Norwegian Trotters Research Articles

Genetic risk factors for osteochondrosis in various horse breeds.

Osteochondrosis (OC) is an injury to cartilage canals with a following necrosis in the growth cartilage, from there it can develop to osteochondrosis dissecans (OCD). Due to its high impact in the equine industry, new insights into predisposing factors and potential high-risk genetic variants are warranted. This article reviews advancements in quantitative and molecular genetics in refining estimation of genetic parameters and identifying predisposing genetic loci. Heritabilities were highest for hock OC with estimates at 0.29-0.46 in Hanoverian warmblood and Norwegian trotters, whereas in Thoroughbreds only very low genetic variation seemed to be present in hock OC lesions. Whole genome scans using the Illumina Equine SNP50 or SNP70 Beadchip were performed in Thoroughbred, Standardbred, French and Norwegian trotter, Hanoverian and Dutch warmblood. Validation studies in Spanish Purebred and Hanoverian warmblood horses corroborated OC risk loci on ECA 3, 14, 27 and 29. Particularly, a strong association with hock-OCD was found for a single nucleotide polymorphism (SNP) on horse chromosome (ECA) 3 upstream to the LCORL gene. Gene expression and microRNA analyses may be helpful to understand pathophysiological processes in equine OC and to connect OCD-associated genomic regions with potential candidate genes. Furthermore progress in elucidating the underlying genetic variants and pathophysiological changes in OC may be expected from whole genome DNA and RNA next-generation sequencing studies.

Profiles of fragments after pulsed-field gel electrophoresis of cleaved genomic DNA from strains of Taylorella equigenitalis isolated from horses in Norway

The genomic DNA of eight strains of Taylorella equigenitalis, isolated from seven Norwegian Trotters and a Norwegian pony with contagious equine metritis in Norway, was examined by pulsed-field gel electrophoresis after separate digestions with two restriction enzymes, namely, ApaI and NotI. The respective electrophoretic profiles of the fragments were essentially identical but differed from those of T. equigenitalis NCTC11184 T and Kentucky 188. They also exhibited slight differences from profiles obtained from Japanese isolates. These results may possibly suggest a common genotype and a common source of infection for all these eight isolates in Norway.

Arthritis in the carpal joints of Norwegian trotter — heritability, effects of inbreeding and conformation

Carpal joint arthritis (carpitis) was diagnosed in a sample of 508 four year old Norwegian trotters born in 1980. The Norwegian trotter is a light Döle-horse, and prevalences of 10 and 27% were reported for bilateral and overall carpitis, respectively. Corresponding underlying scale heritability estimates, based on data of 407 horses sired by 34 stallions, were 0.67 and 0.25. Significant effect of inbreeding on bilateral carpitis was estimated on the same scale. The probability of the disease was, respectively, 6.7% and 12.3% among horses with lower or higher inbreeding coefficient than average. The relationship between faults of conformation and variables of carpitis was examined by a logistic regression procedure. On forelimbs, irregular values for calf knees and anterior broken toe-axis were associated with an enhanced prevalence of bilateral carpitis, while corresponding values for calf knees, standing under, toeing out, anterior broken toe-axis and lower circumference on cannon increased the overall carpitis probability.

Application of standardized, accumulated transformed earnings in breeding of Norwegian trotters

Earnings of horses were accumulated over age-class(es), and unraced horses were assigned zero earnings. The variables were power transformed (0.20) and standard normalized within birth year. Four resulting accumulated transformed and standardized earnings (ATSE) variables, for 1890 offspring by 74 base population sires, were analysed. A multivariate sire model was used in an initial analysis aimed at estimating phenotypic parameters, while a corresponding mate-corrected sire model was applied to estimate genetic parameters. Breeding values of mates were predicted by a multivariate animal model using data of all animals (14054) and parameter estimates from the initial analysis. The heritability estimates of ATSE variables over age-classes 3, 3–4, 3–5 and 3–6 year increased with increasing percent of raced horses and were 0.14, 0.20, 0.23 and 0.22, respectively. Phenotypic correlations were all greater than 0.70, and the genetic correlations approached 1.00. Sex and birth year effects were included in all analyses and in the proposed 4-trait animal model evaluation routine. Young sires should be selected on ATSE3-4 breeding values which showed a significant genetic trend of 3.2% of a phenotypic standard deviation per year.

Demographic Parameters and Inbreeding in the Norwegian Trotter

Abstract A total of 13 979 Norwegian trotters were born in Norway and registered in the Norwegian Trotting Association between 1972 and 1987. The generation intervals between sire and son (n = 333) and sire and daughter (n = 4366) were 11.23 and 10.91 years, respectively. The corresponding generation intervals between dam and son and dam and daughter were 11.71 and 11.12 years. The average mating age of stallions and mares were 9.81 and 9.91 years. Since 1972, the generation intervals between sire and son and sire and daughter increased significantly. Also, the average age of stallions and mares increased in this period. On average, the stallions and mares first reproduced at 4.69 and 6.24 years of age. Mean reproductive life was 6.40 years among stallions and 5.57 years among mares. The average size of progeny groups was 39.5 offspring per sire and 3.6 offspring per dam. Over the years, the amount of total and four-generation inbreeding steadily increased in the population.

Effect of inbreeding on fertility in Norwegian trotter

Inbreeding coefficients were calculated for 41 816 trotters born prior to 1984, and for 5457 reported matings in 1983, 1984 and 1985. The average level of inbreeding for all potential offspring was 0.057. There was great variation in amount of inbreeding. The most extreme value was 0.301. Average inbreeding coefficients among mares and stallions were 0.043 and 0.039, respectively. Foaling rate measured as the frequency of successful to unsuccessful matings in the Norwegian Trotter was 61.6%. The effect of inbreeding on foaling rate was nearly significant ( P = 0.08). The foaling rate declined with 0.43% 1% −1 increase in the inbreeding coefficient of potential offspring. In addition, the foaling rate was negatively influenced by increased age of both stallions and mares and positively influenced by increased number of prior foals per mare. A total of 32 out of 354 mares examined showed early abortion. Early abortion was significantly affected by the inbreeding coefficient and the age of the mare. One per cent increase in the mares' inbreeding coefficient increased the frequency of early abortion by 1.27%.

Antigen-Antibody Crossed Electro-Phoretic Studies and Quantitative Comparisons of Serum Transferrin Types in Horses

Selected transferrin phenotypes from 14 horses were investigated by antigen-antibody crossed electrophoresis. Horse sera were subjected to starch gel electrophoresis followed by right angle electrophoresis in agarose gels containing rabbit produced anti-horse transferrin. This technique gave an additional zone in the front as compared with 2 transferrin zones seen after ordinary starch gel electrophoresis. Comparisons of transferrin concentrations in horse sera were performed by an immunodiffusion technique. Values were related to a chosen reference serum. A total of 372 horses (210 Norwegian Trotters and 162 Warmblood Trotters) were investigated. There were considerable variations among horses, with the highest transferrin value 196% and the lowest 55% of the standard. There were highly significant differences between average values of certain transferrin phenotypes, the highest being TfFF and the lowest TfDO, TfFO and TfRR. In animals with the same transferrin phenotype, the average transferrin values were significantly higher in foals than in mares. No difference in transferrin values were found between sexes.