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Acta vet scand. 1996, 37, 1-12. lntersexuality in Pigs: Clinical, Physiological and Practical Considerations

By R.H. F Hunter and T. Greve

Department of Chmcal Studies, Section for , The Royal Vetennary and Agncultural University, Fredenksberg, Denmark

Hunter, R.H.F. and T. Greve: Intersexuality in pigs: Clinical, physiological and practical considerations. Acta vet. scand. 1996, 37, 1-12. - Vetennary surgeons and practical pig farmers need to be aware of a cond1t1on that can have important deleten• ous consequences m a breedmg herd. The ammals m question have sometimes been re• ferred to as hermaphrodites but would more correctly be termed mtersexes Whilst there 1s a complete spectrum of phenotyp1c sexual development w1thm a population of such , ammals, tlte most common form 1s that of a putative with a promment up-turned vulva. Reflection of the vulva! bps reveals a much-enlarged chtons. There may be scro• tal development, m conjunction with an enlarged pemle and preputlal sheath. Coarse half and mc1pient tusk development may further mdicate differing degrees of mascuhn- 1zatton. Surgical explorat10n of mtersex confirms a complete spectrum of gonadal types, ranging from 2 with a proport10n of testicular m one of them (i.e., an ovotest1s) to 2, much-enlarged test1cular-hke structures w1tlt no detectable ovanan tissue. The usually remam w1thm the abdomen, but those w1tlt testicular tissue may descend to an mgumal or even scrotal location. The gemtal tract mvanably com• pnses a b1cornuate uterus, a partially vestigial Fallopian tube, and some development of one or both Wolffian ducts adJotmng an ovotestls or testicular-like structure to form a convoluted ep1d1dym1s. Spermatozoa are never present, either m abdommal or scrotal testicular tissue, nor are there any germ cells w1thm the semimferous tubules, only Ser• toh-hke cells. Due to the spectrum of gonadal types, sexual behaviour ranges from male-type aggres• sivity on tlte one hand to regular oestrous cycles on tlte other, with penods of standmg oestrus dunng which mtromission may be achieved. In animals with functional ovanan tissue in both gonads, foetal development has been observed, at least until days 25-30 of gestation. Almost all mtersex pigs possess XX chromosomes and usually 36 autosomes; only a very small proportion are chlfnaeras or mosaics. Chromosome banding techmques have failed to demonstrate a portion of the translocated onto an X chro• mosome nor has molecular probmg revealed the presence of the sex determmmg gene Sry or other classical Y-related DNA sequences, except m one mstance. Breeding records suggest that the mtersex condition restilts most frequently from the mfluence of an autosomal recessive gene carried by certam boars. Identification of such boars 1s therefore essential, as the mc1dence ofmtersexuahty in their offspnng may reach 4-5% or more. In terms of the pig industry, economic losses may result from: 1. Lack of fert1hty in mtersex ammals. 2. Aggressive behaviour m groups of growmg/fattenmg pigs. 3. Boar taint in the carcase of antmals possessing ovotestes. 4. Propagation of the deletenous condition, either by matmg or more widely by art1f1- c1al mseminatlon.

hermaphrodites; aetiology; chromosomes; constitution; economics.

