Reduction of gaseous nitrogen loss from pig manure using feeds rich in easily-fermentable non-starch polysaccharides

Three experiments were carried out to determine the level of reduction in gaseous nitrogen loss from pig manure stored over 8 weeks by feeding easily-fermentable non-starch polysaccharides of different origin. In Experiment 1 different feeds were used to increase the content of fermentable non-starch polysaccharides (fNSP) from 160 to 190 g kg−1 dry matter (DM), on average. Feeds high in pectin (citrus pulp) and hemicellulose (beet pulp) were the most effective treatments to reduce gaseous nitrogen loss. The effect of cellulose as the fNSP source (ryebran as well as a mixture of bran and pulps, respectively) was numerically lower. Substituting cassava with maize also reduced gaseous nitrogen losses to a certain degree, presumably as a result of the different properties of the starch contained. In Experiment 2 graded levels of fNSP (150 to 220 g kg−1 DM) from beet pulp almost linearly decreased gaseous loss of nitrogen during storage. In Experiment 3 an increase of fNSP from 150 to 200 g kg−1 DM by the use of citrus pulp was almost as efficient in terms of reduction of gaseous nitrogen loss as a dietary protein reduction from 210 to 180 g kg−1 DM. The effects of fNSP supply were further enhanced by dietary protein reduction leading to a maximum reduction in gaseous nitrogen loss of 18% of initial manure nitrogen and of 38% of the amount daily emitted per pig when manure was stored for 8 weeks. All fNSP-enriched diets reduced the ratio of urinary to totally excreted N on average by 0.07% to 0.18% units with each g of additional fNSP kg−1 dietary DM. The corresponding relative decrease in initial ammonia N concentration in manure and in gaseous nitrogen loss was at a similar level. In the case of protein reduction, the suppression of gaseous nitrogen loss mainly resulted from the associated lower daily nitrogen excretion of the pigs and only to a lesser degree from the alteration of manure composition.