Use of SNP genotyping to determine pedigree and breed composition of dairy cattle in Kenya

High levels of inbreeding in East African dairy cattle are a potential concern because of use of a limited range of imported germplasm coupled with strong selection, especially by disease, and sparse performance recording. To address this, genetic relationships and breed composition in an admixed population of Kenyan dairy cattle were estimated by means of a 50K SNP scan. Genomic DNA from 3 worldwide Holstein and 20 Kenyan bulls, 71 putative cow‐calf pairs, 25 cows from a large ranch and 5 other Kenyan animals were genotyped for 37 238 informative SNPs. Sires were predicted and 89% of putative dam‐calf relationships were supported by genotype data. Animals were clustered with the HapMap population using Structure software to assess breed composition. Cows from a large ranch primarily clustered with Holsteins, while animals from smaller farms were generally crosses between Holstein and Guernsey. Coefficients of relatedness were estimated and showed evidence of heavy use of one AI bull. We conclude that little native germplasm exists within the genotyped populations and mostly European ancestry remains.     

Animal medical genetics: a perspective on the epidemiology and control of inherited disorders

This perspective considers genetic disorders of domestic animal populations, in particular their epidemiology and control. Inherited disorders of animals share the same basic molecular biology as those of human beings, but they differ in their epidemiology due largely to the breed structure of the various species, human control of breeding and a greater influence of the founder effect, particularly due to extensive use of a limited number of sires, and inbreeding. Control of genetic disorders in animals is also more practical through extensive screening for disease, or heterozygous animals within defined breed populations, followed by exclusion of affected or carrier animals from breeding. This is assisted by the fact that, within a breed, many inherited monogenic disorders are associated with a single mutation. However some of the more important disorders may be inherited in a non-Mendelian manner, being influenced by multiple genes as well as environmental factors. These aspects are discussed and contrasted with similar aspects in human medical genetics.     

Comparison of a DNA probe, complement-fixation and indirect immunofluorescence tests for diagnosing Anaplasma marginale in suspected carrier cattle

Most estimates of the prevalence of anaplasmosis have been based on serologic data using the complement-fixation (CF) and/or card agglutination tests. Since these tests are considered to be only about 50 percent reliable for detecting carrier cattle in enzootically stable herds, the need for more sensitive diagnostic tests is widely recognized. The objective in the present study was to compare the sensitivity of the CF test with that of the indirect immunofluorescence (IIF) test and a recently developed DNA probe in determining the prevalence of Anaplasma marginale infection in cattle from an enzootic area. The study herd consisted of 52 8-month-old steers and 13 3-year-old cows of mixed beef breed. All cattle were initially tested for this comparative purpose. All but one animal (one that was a positive reactor as assessed by all three tests, and served as a positive control), were treated with long-acting oxytetracycline in an attempt to clear any carrier infections. Each animal was then retested at 1 month and 2 months post-treatment (PT), in an effort to determine if the DNA probe could be used to evaluate the effectiveness of the drug. Six of the 65 (9.2%) initial serum samples were CF positive. In contrast, 60 (92.3%) and 64 (98.5%) of the samples were positive as assessed with the IIF test and the DNA probe, respectively. The DNA hybridization reactions varied in intensity within the sample population indicating different individual levels of infection. The DNA probe hybridized with two samples taken at 1 month PT, and with two different samples taken at 2 months PT. The mean IIF titers were reduced at both the 1 month and 2 month sampling times. These results suggest that the drug did not eliminate infections in all cattle. Some may have been cleared, but, in any event, the drug did reduce the level of infections below the sensitivity of the DNA probe and interrupted continuity of stimulation of antibody. Therefore, the DNA probe and the IIF test appear to be considerably more sensitive in detecting carrier infections than the CF test, and should be considered in future epidemiologic studies.     

