20. No person may use an instrument which administers an electric shock to make an animal move, except that such an instrument which has been designed for the purpose of making an animal move may be used on adult bovine animals and adult pigs which refuse to move, provided that—
(a)the use of such an instrument is avoided as far as possible;
(b)the shocks last no more than one second each, are adequately spaced out and are not used repeatedly if the animal fails to respond;
(c)the animal has room ahead of it in which to move; and
(d)such shocks are applied only to the muscles of the hindquarters.