Acta vet scand vol 37 no I, 1996 2 R.H. F. Hunter & T. Greve

Introduction General reviews dealing with animals Careful examination of twentieth century liter• published in recent years include those of ature in veterinary and science reveals a Breeuwsma (1970) Backstrom & Henricson sporadic but increasing number of publications (1971), Chalmers (1988), Hunter et al. (1988) on pigs of ambivalent sexuality, frequently re• and Hunter (1989, 1995). The present paper is ferred to as hermaphrodites. As should become intended to offer a concise summary of much of clear in the following pages, such animals are the work that should be of interest to veterinary certainly not true hermaphrodites since no such practitioners and to pig producers with some individual produces representative of background in animal science. both . The expression pseudohermaphro• dite has also entered the literature, qualified by the adjective male or female to denote the con• Results and discussion dition of the gonads. Unfortunately, this more de• Intersex Pigs: Clinical Features tailed terminology is also defective, for an ovo• The following remarks are based on a survey of testis is frequently found. Accordingly, the ani• more than 100 intersex pigs of predominantly mals are better termed , and this word Large White X Landrace background examined will be used throughout the following pages. within the same breeding herd, that of the Uni• Putting aside the question of terminology, com• versity of Edinburgh at Easter Howgate, Mid• ment should be offered on the growing body of lothian, Scotland. literature on these unusual, but by no means Intersex pigs may first come to light in groups rare, animals. First, most of the literature is of weaned animals either due to features of their purely descriptive, listing a variety of anatomi• morphology or to their patterns of behaviour cal features of intersex pigs (eg. Hammond, seemingly not according with their supposed 1912, Crew 1924, Baker 1925 & 1928, Bram• phenotypic sex. bell 1929, Johnston et al. 1958, Scofield et al. External morphology. The specific mor• 1969, Krishnamurthy et al. 1971). Second, phological feature that first attracts attention other studies have adopted a more analytical ap• concerns the vulva, whose lips may present an proach, attempting by techmques such as his• unusual upward turn (>80%) and which, during tology and karyotyping to obtain insights into urination, direct the jet of urine in a steep up• the nature of the anomalies (eg. Breeuwsma ward curve. Upon closer examination, and with 1970, Basrur & Kanagawa 1971, Booth & the bps of the vulva reflected, an enlarged clit• Polge 1976, Hunter et al. 1982, Hunter et al. oris can be demonstrated. This sometimes very 1985). More recently, such analytical studies swollen structure is the first clear indication of have moved to a molecular level in a search for masculmization in animals initially regarded as the presence of supposed sex-determing DNA . Other features that become more sequences (eg. Thomsen & Poulsen 1993, Pail• prominent with the approach of puberty may in• houx: et al. 1994). Third, there have been experi• clude incipient tusks (approx 55%), a penile mental studies that have sought to probe the sheath and/or swollen preputial sac, and en• physiological responses of intersex animals largement of scrotal folds (12%). Palpation of with surgical modifications (eg. Hunter et al. such scrotal development may reveal a de• 1985) or by means of endocrine challenges scended . The hair of such animals is fre• (Hunter et al. 1982 & 1985, Cavazos et al. quently coarser than that of a gilt, the skin much 1987, Chalmers et al.1989, Cook et al. 1995). tougher, and an odour characteristic of a boar

