Topic:Breed Differences
Breed differences in horses encompass variations in physical characteristics, behavior, and physiological traits among different horse breeds. These differences arise from selective breeding practices aimed at enhancing specific attributes such as speed, endurance, strength, or temperament. Physical attributes can include variations in size, coat color, and conformation, while behavioral traits may involve differences in temperament and trainability. Physiological differences can affect metabolism, disease susceptibility, and performance capabilities. This topic includes peer-reviewed research studies and scholarly articles that explore the genetic, environmental, and historical factors contributing to breed differences, as well as their implications for equine management, health, and performance.
Lymphocyte alloantigens of the horse. I. Serologic and genetic studies. A genetic system controlling lymphocyte alloantigens of the horse is described. Alloantisera to paternal histocompatibility antigens induced as a result of pregnancy in mares were used in an antibody-mediated complement-dependent microcytotoxicity assay to define 15 Equine Leukocyte Antigen (ELA) specificities using cluster analysis. In this study 369 sera were screened for alloantibody using lymphocytes from 10 randomly selected, unrelated horses. A high proportion (83%) of these sera were found to be positive for antibody to lymphocyte alloantigens. After initial cluster analysis, 120 of the...
The equine electrocardiogram with standardized body and limb positions. Eleven-lead electrocardiograms (ECGs) were recorded from 50 Thoroughbred (TB) and 50 Standard bred (SB) horses at rest with 40 tracings being selected from each group for more complete analysis. Incomplete atrioventricular block with dropped beats commonly reported in mature horses was recorded only in the TB (15%), while wandering of the atrial pacemaker (WAP) thought also to be associated with variations in tone of the autonomic nervous system was detected almost equally in both breeds (30%). In some horses (12.5%), the initial component of the P wave (P1) did not vary as seen with WAP but h...
Ovarian follicular populations in pony and saddle-type mares. Five pony and 5 saddle-type mares were used to compare total ovarian follicular populations between breeds. The animals were hemi-ovariectomized at the preovulatory stage during the breeding season and the ovary bearing the large preovulatory follicle was studied using histological techniques. Pony and saddle-type mares did not differ as to mean number of primordial follicles, mean number of growing follicles, the variability of these numbers and follicular distribution into various size classes. No difference was detected either in the initiation processes of follicular growth, oocyte growth,...
Pancreatic beta cell function in the neonatal foal. Plasma concentrations of insulin and glucose were measured in Pony and Thoroughbred foals at birth and at intervals thereafter for up to 7 days. The plasma concentrations of insulin in foals of both breeds at birth were 11.2 +/- 2.5 microU/ml (N = 6) and 13.5 +/- 1.5 microU/ml (N = 16) respectively. These values were similar to those obtained for foals in utero but were significantly less than those in adult animals. There was little variation in the plasma concentrations of insulin and glucose during the first 2 h of life and both concentrations tended to rise in the next 24-48 h. Although th...
Serum thyroxine and triiodothyronine concentrations in neonatal foals and mature horses. Serum thyroxine (T-4) and triiodothyronine (T-3) concentrations were assayed in neonatal foals (1.5 to 4 months) and mature horses (2 to 25 years old) by a modified radioimmunoassay procedure. Blood was collected from 52 clinically healthy foals and horses of various breeds (Thoroughbreds, Quarter Horses, American Saddle Horses, and a single cross-bred horse). Neonatal foals had high serum concentrations of T-4 (mean, 4.02 microgram/dl) and T-3 (192.9 ng/dl) as compared with the values in mature horses (T-4, mean of 1.76 microgram/dl; T-3, mean of 98.69 ng/dl). Stallions had slightly higher T-...
Discrimination learning in horses: effects of breed, age and social dominance. The discrimination learning ability of Quarter Horses and Thoroughbreds was compared by means of visual cues in a three-choice test with food as a reward. Quarter Horses learned significantly faster than Thoroughbreds, and learning progressed more rapidly for both breeds in a second discrimination task. Significant negative correlations were observed between age and rate of learning. Quarter Horses tended to be less reactive than Thoroughbreds, but individual emotional reactivity ratings and learning scores were not correlated. No correlation was found between social dominance and learning sco...
