Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Feed design for improved fermentation along the intestinal tract

An experiment was conducted to examine differences in in-vitro fermentability of 4 carbohydrate-rich feed ingredients, and two weaning piglet diets with and without these ingredients, using both the ileal contents and the faeces of un-weaned piglets as inocula. Cumulative gas production was measured in time, using faecal inocula mixed from 9 crossbred piglets (no creep feed or antibiotics) at 3 weeks of age. Inulin, lactulose, unmolassed sugar beet pulp, wheat starch and the two diets, were used as substrates and fermented in vitro for 72h. Gas production was measured as an indicator of fermentation kinetics.

End products including VFA, and ammonia, and organic matter loss, were also measured. To study microbiota changes, PCR/DGGE analyses were done in the initial inoculum and after fermentation. This was repeated one week later, using ileal contents from the same piglets as inoculum. There were significant differences between inocula in terms of overall fermentation characteristics and composition, and between substrates. There was also a significant interaction between inocula and substrates, suggesting local differences in microbial activity. For the two diets with and without addition of these fermentable ingredients, there were significant differences in terms of kinetics, but less so in terms of end products. It was concluded, that inocula from ileum and colon should be used, to obtain a more accurate assessment of potential feed ingredients that will stimulate fermentation in piglet GIT.

Unrelated to this in vitro work, an in vivo production trial was carried out in collaboration. In this experiment the effect of varying the proportions of dietary protein (CP) and carbohydrates (CHO) in weaner diets was examined in relation to feed intake, digestibility, growth performance and several gut parameters (e.g., bacteriology, fermentation end products, villus height/ crypt depth).

Directly after weaning, piglets from different litters were selected and equally distributed over four dietary treatments ; 1=lowCP & lowCHO; 2=lowCP & highCHO; 3=highCP & lowCHO; 4=highCP & highCHO. At day 7 post-weaning, two piglets per treatment were selected and sacrificed to collect chyme from the ileum and colon.

The chyme samples analyzed at Wageningen University (WU) for DM, VFA, NH3 and lactic acid. There was a significant difference between ileal and colonic chyme, with higher values for the VFA, NH3, and branched chain proportions (BCP) in the colonic chyme. Lactic acid and the molar proportions of acetic acids were significantly higher in the ileal chyme. The dietary treatments did not have a significant effect on end products.

However, in the case of colonic chyme, the piglets receiving diets with high CHO (Diets 2 & 4) tended to have higher acetic acid, butyric acid and total VFA concentrations, and lower concentrations of NH3 and BCP. End products (acetic, butyric, iso-butyric, total VFA) of colonic chyme tended to be more affected by fermentable CHO-level in the case of high crude protein diets, whilst for NH3, a reverse effect was observed. This would suggest that when both dietary CP and fermentable CHO are in short supply, extra fermentable CHOs lead to a strong decrease in NH3, which is most likely, a result of increased incorporation of N into GIT microbial biomass. Overall, it was concluded that the dietary contrasts used in the current experiment were not sufficient to significantly affect fermentation processes in the ileum, and only led to small effects in the colon.

In another experiment at INRA in Rennes, France, to test 4 weaning diets, also differing mainly in their protein and fermentable carbohydrate proportions. Samples of digesta were analyzed at WU for DM, VFA, NH3, and lactic acid. In all cases, GIT site had a significant effect on fermentation end products, with increasing concentrations from ileum to colon. Also, the BCP showed a similar pattern with highest values in the colon.

However, the only significant effect found between diets was for NH3. There were some significant differences in the interaction for Diet x GITm for BCP. Diet R1 gave the lowest BCP at the ileal level, but was highest for the colon. This could indicate that the ratio between protein and CHO availability is sufficient to supply the fermentation processes in the ileum, whilst in the colon there seems to be a shortage of CHOs for fuelling hindgut fermentation.

Overall, it would be recommended that increased fermentable CHO in weaning piglet diets, with a concomitant reduction in proteinaceous ingredients will improve piglet health at the critical time of weaning. However, it would seem that an in vitro assessment of a range of potential ingredients prior to the design of new diets may lead to more consistent results in the field. This is an important finding for feed manufacturers with an interest in weaning piglet diets.

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WAGENINGEN UNIVERSITY
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6709 PG WAGENINGEN
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