The aim of the study is to investigate the effects of age, sex, running distance and origin of horse on racing speed for Thoroughbred Arabian horse in Tunisia. Although the occidental type is known to be more successful in racing than the Tunisian type, we undertook this study to try to confirm or deny this supremacy for a sample of racehorses born in Tunisia from occidental father. A total of 333 racing records were considered for race performance. The effects of environmental factors on (sex, age, father’s origin, race distance, number of race seasons) race performance were analyzed using the least-squares method(LSM).The racehorses studied were all Arabian Thoroughbred horses in operation at the racecourse of Ksar Said from 2010 to 2020. They are 180 horses, 90 horses born of a Tunisian father, and 90 horses born in Tunisia ofthe occidentalfather. These horses are the best and most successful in their category. The study revealed that the gender and age effectswere statistically insignificant onracingperformance. Race performance was significantly influenced by the distance and the origin of the father which affirms the improving role of the occidentalhorse in the Tunisian population.

Background: Severe Combined Immuno Deficiency (SCID) is a heritable deficiency transmitted through autosomal recessive gene, carried on by purebred Arabian and crossbred horses. A deletion of five base pairs at the gene encoding the catalytic subunit of the Protein Kinase DNA-dependent (DNA-PKcs) is responsible for this disease and SCID-affected animals always die in the first six months of life. Considering this problem, it is important to perform a molecular epidemiological study to estimate the frequency of the SCID allele in Arabian purebred horses in Tunisia.Methods: The DNA of the peripheral blood lymphocytes of 164 purebred Arabian horses belonging to the Sidi Thabet stud was extracted by the spin-column method, in order to verify the quality of the DNAs used, the samples were dosed by a spectrophotometer. The amplification of the DNA was carried out by two specific primers in a Polymerase Chain Reaction (PCR) to flank the deletion zone of the DNA sample by adding to each PCR sample a marker or a standard of size knowing that the fragment we wanted to amplify is composed of 163 base pairs. Then, the PCR products were sequenced using an automatic sequencer. Result: By analyzing the electropherograms results, we noted the absence of the SCID deletion in the studied group of Arab purebreds. Hence, it is essential to carry out molecular screening of the SCID deletion in other sites in order to determine its prevalence in the country’s purebred Arabian horse population.

The aim of the study is to investigate the effects of age, sex, running distance and origin of horse on racing speed for Purebred Arabian horse in Tunisia. Although the occidental type is known to be more successful in racing than the Tunisian type, we undertook this study to try to confirm or deny this supremacy for a sample of racehorses born in Tunisia from occidental father. A total of 333 racing records were considered for race performance. The effects of environmental factors on (sex, age, father’s origin, race distance, number of race seasons) race performance were analyzed using the least-squares method(LSM).The racehorses studied were all Arabian Purebred horses in operation at the racecourse of Ksar Said from 2010 to 2020. They are 180 horses, 90 horses born of a Tunisian father, and 90 horses born in Tunisia ofthe occidentalfather. These horses are the best and most successful in their category. The study revealed that the gender and age effectswere statistically insignificant onracingperformance. Race performance was significantly influenced by the distance and the origin of the father which affirms the improving role of the occidentalhorse in the Tunisian population.