Single mutation affects horse gaits

Scientists in Sweden have announced an important discovery that helps explain how some horses are limited to “natural” gaits, while others are capable of additional gaits.

Nearly all horses use “natural” gaits (walk, trot, canter and gallop) without special training. Additional “ambling” gaits may occur naturally in some individuals, but usually only in certain breeds.

Researchers have identified a single gene mutation that enables horses to perform gaits such as running walk and pacing. The pace is a lateral two-beat gait; the two legs on the same side of the horse move forward together, unlike the trot, in which the two legs diagonally opposite each other move forward together.

Not only does the mutation play a crucial role in the horse's ability to perform “ambling” gaits, it also affects performance in harness racing.

Leif Andersson and his research team in the Department of Animal Breeding and Genetics, at the Swedish University of Agricultural Science were looking for a genetic basis for gaits in horses. Only some horses can pace, and they wanted to find out why.

 

They studied the genomes of 70 Icelandic horses that could perform extra gaits — 40 could pace, and 30 could perform other alternate gaits. They found that a single mutation in a gene called DMRT3 was strongly associated with the ability to pace. The mutation resulted in the production of a shortened form of the DMRT3 protein. Both copies of the gene were mutated in the pacing horses.

Andersson explained that horses without this mutation cannot move their right hindleg and right foreleg forward at the same time. But with the mutation the movement is not regulated so strictly and becomes more flexible.

“We suspected a strong genetic component, but were almost shocked when we discovered that a single gene, DMRT3, largely explained the genetic difference between pacers and non-pacers’” said Lisa Andersson, one of the PhD students involved in the project.

The researchers developed a diagnostic test and found that the mutation is widespread among horses that show alternate gaits like Tennessee Walking Horse from the USA and Paso Fino from South America.

The mutation must have originated over a thousand years ago, Andersson said, judging by its widespread distribution among breeds. The horses with this gene would have given a smoother ride and thus been kept and bred.

While Andersson's group were investigating the presence of the gene mutation in pacing horses, a second research team was investigating the expression of the DMRT3 gene in the spinal cord of mice.

Klas Kullander and colleagues in the Department of Neuroscience, at Uppsala University, found that the gene was expressed in a previously unknown type of nerve cell within the spinal cord.

Further investigation showed that the DMRT3-neurons cross the midline of the spinal cord, connecting the left with the right side. They also connect with motor neurons that control flexor and extensor muscles. It seems that, as well as coordinating the activity of flexor and extensor muscles, this network of nerve cells also controls the alternate movement of left and right limbs.

‘The discovery of the DMRT3 mutation is an outstanding example of how genetic studies of evolution in domestic animals can lead to basic new knowledge concerning gene function and important biological mechanisms’, said Leif Andersson.

‘It is truly great when this type of interdisciplinary collaboration results in such ground breaking discoveries. There was no information in the scientific literature on the function of the DMRT3 prior to the publication of our article. This protein is present in all vertebrates for which data are available, and it is likely that DMRT3 nerve cells have a central role for coordinating movements in humans as well’, added Klas Kullander.

More details at equinescienceupdate.com

BHA announces new Detection Times

The British Horseracing Authority has announced that it has adopted five new Detection Times for Romifidine, Salbutamol, Firocoxib, Butorphanol and the Romifidine/butorphanol combination.

These Detection Times are harmonised across the member countries of the European Horseracing Scientific Liaison Committee (EHSLC). The EHSLC has been investigating the detection times of commonly-used medications, in response to the need for more information on the time taken for drugs to be eliminated.

In addition, the BHA detection Time for Detomidine/Butorphanol has been harmonised with the Detection Time across Europe and raised from 48 to 72 hours. Most of these new Detection Times result from research performed at the Authority’s Centre for Racehorse Studies in Newmarket.

The “detection time” is the time at which the concentration of the drug (or its breakdown products) in the urine, is not detected using routine or standard methods, in all the horses in the study.

It is important to remember that “detection times” are not the same as “withdrawal times”. An additional safety margin should be added to allow for individual variation.

However, the figures will give some welcome guidance to veterinarians who have to advise on whether a horse is likely to test positive if treated in the days before a race.

Further information, including a downloadable sheet of all 31 BHA Detection Times, together with a full explanation of the limitations of the results, can be found on the Authority’s website

http://www.britishhorseracing.com/resources/equine-science-and-welfare/medication-control.asp

Information on withdrawal of supplements containing Devil’s Claw has also been added to the Notices section of the Authority’s Rules website, where further information the use of a number of medications can also be found.

http://rules.britishhorseracing.com/Orders-and-rules&staticID=126908&depth=2

Possible blood test for inflammatory airway disease?

