Lipid absorption and hepatic metabolism in ruminants
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چکیده
Les matikres grasses sont ajoutCes aux rations des ruminants pour ameliorer l’efficacite d’utilisation de 1’Cnergie B des fins de production. L’intestin gr&le des ruminants posskde une forte capacitC d’absorption des acides gras alimentaires saturCs par l’action des hydrogenases bactkriennes du rumen. La synthkse et la secretion des lipoproteines riches en triacylglycerols (chylomicrons, VLDL) par l’intestin grCle varie avec le degri d’insaturation des chaines grasses alimentaires. Le lent processus d’absorption des acides gras chez le veau prkruminant favorise la sCcrCtion des lipoprotkines riches en triacylglycerols par la voie de la veine porte. La fraction protkique de ces particules lipoprot6iques est dominCe, chez le bovin, par l’apoprotkine B48, forme tronquee de l’apo B resultant de la modification unique post-transcriptionnelle de I’ARN messager de l’apo B. Le metabolisme hepatique des lipides des ruminants prCsente des particularites favorisant la formation de foie gras et le dCveloppement d’une cCtoacidose nuisible B la sante et aux capacites de reproduction des animaux. Le foie possede une forte capacite d’estkrification et de stockage des acides gras exogknes sous forme de triacylglycerols ou d’oxydation de ces acides gras sous forme de corps cktoniques. Les faibles capacitCs de synthkse de l’apo BlOO et de mobilisation des triacylglycCrols stock& dans le cytoplasme limitent fortement la secrktion hkpatique des triacylglycerols sous forme de VLDL. Chez les femelles en debut de lactation, le diveloppement de l’infiltration lipidique du foie n’est pas rCduit par la supplementation lipidique des rations mais plut8t par l’apport alimentaire d’acides amines limitants (mkthionine, lysine). La modulation de I’expression du gkne hkpatique de l’apo B au cours du cycle gestation-lactation explique, en partie, le developpement de l’infiltration graisseuse observee en debut de lactation.
منابع مشابه
Lipid absorption and transport in ruminants.
The objective of this paper is to review new insights on the biological mechanisms of absorption and transport of lipid in ruminants, especially the modern concepts and analytical methods used in studies on structural properties and intravascular and tissue metabolism of lipoproteins and their factors of variation. The intestinal absorption of lipids (including long-chain fatty acids) is detail...
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