Saturday 12 January 2008

>>Self colour

Self colour

The Russian Blue is a cat breed selected for a self blue colour
The Russian Blue is a cat breed selected for a self blue colour
This golden Lhasa Apso has some slight colour variation in his coat, but each hair is a uniform shade and he has no white markings, making him a self coloured dog
This golden Lhasa Apso has some slight colour variation in his coat, but each hair is a uniform shade and he has no white markings, making him a self coloured dog

A self colour refers to the top coat colouration of several domestic animals, such as dogs, pet rodents and cats. It refers to hairs of a uniform shade, with no banding or tipping of another colour. A true self coloured animal should also have no white markings such as bibs or blazes.

In contrast, a sable (dogs), ticked (dogs or cats) or agouti (cats or rodents) coat has two or more different colours along the shaft of the hair, with one colour at the base and usually a darker colour, such as black, at the tip.

>>Pastern

Pastern

The pastern is a part of the horse between the fetlock joint and the hoof, or between the wrist and forepaw of a dog. It is the equivalent to the two largest bones found in the human finger. It was famously mis-defined by Dr Johnson in his dictionary as "the knee of a horse". On this being pointed out to him by a lady, he gave in reply the famous quotation: "Ignorance, madam, pure ignorance."

Anatomy and Importance of the Pastern

Shock absorption of the pastern.
Shock absorption of the pastern.

The pastern consists of two bones, the uppermost called the "large pastern bone" or proximal phalanx, which is located just under the fetlock, and the lower called the "small pastern bone" or middle phalanx, located between the large pastern bone and the coffin bone (also see Equine forelimb anatomy). The joint between these two bones is aptly called the "pastern joint." This joint has very limited movement, but does help to disperse the concussive forces of the horse's step and also has some influence on the flexion or extension of the entire leg.

The length of the pastern is determined by the length of the first phalanx. The short pastern bone is less a determinant because it is smaller, at 2 inches in length, and part of it is encased in the hoof.

The pastern is vital in shock absorption. When the horse's front leg is grounded, the elbow and knee are locked. Therefore, the fetlock and pastern are responsible for all the absorption of concussive forces of a footfall. Together, they effectively distribute it among both the bones of the leg and the tendons and ligaments.

Matching Angles

Image:Broken-pastern-hoof-angle.jpg
Broken hoof-pastern angle, due to long toe.

Shoulder

The slope of the shoulder is often the same as the slope of the pastern. However, differing angles in these two joints will not affect athletic performance.

Hoof

The pastern angle should always match the angle of the hoof after it is trimmed (the angle will change as the hoof grows and may be off in a few weeks). This keeps the bones of the pastern, the coffin bone, and their joints in proper alignment, with a straight line running through their core. An angle broken forward or back increases the stress on these bones, joints, tendons, and ligaments. If the angle does not match, it is often an indication of poor farrier work.

Conformation

The pastern is evaluated when a horse studied conformationally, as it will effect the gait of the horse and the soundness of the joints above it. Traditionally, the ideal pastern of the front leg has a 45 degree angle. However, this angle has been revised to a slightly steeper angle of 47-55 degrees, as the traditional angle, although it makes for comfortable riding, greatly increases the chance of breakdown.

Because there is less need for shock absorption in the hindleg, its pasterns should be shorter and more upright than those of the front leg, to increase its strength (about 49-59 degrees, and sometimes greater). If the hind pasterns are the same angle as the front, or too sloping in general, then they are likely to break down during the horse's career, especially if the horse in employed in strenuous work.

A nicely-sloped pastern increases the likelihood of a long career. It improves the animal's ability to travel on uneven terrain, helps him withstand the rigors of a competition or race, and makes the gait more comfortable for the rider.

The length of the pastern is also important. The best length for the pastern is 1/2 to 3/4 the length of the cannon bone.

Long, sloping pasterns

Image:Long,-sloping-pasterns.jpg
Note the length of the pastern in relation to the cannon bone.