Inflammatory airway disease (IAD) is a common cause of poor performance in the equine athlete. Affected horses may cough as well as showing exercise intolerance, but a definitive diagnosis is based on examination of bronchoalveolar fluid (BALF.) This involves passing a tube into a sedated horse’s lung. A small amount of fluid is introduced and withdrawn, and the cells that have been washed from the lung are collected and examined microscopically.

Research at a laboratory in France may lead to the development of a simpler test for IAD. Eric Richard and colleagues at the Frank Duncombe Laboratory at Caen have been investigating the value of a blood test for a protein present in the lung for identifying horses with IAD.

Surfactant protein D (SP-D) is produced mainly by specialised cells in the alveoli and bronchioles, but has also been found in joint fluid and in the reproductive tract. It plays a role in immune defences in the lung

SP-D is released into the blood stream in response to tissue damage, and is used routinely in human medicine as a marker for inflammatory lung diseases.

The study, which compared SP-D levels before and after exercise in horses with and without inflammatory airway disease, has been reported in the Equine Veterinary Journal.

The researchers found that IAD was associated with a detectable, though moderate, increase in SP-D levels in the blood.

Within the IAD-affected group, they found no significant correlation between serum SP-D concentrations and BALF cytology. Neither did they find a significant effect of exercise on serum SP-D concentration in either the IAD or control groups.

A non-invasive test for IAD would benefit both horse and owner, being less stressful for the horse and cheaper for the owner. However, the report's authors advise that more work is needed to understand the factors controlling blood levels of SP-D. They advise caution before applying their findings to clinical cases.

More details:  equinescienceupdate.com

Music and stress response in weanlings

Scientists at the University of Queensland have found that music therapy may help reduce the stress associated with weaning.

Twelve weanlings that had been raised together were divided into two groups, matched for temperament. At weekends, all weanlings were turned out together. On week days, one group remained in the paddock, while the other group was stabled, with or without soothing music. Eventually both groups had been stabled for five days with music and five days without.

During the music treatment weeks, the Forest Gump Main Theme by Alan Silvestri was played continuously from 09.00 to 15.00 h daily. This particular piece of music was chosen for its constant rhythm, continuity and predictable melody.

The research team recorded heart rates every day from 09.00 to 15.00 h using heart rate monitors. They also recorded each horse's behaviour.

They found that although music did not affect the median heart rate, it significantly reduced heart rate variability. Furthermore, behavioural measurements showed that weanlings were more relaxed, and spent more time eating rather than walking about the stable, when they were exposed to soothing music.

Twice a week the weanlings were exposed to stallions in nearby stables. This gave the research team the opportunity to assess the effect of music on the weanlings' response to stress.

They found that, when music was being played, the peak heart rate in response to stress was substantially lower and the duration of increased heart rate was shorter.

The researchers conclude that their findings suggest that stress responses in weanlings can be modified by playing music whilst in stables. They suggest that the application of music therapy to enrich the equine environment is an area that shows promise and requires further study.

Read more : equinescienceupdate.com

Legibility of hot iron brands

The debate about the use of hot iron branding for identifying horses is becoming as heated as the branding iron itself. Critics of the procedure maintain that it causes pain and stress, which is no longer acceptable since the advent of microchip technology.

Others point out that not everyone carries a microchip reader with them. At least brands are easy enough to read without special equipment. Or are they? Recent work suggests that hot iron branding is not as accurate a means of identification as its supporters claim.

Until recently, horses were generally branded but following concerns that the practice is unnecessarily cruel there has been a gradual switch towards the use of microchips. Branding has essentially been discontinued in the European Union, although it is still accepted in several countries. Breed registries claim that this traditional method is perfectly satisfactory and obviates the need for costly equipment. Typically, a brand will comprise a symbol to indicate the particular breed combined with a two-digit number to identify the individual animal.

Comparisons between the two methods for identifying horses have focused on how they are perceived by the animals: does either method cause more stress or more harm to the horse?

Surprisingly, however, no attention has been paid to the other side of the coin. There is no doubt that microchips can be unambiguously decoded, providing the necessary equipment is available, but how well can brand marks be read? The issue has now been examined by Jörg and Christine Aurich of the University of Veterinary Medicine, Vienna.

According to the study, reported in the Veterinary Journal, three breed experts could only accurately identify the brands on less than half of the horses presented to them.

To assess the legibility of the markings, the researchers asked three experienced people to record the brands of 248 horses participating in an equestrian tournament in Germany.

All three experts were able to recognize the breed symbols on about 90% of the animals. For about 84% of the animals the symbol was recorded correctly by all three people.

However, reading the two-digit numbers proved more problematic. While each of the three readers correctly read the numbers on about half of the horses, the correct number was recorded by all three of them for less than 40% of the animals.

Read more at equinescienceupdate.com