From this link:
Zinc Gluconate (Neutersol®/ EsterilSolTM/Infertile®) is the first permanent, non-surgical method of sterilization for companion animals. It is currently licensed for use only in the U.S. for chemical castration of puppies 3-10 months of age, although it has been shown to be effective in adult dogs and cats as well.
It is delivered via an intratesticular injection, which results in sclerosis of the testes and permanent sterility. It is 99% effective and very safe. The precise mechanism of action is unknown; the testicles atrophy over weeks to months following injection, resulting in a 70-90% reduction in testicular size in very young puppies and 50% in older dogs (atrophy may not be symmetrical). Sterility may take up to 60 days in postpubescent males. In most cases, zinc gluconate can be administered without sedation.
Other methods mentioned in the article:
A deslorelin implant (Suprelorin®) is approved and available for use in male dogs in Australia, New Zealand, and the EU. Deslorelin is a GnRH agonist. When GnRH agonists are given continually at low doses, they suppress pituitary function. This action results in safe, reversible contraception.
An azagly-nafarelin implant (Gonazon®) is approved (but unavailable) in the European Union for one-year, reversible contraception for female dogs. Limited data in cats indicated that queens had suppression of estrus over three years.
GonaCon®: Dr. Lowell Miller and Kathy Fagerstone of the National Wildlife Research Center of the USDA presented data on the GnRH vaccine GonaCon, developed and tested for use in several wildlife species. Data are being submitted to the EPA initially for approval for use in deer and other cervids.
ChemSpay®: Dr. Loretta Mayer of Senestech/Northern Arizona University is studying early stage technology for permanent sterilization of female dogs and cats. The drug is an industrial chemical that has been shown to deplete the ovarian follicles and cause sterility in rodents. This is a totally new approach and is exciting for its potential for permanent sterility. Dr. Mayer is currently working on dose levels and formulation for single-treatment application. Dr. Levy is currently investigating the use of this compound in female cats.
None of these are available in our country yet, so for us, it’s still the relatively safe and effective method of castration and spaying for street animals.
There are some caregivers who opt to use a birth control pill for female cats and dogs, but this product interferes with hormones and has the potential to cause cancer in the animal later on. In fact, when we did mass spaying in Pahang many years ago, we witnessed the cancer in one of the female dogs who was opened up for spaying (the dog was successfully spayed and recovered). Upon checking, the caregiver said she had been giving a birth control product from Thailand to this dog for years. Our vet cautioned her never ever to use the product again. Sadly, we had an applicant from Kedah who said her vet prescribed the birth control pill for her cats too. This applicant is not literate and did not know any better.
Please let’s stick to approved and time-tested safe methods to help the animals.