Long, sloping pasterns are more than 3/4 the length of the cannon bone. They are sometimes bred for in a riding horse because they increase the shock-absorption ability of the leg, making the horse's gaits smoother and more comfortable for the rider. However, they have the distinct disadvantage of being weaker than more upright pasterns. This is because many of the tendons and ligaments that go down the back of the leg continue under the back of the fetlock joint, and attach to either the pastern bones or the coffin bone. When the horse puts weight on his leg, the fetlock sinks closer to the ground, which is a needed response as it helps to absorb the shock of the footfall. However, when the pasterns are too long or sloping it does not support the fetlock enough, and the fetlock may hyper-extend, possibly to the point where the ergot touches the ground. This stresses the soft tissues that run under the fetlock because they are stretched longer. If stretched too much, they may tear or rupture.

Medical problems that may result from long, upright pasterns include:

  • Bowed Tendon
  • Sesamoiditis
  • A fracture of the sesamoid bones found at the back of the fetlock, should the joint hyperextend to the point where it touches the ground. This is especially likely if the horse is tired, such as at the end of a race.
  • Injury to the suspensory ligament
  • Ringbone, due to excessive stress on the pastern joint

Long, sloping pasterns are commonly seen in Thoroughbreds, Saddlebreds

Short, upright pasterns

Draft horse with upright (65 degree) pasterns.
Draft horse with upright (65 degree) pasterns.

Short, upright pasterns are less than 1/2 the length of the cannon bone. They are beneficial in that they decrease the chance that the horse will suffer from soft-tissue injury. However, upright pasterns increase concussion by transmitting more of the shock of footfalls to the bones rather than the tendons. This not only makes the gaits uncomfortable due to the jarring, but also increases the chance of arthritis and may shorten the animal's career. A short, upright pastern also decreases the stride length of the gait, which again makes the gait more uncomfortable and decreases the efficiency of the horse's movement (since he must take more strides per meter than a longer-strided horse).

Medical problems that may be caused by short, upright pasterns are usually a result of excess concussion. They include:

Short, upright pasterns are often seen in draft horses. This is because draft horses bred for pulling rather than riding (and so they were not selected for smooth gaits of a saddle horse), and because upright pasterns give more leverage to dig into the ground as the horse pulls a heavy load.

Short, upright pasterns are also commonly seen in Quarter Horses, Warmbloods, and Paint Horses. However, riding horses are more likely to have problems with upright pasterns than draft horses because they tend to work at faster speeds.

Due to the lack of shock absorption, horses that have upright pasterns should be kept off hard surfaces whenever possible.

>>Natural bobtail

Natural bobtail

A natural bobtail is a tail which due to a mutated gene grows to a shortened length or is completely cut off at the base of the spine. The term also refers to animals carrying the gene for a naturally short tail or animals that naturally have no tail. The genes for the shortened tail may be dominant or recessive depending on the species.

Due to anti-tail docking legislation, natural bobtails are growing in importance in the hobby of dog fancy for some traditionally docked breeds. For example, one Boxer breeder and geneticist in England has successfully petitioned the Kennel Club for permission to cross Corgis into his lines and then backcross to Boxers, introducing the gene into his lines. This would have been unheard of in decades past. A number of these bobtail Boxers have been successfully exported to various countries around the world.

In Australia, the price for a registered purebred Miniature Fox Terrier bitch carrying the gene has more than tripled.

Animals with a natural bobtail

Domesticated breeds with a natural bobtail

Breeds in which bobtails are known to occur

Wild species with natural bobtails

Sunday 6 January 2008

>>Merle (coat colour in dogs)

Merle (coat colour in dogs)

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Blue merle Border Collie puppy
Blue merle Border Collie puppy

Merle (In Welsh:Brych) is a colour combination in dogscoats. It is a solid base color (usually red/brown or black) with lighter blue/gray or reddish patches, which gives a mottled or uneven speckled effect. Although most breeds that can have merle coats also typically have white markings (such as around the neck, under the belly, and so on), and often tan points (typically between the white and the darker parts of the coat), these are separate colors from the merle; some dogs do appear completely merled with no white or tan markings.

Merle can also alter other colors and patterns besides the usual red or black. These combinations such as Brindle Merle or Liver Merle are not typically accepted in breed standards.

