By Philippe Serene

For many years, we focused on improving the feed digestibility in the small intestine. We increased the ingredients with high digestibility and reduced as much as possible the ingredients presenting low digestibility.

But we ignored the basic digestive physiology and namely the importance of the large intestine where bacterial fermentation are contributing as well to the nutritional supply of the animal.

How important are these fermentations?

How nutritionist should adjust their feed formula to optimise both small intestine digestion and large intestine fermentation and provide a more efficient feed conversion. The article below brings some clarifications on that subject.

Generally, carnivores consume animal tissue, which is similar to their own; therefore all the body needs to do is break down the tissue and absorb the different components in the small intestine, which can then be used in the carnivores’ own body.

Herbivores only consume plant materials, which is very difficult to digest. No vertebrates make an enzyme capable of breaking down cellulose. To overcome this, herbivores have developed a symbiotic relationship with a population of microflora that inhabit a specialized region of the gut for fermentation e.g. the caecum or rumen of ruminants. The microflora population of the gut is able to breakdown cellulose and uses the glucose for its own metabolic needs. As a waste product of this process, the microflora population releases volatile fatty acids (e.g. acetate, butyrate & propionate) and lactate, which the herbivore utilizes for energy.

Omnivores consume both meat and plant matter; they have a digestive system which combines both the one stomach of carnivores and bacterial fermentation in the colon as herbivores to digest resistant carbohydrates as cellulose.

In pig, about 30 to 60% of the total gastrointestinal content resides in the large intestine where it is retained for 20 to 38h as compared with 0 to 6h in the stomach and 2 to 6h in the small intestine. This extended retention time in the large intestine provides ample time for bacterial digestion of resistant carbohydrates. Although carbohydrates are the primary substrates for microbial fermentation in the large intestine, all organic substances entering the large intestine are potential substrates for fermentation.

Colon bacterial fermentation creates short-chain fatty acids (mainly acetate, propionate and butyrate) and lactate that can be used for energy and metabolic processes by the animal body. Butyrate is the major energy source for colonocytes. Propionate is largely taken up by the liver. Acetate enters the peripheral circulation to be metabolized by peripheral tissues and lactate (D-lactate) can be metabolized and lead to produce ATP (energy)

The acids produced during the fermentation will have 3 major benefits

1 – The VFA will be absorbed and contribute to the overall net energy for maintenance and growth of the animals. The net absorption of VFA (volatile fatty acids) into the hepatic portal blood has been quantified. It has been calculated that VFA from large intestine could contribute 30% of the maintenance energy requirement in 60kg pigs.

2 – The lactate produced during the fermentation will act as bactericides in the large intestine to prevent the proliferation of pathogens namely clostridium.

3 – The production of butyric acid will be used by the colonocytes as major source of cell energy for activating the water / sodium reabsorption pump.

To optimize the utilization of the fermentation process, it is important for nutritionist to incorporate sufficient resistant carbohydrates in the diet to feed the bacterial population. The ingredient must be fermentable but sufficiently resistant to be carried up to the large intestine. This requirement is not valued by least-cost formulation software. Indeed, for decennials, we have been focusing on optimizing the small intestine digestion and reduce resistant carbohydrates. We were looking for easily digestible materials to be absorbed in the small intestine. The requirement for fermentation will need a new mindset and will call for new ingredients and nutrients. You may need to adjust your software accordingly by either setting a minimum for ingredients rich in fermentable carbohydrates or by creating a nutrient called ‘fermentable carbohydrates’ and updating the matrix for all ingredients about their content in fermentable materials.

When we are optimizing diets with fermentable materials in order to leverage the fermentation process and maximize its impact on the supply of energy, we are observing significant improvement as far as zoo-technical performance is concerned.

More energy for growth and reproduction For lactating diets, this additional energy from fermentation will ensure shorter parturition time and heavier piglets at birth. Experimentations show that an optimal fermentation can reduce parturition time up to 50mn and increase piglet weight at birth between 60 to100g. The incremental energy supports an increase of milk production for sows and piglets or broilers daily gain.

Fewer diarrheas in piglets and wet litter in poultry The increase of colonocytes activities through the supply of natural butyric acid from fermentation will ensure a better water reabsorption and limit the nutritional diarrhea and wet litter. Trials showed an improvement of feces aspect in piglets and a reduction of feet problems in Broilers.

Better gut health

The natural acidification of the large intestine by the production of lactic acid reduces the incidence of MMA in Sow. During gestation, the better gut health is translated into much calmer sows. This is the first sign that farmers immediately notice when they entered pens using optimized diet. In layers, the better gut health will reduce clostridium infections. That will help to get cleaner eggs and to extend the production life of laying hens.

This new paradigm shift would enable feed manufacturers to realize significant and visible improvement in their feed performance. As it is a major change, it is important to educate your sales team on Swine and Poultry digestive physiology and encourage them to communicate these points of differentiation to your customers. The more the farmers understand the importance of fermentation and the easier it will be for your company to value your feed superiority.