Contribution of the hindgut to digestion of diets in growing pigs and adult sows: effect of diet composition

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Three trials were conducted to determine the digestibility of energy and nutrients of fourteen mixed diets which varied widely in ingredient and chemical composition. In the first two experiments, fecal digestibility was measured with 43 kg BW pigs fed close to the ad. libitum level and sows fed at maintenance energy level, respectively. In the third experiment, digestibility was measured at the ileal level with ileo-rectal anastomized (IRA) pigs (42 kg BW ). Fecal digestibility of all nutrients was higher in sows than in growing pigs. Except for ether extract (EE), ileal digestibility coefficients were lower than the fecal values. For energy, mean digestibility coefficients were 85, 76 and 63% in sows, growing pigs and IRA pigs, respectively. The corresponding values were 85, 75 and 71% for crude protein (CP). Therefore, hindgut contributed to 16 and 25% of total DE, in growing pigs and sows, respectively. The proportion varied with the chemical characteristics of the diets. Most of the digestible cellulose (90 to 100%) was degraded in the hindgut while hemicellulose was partly (40 to 50%) degraded before the end of the ileum. Comparison of ileal and fecal digestibility of EE indicates a net appearance of fat at the hindgut level, especially in growing pigs. Ileal digestibility of CP, EE and energy was reduced when fibre content was increased. Digestibility coefficients of nutrients entering the hindgut of growing pigs were 35, 39 and 15% for energy, NDF and CP, respectively. For sows, the corresponding values were higher: 59, 64 and 50%. Equations for predicting the ileal digestibility coefficients of energy and nutrients, the amount of energy which is digested in the hindgut and the ileal nutritional value from fecal value are presented.