RUMEN MOTILITY RESPONSES TO ADRENALINE AND NORADRENALINE AND ORGAN WEIGHTS OF WARM- AND COLD-ACCLIMATED SHEEP

The rumen motility responses to 2.5 h adrenaline (A) and noradrenaline (NA) intrajugular infusions at 0, 0.15, 0.30, 0.60 and 0.90 μg∙kg −1 ∙min −1 were studied in 10 shorn wethers which had been acclimated for 4–8 wk to either a warm (19–24 °C) or cold (8–13 °C) environment. Preinfusion rumen motility was not significantly influenced by acclimation temperature. Adrenaline infusions at the highest dose rates depressed motility in both warm-acclimated (WA) and cold-acclimated (CA) sheep and during the final 90 min of infusion the inhibition appeared greater in the WA sheep. Noradrenaline resulted in a depression of two contractions per hour in rumen motility of WA sheep but an increase of five contractions per hour in CA sheep. The results suggest that the CA sheep were resistent to the inhibitory effects of catecholamines on rumen motility. Six WA and six CA sheep were sacrificed and internal organs and gastrointestinal content weights were compared. Cold acclimation was associated with a significant increase in the weight of the liver, kidneys, reticulorumen and small intestine and of the content of the colon. Because CA sheep were fed 800 g more feed per day than WA sheep the effect of cold acclimation on organ and organ content weights cannot be separated from the effect that the increase in intake alone might have had. Key words: Adrenaline, noradrenaline, rumen motility, sheep, cold acclimation, organ weight