A pregnant mouse model for bovine Tritrichomonas foetus infection.

The economically important effects of Tritrichomonas foetus infection in cattle are abortion and infertility, yet there has not been an animal model to examine the parasite-host interactions during gestation. In this study, 5- and 7- to 8-week-old BALB/cAnNCr, BALB/cJ, and SCID/NCr mice on a BALB/c background were intravaginally infected with T. foetus. All BALB/cAnNCr and BALB/cJ mice, and 89% of SCID/NCr mice sustained infections for 13 weeks, if inoculated before 5 weeks of age. Infection rates were lower in all mouse strains inoculated at 7 weeks of age, although BALB/cAnNCr mice were significantly more susceptible than BALB/cJ or SCID/NCr mice. Vaginal bacterial flora did not account for the variation in mouse-strain susceptibility, although coagulase-negative staphylococci in vaginal flora were associated with failure of T. foetus to infect. As with infected cattle, T. foetus-specific vaginal immunoglobulin (Ig) G and IgA antibodies were elevated after infection. The number and viability of day-10 fetuses were reduced in mice infected at 5 weeks of age and bred 12 weeks after infection. Lesions in pregnant and nonpregnant infected mice, including suppurative and eosinophilic vaginitis; cervicitis; endometritis with distension of the uterine lumen; endometrial ulceration; and glandular ectasia, with neutrophils in the glandular lumen and loss of gland epithelium, were similar to those in cattle. The decidua and placenta were multifocally necrotic. Immunohistochemistry demonstrated trichomonads in vaginal folds and uterine glands, and adjacent to fetal tissues. In summary, experimentally infected BALB/cAnNCr mice showed many pathologic similarities to cattle and may serve as a model to study host-trichomonad interactions.

Comparative histopathology and antibody responses of non-Tritrichomonas foetus trichomonad and Tritrichomonas foetus genital infections in virgin heifers.

The potential pathogenicity of non-Tritrichomonas foetus trichomonads (NTfTs) recently isolated from the prepuce of virgin bulls is not known. The purpose of this study was to determine the ability of these NTfTs to cause disease in the female reproductive tract relative to T. foetus. Forty-four virgin heifers were experimentally infected intravaginally with either one of two NTfTs (Pentatrichomonas hominis or Tetratrichomonas spp.), T. foetus, or sterile media and cultured weekly from 0 time until slaughter at 8 weeks. Serum and vaginal antibody responses during infection were assessed, and the reproductive tracts were histologically examined, scored, and compared based on numbers of neutrophils, eosinophils, lymphocytes, and plasma cells as well as the qualitative appearance of the reproductive tract. The NTfTs did not persist in the reproductive tract, while T. foetus persisted for at least 6-8 weeks. Further, no vaginal IgA response to infection was found in NTfT-infected and control heifers, but a vaginal IgA response was present in the T. foetus-infected group. Heifers infected with NTfT or controls showed little mucosal inflammatory response compared to T. foetus-infected heifers. Among the trichomonads studied, persistent infection by T. foetus alone seems responsible for uterine inflammatory lesions usually associated with pregnancy loss. The NTfTs studied in this work only transiently infected the vagina and were associated with strictly mild inflammatory changes, which probably do not cause significant disease, i.e., pregnancy loss.

Sensitivity and specificity of culture and PCR of smegma samples of bulls experimentally infected with Tritrichomonas foetus.

The sensitivity (Se) and specificity (Sp) of different testing schemes were estimated for detecting Tritrichomonas foetus (T. foetus) in smegma samples from experimentally infected bulls. Culture and polymerase chain reaction (PCR) on smegma samples were evaluated alone and in parallel testing. Mature dairy bulls (n=79) were intrapreputially inoculated with T. foetus (n=19); Campylobacter (C.) fetus venerealis (n=13); both T. foetus and C. fetus venerealis (n=11); Tetratrichomonas spp. (n=9); C. fetus fetus (n=8); or were not inoculated (n=19). For each bull, smegma samples were collected for 6 week post-inoculation and tested for T. foetus by In Pouch TF culture and PCR. Most T. foetus-inoculated bulls became infected, according to culture (86.7%), PCR (90.0%), and both tests together (93.3%). In T. foetus-inoculated bulls, both tests combined in parallel on a single sample had a Se (78.3%) and Sp (98.5%) similar to two cultures (Se 76.0%, Sp 98.5%) or two PCR (Se 78.0%, Sp 96.7%) sampled on consecutive weeks. The PCR on three consecutive weekly samples (Se 85.0%, Sp 95.4%) and both tests applied in parallel on three consecutive weekly samples (Se 87.5%, Sp 95.6%) were similar to the current gold-standard of six weekly cultures (Se 86.7% and Sp 97.5%). Both tests used in parallel six times had the highest Se (93.3%), with similar Sp (92.5%). Tetratrichomonas spp. were only sporadically detected by culture or PCR. In conclusion, we have proposed alternative strategies for T. foetus diagnostics (for the AI industry), including a combination of tests and repeat testing strategies that may reduce time and cost for bull surveillance.

