Inflation of a balloon in the rumen of forage-fed ruminant animals depresses intake. This might be due to the unpleasant over-stimulation of stretch receptors or to mimicking the pleasant after-effects of eating. If the former then cows would be expected to avoid stimuli which they had learned to associate with distension, while if the latter, they should be attracted to such stimuli. The experiment reported here paired small meals of flavoured concentrates with inflation of a balloon in the rumen of dry cows on several occasions and examined their subsequent preferences for the flavour of concentrates.
12 individually-tethered adult Holstein cows, neither pregnant nor lactating, were fed freshly-chopped sugar cane ad libitum with 4 kg/day soya bean meal sprinkled over it. At 1200 h the basal food was removed and 30 min later 6 cows had a balloon inserted into the rumen via a cannula which was filled with 12 litres of water and remained in place for 120 min.