Effects of pectin supplementation on the digestion of different structural carbohydrate fractions and on bacterial nitrogen turnover in the hindgut of adult sows

Abstract

In two consecutive periods, pectin was supplied at levels of 0 and 334 g dry matter day −1 together with a semi-synthetic basal diet to 12 adult sows weighing 166 ± 17 kg. In addition to the pectin treatments, two different levels of thiamine, 0.66 and 2.57 mg day −1 were applied. Aliquot samples of the completely collected feces were analyzed for proximate principles, detergent fiber fractions and nitrogen fractions. In the urine, nitrogen and allantoin N were determined, while the urea content was measured in blood plasma. The pectin fermentation rate was determined by three different methods so as to account for 94–96% of pectin intake. A slight, non-significant decrease in the digestibilities of all analyzed fiber components of the basal diet occurred with pectin. The apparent digestibility of nitrogen was reduced by more than 20% at an almost constant true N digestibility. The increased fecal nitrogen excretion with pectin caused a reduction in protein retention to zero, and was composed of 82% bacterial nitrogen. The changes in the proteinaceous water-soluble fraction of fecal nitrogen indicated an increase in the excretion of endogenous proteins. Calculation of the content of metabolizable energy, by a standard formula estimated from the digestibilities of the proximate contents, was demonstrated to underestimate the true energy content of pectin severely, as evaluated from energy balance trials (5.9 MJ ME kg −1 instead of 10.5 MJ ME kg −1). This occurred because the additional energy excretion in the form of bacterial protein was incorrectly considered as a genuine metabolic energy loss. The efficiency of bacterial protein synthesis using pectin, as estimated by fecal excretion, was 7.4 g per 100 g of pectin fermented. The thiamine treatments did not affect any of the criteria.