Selected diseases and conditions associated with bovine conceptus loss in the first trimester.

The outcomes of insults to the bovine conceptus depend on the predilection of the insulting agent for the gravid reproductive tract, the virulence of the insult, and the developmental maturity/immune competence of the conceptus at the time of the insult. Agents that are lethal at one time during gestation may be harmless at another, or may have completely different effects (some not so harmless) at different gestational ages. This review discusses some of the known physical-mechanical, physiological, and infectious causes of first trimester bovine conceptus losses, including three infectious agents that have been the subject of recent studies for their potential to transmit disease via embryo transfer.

Importation of in vitro-produced Bubalus bubalis embryos from Italy into the United States: a case report.

On December 19, 2005, 14 in vitro-fertilized water buffalo (Bubalus bubalis) embryos, which had been cryopreserved by vitrification, were thawed and transferred into B. bubalis recipients in California. The embryos had been produced in Italy, following transvaginal oocyte pickup (TVOPU), with subsequent in vitro maturation, insemination, and culture. This case study relates our experience in meeting the regulatory criteria, established by the Animal Import/Export Office of the USDA-Animal and Plant Health Inspection Service (USDA-APHIS), in order to successfully import these embryos into the USA.

Production and processing of milk from transgenic goats expressing human lysozyme in the mammary gland.

The potential for applying biotechnology to benefit animal agriculture and food production has long been speculated. The addition of human milk components with intrinsic antimicrobial activity and positive charge to livestock milk by genetic engineering has the potential to benefit animal health, as well as food safety and production. We generated one line of transgenic goats as a model for the dairy cow designed to express human lysozyme in the mammary gland. Here we report the characterization of the milk from 5 transgenic females of this line expressing human lysozyme in their milk at 270 microg/mL or 68% of the level found in human milk. Milk from transgenic animals had a lower somatic cell count, but the overall component composition of the milk and milk production were not different from controls. Milk from transgenic animals had a shorter rennet clotting time and increased curd strength. Milk of such nature may be of benefit to the producer by influencing udder health and milk processing.

Uterine mast cells and immunoglobulin-E antibody responses during clearance of Tritrichomonas foetus.

We showed earlier that Tritrichomonas foetus-specific bovine immunoglobulin (Ig)G1 and IgA antibodies in uterine and vaginal secretions are correlated with clearance of this sexually transmitted infection. Eosinophils have been noted in previous studies of bovine trichomoniasis but the role of mast cells and IgE responses have not been reported. The hypothesis that IgE and mast cell degranulation play a role in clearance was tested in 25 virgin heifers inseminated experimentally and infected intravaginally with T. foetus strain D1 at estrus and cultured weekly. Groups were euthanatized at 3, 6, 9, or 12 weeks, when tissues were fixed and secretions were collected for culture and antibody analysis. Immunohistochemistry using a monoclonal antibody to a soluble lipophosphoglycan (LPG)-containing surface antigen (TF1.17) demonstrated antigen uptake by uterine epithelial cells. Lymphoid nodules were detected below antigen-positive epithelium. Little IgG2 antibody was detected but IgG1, IgA, IgM, and IgE T. foetus-specific antibodies increased in uterine secretions at weeks 6 and 9 after infection. This was inversely proportional to subepithelial mast cells numbers and most animals cleared the infection by the sampling time after the lowest mast cell count. Furthermore, soluble antigen was found in uterine epithelium above inductive sites (lymphoid nodules). Cross-linking of IgE on mast cells by antigen and perhaps LPG triggering appears to have resulted in degranulation. Released cytokines may account for production of predominantly Th2 (IgG1 and IgE) and IgA antibody responses, which are related to clearance of the infection.

An improved molecular assay for Tritrichomonas foetus.