In addition to altering base coat color, merle also modifies eye color and coloring on the nose and paw pads. The merle gene modifies the dark pigment in the eyes, occasionally changing dark eyes to blue, or part of the eye to be colored blue. Since merle causes random modifications, however, both dark-eyed, blue-eyed, and odd-colored eyes. Color on paw pads and nose may be mottled pink and black.

Merle is a distinguishing marking of several breeds, particularly the Australian Shepherd, and appears in others, including the German Coolies in Australia, the Shetland Sheepdog, various Collies, the Welsh Corgi (Cardigan), the Pyrenean Shepherd, the Bergamasco Sheepdog, the Catahoula Leopard Dog, the Koolie, and the Old English Sheepdog. In Dachshunds the merle marking is known as "dapple". Merle is also less commonly found in the Chihuahua, the Pomeranian, the Pit Bull, and the Cocker Spaniel; it is not, however, a recognized color in these breeds. The merle gene also plays a part in producing harlequin Great Danes.

Merle is actually a heterozygote of an incomplete dominance gene. If two such dogs are mated, on the average one quarter of the puppies will be double merles ("double dilute") and some percentage of these double merle puppies could have eye defects and/or could be deaf. Knowledgeable breeders who want to produce merle puppies mate a merle with a non-merle dog; roughly half the puppies will be merles without the risk of vision or hearing defects.

In January 2006, scientists at Texas A&M University announced the discovery of a mobile genetic unit called a retrotransposon, responsible for the merle mutation in dogs.

A phantom merle is one with such small patches of merle--or none at all--that it appears to be a nonmerle.In America, a dog with the phantom merle coloring is described as being "cryptic for merle."

>>Hip score

Hip score

Hip scoring is a procedure used to determine the degree of hip dysplasia in dogs and other animals and reporting the findings in a standard way.

The hip score is the sum of the points awarded for each of nine radiographic tures of both hip joints.

The British Veterinary Association uses the following criteria to determine hip score:

  1. Norberg Angle
  2. Subluxation
  3. Cranial Acetabular Edge
  4. Dorsal Acetabular Edge
  5. Cranial Effective Acetabular Rim
  6. Acetabular Fossa
  7. Caudal Acetabular Edge
  8. Femoral Head/Neck Exostosis
  9. Femoral Head Recontouring

The lower the score, the less the degree of dysplasia present. The minimum (best) score for each hip is zero and the maximum (worst) is 53, giving a range for the total of 0 to 106.

The following table compares the scores recognised by Orthopaedic Foundation for Animals (OFI), Fédération Cynologique Internationale (FCI), the British Veterinary Association (BVA) and Verein für Deutsche Schäferhunde (SV).

OFA (USA) FCI (European) BVA (UK/Australia) SV (Germany)
E A-1 0-4 (no > 3/hip) Normal
G A-2 5-10 (no > 6/hip) Normal
F B-1 11-18 Normal
B B-2 19-25 Fast Normal
M C 26-35 Noch Zugelassen
Mod D 36-50 Mittlere
S E 51-106 Schwere

The average hip scores in the year 2005 for popular breeds from Australia are tabulated below:

Breed Average score
Airedale Terrier 13
Alaskan Malamute 11
Belgian Shepherd 9
Bernese Mountain Dog 11
Border Collie 9
Bull Mastiff 23
Cavalier King Charles Spaniel 15
Curly Coated Retriever 11
Doberman 9
German Shepherd Dog 13
Golden Retriever 16
Irish Setter 15
Japanese Akita 11
Labrador Retriever 12
Mastiff 11
Newfoundland 21
Old English Sheep Dog 17
Rhodesian Ridgeback 7
Rottweiler 10
Samoyed 19
Siberian Husky 6
St. Bernard 18
Staffordshire Bull Terrier 12
Weimaraner 10

>>Hairless dog

Hairless dog

A hairless dog is a dog with a genetic disposition for hairlessness. There are two known types of genetic hairlessness, a dominant and a recessive type.

Dominant genes

Dogs with dominant genes for hairlessness can pass their attributes to their offspring in natural conditions, that is, not under the control of humans. Therefore, it is possible that, in some parts of the world, groups of hairless dogs came into existence without human intervention. Later in history, people developed these groups into a recognized breed.