Within‐ and across‐breed imputation of high‐density genotypes in dairy and beef cattle from medium‐ and low‐density genotypes

The objective of this study was to evaluate, using three different genotype density panels, the accuracy of imputation from lower‐ to higher‐density genotypes in dairy and beef cattle. High‐density genotypes consisting of 777 962 single‐nucleotide polymorphisms (SNP) were available on 3122 animals comprised of 269, 196, 710, 234, 719, 730 and 264 Angus, Belgian Blue, Charolais, Hereford, Holstein‐Friesian, Limousin and Simmental bulls, respectively. Three different genotype densities were generated: low density (LD; 6501 autosomal SNPs), medium density (50K; 47 770 autosomal SNPs) and high density (HD; 735 151 autosomal SNPs). Imputation from lower‐ to higher‐density genotype platforms was undertaken within and across breeds exploiting population‐wide linkage disequilibrium. The mean allele concordance rate per breed from LD to HD when undertaken using a single breed or multiple breed reference population varied from 0.956 to 0.974 and from 0.947 to 0.967, respectively. The mean allele concordance rate per breed from 50K to HD when undertaken using a single breed or multiple breed reference population varied from 0.987 to 0.994 and from 0.987 to 0.993, respectively. The accuracy of imputation was generally greater when the reference population was solely comprised of the breed to be imputed compared to when the reference population comprised of multiple breeds, although the impact was less when imputing from 50K to HD compared to imputing from LD.     

An improved DNA test for bovine leucocyte adhesion deficiency

A modified DNA test, based on the polymerase chain reaction, was developed for the monogenic recessive disease bovine leucocyte adhesion deficiency ( ). The test was improved by the selection of new primers which facilitated the interpretation of the results. An easily scorable banding pattern makes the test useful in cattle breeding schemes and for clinical diagnosis. A total of 2381 samples was analysed over a period of three years. The carrier rate among young bulls at artificial insemination ( ) stations decreased from 11·6 per cent in 1993 to 9·9 per cent in the first five months of 1995. Continuous screening of young bulls before entering is still recommended unless both parents are proven to be genetically free of . The carrier rate among clinically suspect animals was not increased, and carriers are therefore not expected to be immunodeficient. Despite all efforts to eradicate the disease, calves with were still observed in 1995.     

Inbreeding and genetic diversity in dogs: results from DNA analysis

This review assesses evidence from DNA analysis to determine whether there is sufficient genetic diversity within breeds to ensure that populations are sustainable in the absence of cross breeding and to determine whether genetic diversity is declining. On average, dog breeds currently retain approximately 87% of the available domestic canine genetic diversity. Requirements that breeding stock must be 'clear' for all genetic disorders may firstly place undue genetic pressure on animals tested as being 'clear' of known genetic disorders, secondly may contribute to loss of diversity and thirdly may result in the dissemination of new recessive disorders for which no genetic tests are available. Global exchange of genetic material may hasten the loss of alleles and this practice should be discussed in relation to the current effective population size of a breed and its expected future popularity. Genomic data do not always support the results from pedigree analysis and possible reasons for this are discussed.     

北京地区荷斯坦牛脊椎畸形综合征的调查研究

脊椎畸形综合征（Complex Vertebral Malformation,CVM）是由常染色体上SLC35A3基因单碱基突变（G→T）引起的隐性遗传疾病,该基因隐性纯合（CV/CV）时奶牛致死,但CVM携带者表现正常,所以CVM携带者公牛可以通过人工授精技术传播CVM缺陷基因。本研究利用PCR-SSCP方法对北京地区242头公牛样品和403头母牛样品进行了检测分析,研究结果表明,在所检测的样本中,荷斯坦种公牛和母牛CVM携带率分别为8.82%和5.71%,CVM基因频率分别为4.41%和2.85%。通过系谱追踪发现,CVM遗传缺陷的共同祖先是美国名牛＂Penstate Ivanhoe Star＂（USA.1441440,CV）。通过剔除CVM携带者公牛可以有效地控制CVM遗传缺陷的传播,但是,我国许多CVM携带者公牛冻精依然在商业化使用,所以有效地监控CVM携带者在奶牛群中的状况对CVM防控计划是有益的。     

Do traditional sheep breeders perform conscious selection? An example from a participatory breeding program of Morada Nova sheep

