Ch 25: Dogs

Lesson 1: Introduction

Dogs are friendly and social animals with well-developed senses of smell and hearing. The ancestors of the domestic dog are wolves (Canis lupus) who long ago roamed Europe, Asia, and North America in large numbers. Dogs serve as animal models in a variety of areas, such as cardiovascular research and orthopedic (bone) studies.

Lesson 2: Taxonomy

The scientific name of the domestic dog is Canis familiaris. There are many dog breeds. Beagles are the most frequently used breed of dogs in research; thus, the values for biological data provided in Table 25.1 are for beagles.

Dogs used in research are generally purpose-bred, but mixed-breed (mongrel) animals from companies that supply “random-source” animals are also used. There are many regulatory safeguards in place to ensure that dogs used for research are obtained lawfully.

Lesson 3: Anatomy and Physiology

Dogs vary widely in size, shape, and coat color. The chihuahua, for example, weighs around 1 to 2 kilograms, while the St. Bernard can weigh up to 90 kilograms. The average weight for a research beagle is 13.5 – 18.5 kilograms.

Like other animals with a primarily carnivorous diet, dogs have specialized teeth for shearing meat from bone and a relatively short alimentary tract. Like cats, they have a nictitating membrane that provides protection to the eye. They see well at lower levels of illumination as compared to humans due to the presence of an intraocular reflecting structure, which causes what is known as “eye shine” in some vertebrates at night time.¹

Urine is clear and yellow to amber in color. Feces are firm and medium to dark brown in color, depending on the feed they are eating.

Lesson 4: Sexing and Reproduction

The external genitalia of dogs are easily identified and the sex differences are obvious from birth.

A male dog is simply referred to as a “dog,” while a female is called a bitch.

Dogs breed year-round. Mating is permitted by the female only during estrus (heat), which occurs approximately every 7 to 8 months. Estrus lasts for 7 to 10 days. The start of estrus is characterized by swelling of the vulva and a blood-tinged vaginal discharge. Ovulation is spontaneous and takes place during early to mid-estrus.

Several methods are used by veterinarians to determine if a female has become pregnant. The hormone relaxin is secreted from placental tissue and can be detected by blood tests after 21 days gestation. Palpation of fetuses between three and four weeks of gestation is also a useful technique. Ultrasound can detect pregnancy as early as 17 days gestation, a much earlier stage that any other method. X-rays can be used to detect the fetal skull and spine at around 43-46 days.

Several visual signs may indicate pregnancy.

• Teats often become larger and more prominent in color, and may produce a clear fluid.

• Weight gain and a swollen, round abdomen are common after day 40 of pregnancy.

A pregnant female should be given a warm secluded area to deliver her pups. She should be able to deliver pups without intervention, but signs such as discolored discharge or straining without producing pups may indicate the need for veterinary intervention.²

Hormone changes may make the new mom aggressive after her litter is born as her protective instincts are heightened. She should be provided with plenty of quiet time with only necessary visitors. Her pre-pregnancy personality should return as the puppies get older.

Lesson 5: Behavior

Daily contact with animal care personnel seems to improve a dog’s psychological and physical well-being. Dogs will generally seek attention from the humans around them. Attention-seeking postures may be submissive or exuberant.

• A submissive dog may approach the handler in a crouched, sideways movement with its head low, ears flattened, body close to the ground, and tail between the legs but wagging.

• The more confident, exuberant dog will be more direct, with its head held high, eyes bright, and ears extended. Such dogs are often vocal, and approach humans with their tails erect and wagging.

Some dogs may be fearful or possibly aggressive .These dogs should be approached towards the side, rather than toward the head, and avoiding direct eye contact. Watch the dog out of the corner of your eye for signs of fear or aggression. Wrinkling of the nose, lips curled with teeth showing, ears are back and usually pinned to the head, raised hackles, tail tucked, body lowered are all signs of fear or aggression.^3,4

Lesson 6: Handling and Restraint

Individual dogs have distinct personalities, which should be taken into account when the animals are handled. Most dogs have mild, even temperaments and are eager to please their handlers. Some dogs are timid and frighten easily. A few are aggressive and difficult to handle. Dogs that are socialized with people at a young age generally respond favorably to gentle and frequent handling.

Patience and kindness are a successful dog handler’s best assets. A dog should never be forced into a corner where it would feel trapped. A shy or fearful dog may require some extra time to become comfortable in your presence.

The key to restraining any animal is to use only the minimum force necessary to ensure the safety of both the handler and the animal.

Approaching an Unfamiliar Dog

When you first approach an unfamiliar dog, you should do so slowly, making sure the dog is aware of your presence before you get too close to it. Crouching to the dog’s height and speaking in a quiet, soothing voice as you near the dog tends to help keep the dog calm. When you are within arm’s reach of the animal, extend your arm slowly, palm down and fingers folded. Once you are close enough to touch the dog, a leash or loop rope with a slipknot can be placed around the dog’s neck.⁵

Dogs should never be lifted by the scruff of the neck. A handler can lift a dog to carry it by placing one hand underneath the chest and the other under the rump (Figure 25.1).

