Review articleChemical sterilisation of animals: A review of the use of zinc- and CaCl2 based solutions in male and female animals and factors likely to improve responses to treatment

•Chemical sterilisation can be used as an alternative to surgical castration.•Use of zinc and CaCl2-based solutions are reviewed.•Results appear to be more consistent in animals with small testes.•CaCl2 has caused ovarian atrophy in heifers.•Injection technique and dosage are important for success.

Chemical sterilisation can be used as an alternative to surgical castration in some circumstances. This review focuses on responses to treatment with zinc- or CaCl2-based chemosterilants, factors that have affected treatments and their potential use to sterilise female cattle. Successful treatment with a low incidence of adverse side effects in male animals has occurred with the use of zinc gluconate (ZG), neutralised in arginine and a 20% solution of CaCl2 in ethanol. Injection technique plays an important role in success. Less satisfactory results appear to occur following use in animals with relatively larger testes. In animals with relatively small testes adjustment of the dose according to testicular size appears to optimise results. The techniques appear to be most suited to population control strategies in companion animals where low cost treatment of animals in environments where surgical facilities and specialised aftercare are lacking. The need for careful administration and likely slower speed of administration compared to surgical castration are likely to hamper application within the cattle industries. Recently transvaginal, intraovarian administration of CaCl2 in ethanol has been shown to cause complete ovarian atrophy without apparent pain in some heifers, although variable responses were found. Chemical sterilisation can play a role in the sterilisation of animals but careful attention to dose, volume, chemical composition, administration technique are needed to avoid adverse side effects and variability in responses associated with some treatments. Application in female animals requires further study but CaCl2 in ethanol can potentially cause complete ovarian atrophy when administered to heifers.