Dietary effects on the composition of pig slurry and on the plant utilization of pig slurry nitrogen

Abstract

SU MMARYThe composition of animal manure is influenced by the diet fed. Efforts are made to decrease nitrogen emission from pig production by optimizing diet composition. This normally results in a lower proportion of N excreted in urine relative to faeces, and may also influence the turnover and utilization of manure N after field application. The effects of pig feed composition on the excretion of urinary and faecal N, on the dynamics of manure N in soil and on the potential utilization of manure N in the field was studied. Growing pigs and sows were fed 12 different diets with variable contents of fibre and protein (with or without synthetic amino acids). Slurries consisting of a mixture of faeces and urine were stored according to common agricultural practice in Northern Europe. The plant availability of N in the resultant slurries originating from animals fed known diets was tested in small field plots with barley, under conditions with minimal N losses. Separate plots were fertilized with increasing amounts of mineral N. Nitrogen uptake in barley was determined and the utilization of slurry N was compared with that of mineral fertilizer N. The net release of mineral N and C from the slurries in soil was also measured in a parallel incubation study.The mineral fertilizer equivalent of pig slurry N was 72-100 % and significantly influenced by feed fibre composition, but not significantly influenced by the protein content. There was a significant positive correlation between enzyme-digestible organic matter in the pig diet (measurement used for feed evaluation) and the plant availability of pig slurry N (R 2 =0 . 90). The ammonium content of stored pig slurry could not be used for prediction of the N availability since the net mineralization of pig slurry N was variable, but there was a significant negative correlation between the pig slurry C/N ratio and the plant availability of slurry N (R 2 =0 . 86).Increased dietary concentration of fermentable structural carbohydrates (e.g. by including sugar beet pulp in the diet) reduces the excretion of N in urine without affecting the availability of slurry total N, whereas an increased concentration of dietary fibre with a low fermentability (straw) results in less urinary N, but also a lower plant availability of slurry N.

Impact of nutrition on nitrogen, phosphorus, Cu and Zn in pig manure, and on emissions of ammonia and odours

“…In a study of Portejoie et al (2004), the ratio ammoniacal N:total N in fresh manure decreased from 0.79 with the 20% CP diet to 0.63 with the 12% CP diet. However, in the studies of Gerdmann et al (1999) and Sørensen and Fernandez (2003) the plant availability of slurry N was not clearly affected by the dietary protein content.…”

“…The reduction in dietary protein content results in a lower proportion of N excreted in urine relative to faeces, which might affect the utilisation of manure N after field application (Sørensen and Fernandez, 2003). In a study of Portejoie et al (2004), the ratio ammoniacal N:total N in fresh manure decreased from 0.79 with the 20% CP diet to 0.63 with the 12% CP diet.…”

“…With more fermentable non-starch polysaccharides (NSP) in the diet, some of the N excretion is shifted from urine to bacterial protein in faeces (Canh et al, 1998;Kreuzer et al, 1998, Sørensen andFernandez, 2003), while total N excretion is not affected. Moreover, slurry pH is decreased with the use of fermentable NSP due to volatile fatty acid (VFA) formation in the hindgut of the pig and in the slurry.…”

“…The utilisation of manure N after field application may also be affected by the level of NSP in the diet, because a greater proportion of N is excreted in faeces in more complex organic forms. Availability of slurry N was reduced after the inclusion of dietary fibre with low fermentability (Sørensen and Fernandez, 2003), whereas it was not affected when the dietary content of fermentable structural carbohydrates increased (Gerdmann et al, 1998;Sørensen and Fernandez, 2003), although in all cases the proportion of N excreted in urine decreased. Combined with the proportion of urinary N, the fibre content of faeces gives a good prediction of the plant availability of slurry N (Sørensen and Fernandez, 2003).…”

Nitrogen balance, ammonia and odor emissions ingrowing pigs fed reduced protein diets

“…Le et al (22) mostraron que alimentar a los cerdos con dietas con 18 y 12 % PC disminuía el pH de las excretas de 7.83 a 7.10. En contraste, otros autores (23) no pudieron detectar diferencias en el pH del purín cuando alimentaron a cerdos en crecimiento con dietas cuyo contenido de PC fue del 19 o del 22 %; esta falta de efecto, pudiera estar asociada al hecho de que el rango en los niveles de PC que usaron fue más elevado y estrecho que en otros estudios, incluyendo éste. Es claro que la capacidad buffer y el pH de los purines son determinantes de las emisiones de NH 3 (24,25) .…”