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Effects of mesenteric vein L-alanine infusion on liver metabolism in beef heifers fed on diets differing in forage: concentrate ratio*

Published online by Cambridge University Press:  09 March 2007

C. K. Reynolds  and
H. F. Tyrrell
C. K. Reynolds
Affiliation:
USDA, Agricultural Research Service, Livestock and Poultry Sciences Institute, Ruminant Nutrition Laboratory, Beltsville, MD 20705, USA
H. F. Tyrrell
Affiliation:
USDA, Agricultural Research Service, Livestock and Poultry Sciences Institute, Ruminant Nutrition Laboratory, Beltsville, MD 20705, USA
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Abstract

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Effects of 24 h mesenteric vein infusion of L-alanine (75 mmol/h) and diet forage: concentrate ratio on net nutrient metabolism by portal-drained viscera (PDV) and liver were measured in four Hereford-Angus heifers. Heifers were fed on diets containing approximately 750 g lucerne (Medicago sativa) or 750 g concentrate/kg every 2 h at similar metabolizable energy intakes in a balanced single reversal design with 6 weeks for diet adaptation. Measurements of blood flow and net metabolism of nutrients were obtained at 30 min intervals starting immediately before (four measurements) and after (five measurements) beginning, immediately before ending (four measurements) and 1.5 h after ending (three measurements) alanine infusion. Only values obtained immediately before beginning and ending alanine infusion were compared statistically. Net total splanchnic (PDV plus liver) release of glucose was greater when heifers were fed on the 750 g concentrate/kg ν. 750 g lucerne/kg diet due to greater net PDV absorption. Net PDV absorption of ammonia-nitrogen, β-hydroxybutyrate (BOHB) and lactate, and net liver and total splanchnic release of urea-N (UN) were greater when heifers were fed on the 750 g lucerne/kg ν. 750 g concentrate/kg diet. Infusion of alanine increased net liver removal of alanine and α-amino-N, net liver release of UN and net total splanchnic release of alanine, UN and lactate. Infusion of alanine decreased net liver release of BOHB and removal of lactate. Mesenteric vein infusion of alanine altered the net availability of precursors for liver glucose synthesis, but did not affect net glucose release by liver in these beef heifers

Keywords

CattleLiverL-Alanine
Type
Nitrogen Metabolism
Information
British Journal of Nutrition , Volume 66 , Issue 3 , November 1991 , pp. 437 - 450
Copyright
Copyright © The Nutrition Society 1991

References

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