Fermentation in the large intestine of pigs

Feedback from the usage of Levucell SB (LSB) in sow diets is rich of visible signs of success during the lactation period and around farrowing. However, these results are usually obtained after feeding LSB throughout the gestation phase whith no visible signs. Consequently, LSB is often perceived as a cost-increasing factor by nutritionist. Production trials allowing a chance to measure any improvement are very unlikely to be performed. Due to 'natural' variability among sows of a same farm (parity effect first), number of replicates are seldom met. As a consequence, a 10% improvement of fermentation, releasing +4% dietary energy, would increase fat stores by 4 kg : due to variability, neither weighing the sow nor measuring backfat depth could detect such a difference. However, such an improvement in sows is very likely to occur as shown by several research results.

Digestion of plant cell walls in sows has been proven superior to growing pigs. Plant cell walls are commonly referred to as 'fibre' or 'dietary fibre', which is a confusing name because it gives information on physical structure as well. However, if structure makes sense when referrring to forages for herbivores, it is a fooling word to describe the non starch polysaccharides (NSP) fractions in grains and grain by-products used in swine diets. NSP could be described by several analytical procedures or calculations, thus leading to different values and digestibility coefficients, which is a challenge in comparing results from different research groups. Increased NSP digestion in sows compared to

pigs has been related to increased time presence in the gut, in the large intestine mainly. Very little has been done to describe the fermentation process, which increases the value of the trial presented by Nuria Canibe. In a trial performed in Québec on 200 sows in the year 2007, Lallemand measured changes in the profile of faecal bacterial species due to diet composition (corn-soy compared to mixed grains and by-products), farrowing and LSB (LSB addition tempered the effect of farrowing on microflora changes). However, very little knowledge is available for quantifying the improvement in energy yielded from fibre dur to LSB. Litterature show a high potential for SCFA to cover the maintenance requirement, which is the main energetic expense of a gestating sow. Moving the share from 25 to 30% (realistic) would further increase feed efficiency by 2.5 to 3.0%.

To convince nutritionists, modelling is a good tool to summarize knowledge and to point out lacks. Little effort of modelling swine digestion has been performed, and it always referred to growing pigs (40 kg live weight max). Fermentation is usually simplified with fixed ratios and efficiency, the only source of variation being the amount of undigested material coming from the upper gut segments. In order to meet the challenge and opportunities related to feeding more fibrous ingredients to sows, there is a need for more research and understanding of the fermentation in the large intestine.