Ac'la vet scand vol 37 no I, 1996 Intersexuality in pigs 3 may become prominent at the onset of puberty. niscent ofpyometritis, although sometimes yel• Sexual behaviour. Behavioural features are lowish in colour. diverse, for some intersex animals show pro• Turning to proximal portions of the genital gressive swelling and colouration of the vulval tract, the utero-tubal junction was morphologi• lips for 4 or 5 days followed by a period of cally normal as was the isthmus of each Fallo• standing oestrus (approx 20%). Others, by con• pian tube, although the latter was usually trast, undergo no such vulval changes but rather smaller than expected. However, the ampullary show typical masculine behaviour, not only portion of the Fallopian tubes was always with aggressive displays but also with much poorly developed when adjacent to an ovotestis, "chomping" of the jaws and extensive produc• often being completely vestigial and scarcely tion of a frothy saliva. Tusk development in detectable at the macroscopic level. Extremely such animals is invariably pronounced. Mount• prominent, by contrast, in such cases was exten• ing behaviour is also frequent, accompanied by sive proliferation of the Wolffian duct into a pelvic thrusting. prominent epididymis-like structure. Wolffian Further exploration of such intersex animals is duct development did not extend further than possible during surgery or post mortem. In par• the level of the corresponding utero-tubal junc• ticular, the internal reproductive organs can be tion. The epididymal duct usually showed evi• examined with precision, and portions of tissue dence of fluid distension in its caudal portion. removed and prepared for histological section Whether an epididymis was found unilaterally or hormone assay. Comments will focus first or bilaterally depended on the composition of upon the genital tract and then upon the gonads. the adjoining gonad, some testicular tissue be• Genital tract. In mature ammals, the cervix ing required on a local basis. Similarly, the am• varied considerably m dimensions and also in pulla and fimbriated extremity of a Fallopian patency. In animals with paired ovotestes tube only developed in the presence of func• (21.5%), it was seemingly imperforate, leaving t10nal ovarian tissue. little doubt that intromission would not be pos• Composition of gonads. Three features of sible even if the animal would stand for a boar. the gonads in intersex animals were particularly The uterus was well developed in all mstances striking. First, the range of gonadal types (Table m which there was at least one functional 1), with the left frequently being of different (62%), and presented 2 characteristic cornua composition than the nght hand one (Figs. 1-3). fusing caudally to give a small uterme body. In Second, the large size achieved by gonads of the presence of bilateral ovotestes (21.5% ), the testicular type within an abdominal location. uterus was usually of immature appearance. Third, the location of at least one of a pair of Whilst the uterus was freely arranged in the ab• gonads (almost mvanably the right) m the in• dominal cavity m most animals, there were a guinal canal or situated beyond within a scrotal small number of cases (6) in which at least one sac. of the uterine horns had been drawn into an m• As to gonadal type, there was a complete spec• guinal canal by a descending gonad of mascu• trum rangmg from - most frequently - an ovary line type. Scrotal development was always on the left side and an ovotestis on the right noted in such animals. Although the bicornuate (45.7%) to both gonads being composed oftes• uterus appeared morphologically normal, it was ticular-hke structures (Fig. 4) ofredd1sh-brown frequently distended with fluid which had a appearance (2.8%). When present unilaterally, strong, unpleasant odour. The fluid was remi- an ovary usually showed evidence of some cy-

