Digestion of starch and crude fibre in segments of the digestive tract of sheep fed different types and amounts of starch

Abstract

The experiment was carried out on 6 Polish Merino sheep of average 60 kg BW with reentrant cannulas into the proximal duodenum and terminal ileum. The animals were fed a basic diet consisting of meadow hay and rapeseed oilmeal with the addition of 46 or 23% of potato, maize, or wheat starch. The amount of digesta entering the duodenum and large intestine was measured, sampled and the amount of starch and crude fibre determined. All types of starch were digested predominantly in the rumen. Of every 100 g of starch ingested with the high- (or low-, in parenthesis) starch diet, its output from the rumen was: 10.4, 3.3 and 9.6 (15.2, 8.2 and 11.3) g; from the small intestine, 5.3, 0.7, and 2.7 (5.0, 1.9, and 3.2) g; excreted with faeces 1.1, 0.3 and 0.3 (0.4, 0.2 and 0.3) g, of potato, maize or wheat starch, respectively. Maize and wheat starch were more susceptible to digestion in the rumen and small intestine than potato starch. Only a small amount of starch reached the large intestine where it was nearly totally digested and only its traces were excreted with faeces. A higher ratio of starch to crude fibre in the diet depressed crude fibre digestion in the rumen and its total digestibility in the digetsive tract.