African Hairless Dog at the Walter Rothschild Zoological Museum, Tring, England
African Hairless Dog at the Walter Rothschild Zoological Museum, Tring, England

Recognized breeds at this time are the Chinese Crested Dog, the Mexican Hairless Dog, and the Peruvian Hairless Dog. Other breeds there are said to exist are the Hairless Khala, African Hairless Dog (also known as the Abyssinian Sand Terrier, Egyptian Hairless Dog and Elephant Dog, the last being a reference to its grey skin) and the Thai Hairless Dog.

This type of genetic structure is said to be homozygous lethal for the dominant gene. This means that dogs with two dominant genes cannot live. Therefore, all dominant-hairless dogs have a heterozygous gene structure. There is also a homozygous recessive type, which is a coated variety.

On average, every litter of hairless puppies should include some coated ones. Statistically, for every 2 hairless puppies, there should on average be one coated.

However, some breeders claim varying averages from 1:0 to 2:1; that is, some breeders claim to have no coated offspring in any of their litters, while others claim to have an average ratio of 8:1 or 4:1 or 2:1. Averages that show more coated than hairless are not known.

The Chinese Crested coated variety is called "Powder Puff", and is a recognized type. For the other breeds coated varieties are called "coated" and are not recognized as valid varieties for show dogs.

Recessive genes

Dogs with a recessive gene for hairlessness are not known in natural conditions. The only known such breed, the American Hairless Terrier, is created by mankind.

>>Docking (dog)

Docking (dog)

Docking is used as a term for the intentional removal of part of an animal's tail or ears. The term cropping is also used, more commonly in reference to the docking of ears, while docking more commonly—but not exclusively—refers to the tail. The term bobbing is also used.

Other animals (such as sheep and pigs) either historically, or currently, have been subject to tail docking. For information about docking of other animals, see Docking (animal).

History of docking and cropping

For dogs who worked in fields, such as some hunting dogs and some herding dogs, tails could collect burrs and foxtails, causing pain and infection; tails with long fur could collect faeces and become a cleanliness problem; and particularly for herding dogs, longer tails could be caught in gates behind livestock. These arguments are often used to justify docking tails for certain breeds, although the same rationale is not applied to all herding or to all hunting dogs with long or feathered tails.

Many hunting dogs’ tails are docked to prevent them from becoming injured while running through thickets and briars while fetching hunters' prey. The few hunting breeds that are not docked, including English Pointers and the Setter breeds, may have chronic injuries to the tips of their tails. Such injuries cause continuing pain and discomfort and are at risk of infection throughout their lives.

Boxers with natural and docked ears and docked tails
Boxers with natural and docked ears and docked tails

The practice of cropping dogs' ears and cropping their tails is controversial. Studies show that dogs severely docked tails are twice as likely to be involved in aggressive attacks as dogs with longer tails; likewise for dogs with severely cropped ears.[citation needed] However, dogs with cropped ears might make better guard dogs for this reason.[citation needed] Cropped ears and docked tails are less likely to be injured or infested with parasites than long ears and tails. Some owners simply believe cropped ears and docked tails are more appealing than the natural ears and tails that some dogs posses.

Some people believe that docking a dog's tail is a cruel practice. They believe that if a dog is performing its job—such as hunting—then it is fine to dock the tail; if the dog of the same breed is in a home where it doesn't do the job, however, then docking is not necessary. Some people believe that, if a newborn puppy's tail is docked without the use of anesthesia, the puppies are put through much pain. The newborn can't express pain clearly, so most breeders seem to think the puppies don't feel a thing.

In many breeds whose tails (or whose ancestors' tails) have been docked over centuries, such as Australian Shepherds, no attention was paid to selectively breeding animals whose natural tail was attractive or healthy – or, in some cases, dogs with naturally short (or bob) tails were selectively bred but inconsistently (since docking was done as a matter of course, a natural bob did not have an extremely high value). As a result, in many of these breeds, naturally short tails can occur, but medium-length and long tails also occur. Occasionally, tails have developed with physical problems or deformities because the genetic appearance was never visible or because of the inconsistent emphasis on natural bobs. Breeders often consider many of the resulting tails to be ugly or unhealthy and so continue to dock all tails for the breed.

