The urethral process is absent in cervids and the urethra, which runs along the ventral surface of the penis throughout its length, curves dorsally at its extremity. This permits the ejection of urine and a few sperm in an upward direction, which is important during the ‘thrash-urination’ activity indulged in by rutting wapiti and red deer males as they spray upwards almost at right angles on to their ventral abdomens, neck and throat (Haigh, 2007). In these species, the prepuce also has well-developed muscles that are responsible for the remarkable rapid forward and backward movement, often called palpitation, of this region seen during the rut. This behaviour, and the degree of development of these muscles, has not been reported in any other genus (Haigh, 2007).

Rams and bucks have a full complement of accessory sex glands, of which the seminal vesicles are the largest and lie on each side of the caudal part of the dorsal surface of the bladder. The disseminated prostate completely surrounds the wall of the pelvic urethra in small ruminants, whereas in red deer and wapiti, it is a discrete, bilobed body lying anterior to and continuous with the disseminate prostate. The epithelium of the body of the prostate undergoes marked changes according to the season, but few or no changes are seen in the epithelial architecture of the disseminate part. The paired bulbourethral glands are found lying on the dorsal surface of the urethra opposite the ischial arch and are covered by a thick layer of dense connective tissue and by the proximal part of the thick bulbospongiosus muscle (Haigh, 2007).

Abnormal development

Several disorders of sexual development have been studied in depth and documented for domestic small ruminants, but very little information is available for the cervid species. The nature of these disorders is usually complex, involving several factors, and is generally discussed in association with: (i) abnormalities of chromosomal sex, which include syndromes related to sex chromosome monosomy, trisomy, mosaicism, chimerism and translocation; (ii) abnormalities of gonadal sex, which include XX and XY sex reversal syndromes and true hermaphrodites; and (iii) abnormalities of phenotypic sex, which include true hermaphrodites, female and male psuedohermaphrodites, and cryptorchidism (Mastromonaco et al., 2011).

Intersexuality

Intersex animals, which include true and pseudohermaphrodites, may exhibit decreased reproductive efficiency owing to altered sexual behaviour, ambiguous external genitalia and decreased production of viable gametes (Ladds, 1993).

Intersexuality has been well documented in goats, with an association shown between the natural absence of horns and the intersex condition. An increased prevalence is seen in polled dairy breeds (i.e. those lacking in horns) such as the Saanen, Toggenburg, Alpine and Damascus (Basrur and Kochhar, 2007), while the condition is rare or not reported for breeds such as the Nubian and Angora, as it is likely that these breeds have a different mode of horn inheritance (Crepin, 1958). Hermaphroditism and horned traits in goats are controlled by recessive genes, and these two loci are close to each other on the same chromosome (i.e. they are linked) (Mickelsen and Memon, 2007). The polled condition is a result of mutation at the horn locus. The polled trait (P) is dominant to the horned trait (p) and appears together with hermaphroditism (h) in PPhh or Pphh goats because the two loci are linked (Asdell, 1944). Intersexes are thus seen mainly among polled animals and rarely among horned (pp) animals, where they can occur because of occasional crossing over between the two loci. Most polled caprine intersexes are genetically female (XX), as demonstrated by karyotyping, and the breeding history usually indicates that they are homozygous for the polled trait.

Intersexuality is rare in sheep and is caused by whole-body chimeras due to freemartinism. Unlike the situation in cattle, where the incidence of freemartins in female heterosexual twins is close to 90% (Ruvinsky and Spicer, 1999), in sheep only 1% of heterosexual twins are diagnosed as intersex (Smith et al., 1998). Sheep diagnosed with intersex may show an XX/XY karyotype, which may be the result of mosaicism due to failure of cell division of the zygote, or chimerism. The latter may occur when a polar body is accidentally fertilized by a Y chromosome spermatozoon and the corresponding oocyte is fertilized by an X spermatozoon, with the occurrence of a mixture of genetic material of two diploid cells resulting in an individual with two cell populations (Cribiu and Chaffaux, 1990). Intersexuality in sheep results in masculinization of the reproductive tract (Wilkies et al., 1978) and associated abnormalities. These could range from a complete absence of a cervix and bilateral presence of female and male gonads (ovary and testis), to variable degrees of development of the epididymis accompanied by marked agenesis of the deferent ducts and other structures arising from the mesonephric ducts. Extreme cases may sometimes be accompanied by the presence of a pseudoprepuce and hypertrophy of the clitoris.

