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Quantitative studies on ileal digesta in weaning piglets

Balance trials were conducted with artificially reared piglets (milk replacer) to assess the pre-weaning quantitative aspects and post-weaning with weaners fed the four starters already applied in the slaughter trial. The 15N tracer technique was used to estimate the endogenous nitrogen loss and the D-alanine method to assess the bacterial nitrogen contribution.

The both balance trials aimed to investigate the nitrogen digestibility, endogenous and bacterial nitrogen at ileal in unweaned and weaned piglets fed different diets. The 15N tracer technique was applied to estimate endogenous nitrogen losses and calculate real ileal digestibility of nitrogen. Bacterial nitrogen was assessed by means of D-alanine as bacterial marker. Our results demonstrate that in unweaned piglets nitrogen digestibility was highest and endogenous and bacterial N flow (g/100g DMI resp. CPI) significantly lower compared to weaned pigs.

Looking at total ileal N endogenous nitrogen contributed to the greatest and exogenous (dietary) nitrogen to the least part. This underlines the high nitrogen utilisation of milk replacer at the terminal ileum. Similar results were established for the low-fibre starter LF: real nitrogen digestibility was equal to that of milk replacer (98.5 vs. 98.2 %) and endogenous nitrogen was the main contributor to total ileal N.

The remaining starters +AB, -AB and HF showed markedly lower RIDN (90.2, 88.3, 94.0 %). In the reference diets endogenous N was lower and exogenous N contribution greater than in home-produced starters and milk replacer. Bacterial nitrogen proofed to be less affected by weaning itself but influenced by dietary regime. Un-weaned animals and those fed +AB and –AB exhibited equal bacterial nitrogen contribution (11.6, 11.4, 11.8 % of total N), whereas in piglets receiving LF and HF bacterial contribution was markedly lower (9.1, 7.9 % of total N).

This might be attributed to differential microbial population, though these differences were not present in the results of the classical plate counting. One reason could be that the major part of the gastrointestinal microflora belongs to yet uncultured microorganisms, thus not to be proofed by classic microbiological techniques.

However, D-alanine as bacterial marker can be assumed to have well covered the yet uncultured bacteria. D-alanine was used as a novel approach in swine. At present it is used successfully in ruminants, but not in monogastric animals. However, indicate its suitability as a bacterial marker in monogastric animals as well. Our results support this notion. Results obtained from both the balance trials imply that the magnitude of the main components of total ileal nitrogen - endogenous and bacterial N - are more dependent on the applied dietary regime, whether being milk replacer or starter diets, than on the actual weaning process.

Comprising the experiments of this study - slaughter and balance trials - we could demonstrate that the small intestinal environment is subjected to a short-termed adaptation period during the actual weaning process. During this period the ileum adjusts to a physiological equilibrium, which goes along with minor changes in various parameters such as ammonia, VFA and LA. Postweaning our results showed no advantage of dietary supplementation with the in-feed antibiotic avilamycin compared with the other three starters. In fact we could demonstrate considerable beneficial characteristics of the home-produced low-fibre diet LF: higher nitrogen digestibility (apparent and real ileal N digestibility) as evidenced in the balance trial and a promotion of the Lactobacillus spp. population in the terminal ileum as showed in the slaughter trial.

Both features might proof advantageous in the practical application of this diet: higher digestibility has the potential to improve ADG in long-term administration (exceeding 15 days postweaning), which is of great importance for commercial swine production in a financial aspect. Furthermore, enhancing the diversity of Lactobacillus spp. in the terminal ileum indicates that this cereal-based diet has probably prebiotic properties and therefore could be of good use in commercial swine production, particularly with regards to the EU-wide ban of antimicrobial feed additives in weaning piglets.

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Wolfgang-Bernhard SOUFFRANT, (Senior Scientist)
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