The genetic relationship between three Swedish horse breeds was investigated using microsatellite data from 144 loci in 30 horses. The North Swedish Trotter is believed to have been crossed with the Standardbred in the 1950?s to produce a faster trotter. If true, the North Swedish Trotter should be more alike the Standardbred than what the North Swedish Draught Horse is, from which they originate. This was investigated using F-statistics and Nei?s distance in GENEPOP and GENETIX and cluster assignment in STRUCTURE.

A nonsense mutation in the DMRT3 gene has been shown to have a large impact on pattern of locomotion in horses. Horses that can perform several other gaits in addition to the normally occurring gaits, walk, trot and canter, are often hetero (CA)- or homozygous (AA) for this nonsense mutation. Horses that only can perform walk, trot and canter are often homozygous for the wild-type gene (CC). For example the Icelandic Horse is a gaited breed. Five-gaited Icelandic horses can perform both flying pace and tölt, except for the normally occurring gaits, walk, trot and canter, and are often homozygous for this nonsense mutation (AA).

The purpose of this thesis was to analyze conception and foaling results of Swedish warmblood and Standardbred trotters using breeding statistics during the years 2000-2006. Key issues in this thesis were: Have the conception and foaling results of stallions changed during the period 2000-2006? What is the effect of the use of various breeding methods? Is testicle size correlated with conception and foaling results? How important are age, breed and level of inbreeding of the stallion for conception and foaling results? Breeding statistics were available for 537 Swedish Warmblood stallions and 305 Standardbred trotter stallions. To be included in the analyses, a stallion must have mated at least ten mares in total over the period 2000-2006. This criterion was met by 313 Swedish Warmblood stallions and 272 Standardbred trotter stallions.

EVA, Equine Viral Arteritis, was diagnosed for the first time in 1953 in USA. The disease gained international interest in 1984, when there were several outbreaks of abortion at Thoroughbred studs in USA. EAV, Equine Arteritis Virus, is an RNA virus in the Arteriviridae family. There is only one serotype of EAV but several strains and the strains have different virulence. EAV is transmitted in two different ways: by aerosols, or by venereal transmission.

The trotting in Sweden has a good reputation in an international view, both in the perspective of success and how the sport is managed with focus on security, animal protection and animal welfare. A large number of equipment details are fitted on the horses during training and competition. The Swedish law of prevention of cruelty to animals regulate training and competition with racehorses, and propose to protect horses from unnecessary suffering. The equipment permitted in races is regulated in Tävlingsreglementet (The Regulation of Competititon) and in the regulations of equipment, that the Nordic Regulation Committee and Nordic Animal Welfare Committee have worked out. Due to training and competition the equipment must even meet the Swedish law of prevention of cruelty to animals. However, the behaviour or the senses of the horses is often affected by the equipment due to the way the equipment corrects, modifies, restrains or reduces the behaviour of the horse, which may cause the horse stress or discomfort.

There is a need for correct and adequate pain assessment in horses. Methadone is used in pain management in horses but the full pharmacokinetic picture of methadone is not yet known. The aim of this pilot study was to develop a behaviour protocol and suggest a reliable recording method for use in a larger research project with an aim to potentially correlate behaviours to concentration of methadone in blood. In this study two Coldblooded Trotters were given methadone intravenously with doses of 0.1 mg/kg for horse 1 and 0.2 mg/kg for horse 2. The horses were videotaped pre and post methadone administration.

Abortion during late gestation is often caused by placental dysfunction such as placentitis. To prevent this from happening the placenta can be monitored pre partum so treatment can be started at an early stage. Methods for monitoring the placenta include hormonal monitoring, presence of clinical signs of placental dysfunction and ultrasonographic evaluation of the fetus and the placenta. Transrectal ultrasonography provides a very good image of the caudal portion of the allantochorion where an ascending placentitis normally establishes. An increased combined thickness of the uterus and the placenta, CTUP, has been associated with placental failure. This study included ten Swedish standardbred trotter mares in late gestation. They were monitored by transrectal ultrasonography of the placenta two times with approximately a month in between. CTUP was measured on each examination.

Inbreeding has become a problem in some horse breeds. Studies show that it may lead to inbreeding depression which affects e.g. reproduction traits. In the wild there are mechanisms that make horses avoid mating with close relatives. When selection is done by humans this mechanism is removed and intensive breeding for a few traits, for example good racing results, can become a problem.

The harness racing industry has roots hundreds of years back in time and breeders through time have changed the horses to a mix of potential, harmony and speed. Breeding has changed the conditions and created a horse that perform better and better. A risk with high-performance horses is that injuries related to training and racing may occur more often. In training and racing situations, lameness is the most common injury. There are many factors affecting the occurrence of injuries and lameness of the trotter horses, such as how the horse is trained and raced, the surface condition of the racetrack, banking and angle of the curves of the racetrack and how fast injuries are discovered and treated.

Today there is a research project undertaken by the Swedish University of Agricultural Sciences along with Wången (a highschool specialized in trotter training), which focuses on trotting horse training, performance and health. The project investigates how exercise intensity and feeding strategies affect the development of growing horses. The project includes two groups of horses where all 16 horses are fed in the same way. One group of eight individuals are trained 100% compared to conventional training and the other group are trained 20% less than the other group. All horses are trained twice a week and are out at pasture beyond that.

According to the basic values of the Swedish Trotting Association the horse and its welfare should always be held in highest consideration. One part of the animal welfare work in the organization is to ensure good horse management practices by controlling all active trainers through the local licensing committees situated at the Swedish racetracks. The Swedish Board of Agriculture stated that high quality animal welfare assurance programs used by the industry organizations can be used in the risk assessment of the official animal welfare control to make the official control work more effective and the ambition of the Swedish Trotting Association is to establish an animal welfare assurance program which may be approved by the Swedish Board of Agriculture. Racehorses are exposed to welfare hazards both in their management as well as during training and racing and factors like handling, training, feedstuff, stable environment, medication and the possibility to express natural behavior all affect the welfare of the horses. The aim of the project is to investigate and evaluate the animal welfare work performed by the licensing committees and to give advice on how to improve the industry?s animal welfare control.

The aim of the present study was to investigate the effect on growth of foals on two different diets, either a forage-based diet or a diet containing approx. 40 % concentrate. The report also includes a review of the pertinent literature on the effects of diet on mares? milk and growth of horses. The hypothesis of the study was that a forage based diet will result in a similar growth pattern as a diet including more concentrates if the diets contain the same amount of energy, crude protein, lysine, calcium and phosphorous.

Studiens målsättning var att besvara tre frågeställningar. Skiljer sig andningsfrekvensmönstret efter ansträngning hos varmblodstravare med prestationsnedsättning från normalpresterande hästar? Påverkas andningsfrekvensmönstret efter ansträngning av en ökad slemansamling i luftstrupen? Är koncentrationen surfaktantprotein D i blodet en relevant analysparameter vid utvärdering av nedre luftvägsproblem? Hypotesen var att travhästar med subkliniska luftvägsproblem i de nedre luftvägarna har en längre återhämtningsperiod efter ansträngning jämfört med friska hästar. Kopplingen mellan ökad slemansamling i luftstrupen och prestation undersöktes också. 24 varmblodstravare deltog i försöket. Innan försöket undersöktes varje häst kliniskt inkluderande vilo-EKG och luftvägsendoskopi.