Tritrichomonas foetus (T. foetus) is the causative agent of bovine trichomonosis, a sexually transmitted disease leading to abortion (from 1 to 8 months gestation), infertility, and occasional pyometra. The annual losses to the U.S. beef industry are estimated to be in the hundreds of millions of dollars. Currently, the "gold standard" diagnostic test for trichomonosis in most countries is the cultivation of live organisms from reproductive secretions. The cultured organisms can then be followed by PCR assays with primers that amplify T. foetus to the exclusion of all other trichomonad species. Thus, negative results present as null data, indistinguishable from failed PCR amplification during T. foetus specific amplification. Our newly developed assay improves previously developed PCR based techniques by using diagnostic size variants from within the internal transcribed spacer 1 (ITS1) region that is between the 18S rRNA and 5.8S rRNA subunits. This new PCR assay amplifies trichomonad DNA from a variety of genera and positively identifies the causative agent in the bovine trichomonad infection. This approach eliminates false negatives found in some current assays as well as identifying the causative agent of trichomonad infection. Additionally, our assay incorporates a fluorescently labeled primer enabling high sensitivity and rapid assessment of the specific trichomonad species. Moreover, electrophoretic separation of amplified samples can be outsourced, thus eliminating the need for diagnostic laboratories to purchase expensive analysis equipment.

Hot topic: using a stearoyl-CoA desaturase transgene to alter milk fatty acid composition.

Stearoyl-CoA desaturase enzyme converts specific medium- and long-chain saturated fatty acids to their monounsaturated form. Transgenic goats expressing a bovine beta-lactoglobulin promoter-rat stearoyl-CoA desaturase cDNA construct in mammary gland epithelial cells were produced by pronuclear microinjection. The fatty acid composition of milk from 4 female transgenic founders was analyzed on d 7, 14, and 30 of their first lactation. In 2 animals, the expression of the transgene changed the overall fatty acid composition of the resulting milk fat to a less saturated and more monounsaturated fatty acid profile at d 7 of lactation; however, this effect diminished by d 30. In addition, one animal had an increased proportion of the rumen-derived monounsaturated fatty acid C18:1 trans11 converted by stearoyl-CoA desaturase to the conjugated linoleic acid isomer C18:2 cis9 trans11. Milk that has higher proportions of monounsaturated fatty acids and conjugated linoleic acid may have benefits for human cardiovascular health.

Comparison of the 5.8S rRNA gene and internal transcribed spacer regions of trichomonadid protozoa recovered from the bovine preputial cavity.

Sequence analysis of the 5.8S rRNA gene and the internal transcribed spacer regions (ITSRs) was used to compare trichomonadid protozoa (n = 39) of varying morphologies isolated from the bovine preputial cavity. A multiple sequence alignment was performed with bovine isolate sequences and other trichomonadid protozoa sequences available in GenBank. As a group, Tritrichomonasfoetus isolates (n = 7) had nearly complete homology. A similarity matrix showed low homology between the T. foetus isolates and other trichomonads recovered from cattle (<70%). Two clusters of trichomonads other than T. foetus were identified. Eighteen isolates comprised 1 group. These isolates shared >99% homology among themselves and with Pentatrichomonas hominis. The other non-T. foetus cluster (n = 14) did not exhibit a high degree of homology (<87%) with other bovine isolates or any of the trichomonad sequences available in GenBank. The sequence homology among isolates in that cluster was >99%, except for 1 isolate that varied from the others in both ITSRs (approximately 2% dissimilarity). Sequence analysis of the 5.8S rRNA gene and ITSRs was useful for comparing trichomonadid protozoa isolated from the bovine preputial cavity and demonstrated that 2 distinct types of trichomonads constituted the non-T. foetus isolates recovered from the bovine preputial cavity.

Two-step (culture and PCR) diagnostic approach for differentiation of non-T. foetus trichomonads from genitalia of virgin beef bulls in Argentina.