The implementation of sustainable breeding programs requires genetic breeding strategies that are appropriate for the reality production systems. It is also essential that the choice of animal selection criteria be based on breeders’ knowledge and objectives. This work is an ethno-zootechnical study of the Morada Nova sheep breed and its crossbreeds. The goals of this study were to register and analyze indigenous breeders’ knowledge and practices regarding animal selection criteria and to generate technical information to support a participatory breeding program of the breed. This study was conducted in the Morada Nova municipality in the state of Ceará, Brazil. Semi-structured interviews were evaluated using two groups of individuals, purebred Morada Nova sheep breeders (RMN, n = 13) and breeders of Morada Nova crossbreeds (MMN, n = 48). Interview questions were used to identify local selection criteria adopted by each group in the choice of animals for breeding. Data from the interviews were submitted to frequency distribution analysis and the Shapiro-Wilk test to verify their distribution. Later, the Kruskal-Wallis test was used to compare the two groups of farmers based on that information, in addition to multivariate statistical analysis and evaluation of Smith salience index. Breeders in the RMN group used selection criteria related to breed standards, such as pelage color. In contrast, breeders of the MMN group used criteria related to productivity, such as body conformation and milk production. Breeders should be engaged in the development of breeding programs, and it is important to consider their preferences and objectives when evaluating breeding animals.     

A review of genetic resistance to disease in Bos taurus cattle

Cattle show considerable variability in their responses to a wide range of disease challenges, and much of the variability is genetic. This review highlights genetic variation in disease susceptibility in Bos taurus cattle, with variation found at the breed level and also within breeds. Disease challenges come from bacteria and viruses, parasites and feed-borne toxins. For an animal to survive, it needs its own mechanisms for resisting these challenges, or for being resilient to them, or it must be protected artificially from them. Disease challenges have been classified as 'diseases from without', but there is also another class of genetic diseases resulting from inborn errors of metabolism, which might be called 'diseases from within'. Degrees of inheritance (heritabilities) are reviewed for a range of economically important traits including resistance to mastitis, ketosis, lameness, nematode parasites, external parasites, eye disease, respiratory disorders, tuberculosis, brucellosis, Johne's disease, foot-and-mouth disease, bovine spongiform encephalopathy, metabolic disorders caused by toxins found on the feed, and threshold levels of minerals and metabolites. Many, but not all, of the above require an immune response as part of the fight against an external challenge, and measurements have been made of general immune response as a way of describing or predicting how an animal will respond. There are now some examples of industry or breed societies applying selection for resistance to one or more diseases as part of a complete breeding objective in dairy cattle, beef cattle or dual purpose livestock. In most cases, industry and breed societies are in the early stages of applying effective selection pressure for resistance to specific cattle diseases, with the notable exceptions of Scandinavian cattle schemes, which lead the world in this respect.     

Genetic diversity of the Mexican Lidia bovine breed and its divergence from the Spanish population

Lidia bovine breed exists since the XIV century in the Iberian Peninsula. These animals were initially produced for meat but some, showing an aggressive behaviour which difficulted their management, were used to participate in popular traditional and social events. A specialization of the breed giving rise to the original Lidia population is documented in Spain since mid-XVIII century. Following the same tradition than in the Spanish population, Mexico used aggressive animals at the beginning of the XX century until two families of breeders started importing Lidia breed bovines from Spain with the aim of specializing their production. Each family (Llaguno and González) followed different breeding managements, and currently, most of the Lidia Mexican population derives from the Llaguno line. Although genetic structure and diversity of the Spanish population have been studied (using autosomal microsatellite markers, Y chromosome DNA markers and mitochondrial DNA sequences), the Mexican population is not analysed. The aim of the study was to assess both the genetic structure and diversity of the Mexican Lidia breed and its relationship with the original Spanish population using the same molecular tools. A total of 306 animals belonging to 20 breeders issued from both existing Mexican families were genotyped, and the genetic information was compared to the previously existing Spanish information. Slightly higher levels of genetic diversity in Mexican population were found when comparing to the Spanish population, and the variability among populations accounted for differences within them showing mean values of 0.18 and 0.12, respectively. Animals from the Mexican breeders, belonging to each of the two families, clustered together, and there was little evidence of admixture with the Spanish population. The analysis of Y chromosome diversity showed a high frequency of the H6 haplotype in the Mexican population, whereas this haplotype is rare in the Spanish, which is only found in the Miura (100%) and Casta Navarra (38%) lineages. Mitochondrial DNA revealed similar haplotypic pattern in both Spanish and Mexican populations, which is in accordance with most of the Mediterranean bovine breeds. In conclusion, as the Mexican Lidia population had initially a small number of founders and its current population has been reared isolated from their Spanish ancestors since a long time, these bottleneck effects and a combination of mixed cattle origin are the factors that might erase any trace of the Spanish origin of this population.     

