The high cost of surgical sterilization can limit the role as a process of feline population control, chiefly in non-affluent parts of the world. In addition, some people view such surgeries as intolerable infringements on animal rights.
It is obvious that an inexpensive and non-surgical method for permanent contraception would be of gigantic benefit. A multiplicity of approaches to this goal has been investigated, but so far, none have shown sufficient efficiency to be widely deployed.
Many researchers have explored injection of irritating chemicals into the testes or epididymides to sterilize cats. Epididymal injection of such compounds as dilute formaldehyde or zinc tannate chlorhexidine gluconate, have, now and then, appeared a hopeful approach to sterilization. Yet, when larger scale trials were performed, sterility was not consistently accomplished and a noteworthy number of felines developed unsatisfactory inflammatory reactions at the location of injection. This method is rarely used.
A hefty amount of research has been expended to expand vaccines against zona pellucida proteins, and some of this work has focused on both dogs and cats. The thought is that antibodies to the zona pellucida may harm oocyte development, weaken ovulation or block binding of sperm to the zona pellucida; any of these things could lessen or diminish fertility.
Up till now, an effective zona pellucida vaccine for pets has not been announced, and some researches have demonstrated major side effects.
Many shelters offer low cost spay/neuter days for those who can’t afford altering their pets. As of today, this is still by far the best choice.