Reports of sexual abnormalities in wild ruminants are still scarce (Bunch et al., 1991), although a recent report of a case of true hermaphroditism has been described for an Iberian roe deer (Pajares et al., 2009). The animal showed ovarian-like structures with follicles on the surface and the presence of testosterone-producing testes on necropsy. Based on lack of evidence for SRY sequences and the PIS deletion, this roe deer was diagnosed as possessing the SRY-negative XX hermaphroditism syndrome. Similar cases have been documented for captive bred redfronted gazelles (Gazella rufifrons laevipes) at the San Diego Zoo in California, where three animals were evaluated for presence of abnormal genitalia (Mastromonaco et al., 2011). One of the gazelles assessed to be a female showed the presence of a vagina, immature uterus and ovaries, and a lack of testicular tissue, but had a male karyotype (58,XY). It was hypothesized that this animal may have lacked the essential genes for promoting male sex determination, which could be due to a mutation or deletion in the SRY or a related gene, such as SRY-box 9 (SOX-9). These genes have been demonstrated to play a role in case of sex reversal in domestic species. The other two gazelles were diagnosed as a true hermaphrodite and a male psuedohermaphrodite based on their phenotypic ambiguities.

Unlike polled female intersexes, polled male bucks do not generally show any obvious malformation of the external genitalia and undergo normal growth and sexual maturation. However, because of defects in their gonadal ductal system, these animals often suffer from a stenosis of the epididymis (Hamerton et al., 1969). This results in the retention of spermatozoa in large masses in the lumen of the duct. Sometimes, there is a rupture of the seminiferous tubules close to the rete testes, leading to extravasation of sperm in the interstitium, which, in turn, leads to an inflammatory granulomatous reaction often described as a sperm granuloma. This type of epididymal stenosis leading to sterility is detected in less than 30% of polled bucks resulting from polled-to-polled matings, but it is believed that the afflicted bucks are homozygotes for the polled gene (Basrur and Kochhar, 2007).

Thus, homozygosity for the polled mutation (PIS deletion) appears to be disadvantageous to both sexes as in the male it causes poor differentiation of the androgendependent duct system and leads to sterility, and in the female it allows the expression of genes in the testicular differentiation pathway leading to the masculinization of the gonad, gonaduct and external genitalia. The mechanism leading to the interruption of Wolffian duct differentiation in XYPP animals is not yet understood.

Cryptorchidism

Cryptorchidism may be defined as the failure of one or both testes to descend into the scrotum at the appropriate time for the species of interest, and is considered to be one of the most frequent abnormalities of male sex differentiation (Thonneau et al., 2003). The retained testicle is located anywhere along the normal path of descent, or is diverted to an ectopic location. Unilateral cryptorchidism may or may not adversely affect semen quality, whereas bilateral cryptorchidism results in sterility. Among unilateral cryptorchids, the right testis is retained in the abdomen in about 90% of the animals (Ott and Memon, 1980). Cryptorchidism in goats is usually associated with the intersex condition, except in the case of Angora bucks, where it may also be related to a recessive trait (Skinner et al., 1961). Persistent Müllerian Duct syndrome (PMDS), which is a condition distinct from cryptorchidism, is also known to cause bilateral cryptorchidism. Affected animals are karyotypically male with a well-developed penis and are sterile. Failure of the Müllerian duct to regress in PMDS males is attributed either to arrested or delayed function of the fetal Sertoli cells, which normally produce the high molecular weight glycoprotein dimer, Anti-Müllerian hormone (AMH), during the differentiation of the embryonic ducts. Müllerian duct regression could also be impeded by the absence of receptors for binding this hormone on the embryonic paramesonephric derivatives (Basrur and Kochhar, 2007). This anomaly in goats is inherited probably as an autosomal recessive trait and is most often not recognized as such because it is mistaken for the intersex condition (Haibel and Roijko, 1990).

