EFFECT OF BODY-WEIGHT AND FEED COMPOSITION ON THE CONTRIBUTION OF HINDGUT TO DIGESTION OF ENERGY AND NUTRIENTS IN PIGS

The contribution of hindgut to digestion of energy and nutrients was measured at three body weights (BW) or stages of growth (stage 1: 45 kg; stage 2: 100 kg and stage 3: 150 kg) as the difference between fecal digestibility values measured at the three stages and ileal digestibility values estimated with 45 kg BW ileo-rectal anastomized (IRA) pigs. Six diets were tested. Composition of diets allowed calculation (by the difference method) of ileal and hindgut digestion of com starch, sucrose, rapeseed oil and a mixture of fibrous ingredients (so-called ''fibre''). Fecal digestibility of energy and nutrients was improved when BW was increased with higher values in intact pigs at the three stages (except for ether extract) than in IRA pigs. As a consequence, the contribution of hindgut to energy supply amounted to 15, 17 and 18% at stages 1, 2 and 3, respectively. This contribution varied with diet characteristics and ranged from about 11% in high-starch or high-sugars diets to 30% in the high-fibre diet. A major fraction of dietary crude protein (90%) and ether extract (100%) was digested before the end of the ileum while cell-wall fractions were predominantly degraded in the hindgut (70% for NDF). Hindgut digestibility of energy and NDF entering the hindgut averaged 48% and increased (P < 0.01) from stage 1 to stage 3. Accordingly, almost 100% of energy of com starch or sucrose were digested before the end of the ileum. A small proportion of rapeseed oil energy (about 10%) was apparently degraded in the hindgut. A negligible fraction of energy of ''fibre'' (5%) was digested before the end of the ileum. Results demonstrate that methane production in pigs is not a reliable predictor of the fermentation rate in the digestive tract.