GENETIC ARTICLES

 

FROZEN SEMEN VS. FRESH EXTENDED SEMEN

by: Lori Riley

Frozen and fresh extended semen give the ability to breed to a stud when he is not readily available.  They eliminate the need to transport bitches to the stud dog.  Thus decreasing transportation risks to the bitch, boarding costs and stress on the bitch which could alter her ability to conceive.  It will also insure that the stud will not contract an infection from the bitch.

In both cases semen is collected from the dog by normal stimulation.  The semen is completely evaluated before it is collected.  This evaluation includes a total sperm count, progressive mobility evaluation, sperm morphology, pH, and an abnormal sperm count.

The frozen semen is maintained in liquid nitrogen tanks at a temperature of -320 degrees F.  This temperature will allow the sperm to remain viable indefinitely.  After the freezing procedure has been completed, a single sample is thawed for sperm evaluation.  The post thaw progressive motility is evaluated and should result in a figure that is greater than 70%. These sperm will only survive for 12 - 24 hours once inside the bitch.

Fresh extended semen should be used within 24 - 48 hours depending on the semen quality   These sperm will survive for 4 - 6 days once inside the bitch.

The ideal time to freeze your dog's semen is when he is in top form and health.  This is usually between the age of 2 - 6 years for most dogs.  Dogs up to 15 years of age may be capable of producing viable sperm and having their semen successfully frozen is possible.

The recipricol bitch's season is monitored by using the ICG method.  Blood tests are taken to monitor the progesterone which may actually coincide with the LH rise.  This improves the ability to predict the point of maximum fertility.  For the best conception results the sperm is surgically implanted into the bitch.  But, a new machine called the CTI is now being used to non-surgically implant the sperm.

Sperm banks and fertility centers for canines are available around the world. Importation regulations for individual countries vary and information is readily available.

The main costs in storing sperm is in the initial collection.  Monthly storage costs are fairly reasonable.

 

"CHERRY EYE" IN DOGS BELIEVED TO BE GENETIC

Glandular hypertrophy or "cherry eye" is a prolapse of the gland of the third eyelid.  Cherry eye is commonly see in Cocker Spaniels, Bulldogs, Beagles, Bloodhounds, Great Danes, Basset Hounds, Shih Tzus, and Lhasa Apsos.

     Dr. Ralph Hamor, an assistant professor specializing in opthalmology at the University of Illinois Veterinary Medicine Teaching Hospital (VMTH) at Urbana, states that "although we have yet to learn the cause of this condition, cherry eye is believed to be genetic and is usually not caused by trauma."  The VMTH receives several cases per month.

     This condition is not a pretty sight and can be frightening to the owner when first noticed.  Dr. Hamor explains, "the red, fleshy gland that sits between the eyelid and the eyeball pops up and protrudes over the edge of the third eyelid.  In acute stages, dogs with cherry eye exhibit redness, swelling, and a mucous or serious discharg."  He notes that cherry eye frequently occurs in younger dogs - less than a year old.

    Treatment techniques will differ among veterinarians.  Usually, there are three ways to deal with cherry eye.   These are: 1) surgically reposition the gland to its original place at the base of the third eyelid, 2) surgically remove the prolapsed gland, or 3) leave the prolapse alone.

    The gland of the third eyelid is responsible for approximately 30 percent of a dog's tear production.  Tears are necessary to lubricate the cornea.  Complete removal can lead to condition call keratoconjunctivits sicca (KCS) or "dry eye". Dry eye is a vision-threatening disease.  It is caused by tear deficiency and if it is left untreated it may result in persistent redness, mucus discharge, corneal scarring and ulceration.   Unfortunately, if a breed is predisposed to cherry then they are also predisposed to dry eye.  It is believed that complete removal of the gland can further predispose these breeds to dry eye.  As a result, VMTH policy recommends surgically repositioning the prolapsed gland in dogs that are predisposed to dry eye.   Medication, used in humans to prevent transplanted organ rejection, is available to treat dry eye and stimulate tear production.  An approved veterinary product for the medical treatment of dry eye is now available through your local veterinarian.  Of course, the treatment route taken depends on the owner's situation and wishes.

     Ignoring the prolapsed gland, rather than removing it or repositioning it, may also be an option depending on the case.  Dr. Hamor says that usually a prolapsed gland doesn't cause serious disease unless it is complicating another disease process.

     Although the specific reason behind cherry eye has not been discovered, Dr. Hamor encourages dog owners to schedule regular veterinary checkups and eye exams for their dogs.  Many times, early detection can prevent more serious eye complications later on.

 

 

PRA IN DOGS

by: Tara Riley

 


Backgound and Diagnosis


     PRA means progress retinal atrophy.  It is a long recognized, hereditary blinding disorder.  PRA is a disease of the retina.  This is a tissue, that is located inside the back of the eye.   It contains specialized cells that are called photoreceptors that absorbs the light focused on them by the eye's lens, and it converts that light through series of chemical reactions into electrical nerve signals.  From the retina the nerve signals are passed by the optic nerve through to the brain where they are perceived as vision.   For vision in dim light, and cones for vision in bright light, the retinal photoreceptors is specialized in rods.  PRA is usually affective to the rod initially, and then to the cones in a later stage of the disease.  The very first description of this disease was in a breed called Gordon Setters in Europe, it happened in the early twentieth century.  Since then this problem PRA is recognized in most of the purebred dogs.

    In all of the canine breeds PRA has certain common features.  Early on in the disease, the affected dogs go nightblind, it lacks in the ability to adjust their vision to dim light; later on the daytime vision also fails.  As the vision dteriorates, the affected dogs will adapt to their handicap as long as the environment stays the same.  At the same time their pupils of the eyes become increasingly dilated, it causes a noticeable "shine" to the eyes.  The lens of their eyes may become cloudy, or opaque, resulting in a cataract.

     The difference in PRA among all the breeds is the age of onset and the rate of progression of the disease.  The certain breeds, notable the Collie, Irish Setter, Norwegian Elkhound and the Miniature Schnauzer, have early onset forms.  In those breeds this disease the results from abnormal or arrested development of the photoreceptors - visual cells in the retina, affects the pups very early in there life.  In other breeds, like the Miniature Poodle, English and American Cocker Spaniel, and Labrador Retriever, PRA is much later in onset.  The affected dogs develop PRA as adults, but appear normal when young in those types of breeds.

     The diagnosis of PRA is normally made by and examination called opthalmoscopic.  They use and instrument called an indirect ophthalmoscope, and it requires dilation of the dog's pupil by application of eyedrops.  Broadly speaking all the forms of PRA have all the same sequence of opthalmoscopic changes:  increase of shininess of the fundus ( inside of the back of the eye, overlaim by the retina); the reduction in the diameter and the branching pattern of the retina's blood vessels; and then shrinking of the optic nerve head.  By the time the dog has these changes there are already significant signs of the loss of vision.

     Confirmation of this disease can be undertaken by electroretinography.  It is an electrical measurement of the retinal function somewhat similar to an electrocardiographic test of the heart function, but have two differences: electroretinogram (ERG) can only be recorded as a response to a flash of light; and accureate of the ERG requires that the dog be anesthetized.  In all the dogs clinical showing that they have PRA, the ERG is severly diminished or extinguished.

 

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