Cryptorchidism in rams is chiefly attributable to recessive genetic factors and usually occurs bilaterally (Wendt et al., 1960). A recent study (Williams et al., 2007) has provided evidence that this defect in sheep could be associated with the insulin-like hormone 3 (INSL3) gene, which is involved in testicular descent and development of external genitalia. Owing to the heritable nature of this condition, it is highly desirable to cull affected animals from the flock.

Hypospadias

Hypospadias is an abnormality of the external genitalia in the male that is characterized by a congenital defect of the urethra, which fails to fuse along its entire length, so that it opens at some point along the ventral aspect of the penis or in the perineum. This condition is most commonly seen in humans and has also been reported in various species of domestic animals. The aetiology of hypospadias is not well understood; it seems to be multifactorial and may be related to genetic, endocrinological and environmental factors (Silver, 2000). Familial clustering of hypospadias among first-degree relatives, as well as twin studies and segregation analysis, have supported a strong heritable component in this disorder in humans (Fredell et al., 2002).

In goats, hypospadias is usually associated with the intersex condition and affected animals should be culled. In an Iranian study, 24 cases of caprine hypospadias from eight different flocks were evaluated (Sakhaee and Azari, 2009) within a span of 7 months. All affected animals were confirmed to be males based on external phenotypic characteristics, with no true or pseudohermaphroditism detected. However, no karyotyping was performed on these animals. Penile and testicular hypoplasia was detected in all cases, with one animal even showing the presence of an ectopic penis located between the anus and scrotum. The external urethral opening was usually located along the ventral aspect of the penile shaft, except for one case in which it was seen in the scrotal region. Hypospadias in goats may be asymptomatic, and careful examination of the exteriorized penile shaft is often necessary to diagnose the condition. Depending on the location of the defect, some animals may show signs of urine scalding and leakage in the subcutaneous tissue.

In rams, hypospadias is a relatively rare condition, and occurs in animals with a genetic predisposition, as seen in certain breeds such as the Merino (Dennis, 1979). A large abattoir survey in the UK gave a reported incidence rate of 0.23% (Smith et al., 2006). Hypospadias in sheep may or may not be accompanied by other abnormalities of the reproductive tract, such as a divided scrotum or a shortened penis with absence of a sigmoid flexure. In some cases, the urethral process is found to be absent or tightly adhered to the galea. As in goats, the presence and severity of clinical signs depends on the location of the external urethral opening, with severe ulceration of the scrotum seen especially in rams that have a periscrotal opening.

Puberty

In goats, photoperiod does not seem to influence testicular growth and spermatogenesis significantly as bucks can attain puberty during long or short day lengths. Instead, age, body weight and nutrition seem to play important roles. The average age of puberty in bucks often depends on the breed of the animal, with the pygmy breeds achieving puberty earlier (at 2 to 3 months) than Nubian or Boer bucks (4 to 5 months) (Edmondson et al., 2012), whereas Damascus bucks achieve puberty by the age of 24 to 48 months (Epstein and Herz, 1964). Boer goat kids have been found to be capable of spermatogenesis when they are just 84 days old, with sperm found in the epididymis at 140 days of age (Skinner, 1970). In the northern hemisphere, most goat breeds usually attain puberty by the age of 4 to 5 months; natural adhesions between the prepuce and the penis, which preclude the buck from successful mating before puberty, start separating under the influence of testosterone a month earlier (Plate 13). By the age of 4 to 5 months, it is advisable to start keeping the male and female kids separately, as buck kids will start displaying libido and fertile mating may be possible, although bucks belonging to the Nubian or Boer goat breeds do not produce good quality semen until they are approximately 8 months old.