Muscle fibre type composition of a number of limb muscles in different types of horse. Skeletal muscle of the equine was differentiated into three fibre types according to myosin ATPase (pH 9.4) and succinic dehydrogenase activity. The percentage of these types was determined in the musculus deltoideus, m triceps brachii caput longum, m gluteus medius, m semitendinosis, m biceps femoris and m vastus lateralis of the thoroughbred, Shetland pony, pony, heavy hunter and donkey. In addition the m gluteus medius was examined in the arab and American racing quarterhorse. High myosin ATPase activity fibres varied from a mean of 93.2 per cent in the m gluteus medius of the quarterhorse ...
Epidemiology of equine influenza, risk by age, breed and sex. Three hundred and sixty cases of diagnosed equine influenza reported to the Veterinary
Medical Data Program (VMDP) of the National Cancer Institute, U.S.A., were tested for the
independent effects of age, breed and sex, relative to a reference clinic-hospital population of 84,562
equine patients. Horses of age category 2-6 months showed a significant risk above unity for
infection with equine influenza virus whereas, horses in age category 7-10 yr showed a significant,
low and sparing risk. Horses under two months or over 10 years, as well as those in ages from 6
months to 7 yr had non-s...
Differences in the histochemical properties of skeletal muscles of different breeds of horses and dogs. Histochemical profiles of individual muscle fibres were established using myosin adenosine triphosphatase (myosin ATPase), succinate dehydrogenase (SDHase), and glycogen phosphorylase (GPase) reactions in three muscles (semitendinosus, diaphragm, and pectoralis transversus) of the horse and dog. The major histochemical difference between fibres lies in their myosin ATPase activity; fibres can be subdivided into those with a high and those with a low activity. In horse muscle, all fibres have a high activity of GPase. In the diaphragm and pectoralis transversus, all fibres have a high SDHase ac...
Radioimmunoassay technique for detecting urinary excretion products after administration of synthetic anabolic steroids to the horse. 1. Cross-bred and thoroughbred geldings were injected with veterinary doses of various synthetic anabolic steroids. Urines collected sequentially from treated animals were analysed, following solvent extraction, by radioimmunoassay using 19-[3H]nortestosterone and an antibody raised against a 19-nortestosterone immunogen. 2. Urinary excretion of 19-nortestosterone and/or its cross-reacting metabolites was detectable for various times after administration of different nortestosterone esters, as follows: phenylpropionate (400 mg), greater than 14 days; cyclohexylpropionate (100 mg), greather tha...
A new allele in the prealbumin system of horse serum markers. A family study of an index case in the Arabian breed of horses demonstrated the presence of a new allele in the prealbumin (Pr) system of electrophoretically determined markers in horse serum which, when homozygous, results in the absence of any recognizable zones in the Pr region. The symbol PrO is proposed for this allele which has an estimated frequency in Arabian horses of 0.09.
Genetic polymorphism of the vitamin D binding protein and another post-albumin protein in horse serum. Horizontal polyacrylamide gel electrophoreses, on 10% separation gel, of horse serum revealed polymorphism of the vitamin D binding protein (Gc protein) and another post-albumin protein (Pa). Family data supported the hypothesis that Gc and Pa types were controlled by autosomal codominant alleles. For both Gc and Pa proteins, the homozygous types showed a single fraction while the heterozygous type had two fractions. Pa types were found to be identical to the post-albumin types reported earlier by starch gel electrophoresis. Two Gc alleles, GcF and GcS, and three Pa alleles, Pa D, Pa F and Pa ...
Epidemiologic analysis of oral and pharyngeal cancer in dogs, cats, horses, and cattle. Four hundred sixty-nine oral-pharyngeal malignancies diagnosed in dogs, cats, horses, and cattle and submitted to the Viterinary Medical Data Program between March 1, 1964, and Dec 31, 1974, were analyzed. Of these cases, 84% were in dogs. The most frequent oral-pharyngeal cancer in dogs was melanoma; in cats and horses, it was squamous cell carcinoma. In dogs, the risk of developing melanoma increased more with age than did the risk of developing squamous cell carcinoma and fibrosarcoma. Male dogs had significantly greater risk of developing fibrosarcomas and melanomas than did female dogs. T...