Furosemide loading test in a case of homozygous solute carrier family 12, member 1 (SLC12A1) mutation (g.62382825G>A,p.Pro372Leu) in Japanese Black cattle

Hydrallantois is the excessive accumulation of fluid in the allantoic cavity in a pregnant animal and is associated with fetal death. We recently identified a recessive missense mutation in the solute carrier family 12, member 1 (SLC 12A1 ) gene (g.62382825G>A, p.Pro372Leu) that is associated with hydrallantois in Japanese Black cattle. Unexpectedly, we found a case of the homozygous risk‐allele for SLC 12A1 in a calf, using a PCR ‐based direct DNA sequencing test. The homozygote was outwardly healthy up to 3 months of age and the mother did not exhibit any clinical symptoms of hydrallantois. In order to validate these observations, we performed confirmation tests for the genotype and a diuretic loading test using furosemide, which inhibits the transporter activity of the SLC 12A1 protein. The results showed that the calf was really homozygous for the risk‐allele. In the homozygous calf, administration of furosemide did not alter urinary Na⁺ or Cl^? levels, in contrast to the heterozygote and wild‐type calves in which these were significantly increased. These results demonstrate that the SLC 12A1 (g.62382825G>A, p.Pro372Leu) is a hypomorphic or loss‐of‐function mutation and the hydrallantois with this mutation shows incomplete penetrance in Japanese Black cattle.     

Inheritance of diabetes mellitus in Keeshond dogs

The genetic aspects of inherited, insulin-dependent diabetes mellitus of Keeshond dogs were studied retrospectively and in a prospective mating program. The symbol dm was used to designate the gene that causes hypoplasia of the islets of Langerhans. The retrospective study disclosed 4 diabetic dogs; prospective outcross, backcross, and inbred matings disclosed 49 diabetic dogs. Outcrossing demonstrated that the diabetic phenotype was displayed readily against a genetic background of a breed other than the Keeshond. In dogs with the dm/dm genotype, onset of diabetes was most frequent before the dog was 6 months old, but did occur in some older dogs. The dm genotype was best described as autosomal recessive.     

MC1R c.310G>‐ and c.871G > A determine the coat color of Kumamoto sub‐breed of Japanese Brown cattle

Coat color is one of the important factors characterizing breeds for domestic animals. Melanocortin 1 receptor (MC1R) is a representative responsible gene for this phenotype. Two single‐nucleotide polymorphisms (SNPs) in bovine MC1R gene, c.296T > C and c.310G>‐, have been well characterized, but these SNPs are not enough to explain cattle coat color. As far as we know, MC1R genotypes of Kumamoto sub‐breed of Japanese Brown cattle have not been analyzed. In the current study, genotyping for c.296T > C and c.310G>‐ was performed to elucidate the role of MC1R in determining the coat color of this sub‐breed. As a result, most animals were e/e genotype, suggesting the coat color of this sub‐breed is derived from the e allele of MC1R gene. However, we found six animals with E/e genotype, which coat color would be black theoretically. Subsequently, sequence comparison was performed with these animals to identify other polymorphisms affecting coat color, elucidating that these animals possessed the A allele of c.871G > A commonly. c.871G > A was a non‐synonymous mutation in the seventh transmembrane domain, suggesting alteration of the function and/or the structure of MC1R protein. Our data indicated that the A allele of c.871G > A might be a loss‐of‐function mutation.     

深县猪mtDNA CytB基因的遗传多样性与母系起源研究

 研究过氧化物酶体增殖激活受体α (PPARα) 基因第7外显子SNP位点与牛的部分胴体、肉质性状的相关性。以6个牛品种(秦川牛、南阳牛、郏县红牛、鲁西牛、安格斯、夏南牛) 共计717个个体为研究对象,采用PCR SSCP结合DNA测序方法对PPARα基因第7外显子进行SNP检测,并该SNP位点与108头秦川牛的部分胴体、肉质性状的相关性进行分析。结果发现在PPARα基因第7外显子的184位检测到C→T突变,在南阳牛、秦川牛、郏县红牛、安格斯、鲁西牛、夏南牛这6个群体中等位基因E/F的频率分别是0.225/0.775,0.151/0.849,0.125/0.875,0.123/0.877,0.070/0.930, 0.157/0.783;遗传学指标结果显示：秦川牛、郏县红牛、安格斯、鲁西牛和夏南牛这5个群体属于低度多态(PIC<0.25),南阳牛为中度多态（PIC=0.288）;相关分析结果显示：该位点与秦川牛的背膘厚和胴体长两个性状显著相关,表现为FF基因型个体在背膘厚性状方面显著高于EE和EF基因型个体(P<0.05),FF基因型个体的胴体长显著高于EE基因型个体(P<0.05)。这一位点可能是影响牛背膘厚和胴体长的主效QTN或与之紧密连锁,可做为肉牛选育的候选分子标记。     

