Influence of source and concentrations of dietary fiber on in vivo nitrogen excretion pathways in pigs as reflected by in vitro fermentation and nitrogen incorporation by fecal bacteria123

Abstract

The inclusion of dietary fiber (DF) in diets has been suggested as a way to reduce NH(3) emission in pig barns because it contributes to a shift in N excretion from urine to feces owing to enhanced bacterial growth in the intestines. This study compared an in vitro method to measure bacterial protein synthesis during fermentation with an in vivo N excretion shift induced by diets differing in DF concentrations and solubility. The first experiment measured the effect of graded concentrations of sugar beet pulp (SBP; 0, 10, 20, and 30%) in corn- and soybean meal-based diets on in vivo N excretion partitioning between the urine and feces. A second experiment investigated the replacement of SBP, rich in soluble DF, with oat hulls (OH), rich in insoluble DF (20:0, 10.5:10.5, and 0:22%, respectively). In parallel, the fermentation characteristics of the dietary carbohydrates not digested in the small intestine were evaluated in an in vitro gas test, based on their incubation with colonic microbiota, using a mineral buffer solution enriched with (15)N. The N originating from the buffer solution incorporated into the bacterial proteins (BNI) was measured when half the final gas volume was produced (8.5 to 14.5 h of fermentation) and after 72 h of fermentation. Short-chain fatty acids were determined in the liquid phase. In the first experiment, the inclusion of SBP linearly decreased urinary N excretion from 0.285 to 0.215 g of N excreted in the urine per gram of N ingested and decreased the urinary-N:fecal-N excretion ratio from 2.171 to 1.177 (P < 0.01). In the second experiment, substituting SBP with OH linearly increased the urinary-N:fecal-N excretion ratio (P = 0.009). Unlike short-chain fatty acid production, BNI was greater at half-time to asymptotic gas production than at 72 h of fermentation. Sugar beet pulp enhanced BNI linearly (P < 0.001), 2.01, 2.06, and 2.35 mg g(-1) of diet with 10, 20, and 30% SBP, respectively, as compared with 1.51 mg for the control diet. The substitution of SBP with OH decreased BNI (P < 0.01). With the exception of final gas production, all in vitro kinetic characteristics and BNI were correlated with in vivo N excretion parameters, and regression equations for the prediction of N excretion pathways from in vitro data were identified. Even if the presence of resistant starch in the diet might alter the composition of the fibrous residue that is fermented, the in vitro method is a possible useful tool for the formulation of diets, reducing the effects of pig production on the environment.

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

“…The results of that study are published elsewhere (Jha et al, 2011b). Previous studies (Canh et al, 1997;Zervas and Zijlstra, 2002;Bindelle et al, 2009) have shown that the inclusion of isolated DF in pig diet shifts N from urine to faeces, which leads to reduced N excretion in the environment. This study assumed that it is also true when DFs are in their natural matrix as well.…”

“…However, inclusion of fermentable DF (Awati et al, 2006) and reduction of protein (Htoo et al, 2007) in weanling diets reduces protein fermentation along the gastrointestinal tract. Moreover, the presence of fermentable DF in the diet can also reduce the emission of gaseous nitrogenous compounds by shifting N excretion from urine to faeces (Canh et al, 1997;Zervas and Zijlstra, 2002;Bindelle et al, 2009), thus reducing the NH 3 emission from piggery (Mroz et al, 2000;Nahm, 2003). O'Connell et al (2006) found increased urinary N and decreased faecal N when pigs were fed with barley-based fibre-rich diet, with significant interaction between protein levels, fibre source and enzyme supplementation on NH 3 emission.…”

Adaptation of faecal microbiota in sows after diet changes and consequences for in vitro fermentation capacity

“…This was an unexpected finding as the majority of in vitro fermentation studies allow pigs to adapt to the diets for 7 to 14 days (Bauer et al, 2004;Anguita et al, 2006;Awati et al, 2006;Bindelle et al, 2009;Martín-Peláez et al, 2009). Thus, animals in the HL-treatment might have also not been fully adapted on day 1 of the actual experiment, after consuming silage for 3 weeks in the pre-experimental period.…”

“…In this type of in vitro fermentation studies, faecal donor animals are fed a well-defined diet in order to obtain a standardised microbial community. For many in vitro fermentation studies involving pigs, a dietary adaptation time of 7 to 14 days is routinely used when a new diet is implemented (Bauer et al, 2004;Anguita et al, 2006;Bindelle et al, 2009;Martín-Peláez et al, 2009). Interestingly, there is a general lack of information on the time required for the large intestinal microbiota to adapt to the diet fed to the pigs for these in vitro fermentation studies.…”

Forage plants as an alternative feed resource for sustainable pig production in the tropics: a review

“…However, low faecal-N-digestibility values not always mean low protein value. High fermentable fibre content of some forage species decreases the faecal apparent digestibility of N through a shift in N excretion from urinary-N (urea) to faecal-N (bacterial protein) without systematically altering the protein value of the diet (Bindelle et al, 2009). Therefore, the only actual protein value should mention ileal digestibility or possibly the standardised ileal digestible (SID) AAs of the forage ingredients, as these values might strongly differ from raw AA composition (Tables 2 and 4).…”