Squamous cell carcinoma in horses. In a review of neoplasm registry records at Kansas State University (1961 through 1971), 58 squamous cell carcinomas were reported in 10 breeds of horses. Mean age of the affected horses was 12.4 years. The head, eye and ocular adnexa accounted for 43.1%, the external male genitalia, 44.8%, and female perineal region, 12.0% of the squamous cell carcinomas, altogether representing 20.2% of 287 neoplasms recorded.
Equine serum lipids: serum lipids and glucose in Morgan and Thoroughbred horses and Shetland ponies. Concentrations of serum phospholipids, triglycerides, total cholesterol, nonesterified fatty acids, and glucose were determined for 9 months (September, 1972, to May, 1973) in 19 fasting horses and ponies (8 Morgan horses, 7 Thoroughbred horses, and 4 Shetland Ponies). Morgan horses had higher concentrations of total lipid than did Thoroughbreds, although the relative proportions of each type of lipid were similar in the 2 breeds. Shetland Ponies had higher nonesterified fatty acid and lower glucose concentrations than did either breed of horse. In both breeds of horses, concentrations of seru...
Equine serum lipids: serum lipoprotein profiles of Morgan and Thoroughbred horses. The serum of lipoproteins of 10 Morgan and 8 Thoroughbred horses were examined by 2 methods of polyacrylamide gel electrophoresis. A significant breed difference in the beta-lipoprotein to alpha-lipoprotein ratio was seen in gradient slab electrophoresis. A breed difference in the number of peaks, but no difference in beta-lipoprotein to alpha-lipoprotein ratio, was found in disc gel electrophoresis. These results have been correlated to indicate differences in charge of alpha-lipoprotein components and in size of beta-lipoprotein components between these 2 breeds of horses.
Equine serum lipids: lipid composition and electrophoretic mobility of equine serum lipoprotein fractions. The serum lipoprotein fractions from 5 Morgan and 5 Thoroughbred horses were isolated by preparative ultracentrifugation, chemically analyzed for lipid composition, and studied by 2 methods of polyacrylamide gel electrophoresis to determine electrophoretic mobility. Breed differences were not seen in the relative percentages of the lipid classes found in the various fractions. Normally, horses, like most animals, carry the majority of their lipid in high-density lipoproteins. Electrophoretically, the only difference seen between breeds occurred on disc electrophoresis where the extra band, whi...
Empyema of the equine paranasal sinuses. A survey of 28 cases of chronic purulent infection of the sinuses in the horse showed a relationship between incidence and age, and a probable relationship with breed. Dental disease was apparently the cause of half the cases. The conventional treatment of trephination followed by irrigation with antiseptic solutions resulted in freedom from recurrence of the disease for over 1 year in 17 of the 28 horses. Antibiotic therapy appears to be useless in chronic empyema. The prognosis is adversely affected by the development of facial swelling, a sign seen usually only in long-standing cases.
Serum levels of the immunoglobulins IgG and IgG(T) in horses. Levels of the immunoglobulins IgG and IgG(T) in serum in Norwegian horses of the breeds “Døle” and “Fjord” were determined by the quantitative radial immunodiffusion test. No significant differences were apparent between the 2 Norwegian breeds. The immunoglobulin levels were approximately in the same range as previously reported for Shetland ponies. Immunoglobulins could not be detected in the newborn foal. As early as 24 hrs. after birth the mean immunoglobulin level was within the adult range. After a drop during the first month of life, the immunoglobulins increased. IgG(T) rose mo...
Genetic Control of Albumin Phenotypes in Horses. By means of a starch-gel technique suggested by Kristjansson, 3 albumin phenotypes A, AB and B are demonstrable in the serum of horses. As indicated by data on the inheritance of these phenotypes and by a gene-frequency analysis of the distribution of the phenotypes in 2 breeds of horses, the results are consistent with the interpretation that the 3 phenotypes are controlled by a pair of codominant, autosomal alleles. These 3 phenotypes can be diagnosed by examining either the albumin region or the post-albumin region of the gels. Hence, diagnosis in one region serves as an independent check o...