse de l'urée disponible pour le recyclage dans le rumen, observée lors des régimes pauvres en azote.protéine microbienne / allantoïne / urée / mouton

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Section: Discussionmentioning

confidence: 99%

Microbial protein production determined by urinary allantoin and renal urea sparing in normal and low protein fed Corriedale sheep

et al. 2002

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“…Other studies have demonstrated that the ratio of RNA:DNA in duodenal digesta is similar to the distinctive ratio of rumen bacteria, indicating that NAs entering the duodenum are essentially microbial in origin (Mugdal et al, 1978;McAllan, 1982), since dietary or infused exogenous NA entering the rumen are rapidly degraded into nucleotides, nucleosides and free bases (McAllan and Smith, 1973a). End products of rumen NA digestion can subsequently be utilized by rumen microbes as a source of carbon and N (Belasco, 1954;Jurtshuk et al, 1958) or directly incorporated as a NA precursor (Smith and Mathur, 1973).…”

Section: Fate Of Nucleic Acids In the Rumenmentioning

confidence: 99%

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

Shingfield¹

2000

J. Anim. Feed Sci.

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The potential of mammary and renal purine metabolite excretion as a technique for the assessment of microbial protein supply in ruminant animals is reviewed. Data reported in the literature tends to support the validity of the assumptions of the technique that purines entering the duodenum are essentially microbial in origin and that following metabolism, purine catabolites (collectively allantoin, hypoxanthine, uric acid and xanthine) are quantitatively recovered in urine. The most convincing experimental evidence suggests that secretion of purine metabolites in milk is of little value for the assessment of microbial protein supply due a mumal correlation with milk yield. In contrast, use of urinary purine metabolite excretion does appear to provide estimates of microbial protein supply that, are in general, consistent with values derived using standard in vivo procedures. However, the accuracy of this approach is largely dependent on obtaining representative samples of rumen microbes and the ability to account for variations in non-renal excretion and endogenous purine losses. In conclusion, urinary purine metabolite excretion appears to represent a valid noninvasive procedure to assess relative differences, rather than quantitative estimates of microbial protein supply in ruminant animals.

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“…Adding sulfate had no effect on bacterial growth. In vitro experiments by Belasco (1954) indicated that urea was su perior to soybean meal, cottonseed, linseed, and corn gluten in improving cellulose digestion and similar observations were reported by Chalupa e_t al. (1963).…”

Section: Literature Reviewsupporting

confidence: 81%

“…In vitro experiments conducted by Belasco (1954) added to a basal diet in which all N was supplied by urea. Gelatin addition gave no response, so benefits from casein and zein were explained on the basis of improved amino acid nutrition of rumen bacteria.…”

Section: Literature Reviewmentioning

confidence: 99%

Quantitative microbial protein synthesis in the bovine rumen

Pitzen

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New Nitrogen Feed Compounds for Ruminants—A Laboratory Evaluation

Cited by 82 publications

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Microbial protein production determined by urinary allantoin and renal urea sparing in normal and low protein fed Corriedale sheep

Microbial protein production determined by urinary allantoin and renal urea sparing in normal and low protein fed Corriedale sheep

Estimation of microbial protein supply in ruminant animals based on renal and mammary purine metabolite excretion. A review

Quantitative microbial protein synthesis in the bovine rumen

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