The effects of feeding procedure on closure of the oesophageal groove in young sheep.

I . Barium sulphate suspensions were given to young sheep by mouth or by injection via an oesophageal catheter. Closure of the oesophageal groove was assessed by observing radiographically whether the suspension passed to the ruminoreticulum or to the abomasum. 2. Complete closure of the groove took place in lambs that were trained to drink small meals from a trough after being weaned from their dams, a finding similar to that for lambs weaned on to a teat-bottle. 3. When barium was injected into the oesophagus of lambs that were excited by being offered their bottle or trough beyond their reach, the barium passed direct to the abomasum if the normal feeding routine was closely imitated. When the lambs were able to discriminate between this teasing procedure and the normal routine, the barium frequently passed to the ruminoreticulum. If the lambs were not teased the barium passed invariably to the ruminoreticulum. 4. It is concluded that the reflex closure of the groove can be conditioned by the feeding procedure adopted at weaning so that it no longer depends on the stimuli associated with sucking and swallowing.