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Characteristics of Threonine, Valine and Methionine Absorption in the Jejunum and Ileum of Sheep

Virginia Polytechnic Institute and State University², Blacksburg 24061

Abstract

Two-year-old wethers were equipped with double re-entrant cannulae located in either the jejunum or the ileum. These cannulae were used to isolate a 1 m segment of the intestinal section for perfusion purposes in order to study the absorption characteristics of threonine, valine and methionine. Perfusions were conducted for 1 hr, beginning 4 hr after feeding. The absorption of amino acids was measured as the total amount removed from the perfusion solution during the 1-hr period.

Removal of amino acids from the perfusion solution was constant over the 1-hr period, but absorption did vary with time after feeding. Wethers with cannulae located in the ileum absorbed more (P<.05) of each amino acid than those with jejunal cannulae.

Regression equations were determined to predict the absorption of an individual amino acid. These equations accounted for 61.2, 71.4 and 70.8% of the variability for threonine, valine and methionine absorption characteristics, respectively. Three dimensional designs were developed from these equations and indicated that absorption of an individual amino acid was subjected to inhibition and/or stimulation by the presence of the other two amino acids. Valine and methionine were inhibitory toward the absorption by threonine, but the inhibition of threonine absorption by methionine in the jejunal section was overridden by increasing the concentration of valine.

The amount of valine absorbed was decreased by increasing the methionine concentration and by low concentrations of threonine, but higher concentrations of threonine had a stimulatory effect when the valine concentration was high and the methionine concentration was low. Valine exerted inhibitory effects on methionine absorption when threonine was present in low concentrations and threonine was also inhibitory if valine was present at low concentrations. When the concentration of threonine was increased to 7.4 mM, each increase in valine concentration resulted in more methionine being absorbed.

¹ Present address: Southwestern Livestock and Forage Research Station, El Reno, OK 73036.

² Department of Animal Science.

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