The flow of digesta, dry matter and starch to the duodenum in sheep given rations containing straw of varying particle size.

I. Using shccp fitted with re-entrant cannulas in the proximal duodenum, and which were given a ration containing long straw, a series of three experiments was conducted in which the flow of digcsta to the duodenum was measured and sampled continuously for 3 d. Therc appeared to be no consistent effect of this procedure on total flow of digesta to the duodenum from day to day, indicating that under our conditions a 24 h pattern of flow can bc taken as representative of digesta entering the duodenum. 2. In a further series of four experiments, each lasting 3 d, rations identical in composition to that given in the first series of experiments, but differing in the physical form of the roughage component (chopped or ground), were given to the sheep. There was no consistent effect of altering the particle size of the roughage component of the diet on total daily flow of digesta, or in the dry-matter content of the digesta entering the duodenum. 3. Significantly (P < 0-01) more starch entered the duodenum per day when the ration included long or chopped straw than when it contained ground straw; all rations contained ground maize. 4. A peak in the flow of digesta, dry matter and starch to the duodenurn occurrcd between 4 and 12 h after feeding the shcep. T h e usual procedure adopted for obtaining information on flow-rate and representative samples of digesta has involved the use of animals prepared with re-entrant cannulas in the digestive tract and the total collection and return of all digesta flowing from the exit cannula. Goodall & Kay (1965) and Klooster, Rogers & Sharma (1969) measured the flow of digesta at the terminal ileum and distal duodenum of sheep respectively for periods of 72 and 120 h and found an increase in flow-rate from day to day. MacRae & Armstrong (1969) reported that continuous collection of digesta from sheep for periods of 24 h tended to suppress flow-rates possibly owing to disturbance of the animal. Attempts to assess any deviation from the average daily flow using indigestible markers have been made but criticism has arisen because of large variations in the concentration of the marker in the digesta and inconsistent marker recoveries. Since confidence in the accuracy of flow-rate measurements is necessary for any meaningful conclusions to be drawn from this type of experiment, it was decided to conduct on two …