The average age for achieving puberty in rams is around 6 months, depending on the breed of the animal and season of birth. Puberty in rams, unlike that in goats, is greatly influenced by the season of birth, with ram lambs born in the spring and receiving adequate nutrition achieving puberty at 5 to 6 months in the subsequent autumn. In contrast, autumn-born lambs do not achieve puberty until they are about 10 to 12 months old as the long days of the subsequent spring and summer delay its onset. Similarly, rams exposed periodically to cycling ewes also tend to reach puberty faster and display an earlier onset of mating activity than non-exposed rams. Spring-born rams from temperate climates show a gradual increase in testicular size that parallels changes in growth rate, with a more rapid phase of testicular growth occurring in the autumn. Changes in gonadotrophinreleasing hormone (GnRH)-induced LH secretion drive the final maturation of the testes, including the stimulation of testosterone secretion (Fitzgerald and Morgan, 2007). Reproductive efficiency in sheep is improved by various methods, such as selection, the introduction of new sires and crossbreeding. Thus, breeds such as the Romanov, which are characterized by early sexual maturity (3 months old), high prolificacy and out-of-season breeding ability, can be crossed with late-maturing breeds such as the Awassi, which does not achieve puberty until 8 to 9 months old. In rams, body weight rather than chronological age is the more important factor regulating onset of puberty. Hence, optimal post-weaning nutrition management has a strong influence on lamb weight gain, which, in turn, is related to testicular growth and puberty (Mukasa-Mugerwa and Ezaz, 1992). Nutritionally induced fetal growth restriction also has a significant impact on the onset of sexual maturation (Da Silva et al., 2001). High maternal nutritional intakes throughout gestation in adolescent pregnant sheep, resulting in rapid maternal growth rates and significant reductions in both placental and fetal mass at term, can cause a significant delay in the time of onset of puberty in male lambs.

Breeding Soundness Evaluation

Breeding soundness evaluation (BSE) of the ram or buck is an overall clinical assessment of the capacity to impregnate a certain number of healthy females (a common standard is 50 females for a mature ram/buck) during a defined breeding season, usually the fall (autumn) in North America. Most importantly, BSE provides criteria for the identification and culling of potential sub-fertile/infertile males, as they could account for major genetic changes in a flock. A positive correlation has been found between use of a male proven satisfactory on a BSE and both the increased percentage of pregnant females and the size of the offspring crop at the end of the breeding season. The use of proven rams has also resulted in more lambs being born early in the lambing season, which, indirectly, results in heavier lamb weights at weaning. Identifying satisfactory breeders also helps to rule out this parameter as a potential cause of infertility in the herd or flock. Besides confirming a suspected case of male infertility, the result of the examination may allow the owner to receive compensation or a replacement animal from the seller if the ram or buck is insured. A complete BSE includes the evaluation of anatomical and structural correctness, testing for freedom from disease, optimal body condition score, examination of external and internal genitalia, and semen collection and evaluation. Ideally, a BSE should be performed at least 30 to 60 days before a breeding season, thereby allowing time to recheck or replace sub-fertile rams and bucks.

The traditional BSE performed in rams and bucks is usually not performed in farmed male cervids because of the obvious difficulty of handling and examining the conscious male, especially in the rutting season. However, male cervids can be restrained in a crush or squeeze chute or tranquillized/anaesthetized for the purpose of semen collection and evaluation.

Physical examination

The ram/buck should be free of known genetic or possibly hereditary defects such as hernias, jaw malformations or supernumerary teats. Bucks especially should not be phenotypically polled because of the association of this trait with the intersex condition. The presence of extra teats apparently has no relationship to the fertility of the buck, but if the trait is passed on to the next generation, the buck’s female offspring may be less suitable for milking (Schönherr, 1956). Teeth, eyes, feet and joints should be in good condition so that the ram/buck can continue to eat well and can follow and mount the ewe/doe in oestrus. Males with severe structural defects, such as post-leggedness, tend to exert more pressure on their pasterns, resulting in abnormal growth of hooves. Such animals require more frequent trimming of their feet. Similarly, arthritic conditions, foot rot, foot abscesses and overgrown hoofs may severely impair the ram or buck from satisfactorily performing as per expectations. Structural and physical conditions that cannot be corrected should warrant culling of the animal to prevent future economic losses.

In addition to the physical examination, it is important to consider an animal’s breeding history and review records of the past breeding performance, such as length of lambing or kidding period. A thorough medical history, with emphasis on recently treated disease conditions; especially fever, may raise testicular temperature and render the male temporarily infertile for up to 60 days. Lastly the optimal age of the animal should be considered: the optimal breeding age is over 6 months and up to 4 years old.