Acta vet scand vol 37 no l, 1996 4 R.H. F Hunter & T. Greve

Table 1. The d1stnbut1on of gonadal types ma total of 107 arumals descnbed as mtersexes on the basis of the presence of some testicular tissue m pigs karyotyping with XX chromosomes. The results are presented as percentages

I ovary I ovary I ovotestls 2 2 I abdommal and and and ovotestes testes and I ovotestls I testis* I testis* I scrotal gonad

45 7 15.9 7.5 21 5 2.8 6.5

* Testis mdicates testicular-like structure although never contammg germ cells. H1stolog1cal exammat10n reve• aled mterstlt1al cells ofLeydJ.g and Sertoh-hke cells

clic activity, with Graafian follicles of varying Histology of gonads. Histological sections diameter or even fully developed corpora lutea. revealed ovarian tissue of seemingly grossly In the absence of active or regressed luteal tis• normal composition, whether from an intact sue, Graafian follicles did not exceed 4-5 mm ovary or from ovotestis tissue. This was true of in diameter. The ovotestis in such animals both Graafian follicles and, when present, oflu• ranged in proportions from an equal distribu• teal tissue. There was no evidence for luteiniza• tion of ovarian and testicular tissue to greater tion of mtact follicles. But close inspection in• than 90% of testicular tissue. In some instances, dicated degenerative processes in the wall of there was no macroscopic evidence for ovarian Graafian follicles. Whereas granulosa cells re• tissue in the right gonad, and such spherical sembled those of normal control females, the gonads could measure as much as 8 cm m diam• theca intema was frequently poorly developed eter (Fig. 5). However, Graafian follicles within or even absent. In marked contrast to the ovar• an ovotestis seldom exceeded 2-3 mm m diam• ian morphology, the testicular component of an eter and were sometimes haemorrhagic rather ovotestis or of a full testis-like structure was than clear-walled in appearance. more strikingly abnormal. Although there were Testis-like gonads varied in their presence or always prominent interstitial cells of Leydig absence of a tunica albuginea, and this was and semimferous tubules in seemingly conven• seemingly not related to the locat10n of the t10nal proportions (Fig. 7), the content of the gonad. In the presence of a tunica albugmea, semimferous tubules was bizarre. There was no the gonadal surface was usually undulating or central canal or lumen and the occupymg cells lumpy in appearance. In the absence of a tunica, were large, poorly-staining Sertoli-like cells. the gonad tended to have a relatively smooth, There was no evidence of a line. This curved outline. Testis-like gonads had an ex• was a consistent finding in all testicular tissue tremely prominent and extensive vasculature, exammed from intersex animals, irrespective of reminiscent of a pampiniform plexus (Fig. 6). its proportions with respect to neighbouring The blood vessels supplying and draining such ovarian tissues and whether the testis-like struc• gonads were highly coiled and pronounced. ture was abdominal or scrotal. The mesenteries overlying the adjoining epidid• It is now appreciated that spermatozoa cannot ymis also had a prominent vasculature, espe• be produced in animals of XX cially in comparison with those supporting a complement (Fig. 8). It is also evident that contralateral Fallopian tube. whereas the Leydig cells function normally to

