Dr Temple Grandin references topical pain relief product, Tri-Solfen, as the most practical pain relief product for farmers to administer during cattle castration:-

For extensively raised cattle, there is a need to have practical methods to reduce pain that can be applied at the same time the animal is castrated. An anesthetic gel developed in Australia may be a practical method of pain relief (Lomax & Windsor, 2013). Other methods such as NSAID pain relievers, such as Meloxicam, given at the time of castration are less effective than medications given before the surgery (Coetzee, 2013). Researchers need to develop practical methods that would be easy for farmers and ranchers to use. Epidurals and IV injections are not practical for farmers and controlled substance medications with human abuse potential should also be avoided.  READ REPORT IN FULL