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The effect of intake on protein metabolism across splanchnic tissues in growing beef steers

Lapierre, H., Bernier, J. F., Dubreuil, P., Reynolds, C. K., Farmer, C., Ouellet, D. R. and Lobley, G. E. (1999) The effect of intake on protein metabolism across splanchnic tissues in growing beef steers. British Journal of Nutrition, 81 (6). pp. 457-466. ISSN 0007-1145

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To link to this item DOI: 10.1017/S0007114599000811


The contribution of the total splanchnic tissue (TSP; portal-drained viscera (PDV) plus liver) to whole-body protein metabolism was estimated in relation to intake (0×6, 1×0 and 1×6 maintenance requirements), in six multicatheterized growing beef steers used in a double 3x3 Latin square design. At the end of each 21 d experimental period, [1-13C]leucine was infused into a jugular vein (1×05 mmol/h for 5 h, preceded by a priming dose of 1×05 mmol). Arterial, portal and hepatic blood samples were collected hourly during the infusion. The increment in TSP leucine irreversible loss rate (ILR) observed with increasing intake reached significance (P,0×10) only for PDV, while whole-body ILR increased markedly (P,0×001) with intake. The relative contribution of TSP to whole-body leucine ILR averaged 44% (25% from PDV and 19% from the liver). Although these proportions were not affected by intake, on an incremental basis more than 70% of the increase of whole-body leucine ILR between the 0×6 and 1×0 X maintenance originated from the changes in TSP ILR, while the corresponding value was below 13% between 1×0 and 1×6 ´ maintenance. Total whole-body leucine oxidation and fractional oxidation increased (P,0×05) with intake. Protein retention increased with intake (P,0×01), as a result of a greater increase in protein synthesis compared with protein degradation. Protein breakdown had a major impact on protein turnover as 65% of the protein synthesized was degraded when intake varied from 1×0 to 1×6 x maintenance. Net leucine portal absorption increased (P,0×001) with intake and represented 1, 16 and 23% of whole body leucine ILR, for 0×6, 1×0 and 1×6 ´ maintenance, respectively. Although leucine oxidation was not a major component of whole body ILR (9×3–19×9 %), it represented 69% of the net available leucine (portal absorption) even at 1×6 ´ maintenance. The lower relative contribution of the TSP to whole-body leucine ILR at higher intake indicates the proportional increase in the metabolic activity of peripheral tissues as the animals moved into positive protein balance.

Item Type:Article
Divisions:Life Sciences > School of Agriculture, Policy and Development > Department of Animal Sciences > Animal, Dairy and Food Chain Sciences (ADFCS)- DO NOT USE
ID Code:90819
Publisher:Cambridge University Press

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