Cellulose fermentation capacity of the hindgut and nitrogen turnover in the hindgut of sows as evaluated by oral and intracecal supply of purified cellulose

Abstract

Adult sows fed a constant amount of a basal diet received purified cellulose either orally at levels of 0 and 475 g/animal.d (Experiment 1) or intracecally at levels of 0, 285, 570 and 855 g/animal.d (Experiment 2). Each experiment consisted of subsequent periods of faeces and urine collection with the animals re-allocated to the treatments each time. With that, a total of 36 observations on each parameter was achieved. The faecal samples were analyzed for the contents of organic matter, cell wall carbohydrates and various nitrogen fractions such as bacterial N and undigested dietary N. Furthermore, N balance, urinary allantoin excretion and plasma urea concentrations were determined. In a preliminary study, the effects of freeze-drying and of shaking of the faecal samples as suspensions with water (in order to release bacteria from fibre) on content and composition of faecal nitrogen had turned out to be reproducible. Cellulose significantly enhanced faecal nitrogen loss whereas N retention was not affected due to the counteraction of urinary N loss. Plasma urea concentration reflected the situation with urinary N. The proportion of undigested dietary N and of water-soluble protein in total faecal N was somewhat increased by cellulose at cost of the bacterial N proportion which accounted for about 72% of total N on average. Urinary allantoin did not respond to the higher bacterial activity in the hindgut in the presence of supplementary cellulose. Cellulose significantly decreased the apparent N digestibility by on average about 3 percentage units per 100 g of supplementary cellulose. True N digestibility was also reduced by cellulose but did not go below 95%. The supplementary cellulose was fermented in the hindgut at similar rates of on average about 60% regardless of the route of administration. The almost 100 g of native cellulose incorporated in the basal diets were lignified by about 20%, and that is why they were fermented at a rate of only about 30%. The rate of fermentation was only slightly decreasing with increasing amounts of supplementary cellulose, and a daily quantity of 564 g (11 g/W0.75) cellulose was fermented on average if the highest level of cellulose was provided. This was within a range exclusively reported for easily-fermentable carbohydrates but was achieved in the case of cellulose only at a consistently higher level of supply. The true efficiency of bacterial protein synthesis was 5.2 g bacterial protein/100 g supplementary cellulose on average. The apparent efficiency was 60% higher averaging 8.4 g bacterial protein/100 g further apparently fermented organic matter.

Feed ingredients differing in fermentable fibre and indigestible protein content affect fermentation metabolites and faecal nitrogen excretion in growing pigs

“…Overall, the differences in digestibility and fermentation activity can be explained by the differences in ingredient composition, especially the type and amount of DF and the level of iCP in the natural matrix of the ingredients. Lower ATTD of DM for the ingredients rich in insoluble fibre such as WB and DDGS is in agreement with several previous studies (Bach Knudsen and Hansen, 1991;Kreuzer et al, 1991;Hansen et al, 2006). This effect is ascribed to the higher insoluble DF content of these diets, which negatively affects the accessibility and action of the endogenous enzymes in the upper gut and microbial fermentation in the lower gut (Bach Knudsen, 2001), resulting in lower degradability.…”

“…This is ascribed to the fact that highly fermentable DF fractions, such as hemicellulose and pectin, stimulate bacterial growth in the hindgut. This in turn increases faecal N excretion in the form of bacterial biomass and thus reduces apparent N digestibility (Kreuzer et al, 1991;Hansen et al, 2006). However, this interaction might not only be due to the effect of soluble NSP on the digestive process, but also due to an increase in endogenous N excretion (de Lange et al, 1989;Huisman et al, 1992;Leterme et al, 2000).…”

Effects of insoluble dietary fibre differing in lignin on performance, gut microbiology, and digestibility in weanling piglets

“…Dietary fibre additions decreased digestibility of dry DM and crude CP, which is in accordance to numerous other studies (Kreuzer et al 1991;Zhao et al 1996;Hansen et al 2006;Zhao et al 2007). Indeed, the DM digestibility of the fibre sources used in the present study is known to be comparably low especially in case of the pine pollen due to high content of ADF and ADL Zhao et al 2007).…”

“…Corresponding to literature data Lindberg 2004b, 2006), the values of pH in ileal and colonic chyme were not affected by additions of insoluble fibre. This reflects the fact that insoluble fibre is hardly degraded by intestinal microbiota during intestinal passage especially when containing major amounts of lignin (Kreuzer et al 1991;Glitso et al 1998); whereas, reductions in pH are observed only at high intake of bacterially fermentable substrates (e.g. Roth et al 1992).…”

“…However, this does not fully explain the concomitant reduction of CP digestibility. Such an effect is typically characteristic for dietary additions of soluble fibre in terms of bacterially fermentable substrates promoting bacterial growth in the hindgut and hence raising faecal N excretion (Kreuzer et al 1991;Hansen et al 2006). But the fibre sources used in the present study were largely insoluble and non fermentable, especially in case of pine pollen.…”