Castration
Castration is a term usually applied to removal of the testes of the male animal, although technically it can apply to ovariectomy (removal of the ovaries) of the female animal as well.
Castration of male animals is practiced primarily to prevent those of inferior quality from reproducing. Except for colts that exhibit unusual quality meriting reproduction, most male horses are castrated to improve their tractability and utility as performance animals. Early castration also improves the quality of meat animals by inhibiting undesirable secondary sex characteristics (notably the failure to develop marbling of muscle). Table 24-1 lists the common terms for intact and castrated male animals.Sometimes a horse is referred to as being proud cut, meaning that the horse behaves like a stallion in spite of having been castrated. It has been believed in some circles that this results from the failure to remove all of the epididymis and that this part of the reproductive tract somehow produces sufficient testosterone to give the horse the attributes of a stallion. This belief is common but erroneous; the epididymis is entirely incapable of producing male sex hormones. It is much more likely that one or both testes were cryptorchid and that only the epididymis was removed (it can look remarkably like a small testicle), leaving the cryptorchid testis to produce testosterone. Alternatively, a colt castrated correctly but relatively late in life may have already acquired physical and behavioral characteristics of an intact stallion, characteristics that may not be wholly extinguished by removal of the testes.
Vasectomy refers to transection (usually with ligation andIor removal of a section) of the ductus deferentia (formerly called the vas deferens, hence the name of the procedure). This procedure prevents delivery of spermatozoa from the epididymides but has no effect on the production of the male hormones. The behavior and appearance of the vasectomized animal, therefore, are that of the intact male. Vasectomy is sometimes used experimentally or to produce teaser animals used to identify females in heat.