Inheritance patterns in horses refer to the genetic transmission of traits from parent horses to their offspring. These patterns determine how specific characteristics, such as coat color, height, and susceptibility to certain diseases, are passed down through generations. Inheritance in horses follows Mendelian principles, which include dominant and recessive alleles, as well as more complex genetic interactions like incomplete dominance and polygenic traits. Understanding these patterns is essential for breeders aiming to predict the likelihood of particular traits appearing in foals. This page compiles peer-reviewed research studies and scholarly articles that explore the genetic mechanisms, hereditary traits, and implications of inheritance patterns in equine breeding and health.
Lazary S, Bullen S, Müller J, Kovacs G, Bodo I, Hockenjos P, De Weck AL.Mono- and oligospecific lymphocytotoxic alloantibodies from primiparous mares were tested on cells from horse families of various breeds in the two-step microcytotoxicity assay. The results showed that the detected antigens were inherited co-dominantly and autosomally as simple Mendelian traits. The membrane antigens showed different linkage with one or more other antigens and seem to be coded by a limited number of loci (at least three) from one chromosome. In the families tested one recombinant for the serologically defined antigens was recognized. The mixed leukocyte reactions of cells from...
Perryman LE, Torbeck RL.A 3-year prospective breeding trial was designed to verify the mode of inheritance of combined immunodeficiency (CID) in Arabian horses. Twenty-six mares that had previously produced foals with CID were mated to a stallion that had sired foals with CID. Of 53 foals obtained, 15 (28.3%) had CID. The ratio of female to male foals was 28:25, and the ratio of female CID to male CID foals was 8:7. The results of this trial confirmed a suggestion that CID in Arabian horses is inherited as an autosomal recessive trait.
Shupe JL, Leone NC, Olson AE, Gardner EJ.Investigation of hereditary multiple exostoses in horses under controlled research conditions for 10 years and epidemiologic studies that have spanned up to five generations of human families contain notable similarities. The present study demonstrated that a single dominant autosomal gene is responsible for hereditary multiple exostoses in horses and man. Affected individuals transmit this trait to approximately 50% of their progeny, whereas nonaffected individuals do not transmit the condition to their offspring. The tumors in affected horses are most often present at birth. They tend to be ...
The Journal of heredityJanuary 1, 1976
Volume 67, Issue 1 6-10 doi: 10.1093/oxfordjournals.jhered.a108667
Trommershausen-Smith A, Suzuki Y, Stormont C.The chestnut rule in equine coat-color genetics asserts that the inter se mating of chestnut horses never produces bay, black, brown or gray offspring. The gray rule asserts that a gray offspring must have at least one gray parent. Nine alleged exceptions to the chestnut rule, all involving bay offspring, and eight alleged exceptions to the gray rule, including four offspring that were also exceptions to the chestnut rule, were examined for parent-offspring genetic incompatibilities in as many as 17 genetic systems of blood-group markers. In all except one of the 17 cases it was possible to sh...
The Journal of heredityNovember 1, 1975
Volume 66, Issue 6 318-326 doi: 10.1093/oxfordjournals.jhered.a108640
Gardner EJ, Shupe JL, Leone NC, Olson AE.Comparative studies are being conducted on hereditary multiple exostosis in man and the horse. In both, there is an unquestionable inheritance pattern of a typical single, dominant, autosomal gene. Those who carry the gene have a one-half chance of transmitting it to each offspring, whereas, those who do not carry the gene do not transmit this abnormality to their progeny. The lesions are clinically and histologically similar; no persistent chromosomal irregularities have been associated with the abnormality in either man or the horse and no single evidence of malignancy in either man or anima...
Thompson DB, Studdert MJ, Beilharz RG, Littlejohns IR.A fatal syndrome of certain Arabian foals which begins at about 25 days of age (range 14 to 46 days) and which runs a course of about 23 days (range 13 to 42 days) is described. The syndrome, which affected 17 foals on a single farm is further characterised by pneumonia, in some instances by dermatitis (dermatophilosis) and other infections, together with a progressive decline in health till death at about 49 days of age (range 34 to 77 days), despite intensive therapy. Four of the foals, on histopathological evidence, had adenviral pneumonia, in 2 foals there was histopathological evidence of...
Exertional rhabdomyolysis (ER) and its familial basis in Warmblood horses is incompletely understood. Objective: To describe the case details, clinical signs and management of ER-affected Warmblood horses from a family with a high prevalence of ER, to determine if histopathological signs of polysaccharide storage myopathy (PSSM) and the glycogen synthase (GYS1) mutation are associated with ER in this family, and to investigate potential risk factors for development of ER. Methods: A family consisting of a sire with ER and 71 of his descendants was investigated. History of episodes of ER, husba...