Acta vet scand vol 37 no i, 1996 Intersexuality in pigs 5

Figure 1. The of an XX fe• Figure 2. Close - up view m another XX mtersex male mtersex pig as revealed at mid-ventral laparot• pig of a left gonad featunng as a normal ovary and a omy. The left gonad 1s represented by a normal ovary nght gonad as a testis-hke structure. A promment whereas the nght 1s a much enlarged testJs-hke struc• ep1d1dymis adJoms the rete regmn of the testis, with ture with an adJommg ep1d1dym1s. Note the normal its lumpy morphology at one pole b1comuate uterus. However, development of the nght Fallopian tube has been suppressed, especially m its ampullary port10n.

Figure 3. A functional left ovary revealed m con• Figure 4. The b1comuate uterus of an XX mtersex trast to a lumpy testls-hke gonad on the nght, encased pig with both gonads appeanng as testls-hke struc• m a tumca albuginea tures. A tumca albugmea was not detected.

Acta vet scand vol 37 no 1, 19% 6 R.H. E Hunter & T. Greve secrete testosterone, the Sertoli-like cells are spouses m the genital tract (Hunter et al. 1982). deficient either in their synthesis and secretion In a further intersex animal with a small ovary of anti-Mullerian hormone (AMH) or in the on the left and a large ovotestis on the right, timmg of these processes (reviewed in Hunter ovarian tissue in the right gonad failed to re• 1995). spond detectably to a similar dose of PMSG Chromosome constitution. On the basis within one week of treatment. Nor did unilat• of examination of blood leucocytes, all the ani• eral ovariectomy prompt compensatory hyper• mals karyotyped from the Edinburgh herd were trophy by endogenous gonadotrophins in the genetically female with an unambiguous XX ovarian portion of an ovotestis (Hunter et al. compliment of sex chromosomes. There was no 1985). evidence for sex chromosome chimaeras or mo• In both of these experimental models, failure of saics, nor did banding techniques produce any the ovarian tissue to respond to gonadotrophic evidence for a portion of a Y-chromosome stimulation was ascribed to an influence of the translocated onto an X. The standard diploid neighbouring testicular tissue within the ovo• number of38 chromosomes was not revealed in testis. However, there remains the intriguing all spreads, but the presence of only 35 and 36 paradox that Graafian follicles in the ovotestis chromosomes in 2 preparations reflected break• had achieved a diameter of 1-2 mm before com• age of cells on the microscope slide and a con• mencement of experimental manipulation, in• sequent loss of chromosomes from the meta• ferring a sensitivity to gonadotrophic hormones phase plate. at some earlier stage of development. Protein In other reports of intersex pigs, an XX sex secretion from the ovotestis, such as anti-Mul• chromosome constitution has been the predom• lerian hormone (AMH), may have inhibited or inant finding, but there has also been an ex• destroyed receptors for gonadotrophins in the tremely low incidence (<5%) of mosaics or chi• follicular tissue. maeras (eg. see McFeely 1967, Breeuwsma Response to positive feedback. A sec• 1970, Basrur & Kanagawa 1971, Thomsen & ond experiment has been to examme the sensi• Poulsen 1993). tivity of the hypothalamus and anterior pitui• tary gland m terms of the luteinizing hormone Experimental observations in intersex pzgs (LH) response to an oestrad10l challenge in Three kinds of challenge experiment have been intersex pigs possessing ovotestes or testis-like performed to examine the responsiveness of gonads. A mature female would be expected to XX gonads to endogenous or exogenous endo• respond to the positive feedback influence of an crine stimulation. oestradiol challenge with a surge ofLH release, Response to gonadotrophins. The sensi• so this experiment should offer some descrip• tivity of ovarian tissue combined with testicular tion of " sex" in mtersex animals (see tissue withm an ovotestis has been examined in Short 1982). response to a systemic mjection of placental After challenge with an injection of oestradiol gonadotrophin. A single subcutaneous injec• benzoate (Intervet, Cambridge, UK) given tion of 1,000 i.u. PMSG (Folhgon; Intervet) to intramuscularly in oil at 60 µg/kg bodyweight, each of 2 animals with bilateral ovotestes con• the maximum LH concentration in systemic taining Graafian follicles of 1-2 mm diameter blood in 5 intersex pigs possessmg both ovarian failed to stimulate any visible development of and testicular tissue or only testicular tissue was ovanan tissue or charactenstic oestrogenic re- one quarter of that in mature females (2.1 ng/ml

Acta vet scand vol 37 no i, i996 Intersexuality in pigs 7

Figure 5 Abdomrnal gonad and adJommg duct Figure 6 Another XX mtersex ammal with the structure m a female (XX) mtersex pig showmg an gonadal rete region exposed at surgery to reveal the oval testis-like structure with adJommg fully-devel• extensive pampm1form plexus form of vasculature oped ep1d1dym1s. charactenstlc of a mature male

Figure 7. H1stolog1cal preparat10n oftestis-hke tis• Figure 8 Representative section through the ad• sue from an XX female pig showmg the arrangement J01mng ep1d1dymal duct of specimens such as seen m of semm1ferous tubules and mterst1t1al cells of Ley• Figs 5, 6 and 7 to emphasize the complete absence of d1g Although the latter are well-developed, the tu• a sperm suspens10n m these mature XX mtersex an• bules contam only Sertoh-hke cells There 1s no evi• imals dence of a germ cell lme.

