![]() Congenital cryptorchid stallions should not be considered for breeding. The left testicle is the one most commonly retained. Cryptorchidism is common in stallions and its genetic control is not fully understood. Certain medications, particularly androgens, adversely affect testicular size. Stallions older than 7 years of age tend to have greater scrotal widths than younger stallions. Normal scrotal widths range from 9 to 13 cm. Scrotal width is positively correlated with daily sperm production and output. Measure scrotal width using calipers at the point of greatest width with a nonerect penis. Determine testicular size by measuring scrotal width of both testicles. The right testis is normally slightly smaller than the left. Palpation should reveal that they have the same consistency with no abnormalities of shape or texture. The testes and epididymides are palpated through the scrotal wall to determine their presence, size, symmetry and consistency. The body of the epididymis continues along the testicle’s back side until it terminates at the rather large tail of the epididymis that is loosely attached to the testicle’s tail. The head of the epididymis is closely attached to the testicle’s anterior dorsal aspect. The epididymides are divided into 3 parts: (1) head (2) body and (3) tail. The testicles should be freely movable within the scrotal sac. They consist of seminiferous tubules in which spermatogenesis occurs and interstitial tissues of which the Leydig cells produce testosterone. The testes are ovoid structures, measuring 8 to 12 cm long by 6 to 7 cm high by 5 cm wide. The scrotum is important in thermoregulation of the testicles. The scrotum’s skin is soft and pliable with a greasy texture due to sebaceous glands. The stallion’s scrotum is not as pendulous as a bull’s and is held closer to the abdomen. ![]() The scrotum may be examined at the time of washing or after ejaculation, which may be safer for everyone involved. It has a longitudinal midline where the two sacs are fused. ![]() The scrotum is an outpouching of skin in the inguinal area that encloses the testes. Trauma can also occur by improper handling of artificial vaginas. This is particularly true if the stallion is kicked by the mare while attempting to breed her. Any trauma or injury to the penis or prepuce can be very detrimental to the stallion’s ability to cover a mare and could result in long term psychological problems. Usually a small amount of greasy smegma is found at the base of the penis. With the penis exposed, examine the internal and external portion of the prepuce. The examination continues up the shaft where any injuries, scars or other lesions are noted. Examine the urethral process for lesions and the associated structures for debris or other foreign material. Grasp the shaft of the penis just behind the glans. Examine the penis and prepuce both manually and visually. Exercise caution because some stallions may be reluctant to be examined and cow kick or kick backwards at the examiner. Allow the stallion to approach the mare in order to be stimulated to let down, at which time the penis extends from the sheath. ![]() Examination of the penis and prepuce is most conveniently done at the time of washing. The prepuce or sheath is a double invagination of the skin that covers the distal portion of the penis when not erect. When erect, the penis doubles in length and thickness and the glans increases by 3 to 4 times. When not erect, the penis is 50 cm long and 2.5 to 6 cm in diameter with the distal end 15 to 20 cm free in the prepuce. The stallion’s penis consists of 3 parts: (1) the root or bulb, (2) the body or shaft, (the main part), and (3) the glans, the enlarged free end of the penis. External Reproductive Organs Penis and Prepuce ![]()
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