Page 547 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

522 CHAPTER 2

VetBooks.ir Determination of adequate libido is subjective and 2.132
based on many factors such as season of the year,
temperament, age and previous handling and breed-
ing experience. For details on normal and abnormal
libido see Observation of libido and breeding behav-
iour (p. 526) and Poor libido (p. 532).

Examination of the external genitalia
The penis and prepuce are most easily examined
during teasing and washing for breeding. The skin
of the penis and prepuce should be intact and free
from erosions, crusts or masses (Fig. 2.132). Careful
attention should be paid to the fossa glandis and
urethral process during examination, which should
be free from growths, ulcers or masses. The fossa
glandis should be checked for the accumulation
of smegma, termed a ‘bean’. The scrotal contents
may be most easily examined after semen collec-
tion. The scrotal skin should be free from erosions,
crusts and masses. Structures on either side of the
scrotum should be of similar size and consistency.
Asymmetry creates suspicion of disease. The testicle Fig. 2.132 Lesions on the penis of a 16-year-old
should be uniformly firm and freely moveable in the Thoroughbred stallion with squamous cell carcinoma.
scrotum. The head and body of the epididymis are The disease had already spread to inguinal lymph
palpable on the cranial and dorsolateral aspect of nodes at the time of presentation.
each testicle respectively, while the tail of the epi-
didymis is clearly palpable at the caudal pole of the
testicle. The ligament of the epididymis is palpable 2.133
running dorsocranially from the tail. If the tail and
ligament are difficult to locate, testicular torsion
should be suspected. The spermatic cord is palpated
running dorsally from the testicle to the external
inguinal ring.
Measurement of scrotal contents is an impor-
tant component of a stallion BSE. Total scrotal
width (TSW) is measured using calipers or ultra-
sound (Fig. 2.133); larger widths are associated with
increased sperm output. The average TSW for light
horse stallions is 9–12 cm. Stallions with total scro-
tal width <8 cm generally will not produce enough
sperm to meet the BSE standard. Caliper measure-
ments should be used judiciously based on their
inherent potential sources of error including cali- Fig. 2.133 Measurement of the total scrotal width
per sensitivity, operator technique and testis loca- of a stallion. The testes are pushed ventrally into the
tion within the scrotum. To measure the TSW, the scrotum with one hand, while the calipers are placed
examiner stands close to the stallion’s left flank and over the widest part of the scrotum with the other
reaches under the abdomen to grasp both testicles hand.