Acta vet scand vol 37 no 1, 1996 8 R. HR Hunter & T. Greve versus 8.9 ng/ml plasma). This indicates a mod• proaches has provided a specific explanation ification of brain (masculin1zation) in for the formation of the condition. Even so, the such intersex animals and hence of the gonadot• results of the PMSG and ACTH challenges do rophm response due to the presence of testicu• offer tentative clues. It has already been sug• lar tissue (Chalmers et al. 1989). Even so, be• gested that the failure of Graafian follicles to cause some animals with ovotestes can exhibit respond to PMSG may have been a conse• normal oestrous cycles, it must be concluded quence of protein secretion from the testicular that the LH response modification in the pres• portions of an ovotestis. More specifically, it ence of testicular tissue is primarily quantitative can now be proposed that death of oocytes and rather than qualitative. gradual breakdown and dissolution of vesicular Gonadal response to ACTH challenge. follicles m an ovotestis is due to the influence of A third experiment bears on the proximity dur• AMH from Sertoli-like cells. Testicular tissue ing embryonic development of the gonads to may have arisen in the first place as a result of the adrenal glands and the possibility that a limited colonisation of the embryonic gonad adreno-cortical cells may have colonised the by adreno-cortical cells and a subsequent influ• developing gonad, in due course leading to par• ence from these cells that has masculinized ad• tial masculinization as an ovotestis. The pres• joining tissues (Breeuwsma 1970). ence of adrenal tissue m an ovotestis might be Because intersex animals can be shown to have established by histology, although this would be a genetic predisposition, and can be generated a formidable undertaking in a structure as large at an elevated incidence by certain boars as a pig gonad. An alternative, more elegant ap• (Backstrom & Henricson 1971), it is important proach would be to challenge the gonad with an to consider possible underlying genetic expla• injection of ACTH and then monitor cortisol in nations. The involvement of one or more auto• the gonadal effluent. A standard clinical chal• somal recessive genes has been invoked (Sitt• lenge of synthetic ACTH (Synacthen; Ciba), mann et al. 1980). One model that may still used to monitor human adrenal function, would have validity in this context was proposed in be appropriate in pigs because of comparable 1988 (Fig. 1). In essence, it focuses on the pres• bodyweights. Such a challenge experiment has ence of a deleterious gene (ie. male determining been performed in a series of 6 animals. In sequence) carried on a paternal every instance, there was a response in terms of or generated spontaneously as a mutation, and a elevated cortisol secretion from the mtersex variable timing ofX inactivation involving such gonad, suggesting that adrenal cells must have a DNA sequence to account for the spectrum of been present to enable a response to ACTH gonadal types so imposed (Fig. 9). A necessary (Cavazos et al. 1987, Cook et al. 1995). Whilst presumption also is that development of the 2 such an interpretation accords with dogma, the gonads is asynchronous. Despite the relative studies of Juniewicz & Johnson (1984) need to simplicity and attractiveness of such an expla• be taken into consideration, for they found that nation, the male determining DNA sequence - testicular tissue in normal boars appears to have that is the offending gene - has yet to be identi• ACTH receptors. fied. Molecular techniques are essential here. Aetiology of in"tersexuality. Whilst each In fact, molecular probes have now been ap• of the above experiments in turn sheds a valu• plied to the tissues of XX intersex animals con• able light upon potential physiological re• taining testicular tissue in the hope of revealing sponses in intersex pigs, none of these ap- the putative testis-determining gene, Sry, or the

Acta vet scand vol 37 no l, 1996 lntersexuality in pigs 9

TRANSLOCATION OF THE PRIMARY MALENESS DETERMIN ING FACTOR ON TO THE X- CHROMOSOME OR IN THE BOAR

MUTATION ON THE X- CHROMOSOME +

PATERNALX - CHROMOSOME INACTIV A TION (IN THE EMBRYO)

TIME OF X - CHROMOSOME t LEFT RIGHT INACTIVATION GONAD GONAD

EARLY •OVARY OVOTESTIS

INTERMEDIATE OVARY •TESTIS

LATE

OVOTESTIS TESTIS

Figure 9. The model suggests the manner whereby varymg gonadal const1tut10ns could anse from transloca• tlon of male-determmmg sequences onto an X-chromosome, or by an appropnate mutalion on an X-chromo• some, m the boar followed by mactlvatlon of the paternal X-chromosome at different times m the embryo. A pre• sumption m this model 1s that the nght hand gonad develops at a different rate than the left

Acta vet scand vol 37 no 1, 1996 10 R. HE Hunter & T. Greve

Tab 1 e 2. Summansed molecular observat10ns on mtersex pigs possessmg some testicular tissue Adapted from Thomsen & Poulsen (1993) andPazlhoux et al (1994).