Kakoi H, Gawahara H, Miura N.An unusual D system phenogroup appeared in one family line of Anglo-Arab horse. This phenogroup probably originated from inheritance with an apparent absence of factors and was transmitted through successive generations.
Cothran EG, Henney PJ, King JA.The inheritance of the equine Tf F3 allele was examined in 39 parent-offspring combinations. For 26 of the cases the allele inherited by the offspring from the heterozygous parent could be determined. The proportion of individuals that inherited the F3 variant compared to the alternative allele was exactly 1:1. In five cases the parental phenotype was identical to that of the offspring. For the remaining eight cases the parent was homozygous for the F3 allele and all offspring had the F3 allele. The results were consistent with Mendelian inheritance.
Brooks SA, Gabreski N, Miller D, Brisbin A, Brown HE, Streeter C, Mezey J, Cook D, Antczak DF.Lavender Foal Syndrome (LFS) is a lethal inherited disease of horses with a suspected autosomal recessive mode of inheritance. LFS has been primarily diagnosed in a subgroup of the Arabian breed, the Egyptian Arabian horse. The condition is characterized by multiple neurological abnormalities and a dilute coat color. Candidate genes based on comparative phenotypes in mice and humans include the ras-associated protein RAB27a (RAB27A) and myosin Va (MYO5A). Here we report mapping of the locus responsible for LFS using a small set of 36 horses segregating for LFS. These horses were genotyped usin...
Ewart SL, Ramsey DT, Xu J, Meyers D.Anterior segment dysgenesis syndrome occurs frequently in Rocky Mountain horses and has two distinct ocular phenotypes: (1) large cysts originating from the temporal ciliary body or peripheral retina and (2) multiple anterior segment anomalies including ciliary cysts, iris hypoplasia, iridocorneal adhesions and opacification, nuclear cataract, and megalocornea. To determine if anterior segment dysgenesis syndrome is heritable in horses we performed ophthalmic examinations and collected pedigree information on horses (n = 516) in an extended Rocky Mountain horse pedigree. Logistic regressive se...
Valberg SJ, Nicholson AM, Lewis SS, Reardon RA, Finno CJ.To report a novel exertional myopathy, myofibrillar myopathy (MFM) in Warmblood (WB) horses. Objective: To 1) describe the distinctive clinical and myopathic features of MFM in Warmblood horses and 2) investigate the potential inheritance of MFM in a Warmblood family. Methods: Retrospective selection of MFM cases and prospective evaluation of a Warmblood family. Methods: Retrospectively, muscle biopsies were selected from Warmblood horses diagnosed with MFM and clinical histories obtained (n = 10). Prospectively, muscle biopsies were obtained from controls (n = 8) and a three generation WB...
Exertional rhabdomyolysis (ER) and its familial basis in Warmblood horses is incompletely understood. Objective: To describe the case details, clinical signs and management of ER-affected Warmblood horses from a family with a high prevalence of ER, to determine if histopathological signs of polysaccharide storage myopathy (PSSM) and the glycogen synthase (GYS1) mutation are associated with ER in this family, and to investigate potential risk factors for development of ER. Methods: A family consisting of a sire with ER and 71 of his descendants was investigated. History of episodes of ER, husba...
Tryon RC, White SD, Famula TR, Schultheiss PC, Hamar DW, Bannasch DL.To assess heritability and mode of inheritance for hereditary equine regional dermal asthenia (HERDA) in Quarter Horses. Methods: 1,295 horses with Quarter Horse bloodlines, including 58 horses affected with HERDA. Methods: Horses were classified as affected or unaffected or as undetermined when data were insufficient to assess phenotype. Pedigree data were analyzed to determine the probable mode of inheritance. Heritability was estimated by use of Bayesian statistical methods. Results: Heritability (mean+/-SD) of HERDA was estimated to be 0.38+/-0.13, with both sexes having an equal probabili...
The Journal of heredityJanuary 1, 1976
Volume 67, Issue 1 6-10 doi: 10.1093/oxfordjournals.jhered.a108667
Trommershausen-Smith A, Suzuki Y, Stormont C.The chestnut rule in equine coat-color genetics asserts that the inter se mating of chestnut horses never produces bay, black, brown or gray offspring. The gray rule asserts that a gray offspring must have at least one gray parent. Nine alleged exceptions to the chestnut rule, all involving bay offspring, and eight alleged exceptions to the gray rule, including four offspring that were also exceptions to the chestnut rule, were examined for parent-offspring genetic incompatibilities in as many as 17 genetic systems of blood-group markers. In all except one of the 17 cases it was possible to sh...