Bovine Leukocyte Adhesion Deficiency in Danish Holstein-Friesian Cattle: I. PCR Screening and Allele Frequency Estimation

Jergensen, C. B., J. S. Agerholm, J. Pedersen and P. D. Thomsen: Bovine leukocyte adhesion deficiency in Danish Holstein-Friesian Cattle I. PCR screening and allele frequency estimation. Acta vet. Scand. 1993,34,231-236.–A screening program for bovine leukocyte adhesion deficiency (BLAD) in Danish Holstein-Friesian cattle has been initiated. During the first months 1611 animals were tested by a PCR based assay. Of these animals 1256, 346, and 8 were assigned normal, BLAD carriers, and BLAD affected animals, respectively One bull, born as a co-twin, showed weak reaction for the BLAD allele on DNA isolated from leukocytes, but a normal genotype on DNA isolated from semen. Chromosome analysis showed that this bull was a blood chimaera. Estimation of the BLAD allele frequency upon the PCR test results showed that around 450 Danish calves born in 1991 might have been affected with the recessive disorder.     

天津地区荷斯坦公牛CVM、DUMPS和CN遗传缺陷检测

本文旨在研究天津地区中国荷斯坦公牛脊椎畸形综合征（Complex vertebral malformation,CVM）、尿苷酸合酶缺乏症（Deftciencv of uridine monophospham synchase,DUMPS）和瓜氨酸血症（Citrullinemia,CN）3种遗传缺陷的携带者比率及系谱来源。通过PIRA—PCR和PCR—RFLP方法分别对天津奶牛发展中心参加全国青年公牛联合后裔测定和国家良种补贴项目的110头荷斯坦公牛进行了CVM、DUMPS和CN三种遗传缺陷检测。共发现6头CVM隐性有害基因携带公牛,携带者比例为5．45％,隐性有害等位基因频率为2．72％。经过系谱分析,其中4头CVM携带者均为美国公牛Carlin—MIvanhoeBell的后代,另外2头因系谱不完整而无法查询。未检测到DuMPs和CN隐性有害基因携带者。基于此,我国有必要尽快建立荷斯坦牛隐性遗传缺陷监控体系并进行系谱标注,避免携带公牛进入后裔测定和良种补贴项目,以逐步降低我国奶牛群体中遗传缺陷隐性等位基因频率。     

Mendelism in animal breeding as developed by professor Leopold Frateur,Louvain (1877-1946)

Educated as a veterinarian at Cureghem, Leopold Frateur started his scientific career in 1899 as a professor at the Faculty of Sciences of the Catholic University of Louvain, Belgium, in charge of the course in zootechnology. After a study tour to zootechnical institutes and centres of animal breeding in Europe he was invited by the governmental department of Agriculture and the Belgian Society of Zootechnology to investigate the relevance of the Mendelian laws of heredity for the improvement of cattle breeding. In the early years of the century, Frateur conducted field research in order to determine the characteristics of the cattle breeds in Belgium. In 1908 Frateur founded the Institute of Animal Husbandry at his university. Here he worked out his programme of experimental genetics until his retirement in 1936. The last six years of his professorship he teached also agricultural economics in the Faculty of Economical Sciences. In Frateur's experimental research the following main lines can be distinguished: 1) The analysis of simple and complex hereditary factors in cattle, rabbits and poultry; 2) The study of qualitative and quantitative characteristics of importance for the improvement of animal breeds; 3) The synthesis of genetic factors from different stock in order to obtain higher yielding breeds with stable characteristics; 4) Theoretical study of the relationship between genotype and phenotype and the influence of environment factors; 5) Theoretical exploration of the issue of variability and modification of newly formed characteristics; 6) Research leading to an explanation of telegony and atavism; 7) The formulation of a theory on the creation of new breeds in domestic animals and plants, and the relation between breed and species. Also he was responding to topical needs, e.g. he determined the causal factor of pullorum epidemic in chicken farming, or he investigated the hereditary resistance against diphteric infection amongst chickens. Frateur took the theoretical knowledge on heredity as the starting point for practical application in cattle breeding. During and right after W. W. I. he stated that the current scientific knowledge is enough advanced to consider the start of a large breeding programme for the improvement of cattle livestock. In order to realise this reinstatement Frateur received important support from the authorities (Royal Decree, August 1919). From then onwards he focussed his efforts on the realisation of a national framework for improvement of cattle livestock, in collaboration with regional centres and societies for animal selection, breeding and production. Later he also started programmes for the improvement of chicken and pig breeding, again in a joint effort with official consultants and members of breeding societies. He was not only the architect of these programmes, providing the necessary scientific and technical guidance, but he had also a chair in the governing bodies, supervising the execution and control of the breeding programmes. In order to draw a picture of the research community engaged in animal breeding during the first decennia of the 20th century Frateur's contacts through study tours, congresses and learned societies are investigated. The life and work of Frateur is described by the author in two volumes, published in 1999. The second volume consists of a reprint of 50 selected papers on animal breeding.     