Current status

A Doberman Pinscher puppy with its ears taped to train them into the desired shape and carriage after cropping
A Doberman Pinscher puppy with its ears taped to train them into the desired shape and carriage after cropping

Docking is usually done almost immediately after birth to ensure that the wound heals easily and properly. An old belief said that newborns hardly felt the injury, but now reputable breeders have cropping and docking performed only under licensed veterinary care. Today, many countries consider cropping, docking to be cruel, or mutilation and ban it entirely. This is not true in the United States, and the breed standards for many breeds registered with the American Kennel Club (AKC) make undocked animals presumably ineligible for the conformation show ring. The AKC states that it has no rules that require docking or that make undocked animals ineligible for the show ring, but it also states that it defers to the individual breed clubs (who define the breed standards) to define the best standards for each breed.

In such an environment, even people who desire undocked dogs often cannot get them. Most people prefer to choose a puppy from a reputable breeder after the puppy is old enough to determine personality and conformation, whereas docking is done immediately after birth. A breeder normally will not withhold docking on an entire litter so that a potential owner can later have one of the puppies with an undocked tail, as docking an older dog is a major surgery-requiring anaesthesia.

Show dogs are no longer docked in the United Kingdom. A dog docked before 28 March 2007 in Wales and 6 April 2007 in England may continue to be shown at all shows in England, Wales, Scotland and Northern Ireland throughout its natural life. A dog docked on, or after, the above dates, irrespective of where it was docked, may not be shown at shows in England and Wales where the public is charged a fee for admission. However, where a working dog has been docked in England and Wales under the respective regulations, it may be shown where the public are charged a fee, so long as it is shown “only to demonstrate its working ability”. It will thus be necessary to show working dogs in such a way as ONLY to demonstrate their working ability and not conformity to a standard. A dog legally docked in England, Wales, Northern Ireland or abroad may be shown at any show in Scotland or Northern Ireland.

Legal status by country

In Europe, the cropping of ears is prohibited in all countries that have ratified the European Convention for the Protection of Pet Animals.

Legality in the United Kingdom

In England and Wales, ear cropping is illegal and no dog with cropped ears can take part in any Kennel Club event (including agility and other nonconformation events). Tail docking is also illegal, except for a few working breeds, but only when carried out by a registered veterinary surgeon.

The Royal College of Veterinary Surgeons (RCVS), the regulatory body for veterinary surgeons in the United Kingdom, has said that they consider tail docking to be "an unjustified mutilation and unethical unless done for therapeutic or acceptable prophylactic reasons". In 1995 a veterinary surgeon was brought before the RCVS disciplinary council for "disgraceful professional conduct" for carrying out cosmetic docking. The vet claimed that the docking was performed to prevent future injuries and the case was dismissed for lack of evidence otherwise. Although cosmetic docking is still considered unacceptable by the RCVS, no further disciplinary action has been taken against vets performing docking.

In March 2006, an amendment was made to the Animal Welfare Bill (now the Animal Welfare Act 2006) which makes the docking of dogs' tails illegal, except for working dogs such as those used by the police force, the military, rescue services, pest control and those used in connection with lawful animal shooting. Three options were presented to Parliament with Parliament opting for the second:

  • An outright ban on docking dogs' tails (opposed by a majority of 278 to 267)
  • A ban on docking dogs' tails with an exception for working dogs (supported by a majority of 476 to 63)
  • Retention of the status quo.

Those found guilty of unlawful docking would face a fine of up to £20,000, up to 51 weeks' imprisonment or both.

In Northern Ireland legislation regarding docking has not yet been drawn up. It is therefore still legal.

In Scotland docking of any breed is illegal. The Animal Health and Welfare (Scotland) Act 2006 contains provisions prohibiting the mutilation of domesticated animals.

Queen Elizabeth II, who owns and breeds Pembroke Welsh Corgis (a docked breed), is on record as having stated: "As dog breeders we have been given a charter to maintain the appearance of the breeds as handed down by our forebears through the various breed standards."

