The unprotected horn will absorb urea, which can destructure hoof horn and soles at molecular level. Effectively it unwinds the keratin molecule from its spring like appearance, breaking the intermolecular bonds and leaving the hoof and sole soft and weak. Usually the horn below the clenches will start to crumble, the sole will become prone to bruising and there will be an increase in fungal and bacterial infections in the hoof capsule. These symptoms are becoming increasingly apparent in horses kept on these new types of bedding. Equally the structure of straw allows urine to drain through more effectively, with little wetting or absorption.
Soiled straw is easy to identify and remove.
All this helps prevent the development and reproduction of micrococcus ureus and ensures low concentrations of ammonia in, or under clean straw bedding. Deep littering with any type of bedding is to be discouraged in the interests of good hoof health for the same reasons as stated above. If paper, straw or hemp are the only options then it is essential to take care to properly protect the hoof and soles against the effects of ammonia. See Keratex Hoof Gel for protection against these problems. This is not the case with stabled horses, so it is not surprising to find that hooves have no natural protection against the effects of ammonia.