Page 464 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Male Reproductive System / 449

spermatozoa are produced. A unilateral failure to remove all of the epididymis
VetBooks.ir cryptorchid (one testis retained, one and that this part of the reproductive
tract somehow produces sufficient
descended) is fertile insofar as the
descended testis produces normal sper-
utes of a stallion. This belief is common
matozoa; however, the tendency toward testosterone to give the horse the attrib-
cryptorchidism is heritable in many but erroneous; the epididymis is not
species. Additionally, testes retained in capable of producing male sex hor-
the abdomen develop testicular tumors mones. It is much more likely that one
at a higher rate than scrotal testes. For or both testes were cryptorchid and that
these reasons, it is recommended that only the epididymis was removed (it can
cryptorchid animals be castrated, look remarkably like a small testicle),
including removal of the retained testicle leaving the cryptorchid testis to pro-
or testicles. duce testosterone. Alternatively, a colt
castrated correctly but relatively late in
life may have already acquired physical
Castration and behavioral characteristics of an
intact stallion, characteristics that may
Castration is a term usually applied to not be wholly extinguished by removal
removal of the testes of the male animal, of the testes.
although technically it can apply to ova- Vasectomy refers to transection (usu-
riectomy (removal of the ovaries) of the ally with ligation and/or removal of a
female animal as well. Castration of male section) of the ductus deferentia (formerly
animals is practiced primarily to prevent called the vas deferens, hence the name of
those of inferior quality from reproducing. the procedure). This procedure prevents
Except for colts that exhibit unusual quality delivery of spermatozoa from the epididy-
meriting reproduction, most male horses mides but has no effect on the production
are castrated to improve their tractability of the male hormones. The behavior and
and utility as performance animals. Early appearance of the vasectomized animal,
castration also improves the quality of therefore, are that of the intact male.
meat animals by inhibiting undesirable Vasectomy is sometimes used experimen-
secondary sex characteristics (notably the tally or to produce teaser animals used to
failure to develop marbling of muscle). identify females in heat.
Table 24‐1 lists the common terms for
intact and castrated male animals.
Sometimes a horse is referred to as Accessory Sex Glands
being proud cut, meaning that the horse
behaves like a stallion even though it The male accessory sex glands produce the
has been castrated. In some circles, it is bulk of the ejaculate, or semen, the
believed that this results from the medium for transport of sperm. Semen
provides favorable conditions for nutrition
of sperm and acts as a buffer against the
Table 24-1. Common Terms for Male Animals natural acidity of the female genital tract.
The accessory sex glands include the
Species Intact Adult Male Castrated Male ampulla of the ductus deferens, vesicular
Horse Stallion Gelding glands, prostate gland, and bulbourethral
Ox Bull Steer gland. Except for the prostate, these glands
Pig Boar Barrow are paired. There is considerable variation
Sheep Ram Wether in shape and size of the various accessory
Goat Buck (billy) Wether sex glands among species, but the relative
location is similar in all animals (Figs. 24‐1
Chicken Rooster Capon and 24‐10, and Table 24‐2).