Breeding Soundness Examination in Goats
The external genitalia of does should be examined for abnormalities such as an enlarged clitoris, hypotrophic vulva, or increased urogenital distance that suggest intersex, a condition common in homozygous polled females, especially in Alpine, Saanen, and Toggenburg breeds. Intersex goats are sterile and should be culled. Occasionally, a doe has a shortened vagina and no cervix, and segmental aplasia of various parts of the tract can occur. A speculum can be used to examine the walls of the vagina, vestibules, and cervix to search for lesions in does with fertility issues. Transabdominal and/or transrectal ultrasonography can be used to examine the uterus and ovaries for cysts, pseudopregnancy, or other abnormalities. In cases of valuable breeding does, surgical laparoscopy or laparotomy may be used to check for causes of infertility such as oviductal blockage, tumors, adhesions, or segmental aplasia that may not be visible on speculum examination or ultrasonography.
A thorough physical examination of the buck before the breeding season is important to determine the ability of the buck to safely mount and breed a doe. Bucks should have a body condition score of 3–3.5 (out of 5) and be structurally sound with no visible foot or leg abnormalities. The buck should be in overall good health, because anemia due to heavy parasite infections and chronic debilitating diseases, such as pneumonia, can lead to loss of libido. Any degree of foot abnormalities, from overgrown hooves to severe laminitis, may cause the bucks to be reluctant to mount and should be treated appropriately. Bucks with caprine arthritis-encephalitis virus infection (see Caprine Arthritis and Encephalitis) may have painful, enlarged stifles, and if they are even able to mount, are usually reluctant to ejaculate because of pain.
A complete assessment of the reproductive organs should be performed and include an evaluation of the penis and prepuce. The buck is set on his rump, and the shoulders pushed down to curve the spine convexly; this makes it easier to protrude the penis. Shearing wounds (especially in Angoras), prior balanoposthitis, and old fly-strike wounds and scarring around the prepuce may make protrusion of the penis impossible. Prior amputation of the urethral process to prevent obstruction by a calculus has no apparent deleterious effect on breeding ability. Although cryptorchidism is rare, a thorough reproductive examination in a young breeding buck should include confirmation that both testicles have descended. The scrotum should be evaluated for size, lesions, or other signs of injury. Testicular hypoplasia occurs in only ~2% of intact bucks and is mostly associated with intersex condition, but it may also be a manifestation of malnutrition. As in other species, scrotal circumference is positively correlated with semen production capacity and should be >25 cm in mature bucks (>14 mo old). Scrotal circumference can vary by season and decrease by as many as 3 cm outside the breeding season. Because scrotal circumference and body weight are positively correlated in bucks, scrotal circumference measurements are of minimal value before 14 mo of age. The testicles and epididymis should be symmetrical and firm on palpation. Any asymmetry or changes in tone may indicate infection or injury and will likely adversely affect fertility. Orchitis and epididymitis are both rare, occurring in ~1% of breeding bucks, and affected bucks should be tested for Brucella melitensis, because bred does are at risk of stillbirths and abortions. Other causes of orchitis and epididymitis are of minimal concerns for transmission; however, treatments are generally unrewarding. Caseous lymphadenitis (see Lymphadenitis and Lymphangitis), spermatic granuloma, and calcification of the testicles (which also may be due to Corynebacterium pseudotuberculosis infection) all reduce or eliminate the buck’s fertility, and infected bucks should be culled. In extreme cases, ultrasound may be used to determine whether one or both testicles are affected and if hemi-castration is an option.
Evaluation of semen quality is another important part of the breeding soundness examination. Semen can be collected either by use of an artificial vagina or with an electroejaculator. The former yields a higher quality sample but requires the presence of a doe in heat to perform. Electroejaculation is more convenient and, thus, used more commonly. Once semen is obtained, it should be maintained at 37°C (98.6°F) and evaluated as quickly as possible. Grossly, the semen should be cloudy, white, and free of urine, blood, pus, or dirt. Occasionally, semen will be an off-yellow color and may be normal but should be examined more closely for urine contamination. The semen should be evaluated microscopically for motility, morphology, and presence of WBCs. Gross motility can be measured by placing a drop of undiluted semen on a warmed slide and evaluating on low-magnification. A satisfactory sample should exhibit anywhere from general oscillation to vigorous swirling. Sporadic oscillation to no motility at all indicates poor semen viability. Individual and progressive motility should also be measured by diluting the semen with an isotonic diluent (eg, 0.9% saline) and evaluating microscopically. Sperm cells should be counted to determine a percentage of progressively motile sperm, with a minimum of 30% being acceptable. Sperm morphology should also be assessed microscopically, with a minimum of 70% normal being acceptable. (Also see Breeding Soundness Examination of the Male.)