It's best to start training a pig for nail cutting a very early age if possible. Begin by accustoming her to having her feet touched by gently stroking the legs and feet. Make it a fun experience with pets, belly rubs and treats. You can try filing the nails , one foot each time, when you think your pig is ready although filing might not work on an adult pig's hard nails. Then purchase a good quality stainless steel diagonal cut mini pliers. Use with care as there are nerves and blood vessels in the hooves.
