Improving the feed efficiency of livestock is a major challenge, for both economic and ecological reasons. By making better use of feedstuffs, efficient animals emit less waste and reduce the environmental footprint of the crops used to feed them. Characterizing the factors that influence feed efficiency is the subject of much research at INRAE. There is growing interest in the role of gut microbiota in this efficiency, but studies on laying hens are still rare.

To explore the hypothesis of a link between microbiota composition and feed efficiency, the researchers characterized the gut microbiota of two experimental chicken lines selected almost 50 years ago to diverge on feed efficiency (an efficient line and a non-efficient line). Animals from each line were fed two different diets. The first is particularly rich in starch (thanks to wheat), while the second is richer in hard-to-digest fibers such as cellulose (thanks to sunflower, rapeseed or oats) and has a lower energy intake.

Le microbiote est modulé à la fois par le régime alimentaire et la lignée

The sequencing of a gene present in all bacteria, but in a form specific to each bacterial species, the 16S RNA gene, has enabled bioinformatics analysis to identify the different bacterial families and species present in the microbiota of the four groups of hens, their respective quantities and to estimate the biological functions they perform.

Scientists have shown that fiber content strongly influences the composition of the microbiota, but they have also shown that this influence varies according to hen lineage. Two digestive ecosystems were revealed. The first, common to both the efficient line and the high-fiber diet, whatever the line (efficient or not), is characterized by a high bacterial richness. In this case, the microbiota is made up of a wide variety of bacterial species, including bacteria capable of digesting cellulose. The second, specific to the non-efficient line fed the wheat-rich diet, is characterized by lower bacterial diversity, and the increased presence of bacteria capable of fermenting starch.

Microbiota composition can influence feed efficiency

In addition to characterizing bacterial species, the scientists also looked at the biological activities of the bacteria present in the various microbiota. To this end, they quantified the molecules produced by the intestinal microbiota and capable of influencing the host's metabolism. They showed that, in addition to having a high bacterial richness, the microbiota common to efficient animals on a high-fiber diet produced more propionate, a fatty acid that crosses the intestinal membrane and reaches the liver, where it is used for the production of glucose, the hens' main source of energy. A rich microbiota can therefore help improve feed efficiency by enhancing the nutritional value of low-value feeds through the production of an additional energy source.

Modulating the composition of the microbiota and its biological functions therefore seems a possible way of improving feed efficiency in laying hens. Further work is needed to clarify the interactions between the microbiota and the various factors involved, in particular diet composition, and to better understand how to modulate the biological functions carried by the microbiota.

Contact :

• Maria Bernard (maria.bernard@inrae.fr)
• Tatiana Zerjal (tatiana.zerjal@inrae.fr)

(1) The ability of animals to use ingested food to extract nutrients and energy that can be used by the body.