Splanchnic and Mammary Nitrogen Metabolism by Dairy Cows Fed Steam-Rolled or Steam-Flaked Corn

Delgado-Elorduy, A.; Theurer, C.B.; Huber, John; Alio, A.; Lozano, Óscar Moralejo; Sadik, M.; Cuneo, P.; Young, H. D.; Simas, I.J.; Santos, J.E.P.; Nussio, Luiz Gustavo; Nussio, C.; Webb, K. E.; Tagari, H.

doi:10.3168/jds.s0022-0302(02)74064-2

Cited by 19 publications

(13 citation statements)

References 37 publications

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“…For example, Blouin et al (2002) showed a 0·21 difference in AA portal absorption despite similar crude protein intakes between diets. Furthermore, in cows ingesting the same amount of N, steam-fl aking of corn increased portal absorption of AA compared with steam-rolling (Tagari et al, 2004), probably the result of a change in the N-energy interactions in the rumen, as steam-fl aking has been shown to increase in vitro starch hydrolysis (Delgado-Elorduy et al, 2002b). Maximal AA absorption does not depend solely on crude protein intake.…”

Section: Ureamentioning

confidence: 90%

“…The estimation of peptide absorption is fraught with technical diffi culties as the 'traditional' method relies on differences between the AA in a 'protein-free' plasma fi ltrate before and after acid hydrolysis. Such calculations can be set against a recent study in dairy cows that reported substantial absorption of AA as peptides, but the total absorption of AA, as free plus peptide, in the steam-fl aked corn treatment was larger than estimated digested N (Delgado-Elorduy et al, 2002b;Tagari et al, 2004) : this clearly indicates the technical challenge and limitation of measurements of veno-arterial difference of AA and peptides. More recently, use of stable isotope labelled di-and tri-peptides of alanine and leucine infused into the abomasum of sheep failed to detect any enriched forms of these peptides in the portal vein plasma (G. Le and G. E. Lobley, unpublished results).…”

Section: Ureamentioning

confidence: 99%

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The route of absorbed nitrogen into milk protein

et al. 2005

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A database reviewing the metabolism of nitrogen (N) compounds from absorption to milk has been compiled from 14 published and unpublished studies (33 treatments) that measured the net fl ux of N compounds across the splanchnic tissues in dairy cows. Apparent N digestibility averaged 0·65, with this then partitioned between 0·34 excreted in urine and 0·31 secreted as milk. Nitrogen metabolites are absorbed from the lumen of the gut into the portal vein, mainly as free amino acids (AA) and ammonia; these represented 0·58 and 0·57 of digested N, respectively. All of the ammonia absorbed was removed by the liver with, as a result, a net splanchnic fl ux of zero. Detoxifi cation of ammonia by the liver and catabolism of AA results in production of urea as an end-product. Hepatic ureagenesis is a major cross-road in terms of whole body N exchange, being the equivalent of 0·81 of digested N. Therefore, salvage of a considerable part of this ureagenesis is needed to support milk protein synthesis. This salvage occurs via transfer of urea from the blood circulation into the lumen of the gut. On average, 0·47 of hepatic ureagenesis was returned to the gut via the portal-drained viscera (equivalent to 0·34 of digested N) with 0·56 of this then used for anabolic purposes e.g. as precursor N for microbial protein synthesis. On average, 0·65 of estimated digestible AA was recovered in the portal vein. This loss (0·35) is due to oxidation of certain AA across the gut wall and non-absorption of endogenous secretions. The magnitude of this loss is not uniform among AA and varies between less than 0·05 for histidine to more than 0·90 for some non-essential AA, such as glutamine. A second database (six studies, 14 treatments) was constructed to further examine the subsequent fate of absorbed essential AA. When all AA are aggregated, the liver removed, on average, 0·45 of portal absorption but this value hides the considerable variation between individual AA. Simplistically, the AA behave as two major groups : one group undergoes very little hepatic removal and includes the branched-chain AA and lysine. For the second group, removal varies between 0·35 and 0·50 of portal absorption, and includes histidine, methionine and phenylalanine. For both groups, however, the effi ciency of transfer of absorbed AA into milk protein decreases with increasing supply of protein. This loss of effi ciency is linked directly with increased hepatic removal of AA from the second group and, probably, increased catabolism by peripheral tissues, including the mammary gland, of AA from the fi rst group. Therefore, we must stop using fi xed factors of conversion of digestible AA to milk in our predictive schemes and acknowledge that metabolism of AA between delivery from the duodenum and conversion to milk protein will vary with nutrient supply. New information evolving from re-analysis of the literature and recent studies will allow better models to be devised for the prediction of nutrient-based responses by the lactating cow. Consideration of biological...

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Section: Ureamentioning

confidence: 90%

Section: Ureamentioning

confidence: 99%

The route of absorbed nitrogen into milk protein

et al. 2005

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“…Upon entering the rumen, urea is reconverted by bacterial urease to release 2 mol of NH 3 per mol of urea ( Figure 6). In dairy cows, absorption of ammonia can reach 25 mol/d (Delgado-Elorduy et al, 2002), whereas secretion of up to 10 mol/d of urea has been observed . Unless dietary N intake is low, urea secretion into the rumen usually greatly exceeds the needs of microbial protein synthesis (Reynolds and Kristensen, 2008).…”

Section: Interaction Of Ammonia and Scfamentioning

confidence: 97%

RUMINANT NUTRITION SYMPOSIUM: Role of fermentation acid absorption in the regulation of ruminal pH12

