I – Pododermatitis, a multifactorial issue

Pododermatitis (footpad dermatitis or FPD) is an inflammation of the skin located on the basal part of a chicken’s foot. Necrotic lesions, with or without infection, may also be present. It can lead to lameness and poor performance. The causes of pododermatitis are multifactorial and can therefore be an indicator of farming conditions – hence welfare status. The prevalence of pododermatitis is included in some countries’ (Sweden, Denmark) welfare regulations, as well as in the evaluations of certain food retailers (like McDonalds). The EU recognizes pododermatitis as a marker of animal welfare and EFSA is putting pressure on integrators to reduce scores. This condition is often associated with poor litter quality and high stocking density in broiler houses. There are numerous causative factors which affect fecal content, litter quality or integrity of the skin. Feed formulation, gut health, and environmental conditions all influence the feces. They affect microbial load as well as the protein and water content; which in turn, influences ammonia production, and bacterial and toxin loads. Other factors that play a role in the overall quality of the litter include litter material, humidity of the house, management, and biosecurity on the farm. Apart from environmental factors, the robustness of the skin also depends on other factors, such as genetics, vitamin and mineral status, amino acid levels, gut health and any issues with collagen synthesis.
Broiler processing plants may simply dispose of chicken feet as waste, or some may be used in pet food. In terms of human food, there is a significant market for chicken feet in China, Taiwan, and Hong Kong. China alone imports 300,000 tons per year, with a value of US$ 450 million. There is additional demand coming from the rest of Asia, as well as Central and South America, e.g., Mexico and Peru. When feet have a severe form of FPD, they are downgraded, and their market value is decreased. 99% of downgraded feet are due to FPD.

II. Nutritional strategies to avoid pododermatitis

1. Manage the dietary electrolyte balance to avoid wet litter

The Dietary Electrolyte Balance (dEB) is the ratio of cations and anions in the diet. The three major ions are sodium (Na⁺), chloride (Cl^–), and potassium (K⁺). The dEB is calculated as follows: dEB=(Na/22.99)+(K/39.1)-(Cl/35.45). These elements are key for body fluid homeostasis and to maintain a stable blood pH. It has been shown that dEB is correlated with water intake and subsequent litter moisture. A trial was conducted at Schothorst Feed Research (the Netherlands) on broilers to check if AdiSodium™ (Adisseo’s sodium sulfate) can fully replace sodium bicarbonate to supply sodium and contribute to dEB, without increasing Na or having any adverse effect on performance and health. Feed consumption, FCR and body weight gain of broilers did not differ between the sodium sources. Feces and litter moisture were reduced at day 20 (p=0.028) with AdiSodium™. An interesting point was the pH measurements of both litter and feces, which showed lower numerical or statistical values with AdiSodium. Lastly, the impact on foot pad dermatitis was recorded using the Bristol foot burn scale 0-4 (0 means no lesions). This impact was quite low for all broilers, demonstrating very low scores, and even showed a statistical improvement at slaughter with AdiSodium™ (Figure 1). In the context of this trial, the replacement of sodium bicarbonate by AdiSodium™ is beneficial in terms of feed cost, offering some savings, and does not impair zootechnical or welfare parameters of broilers. It even shows positive effects on litter moisture and foot pad lesion score.

Figure 1. Foot pad lesion scores of broilers, according to sodium source

2. Decrease digesta viscosity thanks to multi-NSPase

The non-starch polysaccharides (NSP) from feed ingredients, mainly soluble NSP fractions, are known to increase the digesta viscosity, and consequently increase litter humidity. NSPs, which include hemicellulose, cellulose, lignin, pectin and so on, are indigestible for birds, as they do not have the endogenous enzymes to break them down. When given to birds, NSPs can disturb the gut microbiota already established. As all these micro-organisms use the digesta as substrate to develop and grow, when birds are fed NSPs, the microbiota will adapt, and certain bacteria will flourish, while others will diminish. Moreover, the production of mucus increases. These microbiota disturbances can lead to dysbiosis and create inflammation in the gut, leading to diarrhea, especially in young animals. Rovabio® Advance, a multi-carbohydrase, breaks downs NSP and therefore reduces viscosity. It was tested on a wheat-based diet to measure its effect on litter quality and nitrogen excretion. After 42 days, the litter was collected and scored on a scale from N0 (completely dry and flaky), N1, N2, N3 to N4 (Wet). Figure 2 shows how Rovabio® Advance successfully improved litter quality compared to the positive control (PC – standard feed) and negative control (NC – reformulated diet with – 5% AME and – 5% dAA). Further analysis of feces showed that Rovabio® Advance reduces litter humidity by 7.1 %.

Figure 2. Effect of Rovabio® on litter score

3. Strengthen gut health for a better pododermatitis score

Gut health can be described as the symbiotic relationship between the host and its microbiota.
If there is an imbalance in the interactions between the microbiota, the mucosal barrier, the immune system and the redox balance, inflammation will occur – leading to ‘leaky gut’ (increase of the permeability of the intestinal barrier) and other gut-related disorders.
Probiotics are used in poultry nutrition to improve gut health through their influence on microbiota, gut morphology and inflammatory responses. By improving gut health, probiotics not only enhance broiler performance but also improve litter condition and footpad scores.
A trial was conducted to evaluate the effect of a probiotic solution, Alterion® (Bacillus subtilis DSM 29784), on the performance and welfare of broilers raised under commercial conditions.
In this trial, Alterion® was fed to broilers on three farms that belong to a French poultry production organization, over four consecutive cycles. These three farms were selected from among the top 30% of performing farms. The bacterial enteritis and coccidiosis scoring system applied to these farms confirmed that all the flocks had good health status.
When gut health status and performance was already excellent, the data showed that the addition of Alterion® reduced the level of severe FPD scores by over 10%, which resulted in a higher carcass value for the producers (Figure 3).

Figure 3. Alterion reduced severe foot pad dermatitis scores in broilers under commercial conditions

Pododermatitis lesions were evaluated at a slaughter level as the % of the birds of the flock that showed severe FPD lesions. The obtained % is the proportion of birds from the flock that showed less than 30%, 30 to 50%, 50 to 70% and over 70% severe FPD lesions.

Conclusion

The export of chicken feet makes for good business. China imports chicken feet at a value of $ 450 million per year. Pododermatitis leads to feet downgrading, and their market value thus decreases. By improving gut health, probiotics not only enhance broiler performance, but also improve litter condition and footpad scores. Alterion® was effective in improving litter quality and pododermatitis in high stocking density conditions.

Decreasing the digesta viscosity by using a multi-carbohydrase, such as Rovabio® Advance, leads to reduced litter humidity (-7.1%).

AdiSodium®, a source of sodium sulfate, helps manage dietary electrolyte balance to avoid wet litter. It also decreases feces and litter moisture, allowing a better foot pad lesion score.

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