Preputial fluids from 567 virgin Angus and Hereford bulls, 1-2 years old, were inoculated into Sutherland medium, and approximately 8.4% produced cultures with a protozoan suggestive of Tritrichomonas foetus. Under brightfield microscopy, large numbers of single-celled motile organisms with multiple anterior flagellae, a posterior flagellum, axostyle, and a visible undulating membrane were detectable. Motility was jerky and rolling, as described for T. foetus. Air-dried smears of cultures stained with Giemsa or Diff-Quick + iodine revealed an organism similar to T. foetus, although somewhat more rounded. Several organisms appeared to have four anterior flagellae. Scanning electron microscopy (5000x) of representative samples revealed four anterior flagellae on most organisms, and an axostyle that was consistently longer than that seen in T. foetus. Using pan-trichomonal primers and T. foetus-specific primers in a polymerase chain reaction (PCR) assay, amplification products of 372bp were detected in all virgin bull isolates, but only with the pan-trichomonal primers. Positive control isolates of T. foetus yielded amplification products of the expected size (372 and 347bp) with the two sets of primers, respectively. We conclude that these protozoa are not T. foetus, and note the similarity of these findings with those reported earlier in North American beef cattle. Because in several countries there is no legal treatment for bovine trichomonosis, veterinarians recommend slaughter of bulls with positive preputial cultures. The existence of easily mis-identified non-T. foetus trichomonads in the bovine prepuce suggests that the current "gold standard" diagnostic test (culture of preputial scrapings or washings) should be augmented with a more specific confirming test, such as the PCR employed in this study.

Immunity to bovine reproductive infections.

Protective immune responses in the genital tract are robust, as shown by convalescent and vaccine-induced immunity. Systemic immunity is crucial for systemic infections that result in reproductive failure (such as brucellosis, leptospirosis, and the systemic forms of C. fetus and H. somnus infection). Although IgA responses can protect against sexually transmitted or venereal infections, systemically induced IgG antibody responses also protect. IgA responses can be induced by immunization of the genital tract, where inductive sites develop after antigenic stimulation. The common mucosal immune system can also be used to induce a genital IgA response, as shown by intranasal vaccination. Lastly, it is necessary to determine which antigens of each infectious agent are protective and which types of immune responses protect best.

Immunological and biochemical analysis of glycosylated surface antigens and lipophosphoglycan of Tritrichomonas foetus.

Immunoaffinity-purified TF1.17 adhesin antigen was compared biochemically and antigenically to Tritrichomonas foetus (TF) lipophosphoglycan (LPG) and a soluble glycosylated antigen (SGA) released from T. foetus and implicated in pathogenesis and immunity. The monoclonal antibodies (Mabs TF1.15 and TF1.17) specific for a glycosylated TF1.17 antigen were previously shown to prevent adhesion of the T. foetus parasites to bovine vaginal epithelial cells and to mediate killing by bovine complement. SGA was isolated from T. foetus-conditioned buffer and purified by octyl-Sepharose hydrophobic column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of SGA showed a major SGA1 component (approximately 190 kDa) and a minor SGA2 component (50-70 kDa), which migrated close to TF-LPG and TF1.17. The carbohydrate and lipid compositional analyses of affinity-purified TF1.17 and SGA2 by high-performance liquid chromatography (HPLC) and gas-liquid chromatography revealed the presence of monosaccharides and fatty acids as found in TF-LPG. All antigens contained terminal fucose as determined by alpha-fucosidase digestion followed by HPLC. ELISA and western blots were used to further characterize these glycosylated antigens and to analyze their relationships. The Mabs TF1.15 and TF1.17 reacted very strongly to TF-LPG and SGA2. as well as TF1.17 antigen, indicating that these molecules share common epitopes. These Mabs did not react with the SGA1 component either in ELISA and western blot analyses. Also, the monosaccharide composition of SGA1 was very different from the other three antigen, suggesting SGA1 was different from LPG, SGA2 and TF1.17. Although LPG reacted with Mabs to native TF1.17 antigen, LPG did not induce an immune response in cattle with the same route and adjuvant used to produce strong antibody responses to the native antigen. The latter response suggests that the tightly bound peptide present in the immunoaffinity-purified antigen is necessary for induction of a response to (an) epitope(s) in TF-LPG and TF1.17. Furthermore, vaginal fluid from T. foetus-infected heifers and serum from a cow with a T. foetus-associated pyometra recognized both TF1.17 and TF-LPG in western blots. These results suggest that T. foetus LPG and SGA2 are related to TF1.17 antigen, which was previously shown to play an important role in the pathogenesis and host response in bovine trichomoniasis.

Reproductive effects of estradiol cypionate in postparturient dairy cows.

