Much attention has been paid to the condition of the litter in the last week or so of a bird’s life in regards to poor quality paws. However, by then it’s too late. Poultry paw lesions, or footpad dermatitis, begin to form in the first week of the bird’s life when the foot is still tender and easily damaged.
Ammonia levels at bird height do not seem to influence the development of paw lesions. The two factors that need to be present for lesion development are substantial levels of ammonia deep in the litter and moisture at the litter surface. Ammonia in the gas phase does not seem to be sufficiently irritating to the skin of the feet. Ammonia in solution, however, in the damp areas of the litter is corrosive to the skin and causes foot pad damage.
The formation of liquid ammonia at the litter surface occurs anywhere there is even the least bit of damp litter. The stickiness and moistness of the caking present in the houses seems to play the predominant role in paw damage. Common culprits are small wet spots under the drinkers (commonly referred to as donuts) and caked areas along the sidewalls. Anything that makes the litter tacky and sticky, even if only in the top few millimeters of the litter, will cause the litter to stick to the chick’s foot and begin to damage it. When newly hatched chicks step onto those damp areas, the damp litter sticks to their feet and ammonia in the litter begins to erode the skin.
Visible paw lesions are evident by the time the bird is 7 days old and the lesions continue to worsen over time. Serial examination of these birds shows that the lesions do not tend to heal even if the litter dries out. Surprisingly, in houses with dry litter and good relative humidity control, the bottoms of the birds’ feet are very clean and it is unusual to find a footpad lesion on a bird with clean feet. The adherence of wet litter to the bird’s foot at a young age seems to be the key to damaging the paws. This is consistent with literature reports of decreased paw quality in houses with higher relative humidity and moisture at the litter surface.
Houses with no or low ammonia at bird level can still have a substantial percentage of poor paws if the litter is damp or tacky. This is most commonly seen in brand new houses or on new litter where the relative humidity is high even though the ammonia is not, and litter slicking occurs. At the same time, houses with dry litter except for quarter size donuts under the drinkers due to leaky nipples or sticky litter from high relative humidity will still have a substantial number of birds with paw lesions.