Ongmal descnptton of mtersex arumals 38, xx 38,XX 38, xx Malew1th ''true mtersexes amb1gmttes hermaphrodite"

Ongm of study French French Darush No. of animals 5 6 5 Sry gene present 1 0 Not tested Sry gene absent 4 6 Not tested Zfy gene absent Not tested Not tested 4* DYZ 1 gene absent Not tested Not tested 4

* A fifth animal exhibited a weak male-specific band dunng Southern blot analysis with a human ZFY probe and a male-specific PCR product with DYZ 1 pnmers, suggestive of an XX/XY gonadal chimaera.

associated male determming genes, Zfy and tissue (Vigier et al. 1987). AMH is now appre• DYZ 1. In 2 separate studies, there was minimal ciated to be closely related to the hormone inhi• evidence for such genes (Table 2). In one study bin, both AMH and inhibin bemg members of a at INRA, France, on 38 XX intersex animals, bioactive glycoprotem family and sharing a the Sry gene was present in only 1 of 11 animals common subunit (Matzuk et al. 1992). Inhibm (Pailhoux et al. 1994). In Danish intersex pigs is synthesized by Graafian follicles. In the light examined at the Royal Veterinary and Agricul• of this background information, a current hy• tural University, Copenhagen, no detectable pothesis - yet to be confirmed by molecular male-specific DNA sequences were revealed in techniques - is that a mutation of the inhibm 4 of five 38 XX animals, monitoring both Zfy gene in XX animals prompts AMH activity, and with a human probe and the porcine male-spe• thereby underlies formation of testicular tissue cific DYZl gene (Thomsen & Poulsen 1993). in the embryonic ovaries (Hunter 1995). Vary• The fifth animal revealed a weak male-specific mg amounts of AMH secretion or differing polymerase chain reaction product with DYZl timescales for the transition from inhibin to primers, a situat10n that was interpreted as ten• AMH could explain differmg degrees of testis tative evidence for an XXIXY chimaeric gonad. formation. In the light of this molecular evidence, ovotes• Practical considerations. It might be tis formation in XX animals requrres a primary argued that since a majority of pigs produced in explanation not involving these particular sex• breeding herds will be destined for the meat fat• determining genes. There must be a role for tening trade, the nature and function of their other genes or mutations. gonads are not important. This is by no means One such explanation has recently been pro• true, and it also overlooks the fact that a propor• posed. It concerns the well-known masculiniz• tion of young females will be required as re• mg influence of AMH upon the gonad, this pro• placements for the breeding herd. tein actmg first to cause death of the oocytes Losses associated with intersexuahty anse with, in turn, failure of follicular development from 4 practical considerat10ns. First, the lack and then of the resultant gonadal of fertility in intersex animals due to the com-