OBJECTIVE: To determine the effects of estradiol cypionate (ECP) on measures of reproductive efficiency in postparturient dairy cows. DESIGN: Randomized clinical trial. ANIMALS: 273 cows in a single herd in California. PROCEDURE: Twenty-four hours after parturition, 122 cows were treated with ECP (4 mg, IM); the remaining 151 cows were untreated controls. Percentages of cattle with abnormal findings during uterine palpation 27 to 40 days after parturition were compared between groups, along with days to first artificial insemination (AI), percentages of cows that were not pregnant after the first AI, and days to pregnancy. RESULTS: Treatment with ECP did not have a significant effect on whether results of uterine palpation 27 to 40 days after parturition were abnormal, days to first AI, or odds that a cow would be pregnant after the first AI. Treatment with ECP appeared to have a negative effect on days to pregnancy (hazard ratio, 0.72) CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that prophylactic administration of ECP during the early postparturient period in dairy cows did not have measurable beneficial effects on reproductive efficiency.

Bovine trichomoniasis as a model for development of vaccines against sexually-transmitted disease.

PROBLEM: Human sexually transmitted diseases (STDs) are widespread but effective vaccines are rare. Experimental and commercially available vaccines for bovine trichomoniasis have been well studied. Principles for immune protection of the female genital tract derived from studies of bovine trichomoniasis may be generally applicable to human trichomoniasis and other STDs. METHOD OF STUDY: A bovine model of trichomoniasis has been developed for study of mechanisms of immunoprophylaxis. RESULTS: Both systemic and local immunization with an immunoaffinity purified antigen cleared the genital tract of trichomonads significantly earlier than non-immunized controls. Predominantly IgA responses or predominantly IgG responses in uterine and vaginal secretions were essentially equally protective. Uterine and vaginal IgA responses could be induced by systemic priming and local boosting via either the vaginal or nasal mucosa. In either case, lymphoid aggregates were formed in the uterine and vaginal mucosa which were not present in the genital mucosa of naïve animals. CONCLUSIONS: Systemic immunization or systemic priming with local boosting protects against bovine trichomoniasis via IgG or IgA antibodies (respectively) to a major surface antigen of trichomonads. Immunization of the genital mucosa results in formation of inductive sites for a local IgA response.

Hematopoietic stem cell transplantation in utero produces sheep-goat chimeras.

Both allogeneic and xenogeneic hematopoietic chimera models have been developed, including fetal sheep models that demonstrated high levels of stable, multilineage engraftment created by in utero hematopoietic stem cell transplantation. The aim of this study was to test the efficacy of in utero transplantation to create xenogeneic sheep-goat hematopoietic chimeras. Fetal liver cells and T-cell-depleted adult bone marrow were tested as sources of hematopoietic stem cells. Donor cells were injected intraperitoneally into 130 recipient fetuses between 49 and 62 days of gestation. Groups 1 and 2 received crude fetal liver cell preparations. Group 3 received fetal liver cells that were incubated overnight in a phytohemagglutinin-stimulated lymphocyte-conditioned medium (PHA-LCM). In Group 4, hematopoietic stem cells were concentrated by using additional density separations. Group 5 fetal recipients received low-density, T-cell-depleted adult bone marrow cells. In Group 1, fetuses were accessed via hysterotomy. Hematopoietic stem cells were injected into Groups 2, 3, 4, and 5 without cutting through the uterine wall. Fetal survival in the five groups ranged from 56 to 100%. The percentage of chimeras from injected fetuses ranged from 43 to 92% by FACS and PCR analyses; however, levels of chimerism were low (<1%). The highest rates of chimerism were found among recipients of low-density fetal liver cells. Despite the pre-immunocompetent status of the fetal recipients and the genetic similarities between sheep and goats, high levels of engraftment were not observed. The consistently low levels of chimerism observed in this study, as well as the poor results recently reported by others using these procedures, indicate that significant barriers exist to transplanting hematopoietic stem cells in utero.

Evidence against humoral immune attack as the cause of sheep-goat interspecies and hybrid pregnancy failure in the doe.

The failure of interspecies and hybrid pregnancies between the domestic sheep (Ovis aries) and goat (Capra hircus) is not completely understood. The sheep-goat hematopoietic chimera is a unique model for studying the role of the maternal immune response in failure of interspecies and hybrid pregnancies between these species. Hematopoietic chimeras were created by in utero transplantation of sheep fetal liver cells into goat fetuses. The resulting chimeric females were recipients of sheep demi-embryos genetically identical to their sheep cells and/or were bred to a ram to create a hybrid pregnancy. Pregnancy sera were analyzed for the presence of anti-species antibodies (Ab) using a lymphocyte microcytotoxicity assay. None of the concepti survived to term. Gross and histological evaluations of two interspecies sheep concepti revealed abnormal placentome formation. The humoral immune response of several hematopoietic chimeras to the challenging concepti differed from control animals. We observed delayed onset of Ab production, low and absent titers, and persistent Ab titers with delayed fetal death. Ultrasonography typically revealed normal fetal development associated with high volumes of placental fluids and retarded placentome development. We conclude that fetal death was associated with abnormal placental development that was not the result of maternal humoral immune attack.