Disease testing

Ovine epididymitis caused by Brucella ovis is an important cause of orchitis and infertility in rams. Similar symptoms have been reported in the male red deer in New Zealand. B. ovis is occasionally associated with abortion in ewes, and can cause increased perinatal mortality in lambs. Experimental infections have been reported in goats and cattle, but there is no evidence that these species are infected in nature. B. ovis is often transmitted via homosexual activities, or via the ewe during the breeding season. Rams often become persistently infected, and many of these animals shed B. ovis intermittently in the semen for 2 to 4 years or longer. Direct non-venereal ram-to-ram transmission is poorly understood and may occur by a variety of routes, including oral transmission. Shedding has been demonstrated in the urine as well as in semen and genital secretions. The demonstration of the existence of genital lesions (unilateral, or, occasionally, bilateral epididymitis) by palpating the testicles of rams may be indicative of the presence of this infection in a given flock. However, this clinical diagnosis is not sensitive enough because only about 50% of rams infected with B. ovis present with epididymitis. Moreover, the clinical diagnosis is extremely non-specific due to the existence of many other bacteria causing clinical epididymitis. The most frequently reported isolates causing epididymitis in rams include Actinobacillus seminis, A. actinomycetemcomitans, Histophilus ovis, Haemophilus spp., Corynebacterium pseudo-tuberculosis ovis, B. melitensis and Chlamydophila abortus (formerly Chlamydia psittaci). It must be emphasized that many palpable epididymal lesions in rams are sterile, trauma-induced spermatic granulomas (OIE, 2013).

Direct diagnosis of B. ovis infection is made by means of bacteriological staining (Stamp’s method) or isolation of B. ovis from semen samples or tissues of rams, or vaginal discharge and milk of ewes, on adequate selective media (modified Thayer–Martin’s medium). Molecular biological methods have been developed that could be used for complementary identification based on specific genomic sequences. PCR methods provide additional means of detection. Rams that test positive should be immediately culled. As B. ovis has the potential of being in a latent stage and not showing a positive test in a multi-sire flock, the entire group of rams should also be retested at the end of the breeding season/at shearing, once again culling all positive rams.

Examining the scrotum and measuring its circumference

Scrotal examination includes palpation of the scrotum and its contents as well as assessment of testicular size by measuring the scrotal circumference. The testes and the epididymides should be examined by visual assessment and palpation for tone and symmetry. Testicular tone may be scored quantitatively in bulls and rams as softness or flabbiness may indicate testicular dysfunction or degeneration. Likewise, irregular contours, lumps or an excessively hard texture may be due to testicular fibrosis or calcification secondary to degeneration and inflammation (Plate 14). As additional procedures for evaluation of the scrotal contents, thermography and testicular ultrasonography are fast gaining popularity, even under field conditions. The caput (head), corpus (body) and cauda (tail) can easily be palpated in the ram and buck. The examination of the cauda epididymis in rams is particularly important in view of the infectious causes of epididymitis in this particular species. The scrotal neck and the spermatic cord should be palpated for presence of vasectomy scars as well as for signs of scrotal hernia. Lastly the scrotal skin should be examined for signs of dermatitis, mange and trauma.

Scrotal circumference, testicular volume and daily sperm output are highly correlated with each other. Measuring the scrotal circumference is an integral part of BSE in bulls and The Society for Theriogenology has developed scoring methods for evaluating the bull and ram. Although scrotal circumference or testicular diameter charts are lacking for most breeds of goats, it is reasonable to assume that, as for bulls and rams, the male with the larger testicular size at a given age is likely to produce more sperm. There is a positive correlation between scrotal circumference and body weight in bucks.

The artificial vagina

The artificial vagina (AV) is the method of choice for collecting semen in small ruminants because it gives the most reliable and representative semen sample for laboratory evaluation. At the same time, it also requires adequate training of the males and the presence of an oestrous female for optimal stimulation. During the breeding season, most bucks will be willing to mount any restrained female. It may be beneficial to induce oestrus in cycling does or ewes with 5 mg of prostaglandin F2 alpha, or to treat them with oestrogen (1 mg oestradiol administered 1–2 days previously) (Memon et al.