PREVALENCE

Intersexes are relatively common in domestic goats. Even though they occur in all goat breeds, their prevalence varies, depending upon the breed, prolificacy of the line, and the selection practice adopted by breeders.² Among the domesticated goats, male pseudohermaphrodites are more frequently seen in dairy breeds than in wool breeds. Their prevalence is extremely low among horned feral goats, whereas they occur at a high rates in lines selected for twinning and/or lack of horns.² In the Saanen and Toggenburg breeds raised in the United States, the prevalence of intersexes during the early part of this century was as high as 11% and 6%, respectively, whereas more recent surveys on European dairy goats cross bred to native breeds from different parts of India indicate the prevalence to be under 2%. Among the Shami breed of goats raised in Jordan, 6% of the newborn kids surveyed over a period of 8 years were intersexes.³ In this breed, selected for the hornless (polled) trait, the most prevalent type (33.6%) of malformation seen was that involving the reproductive system.³ A majority of goats displaying malformation of the reproductive system are male pseudohermaphrodites, which are sex-reversed genetic females, whereas true hermaphrodites constitute a much smaller percentage of caprine intersexes.

MALE PSEUDOHERMAPHRODITES

The appearance of caprine male pseudohermaphrodites varies from nearly normal females to nearly normal males in their external genitalia, although a majority of these are female-like at birth. As the age of sexual maturity approaches, these animals become larger than their normal female counterparts and acquire a more masculine head with more erect hair on their neck. Their teats are generally small, and the external genitalia are often represented by a short penis or a bulbous clitoris, which becomes enlarged and externally visible at the age of puberty. Hypospadias, represented by narrow slits of varying lengths on the ventral midline due to incomplete fusion of urethral folds, may be present. In some cases the slit may lead into a pouch that, when filled with urine, may overtly resemble a scrotal sac in the normal location, or anywhere between the anal and the urethral openings. The anogenital distance may vary from 3 to 33 cm in length among caprine intersexes depending upon the type of gonads and gonaducts they carry.⁴ As a rule, intersexes showing short anogenital distances (3 to 6 cm) have intra-abdominal gonads; poorly developed epididymis, vas deferens, and seminal vesicles; and moderately well developed müllerian duct derivatives, including oviducts, uterine horns, and body of the uterus. Intersexes with greater anogenital distance show exaggerated masculinization of the external and internal genitalia, including scrotal or inguinal gonads, enlarged clitoris or a penis with sheath, and poorly developed body and horns of the uterus.⁴ At the age of sexual maturity, intersex goats may start to butt like bucks and act aggressively toward other goats and people and may begin to dribble their urine or stretch out with a concave back and urinate forward between the legs. They also develop the odor characteristic of bucks, and show pronounced male libido in the presence of a normal doe in estrus. The testes are generally intra-abdominal in the normal location of the ovaries, or they may be partially or totally descended. The partially descended testes located in the inguinal region sometimes can be mistaken for udders, especially when the animal reaches the age of puberty and the fat pads become prominent. The testes are generally intra-abdominal, in the normal location of the ovaries, or they may be partially or totally descended. Occasionally, the uterine horn, wrapped around or attached to the ipsilateral testis, herniates through the corresponding inguinal ring into the scrotum. In some cases, the posterior parts of the horns are either connected to a short body of the uterus that opens into a cervix, or in close association with the vas deferens. The uterine horns are generally filled with mucus and distended in adult life. In some cases the bilateral hysteroceles, resulting from the herniation of the uterine horns into the scrotum, may be mistaken for highly enlarged scrotal testes at the age of puberty.⁵

Intra-abdominal testes of the intersex are invariably smaller than those of normal bucks of corresponding age. The seminiferous tubules of younger intersexes resemble those of immature males but, as they reach the age of sexual maturity, the tubules appear more narrow or irregular in outline and internally lined exclusively by Sertoli cells. In older intersexes the tubular basement membrane is thick and hyalinized, and the seminiferous tubules generally appear atrophic with abundant interstitium consisting of mature and immature Leydig cells and cells resembling fibroblasts. The principal steroid produced by the gonads of caprine intersexes is generally testosterone, although the plasma concentrations of testosterone tend to be lower than those of normal bucks of corresponding age. Because germ cells are always absent in the testes of adult intersexes, these male pseudohermaphrodites are always sterile.^2,4

TRUE HERMAPHRODITES

True hermaphrodites among caprine intersexes carry bilateral ovotestes or an ovotestis on one side and a testis or an ovary on the other side. Follicles at various stages of development and hormonal activity are seen in the ovaries or on the ovarian structures located on the periphery of the ovotestes. Seminiferous tubules, generally located toward the middle of an ovotestis, are devoid of male germ cells and generally inactive. Adult intersexes of this category with abdominal ovotestes and ovaries often show gonadal hyperplasia or gonadal tumors, or both. These animals generally resemble females more closely in their external and internal genitalia.^2,4

True hermaphrodites are generally whole-body chimeras. This type of chimerism results from the admixture of cells from male and female embryos at an early stage in embryogenesis or through the fertilization of the second polar body and the ootid by different spermatozoa, one of which carries an X and the other a Y chromosome. This type of intersex may occur in all breeds of goats because accidents of this nature during fertilization or during early embryonic development can take place in any breed. However, the prevalence of this category of intersexes is relatively low in goats, but male pseudohermaphrodites are encountered more frequently in lines of dairy goats selected for twinning and multiple births.²

INTERSEXES IN TWINS

Twinning occurs in goats as often as single births, and in selected lines of domestic goats, twins and triplets occur more frequently than singles. Although the birth weight of the kids in twin births is similar to that of single-born normal kids and the incidence of perinatal death is lower in twins compared to that in single births and triplets, the prevalence of intersexes is higher among twins and triplets than in singles.⁶ Caprine intersexes among twins and multiple births generally represent the counterparts of freemartins in cattle. As in cattle, caprine freemartinism is caused by the fusion of fetal membranes in twin gestation and the subsequent vascular anastomosis that allows the passage of cells and hormones from a male fetus to the female fetus. Freemartins can be differentiated from the other types of caprine intersexes from their birth history and chromosome makeup. Sometimes the birth status as a twin may not be recognized if one of the twins died in utero. In these cases, confirmation of freemartinism can be obtained by chromosome analysis of peripheral blood cultures. Caprine freemartins would reveal exclusively female cells in solid tissues and the coexistence of male and female cells in blood, even though the proportion of male cells in hematopoietic tissues may often be very low. The external and internal genitalia of caprine freemartins, as in other male pseudohermaphrodites, vary greatly. However, the masculine features are generally more exaggerated and the gonads are partially descended testes devoid of germ cells.⁶ Unlike the situation with twinning in cattle, vascular anastomosis does not occur in a majority of caprine twin pregnancies, or it occurs later in gestation after the critical period in ovarian differentiation in the female fetus. As a result, freemartinism is encountered at a much lower rate than that of gestation involving heterosexual twins or triplets in goats. Twinning and multiple births occur in horned and polled goats. Because of this, freemartin-type intersexes can be seen in both types of goats, although polled does, which are more prone to produce twins and triplets, are also more likely to produce freemartins. It would appear that the freemartin-type of male pseudohermaphroditism accounts for approximately 6% of all caprine intersexuality whereas the remaining (over 90%) belong to the category of intersexuality associated with the polled trait.⁶