荷斯坦牛脊椎畸形综合征分子诊断方法的建立与应用

脊椎畸形综合征(Complex Vertebral Malformation,CVM)是由常染色体上SLC35A3基因单碱基突变(G→T)引起的隐性遗传疾病,该基因隐性纯合(CV/CV)时奶牛致死,但CVM携带者表现正常,所以CVM携带者公牛可以通过人工授精技术传播CVM缺陷基因。本研究自行设计检测CVM特异性PCR引物,扩增长度为173bp,然后利用PCR-SSCP方法对186个公牛样品和140个母牛样品进行了检测分析,该方法简便快捷、准确率高,使用样品宽泛,适合大样本筛选。研究结果表明,在所检测的样本中,荷斯坦种公牛和母牛CVM携带率分别为11.3%和12.1%,并通过系谱追踪发现,CVM遗传缺陷的共同祖先是美国名牛"Penstate Ivanhoe Star"(USA.1441440,CV)。通过剔除CVM携带者公牛可以有效地控制CVM遗传缺陷,但是,我国许多CVM携带者公牛冻精依然在商业化使用,所以,有效地监控CVM携带者在奶牛群中的状况对CVM防控计划是有益的。     

Genetic diversity and differentiation of five Cuban cattle breeds using 30 microsatellite loci

Conservation and improvement strategies in farm animals should be based on a combination of genetic and phenotypic characteristics. Genotype data from 30 microsatellites were used to assess the genetic diversity and relationships among five Cuban cattle breeds (Siboney de Cuba, Criollo Cubano, Cebú Cubano, Mambí de Cuba and Taíno de Cuba). All microsatellite markers were highly polymorphic in all the breeds. The expected heterozygosity ranged from 0.67 ± 0.02 in the Taíno de Cuba breed to 0.75 ± 0.02 in the Mambí de Cuba breed, and the observed heterozygosity ranged from 0.66 ± 0.03 in the Cebú Cubano breed to 0.73 ± 0.02 in the Siboney de Cuba breed. The genetic differentiation between the breeds was significant (p < 0.01) based on the infinitesimal model (F_ST). The exact test for Hardy‐Weinberg equilibrium within breeds showed a significant deviation in each breed (p < 0.0003) for one or more loci. The genetic distance and structure analysis showed that a significant amount of genetic variation is maintained in the local cattle population and that all breeds studied could be considered genetically distinct. The Siboney de Cuba and Mambí de Cuba breeds seem to be the most genetically related among the studied five breeds.     

An immunofluorescence test to determine the occurrence of type II collagen in muscle biopsies from cattle with rectovaginal constriction

Type II collagen occurs in the muscles of rectovaginal constriction (RVC) affected and carrier cattle but not in normal cattle. Muscle biopsies from known RVC affected and carrier cattle and normal cattle were examined for the presence of Type II collagen using affinity purified goat anti-collagen II serum in a fluorescent antibody test. Type II collagen was consistently found in RVC affected animals (22 of 23 samples score positive). Rectovaginal constriction carrier animals had variable staining for the Type II collagen (25 of 47 samples scored positive). Some positive staining was also observed in the control animals (8 of 34 samples scored positive). Because of the variable occurrence of Type II collagen, the value of fluorescent antibody staining to identify RVC carrier animals is uncertain.