Fetal leukocyte trafficking as a stimulus for the production of maternal antibodies in the goat.

The production of antibodies during pregnancy or after parturition is a natural occurrence in many mammalian species. Fetal cells have been detected in the peripheral blood of women and mice and are thought to be the immune stimulus for antibody production. The aim of this study was to investigate if the production of maternal anti-fetal antibodies during ruminant pregnancy is the result of fetal leukocyte trafficking across the placenta. Maternal pregnancy serum was collected from 94 does whose fetuses received sheep hematopoietic stem cells via in utero transplantation at 49 to 62 d of gestation. Serum samples were collected before surgery and at weekly intervals throughout gestation. A lymphocyte microcytotoxicity assay was used to screen the serum samples from does that carried chimeric fetuses to term (n = 75). Of these 75 does, 28 parous does had presurgery serum that contained alloreactive antibodies. Nine of the 75 does had nonreactive presurgery serum, but they produced alloreactive antibody titers during gestation. Xenoreactive antibodies were detected in the pregnancy sera from 2 of the 75 does tested. Hemolytic assays confirmed the species-specificity of the xenoreactive serum from these 2 does. In view of the fact that hematopoietic cells were the only source of anti-sheep antibody stimulation in this model, we propose that fetal leukocyte trafficking does take place across the caprine placenta.

Degradation of bovine complement C3 by trichomonad extracellular proteinase.

Bovine trichomoniasis is a local infection of the reproductive tract making interaction with mucosal host defenses crucial. Since the parasite is susceptible to killing by bovine complement, we investigated the role of the third component of complement (C3) in host parasite interactions. Bovine C3 was purified by anionic and cationic exchange chromatography. The purified protein was characterized by immunoreactivity, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and peptide sequencing of the amino terminus of the beta chain. When purified bovine C3 was incubated for varying time periods with trichomonad extracellular proteinases, SDS-PAGE gels revealed digestion of the alpha chain to small fragments. Such degradation in vivo would prevent formation of C3b and completion of the complement cascade, resulting in evasion of killing. To evaluate the relevance of this data, we determined whether C3 was present in bovine genital secretions. With a quantitative ELISA assay, C3 could be demonstrated in both uterine and vaginal washes. To our knowledge, this is the first demonstration of bovine C3 in genital secretions. The C3 concentration increased significantly in vaginal secretions by 8 and 10 weeks in heifers infected with Tritrichomonas foetus. An increase was also seen in uterine secretions of infected heifers, but sample numbers were insufficient for statistical analysis. Transcription of the major extracellular cysteine proteinase (TFCP8) was demonstrated in T. foetus cells from uterine secretions of infected heifers by RT-PCR and Southern blotting. The results indicate that C3 may be important in genital defense and that trichomonad extracellular proteinases may play a role in evasion of complement-mediated killing.

Successful pregnancy in goats carrying their genetically identical conceptus.

Mammalian pregnancies are naturally allogeneic, but syngeneic pregnancies have been carried to term in laboratory animal species. The need for maternal immune recognition during mammalian pregnancy is still unclear. Allogeneic pregnancies are protected from maternal immune attack by the nature of the trophoblast and its interactions with maternal tissues at the maternal-fetal interface. Syngeneic pregnancy models and the success of pregnancies in immunosuppressed mice challenge the necessity of a maternal immune response in mammals. This study was designed to investigate if outbred, domestic sheep and goats can successfully establish and maintain a syngeneic pregnancy. Embryo splitting and cryopreservation techniques were used to enable sheep and goat demi-embryos to be transferred to genetically identical females. Allogeneic pregnancies were established from the transfer of demi-embryos subjected to the same manipulations to assess demi-embryo survival and pregnancy rates under conventional immune compatibility conditions. Syngeneic pregnancies were established and carried to term in goats (2/11) but not in sheep (0/24). Microsatellite and DNA fingerprinting analyses confirmed that each kid was a genetically identical twin to the female that carried it to term. Our results demonstrated that genetic disparity is not required for the establishment and maintenance of pregnancy in goats, but our results were inconclusive for sheep.