Influence of intravascular infusion of short-chain fatty acids on forestomach motility of sheep not receiving food

Abstract

Intrahepatic portal and intrajugular infusions of short-chain fatty acids (SCFA) (as sodium acetate, propionate and butyrate) singly and mixed were given to unfed adult sheep. Reticulum motility was significantly inhibited by 3-h infusions of a mixture of the three SCFA at 4 mmol min −1 and by propionate alone at 1.2 and 2.0 mmol min −1 via jugular or hepatic portal route. Rumination was also inhibited by those infusions and additionally by the mixture at 2 mmol min −1 and by acetate at 2.2 mmol min −1, the latter via the portal route. α-1 and α-2 adrenoreceptor antagonists did not reverse the effect of propionate when administered during a period of inhibition. Rapid i.v. adrenaline injection during a period of inhibition induced a single biphasic contraction of the reticulum. Vagal efferent stimulation under general anaesthesia during intraportal propionate infusion always caused reticulum contraction. Propionate reduced motility by acting at an unknown site in the reflex control system, not by paralysis of the muscle or over activation of the sympathetic system. Normal plasma concentrations would not of themselves cause severe inhibition of motility, but could contribute to this multifactorial control system. Rumination was more sensitive than resting motility cycles to the inhibitory effect.