Pascal Leterme

LeAnn Johnston

Summary

The objective of this study was to use a laboratory technique that mimics what happens in the intestines of pigs to evaluate the fermentation characteristics of some nonconventional feed ingredients with varying fermentable fibre and their possible influence on intestinal environment and nitrogen excretion. We concluded that fibre fermentation characteristics in the pig gastrointestinal tract are extremely variable from one ingredient to another. Of the feed ingredients evaluated, peas and pea fibres had higher fermentability and bacterial protein synthesis capacity.

Introduction

The pork industry is looking for alternative feed ingredients that have functional properties to improve gut health and a positive impact on the environment. The intestinal fermentation of dietary fibre results in the formation of short-chain fatty acids (SCFA), which in turn stimulate the growth of beneficial bacteria such as lactobacilli and bifidobacteria and limits the activity of proteolytic microbes in the pig intestine. This might positively affect gut health. In addition, depending on the fermentation kinetics, the nitrogen excretion pathway may be shifted from urine to faeces, reducing ammonia emission from swine facilities. However, there is limited information available on these properties of feed ingredients.

Materials and Methods

Eight ingredients (wheat bran (WB), solka floc® (SF, wood cellulose), peas, pea hulls fibre (PHF), pea inner fibre (PIF), sugar beet pulp (SBP), flaxseed meal (FSM) and corn distiller dried grains with solubles (DDGS)) with diverse carbohydrate composition were selected for the study (Table 1).

The ingredients underwent an in-vitro pepsin-pancreatin hydrolysis. The hydrolysed ingredients were then fermented in-vitro with minerals and buffer, using pig faeces as the inoculum (Bindelle et al., 2009). The gas production kinetics during fermentation were modeled (Figure 1 and Table 2) according to France et al. (1993). Bacterial nitrogen incorporation (BNI) in fermented substrates was determined using 15N as a marker (Bindelle et al., 2009) (Table 3). Fermented residues were analysed for SCFA content (Figure 2). There were two replications of eight ingredients and six blanks in each of four batches. The influence of the ingredient on the fermentation kinetics, SCFA and BNI was compared in the statistical analyses.

Figure 1. Gas production kinetics of different ingredients studied in vitro (in test tube)
*Representative of kinetic parameters of gas production curve (Gf, L, T/2 and ì) modeled according to France et al (1993)

Figure 2. Short chain fatty acid production of different ingredients studied in vitro (in test tube)

Results

The source of fibre affected the in-vitro dry matter degradability (IVDMD), the fermentation kinetics and the gas production profile (P<0.05). The highest (P<0.001) IVDMD values were observed for peas (0.80) and FSM (0.70), whereas SF was essentially undegraded (0.06), as would be expected.

The fractional rate of degradation appeared to be lower (P<0.001) for WB and DDGS (0.07 and 0.05 per hour, respectively) and highest for SBP (0.20 per hour). Peas started to ferment rapidly (lag time 1.3 hours). Half gas production (T/2) was achieved sooner for PIF (8.4 hours) and was the longest for DDGS (19.8 hours).

Total gas production was the highest for PH, followed by SF, PIF and peas (276, 266, 264 and 253ml/g DM incubated, respectively) and lower for FSM and WB (130 and 124ml/g DM incubated, respectively). There was no difference (P>0.05) in SCFA production after the fermentation of SF, P, PH, PIF and SBP (ranging from 3.8 to 4.5mMol/g DM incubated) while WB and FSM yielded lower (P<0.05) SCFA.

The bacterial nitrogen incorporation (BNI), both at T/2 and after 48 hours of fermentation was the highest (P<0.001) for PIF (18.5 and 15.6mg/g DM incubated, respectively) and the lowest for DDGS and WB.

Implications

Peas and pea fibres had higher rates of fermentability, produced more SCFA and had high bacterial protein synthesis capacity. They thus have the potential to be included in pig diets as a source of fermentable fibre to modulate the gut environment, extend health-promoting properties and reduce ammonia excretion.

Conclusions

Fibre fermentation characteristics in the pig gastrointestinal tract are extremely variable between ingredients. Pea and pea fibres have high fermentability and bacterial protein synthesis capacity and thus have potential to be a source of fermentable fibre when included in swine diets.

Acknowledgements

Project funding was provided by the National Pork Board. Strategic Programme funding from Sask Pork, Alberta Pork, the Manitoba Pork Council and the Sask. Ag. Dev. Fund is gratefully acknowledged.

Further Reading

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You can view other papers from the Prairie Swine Research Centre Annual Report 2009 by clicking here.