Possible effect of probiotics on the brain-intestinal communication axis in laying hens

As consumer expectations for animal welfare increase, questions arise about egg production in cages. From a global perspective, egg production is growing every year, both in centralized farms (modern facilities with vertical cages) and in cageless or free systems. There is limited scientific data compared to the welfare of caged laying hens versus alternative nesting systems. As a result, very little evidence is available to support the assumption of increased or no welfare in one system or another. In addition, all nesting systems have their inherent problems. The three most common commercial egg production systems around the world are:

the cage:

Birds are housed in cages in shelters with controlled environmental conditions or open front. Cages may be developed to improve welfare.


The birds are in bed and have daily access to the outdoors. Nest space can be very variable but may be similar to the cage system used.

Floor cages:

Birds are comfortable in bed but do not have access to the outdoors. The shelf system has spawning nests and soil baths and may be single-storey or multi-storey (poultry).

In addition, equipped cages are also made in Europe. These cages include an egg-laying nest, a soil bath and a living room. However, as there is no evidence that non-shelf systems are superior to bird welfare, this becomes largely a moral issue that society deems appropriate.

Why are probiotics involved in animal behavior?

For laying hens, intestinal health should be considered to achieve proper nutrient uptake, disease prevention, and optimal bird function. In poultry production, the main purpose of specific use of probiotics is to reduce the stressful effects on final performance (eg egg production, feed efficiency).

In relation to human health, in recent years there has been an increase in research on probiotic strains through the gut microbiota axis with the brain interacting with cognitive functions. In addition, various articles have reported that certain strains of probiotics, including Bacillus subtilis, affect behavioral patterns.


Figure 1- Behavioral parameters (white laying hen)                     Figure 2 – Behavioral parameters (brown laying hen)

summary of results

GalliPro MS supplementation in the diets of white or brown laying hens significantly improved well-being. Indicators such as percentage of full tip, fights and aggression, hidden hens or cracked eggs in the uterus were positively affected by the use of probiotics.

In both experiments, it was reported that for both white or brown laying hens, the addition of GalliPro MS improved behavior and calmed the birds during the 84-day trial period. In parallel with these observations, laying performance, independent of laying hen genetics and probiotic dose, showed significant improvement in both experiments with probiotic supplementation (P <0.05).

A low percentage of dirty eggs is usually a good indicator of intestinal health. This often indicates the development of low dysbacteriosis through better control of pathogenic bacteria and intestinal microbiome.

Positive effect on egg production

These effects can be explained by several main mechanisms:

The special strain of Bacillus subtilis, which has the ability to colonize the intestinal villi, has two main advantages for the bird intestine:

Protects the villi for a higher absorption level through competitive removal.
Release of enzymes to improve the digestibility of undigested nutrients

A specific strain of Bacillus lichene formis that produces the active lichen peptide to inhibit Clostridium bacteria. As a result, they potentially reduce dysbacteriosis or intestinal inflammation.

The cellular mechanism underlying these behavioral changes in laying hens fed GalliPro MS is still unclear but may be similar to that described in humans and mice.

In fact, some probiotic supplements cause the release of neurotransmitters and endocrine glands that affect neurotransmitters such as serotonin and neurotransmitters such as tryptophan through the gut microbiota axis with the brain.

Synthetic view of the brain and intestine axis: 90% of serotonin is produced in the intestine.

In the poultry industry, in addition to improving productivity, the use of probiotics in diets is assumed to have a positive effect on broilers or the welfare of laying hens.

What can be expected?

In order to evaluate the effects of 1: 1 combination of Bacillus subtilis, Bacillus licheniformis in GalliPro MS on laying hens at the end of the production cycle, in two simultaneous experiments. Experiment 1 with 288 white laying hens (Nick Chick) and Experiment 2 with 288 brown laying hens (Lohmann brown) were performed to observe the potential genetic effect. In both experiments, laying hens were 71 weeks old, using the same experimental design and data collection method. Two treatments with 12 replications included: control, control + 400 g probiotic (GalliPro MS) per ton of feed.

The trial period was 84 days and the birds were housed in a nest in California (conventional system) with eight birds in each cage. Classic yield parameters such as feed intake, egg production, egg weight, feed conversion ratio and percentage of dirty eggs were collected. In addition to these data, behavioral and welfare parameters were assessed once a week. Parameters such as percentage of full tip, fights, hidden hens or cracked eggs in the uterus were measured as indicators of animal welfare. The results of experiments 1 (white laying hen) and 2 (brown laying hen) for behavioral and welfare parameters are summarized in Figures 1 and 2.

Agonistic behaviors in laying hens were significantly reduced when using GalliPro MS. Such results create a new entry for probiotics, as GalliPro MS has been shown to be beneficial to animal performance and well-being in laying hens.

Translation and research: Dr. Negin Amiri. Scientific Department of Arian Roshd Afaza Company (ARA)