Aschenbach

Penner

Stumpff

et al. 2011

Journal of Animal Science

385

373

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Highly fermentable diets are rapidly converted to organic acids [i.e., short-chain fatty acids (SCFA) and lactic acid] within the rumen. The resulting release of protons can constitute a challenge to the ruminal ecosystem and animal health. Health disturbances, resulting from acidogenic diets, are classified as subacute and acute acidosis based on the degree of ruminal pH depression. Although increased acid production is a nutritionally desired effect of increased concentrate feeding, the accumulation of protons in the rumen is not. Consequently, mechanisms of proton removal and their quantitative importance are of major interest. Saliva buffers (i.e., bicarbonate, phosphate) have long been identified as important mechanisms for ruminal proton removal. An even larger proportion of protons appears to be removed from the rumen by SCFA absorption across the ruminal epithelium, making efficiency of SCFA absorption a key determinant for the individual susceptibility to subacute ruminal acidosis. Proceeding initially from a model of exclusively diffusional absorption of fermentation acids, several protein-dependent mechanisms have been discovered over the last 2 decades. Although the molecular identity of these proteins is mostly uncertain, apical acetate absorption is mediated, to a major degree, via acetate-bicarbonate exchange in addition to another nitrate-sensitive, bicarbonate-independent transport mechanism and lipophilic diffusion. Propionate and butyrate also show partially bicarbonate-dependent transport modes. Basolateral efflux of SCFA and their metabolites has to be mediated primarily by proteins and probably involves the monocarboxylate transporter (MCT1) and anion channels. Although the ruminal epithelium removes a large fraction of protons from the rumen, it also recycles protons to the rumen via apical sodium-proton exchanger, NHE. The latter is stimulated by ruminal SCFA absorption and salivary Na(+) secretion and protects epithelial integrity. Finally, SCFA absorption also accelerates urea transport into the rumen, which via ammonium recycling, may remove protons from rumen to the blood. Ammonium absorption into the blood is also stimulated by luminal SCFA. It is suggested that the interacting transport processes for SCFA, urea, and ammonia represent evolutionary adaptations of ruminants to actively coordinate energy fermentation, protein assimilation, and pH regulation in the rumen.

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“…The butyrate fermentation following intake of grass with high sugar content might be part of the explanation for the typical decreasing milk production and milk fat production experienced when cows start to graze in the spring. In an experiment with intraruminal infusion of Figure 4 Portal-drained visceral (PDV) extraction of arterial urea-nitrogen in lactating dairy cows plotted against the arterial concentration of urea-N. Means from the following studies were used to establish the regression line (R 2 5 0.50) closed square (Reynolds et al, 2003); closed triangle up (Benson et al, 2002); closed triangle down (Blouin et al, 2002); closed diamond (Delgado-Elorduy et al, 2002a); closed hexagon (Delgado-Elorduy et al, 2002b); open square (Casse et al, 1994); open triangle down (Bach et al, 2000); open triangle up (Berthiaume et al, 2006); closed circle (Reynolds et al, 1988b); and open circle (Raggio et al, 2004). The mean PDV extraction of urea-N observed in the present study is indicated as an open diamond.…”

Section: Hourmentioning

confidence: 99%

Urea and short-chain fatty acids metabolism in Holstein cows fed a low-nitrogen grass-based diet

Røjen

Lund

Kristensen

2008

Animal

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Three ruminally cannulated and multicatheterised lactating dairy cows were used to investigate the effect of different supplement strategies to fresh clover grass on urea and short-chain fatty acid (SCFA) metabolism in a zero-grazing experiment with 24-h blood and ruminal samplings. Fresh clover grass was cut every morning and offered from 0800 to 1500 h. Maize silage was fed at 1530 h. The three treatments, arranged in a Latin square, differed by timing of feeding rolled barley and soya-bean hulls relative to fresh clover grass. All diets had the same overall composition. Treatments were soya-bean hulls fed at 0700 h and barley fed at 1530 h (SAM), barley fed at 0700 h and soya-bean hulls fed at 1530 h (BAM), and both soya-bean hulls and barley fed at 1530 h (SBPM). The grass had an unexpectedly low content of crude protein (12.7%) and the cows were severely undersupplied with rumen degradable protein. The treatment effects were numerically small; greater arterial ammonia concentration, net portal flux of ammonia and net hepatic flux of urea during part of the day were observed when no supplementary carbohydrate was fed before grass feeding. A marked diurnal variation in ruminal fermentation was observed and grass feeding increased ruminal concentrations of propionate and butyrate. The net portal fluxes of propionate, butyrate, isovalerate and valerate as well as the net hepatic uptake of propionate, butyrate, valerate and caproate increased after feeding at 0700 h. The hepatic extraction of butyrate showed a relatively large depression with grass feeding with nadir at 1200 to 1330 h. The increased net portal absorption and the decreased hepatic extraction resulted in an approximately six-fold increase in the arterial blood concentration of butyrate. The gut entry rate of urea accounted for 70 6 10% of the net hepatic production of urea. Saliva contributed to 14% of the total amount of urea recycled to the gut. Urea recycling to the gut was equivalent to 58% of the dietary nitrogen intake. Despite the severe undersupply of rumen degradable protein, the portaldrained viscera did not extract more than 4.3% of the urea supplied with arterial blood. This value is in line with the literature values for cows fed diets only moderately deficient in rumen degradable protein and indicates that cows maximise urea transfer across gut epithelia even when the diet is moderately deficient in rumen degradable protein.

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Splanchnic and Mammary Nitrogen Metabolism by Dairy Cows Fed Steam-Rolled or Steam-Flaked Corn

Cited by 19 publications

References 37 publications

The route of absorbed nitrogen into milk protein

The route of absorbed nitrogen into milk protein

RUMINANT NUTRITION SYMPOSIUM: Role of fermentation acid absorption in the regulation of ruminal pH12

Urea and short-chain fatty acids metabolism in Holstein cows fed a low-nitrogen grass-based diet

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