Acta vet scand vol 37 no 1, 1996 Intersexuality in pigs 11 position of their gonads. Second, the displays of Cavazos F, Chalmers CA, Cook B, Kelly ASL, Hunter aggressive behaviour m groups of growing or RHF- ACTH affects gonadal steroid synthesis m mtersex pigs Proceedmgs of the Society for the fattening pigs which may mflict physical dam• Study ofFert1hty, 1987, no 46, 30 age and also retard the rate of fattening. Third, Chalmers C PhD. D1ssertat10n, 1988 Umvers1ty of the presence of boar taint in the carcase of ani• Edmburgh. mal possessmg ovotestes, due to the influence Chalmers C, Cook B, Foxcroft GR, Hunter RHF Lu• of circulatmg androgens. And fourth, the prop• tem1zmg hormone response to an oestrad1ol chal• lenge m 5 mtersex pigs possessmg ovotestes agation of the deleterious condition by wide• JReprod.Fert, 1989, 87, 455-461 spread use of from carrier boars. To• Cook B, Hunter RHF, Kelly A Gonadal steroid syn• gether, these negative components make it a thesis responds to an ACTH challenge m mter• priority to specify the precise causes of inter• sexes J Endocnn, 1995 (m press) sexuality m pigs and essential to adopt breedmg Crew FAE Hermaphroditism m the pig Journal of Obstetrics and of the Bnt1sh Com• policies to keep its incidence to a minimum. In monwealth, 1924, 31, 369-386 an industry that may increasingly extend the Hammond J A case ofhermaphrod1t1sm m the pig J. practice of artificial , this last Anat & Phys1ol, 1912, 7, 307-312 point is especially significant. Artificial insem• Hunter RHF, Baker TG, Cook B Morphology, histol• ogy and steroid hormones of the gonads m mter• ination is a powerful means of disseminating sex pigs. J. Reprod Fertility, 1982, 64, 217-222 beneficial genes. Unfortunately, its influence is Hunter RHF, Cook B, Baker TG Intersexuahty m equally powerful with deleterious genes. five pigs, with particular reference to oestrous cycles, the ovotestts, steroid hormone secret10n and potential fertility Journal of Endocnnology, Acknowledgements 1985, 106, 233-242. Gratitude 1s expressed to colleagues who assisted m Hunter RHF, Chalmers C, Cavazos F Intersexuahty the ongmal expenments m Edmburgh T. G Baker, m domestic pigs A gmde to mechamsms of gon• F Cavazos, C A. Chalmers, B Cook and R Nichol adal d1fferent1at10n? Amm Breed Abstr, 1988, Amtta Luplau J0rgensen kmdly prepared the type• 56, 785-791 scnpt Hunter RHF Vmtersexuahte chez le pore. une emgme b1olog1que en VOie de resolution References Med.Vet Quebec, 1989, 19, 125-135. Baker JR On sex-mtergrade pigs thelf anatomy, ge• Hunter RHF Sex determmatlon, differentiation and netics, and development phys10logy Journal of mtersexuality m placental , 1995. Cam• Expenmental Biology, 1925, 2, 247-263 bndge Umvers1ty Press, UK Baker JR A new type of mammalian mtersexuality Johnston EF, Zeller JH, Cantwell G Sex anomalies Journal ofExpenmental Biology, 1928, 6, 56-64 m swme J Heredity, 1958, 49, 255-261 Basrur PK, Kanagawa H Sex anomalies m pigs Junzew1cz PE, Johnson BH Ab1hty of cortisol and JReprod Fert, 1971, 26, 369-371 progesterone to mediate the stimulatory effect of Booth WD, Paige C The occurrence of Ci9 steroids ACTH upon testosterone production by the por• m testicular tissue and submax1llary glands of cme testis B10logy of Reproduct10n, 1984, 30, mtersex pigs m relat10n to morphological charac• 134-142 tensttcs J ReprodFert., 1976, 46, 115-121 Krishnamurthy S, Macpherson JW, Kzng GJ Inter• Brambell FWR The histology of a hermaphrodite sexuahty m Ontano swme. Canad. J.An1m.Sc1 , pig and its developmental s1gmf1cance Journal 1971, 51, 807-809 of Anatomy, 1929, 63, 397-407 Matzuk MM, Fznegold MT, Su JGJ, Hsueh AJW, Breeuwsma AJ· Studies on mtersexuality m pigs. Bradley A a-mh1bm 1s a tumour suppressor gene Doctoral Thesis, 1970 DrukkenJ Bronder-Offset with gonadal spec1f1c1ty m mice. Nature (Lon• N V Rotterdam don), 1992, 360, 313-319 Backstrom L, Henncson B Intersexuahty m the pig. McFeely RA Chromosome abnormahttes m early em• Acta vet scand, 1971, 12, 257-273 bryos of the pig J.Reprod Fert, 1967, 13, 579-581

Acta vet scand vol 37 no i, i996 12 R.H. F Hunter & T Greve

Paz/how: E, Popescu PC, Parma P, Boscher J, Legault ti! 2 store test!kelhgnende strukturer uden ovanev

(Received June 8, 1995, accepted September 14, 1995)

Repnnts may be obtamed from· T. Greve, Department of Chmcal Studies, Reproduction, The Royal Vetermary and Agncultural Umvers1ty, BiilowsveJ 13, DK-1870 Fredenksberg C, Denmark

Acta vet scand vol 37 no 1, 1996