Footpad Lesions: The True Cause of Burns and Downgrades

By September 4, 2019News, PLT, PWT
Moisture
Litter depth
Bedding material
Nutrition
Bird Density
Waterline Management
Footpad dermatitis (FPD). Paw burns. Footpad lesions. FPD. Regardless of the name, burns found on the bottom of chicken feet reduce profits through the loss or downgrading of edible paws. They also serve as a valuable indicator of animal welfare during audits.
But what actually causes footpad lesions on broilers and what are the best ways to reduce them? We’re going to help you understand paw lesions by answering some of the most common questions we get in the field.

What is the top factor impacting the development of lesions or burns?

Litter that sticks to the bird’s feet the first 10 days or so of life.  If the litter doesn’t stick to the feet, then paw burns will not develop.  The litter will get sticky or tacky at the surface due to high relative humidity at the air/litter interface or poor moisture wicking due to over-worked litter. Humidity can be high due to ventilation issues, poor waterline management, low floor temperatures, or increased bird density.  When newly hatched chicks step onto those damp areas, the damp litter sticks to their feet and ammonia deep in the litter begins to erode the skin. In houses with small-bird programs, new litter, or high density, the lesion development is moisture dominant. In large-bird farms or houses with fine, over-worked litter, or those on all-veggie diets, it is ammonia dominant.

Why does litter depth affect paw quality?

Litter essentially serves as a French drain in a commercial poultry house, absorbing moisture and wicking it away from the surface where it can impact paw quality. A French drain works by removing moisture from the surface and then allowing it to evaporate back into the environment over time.  If the drain is too small, i.e. litter not deep enough, then moisture accumulates and backs up onto the litter surface.

The ability of the litter to wick away surface moisture is known as capillarity and is similar to how moisture moves through soils. Increasing litter depth gives you a bigger drain to handle the moisture the birds put into the system and reduces relative humidity at the litter surface making the litter less sticky.  This is why research shows that increasing litter depth improves paw quality and other production parameters that are influenced by the house environment.

Does the type of bedding material matter?

Yes and no.  The different characteristics of bedding influence how good of a job it does wicking moisture off of the surface (capillarity). The key is to preserve the capillarity of the litter so it can wick away moisture then release it back in to the environment over time. The ability to handle moisture is impacted by material’s particle size, incoming moisture content and other characteristics. Some plant materials just don’t handle moisture well, but often these shortcomings can be overcome.

Rice hulls, for example, are waxy and don’t handle moisture as well as wood shavings.  However, if the depth of rice hull litter is increased to 6-8 inches, it will handle moisture just fine.  The increased depth gives rice hulls enough time to release moisture back into the air before the French drain becomes overwhelmed. Less depth than that, and rice hulls can cake easily because the drain gets saturated.

Is my litter treatment contributing to paw lesions?

No. In fact, production trials show that the proper use of PLT (sodium bisulfate) improves paw quality by neutralizing the ammonia in the litter that causes the paw burns in the first place. So even if the litter should stick to the bird’s foot, the litter is no longer corrosive because the ammonia is neutralized by the PLT.

In one large field trial, ten farms (618,204 birds) applied sodium bisulfate and six farms (463,177 birds) served as an untreated control.  The birds raised on PLT showed significant improvement in paw quality with 55% of the birds having no paw lesions at all compared to only 16% of the birds without a litter amendment.  The PLT group had 19% fewer Major Paw Lesions and 20% fewer Minor Paw Lesions than the untreated birds.

PLT is a safe mineral acid that breaks down into products naturally found in the environment, and it’s the only EPA Safer Choice litter treatment safe enough to apply with birds in the house.

Can changes in nutrition impact paw quality?

Nutrition can impact the development of FPD in various ways positively and negatively. Proper biotin levels in the feed are important for good skin integrity that can keep the foot skin healthy. High protein levels in the diet, though, can make the birds’ feces really sticky making it easier to cause footpad burns.  In fact, the worst burns are usually seen in birds on an all-veggie diet because no matter how many enzymes are added, the feces are so sticky that bottom of the birds’ feet gets coated with manure causing ammonia burns. This overfeeding of protein also causes the birds to excrete high levels of ammonia in their manure dramatically increasing the ammonia challenge in the house.  One study that examined diets with equal protein-to-energy ratio showed broilers raised on the low-protein diet had significantly fewer FPD cases than the high-protein fed birds (de Jong, et al 2015).  Excess salt in the diet can cause birds to flush and houses to get wet.

Can bird density affect paws?

Absolutely. Increased bird density, whether intended or not, puts tremendous moisture pressure on the floor in the form of higher relative humidity. A high placed-density occurs in small-bird programs, houses that third-house brood, etc. and increased ventilation is needed to overcome the humidity pressure on the floor. But even in houses with a low placed-density, a high actual-density due to uneven bird distribution will also cause the litter to get damp and sticky due to high relative humidity where the birds are congregating. The most common cause of uneven bird distribution is improperly cured litter with core temperatures below 90°F.  Sometimes it only takes an additional degree of floor heat to be enough to drop the relative humidity below the breakpoint for litter caking and to get chicks to spread out evenly.  Ventilating houses to maintain a relative humidity (RH) between 50% and 65% can help to control moisture at any stocking density.

I de-cake my litter. Can paw burns still be a problem?

Of course. De-caking litter only removes the cake formed during the last flock. It doesn’t determine whether or not cake will form in the next flock.  But, by walking the house prior to de-caking and observing the location and depth of the caked litter one can gather the information necessary for proper de-caking and allow corrections to be made to prevent cake formation during the next flock.

Also, it is important to only run the housekeeper just deep enough to remove the cake without disturbing the litter underneath. Overworking the litter by running a housekeeper all the way to the floor and sidewall-to-sidewall, tilling the litter or windrowing, will not only make the litter so fine it will no longer wick moisture away from the surface, it will also increase the surface area of the litter causing high levels of ammonia to be released during the next flock. In other words, overworking the litter will actually increase the potential for paw burns on the next flock.

How do I manage water systems to help improve paw health?

Don’t let them drip. Be sure to reduce the pressure of the waterlines for baby chicks and replace any nipples that are leaking.  Use a mineral acid between flocks to remove scale that prevents the nipples from seating tightly. And always do an extended, high-pressure flush after waterline cleaning to remove any debris from the lines before it can settle into the nipple housing causing leaks.

A good rule of thumb is to make sure you get five 5-gallon buckets in a row of clear water before you stop flushing.

 

References

Harms, R.H., B.L. Damron, and C.F. Simpson. Effect of wet litter and supplemental biotin and/or whey on the production of foot pad dermatitis in broilers. Poult. Sci. 56(1):291-6. 1977.

Harms, RH., and C.F. Simpson.  Influence of wet litter and supplemental biotin on foot pad dermatitis in turkey poults. Poult. Sci. 56(6):2009-12. 1977.

Jones, T.A., C.A. Donnelly, and M. Stamp Dawkins. Environmental and Management factors affecting the welfare of chickens on commercial farms in the United Kingdom and Denmark at five densities. Poult. Sci. 84(8): 1155-65. 2005

Kjaer, J.B., et al.  Foot pad Dermatitis and hock burn in broiler chickens and degree of inheritance.  Poult. Sci. 85(8):1342-8. 2006.

Mayne, R.K., P.M. Hocking, and R.W. Else. Foot pad dermatitis develops at an early age in commercial turkeys.  Br. Poult. Sci. 47(1):36-42. 2006.