Arguments against docking dogs' tails

Robert Wansborough argues in a 1996 paper that docking dogs' tails puts them at a disadvantage in several ways. Firstly, Wansborough argues that dogs use their tails actively in communicating with other dogs (and with people); a dog without a tail might be significantly handicapped in conveying fear, caution, aggression, playfulness, and so on. In addition, certain dog breeds use their tails as rudders when swimming, and possibly for balance when running, so active dogs with docked tails might be at a disadvantage compared to their tailed peers.

Wansborough also investigates seven years of records from an urban veterinary practice to demonstrate that undocked tails result in less harm than docked tails.

Each of these criticisms has its counterarguments , as shown by the Council for Docked Breeds.

There is controversy over whether evidence shows that docking does or does not cause significant pain, does or does not lead to behavioural problems, whether it prevents chronic injuries that cause more pain and risk of infection than the docking procedure done a few days after the puppy is born.

Docking proponents argue that the pain felt by the puppy is insignificant compared to the pain felt by an adult dog with a tail injury, so that docking should be allowed as a preventative measure in traditionally docked breeds.

>>Dewclaw

Dewclaw

The dog's front dewclaw grows on the side of the foot, above the other four toes but below the carpal pad. This one is well worn from contact with the ground when the dog is running.
The dog's front dewclaw grows on the side of the foot, above the other four toes but below the carpal pad. This one is well worn from contact with the ground when the dog is running.

A dewclaw is a vestigial digit of the paw of many mammals, birds, and reptiles (including some extinct orders, like certain theropods). It grows higher on the leg so that in digitigrade species, when the animal is standing, it does not make contact with the ground.

Dogs

Dogs almost always have dewclaws on the inside of the front legs and occasionally on the hind legs. Unlike the front dewclaws, the rear dewclaws tend to have little bone or muscle structure in most breeds. Occasionally some dogs will even have more than one dewclaw on the same foot; often at least one of these dewclaws will be poorly connected to the leg and may require a dewclaw removal. When a dog has extra dewclaws in addition to the usual one on each front leg, the dog is said to "double dewclawed." There is some debate about whether the dewclaw helps dogs to gain traction when they run because, in some dogs, the dewclaw makes contact when they are running and the nail on the dewclaw often wears down in the same way that the toenails on their other toes do, from friction with running surfaces. However, in many dogs, the dewclaws never make contact with the ground; in this case, the dewclaw's nail never wears away, and it must be trimmed to keep it at a safe length.

The dewclaws are not dead appendages.They can be used to lightly grip bones and other items that dogs hold with the paws. However in some dogs these claws may not appear to be connected to the leg at all except by a flap of skin; in such dogs the claws do not have a use for gripping as the claw can easily fold or turn (this is esp. true for most dewclaws on the hind legs), and it may be better to remove the dewclaws instead.

This dog's dewclaw never makes contact with the ground and has grown.
This dog's dewclaw never makes contact with the ground and has grown.

There is also some debate as to whether dewclaws should be surgically removed. The argument for removal states that dewclaws are a weak digit, barely attached to the leg, so that they can rip partway off or easily catch on something and break, which can be extremely painful and prone to infection. There is also a slight risk that the dog may scratch and damage the eyes when rubbing their face with their front paws. Dewclaw removal is usually done when the dog is a puppy, sometimes as young as 3 days old, though it can also be performed on older dogs if necessary (though the surgery may be more difficult then). The surgery is fairly straight-forward and may even be done with only local anesthetics if the digit is not well connected to the leg. Unfortunately many dogs can't resist licking at their sore paws following the surgery, so owners need to remain vigilant.

In some countries removing the dewclaws is illegal, as removing it is said to be unnecessarily painful to the dog, in addition to the claim that the dewclaw will rarely or never suffer injury leading to amputation.

In addition, for those dogs whose dewclaws make contact with the ground when they run, it is possible that removing them could be a disadvantage for a dog's speed in running and changing of direction, particularly in performance dog sports such as dog agility.

There also exists in folklore a story that claims that dogs that have not had their dewclaws removed are immune to snakebite. In America, some pups are commonly sold by breeders "dewclawed", that is with the dewclaws removed (as by a vet) for perceived health and safety reasons. A few breed standards also call for it.