Techniques are described for testing the ability of chemicals to penetrate through ovine hoof horn. Most chemicals tested had penetration rates of less than 0.1 mm per hour and
formalin, a chemical widely used for treatment of
foot rot, penetrated very poorly (less than 0.02 mm per hour).
Chloramphenicol in
ethanol solution gave the highest penetration rate (0.21 to 2.38 mm per hour) and other penetrative chemicals were
zinc sulphate (0.06 to 0.58 mm per hour),
copper sulphate (less than 0.05 to 0.38 mm per hour) and
sodium azide (less than 0.05 to 0.24 mm per hour) in aqueous
solution. Inclusion of
sodium lauryl sulphate in treatments enhanced the penetration rates of
zinc and
azide approximately sixfold.
Ethanol and
nickel ammonium hydroxide also improved the penetration of
zinc and
azide, particularly through the hard horn from the abaxial wall of the claw. Absorption of
zinc from solutions containing 10 per cent
zinc sulphate gave hoof tissue concentrations of
zinc from 0.22 to 0.88 mg
zinc ions per g tissue (10 to 20 times that found in normal hoof samples) and most of this
zinc was retained after the horn was washed continuously in running water for 24 hours.