Chest-down Position

A cooperative dog may be restrained for an injection or similar manipulation by placing it on a secure surface and holding it in a chest-down position, as illustrated in Figure 25.2. Place one arm around the animal’s neck and bring its head up to your shoulder. While holding the head and neck firmly in this position with one arm, place the other arm around the dog’s chest to immobilize its foreleg.

Lateral Recumbency

When restraining a dog in lateral recumbency, position the dog so that its feet extend away from you. Reach across the animal’s body and grasp the front legs with one hand, resting your forearm across the dog’s neck. Grasp the hind limbs with your other hand, resting that forearm against the animal’s rump. When the dog is adequately restrained, a second handler can perform manipulations such as drawing blood or giving an injection.

Restraint Devices

A catch pole may be necessary to restrain an aggressive dog. The loop is used to control the dog’s head. A second person can hold the hind leg and administer a sedative or tranquilizer.

Dogs that are aggressive and likely to bite may need to be muzzled. There are several types of commercially available muzzles. Alternatively, you may muzzle a dog using a 2-foot strip of gauze bandage, as illustrated in Figure 25.4; wrap the gauze snugly around the dog’s mouth twice, tie it under the jaw, and knot it behind the head. Animals should only be muzzled for short periods of time – always remember to remove a muzzle once the procedure is complete.

Chemical restraint may be necessary to immobilize the dog for X-ray radiography or other procedures. Administering tranquilizers, narcotics, or barbiturates should only be done by trained personnel under the supervision of a veterinarian.⁶

Lesson 7: Identification Methods

As with cats, the USDA requires that dogs be identified with sturdy tags on a collar, a microchip, or a tattoo. A unique number is usually assigned to each animal at the breeding facility. This number is often tattooed on a hairless area of the dog’s ear.

Lesson 8: Husbandry and Diet

Housing

Dogs are social animals and can be group housed with other dogs in pens or runs. Outdoor runs are acceptable if provided with appropriate heating and cooling, access to shade, and protection from rain and wind. Alternatively, some facilities have indoor housing with access to outdoor runs. In general, runs have sealed cement floors to facilitate cleaning and reduce parasite problems. Indoor cages can have solid, slatted, or coated metal floors. Slatted flooring allows urine to drain away from the animal. The spacing between the slats should be small enough to prevent toes and collars from getting caught between slats. A layer of absorbent bedding material may be used on solid flooring to absorb urine and cover feces. Individual caging must be large enough to allow for normal postural adjustments, such as standing, turning around, and lying down. The AWA also requires that dogs be provided the opportunity for exercise outside of their pens or runs if these areas do not offer enough floor space to do so inside.

Cage Maintenance

Cages should be cleaned and the bedding changed daily, and should be regularly sanitized at least every 2 weeks. Floors of pens and runs should be cleaned and sanitized on a regular basis. Make sure that the animals do not get wet during cage or run cleaning.

Feed and water bowls need to be cleaned, and refilled daily, and sanitized at least once every two weeks. Check automatic watering systems every day to ensure that they are functioning properly.

Diet

Dogs, like cats, are primarily carnivores but need a balanced diet that includes meat products, grains, and vegetables. Commercial dog diets offer balanced nutrition; the amount of feed required is determined by the dog’s size, age, health, activity, and whether it is pregnant or lactating. Special research requirements may also be a factor in the amount of feed offered to the dog. Adult dogs are generally fed once a day; leftover feed should be removed after a reasonable period of time. Fresh, clean water should be available ad libitum.⁷

In groups, dogs tend to establish a social hierarchy; make sure that the less dominant animals in the group get their share of feed and water by providing sufficient feed and water bowls for all animals.

Lesson 9: Environmental Enrichment

Modern dogs have been bred to be companions to people; therefore, human interaction is very important to them. Daily interaction, play sessions, and general socializing are encouraged.

Training is another form of enrichment. Dogs greatly enjoy being trained to walk on a leash and perform tasks such as sitting still and waiting for a treat. This training can also be used to condition them to accept medications such as flea and heartworm control.

Dogs may use raised resting boards, especially if the boards are heated. Dogs will also enjoy toys, such as balls, ropes, and chewing objects, as well as specially designed toys that can be filled with food treats. The AWA has specific requirements for exercising dogs that must be followed unless exempted by the attending veterinarian or the IACUC. Dogs benefit from having ample space to run, jump, and walk around. Exercise with agility equipment can also be useful. Environmental enrichment must be documented.

Lesson 10: Signs of Pain, Distress, or Illness

Stiff body movements or an unwillingness to move are indications of pain in dogs. A dog with less severe pain may just appear restless. Shivering, heavy panting, whimpering or howling are also signs of pain or distress. Dogs may bite or scratch irritated or painful areas.

A dog in pain is often more apprehensive and aggressive than normal. A sick dog, on the other hand, will often try to isolate itself in a corner of its cage, often in a curled position with its feet tucked under and its head and tail curled around the body. Sick or injured dogs usually will not respond to the handler’s call and may tremble, growl, snarl, or whimper.

Lesson 11: Euthanasia

An overdose of barbiturates administered by trained personnel is an acceptable method for euthanasia. An overdose of inhalant anesthetics or potassium chloride delivered to the heart while the dog is under anesthesia may also be used. As with all other laboratory animals, death must be verified prior to disposal. Your institution’s SOPs may require an additional procedure to be performed for this verification. In addition, the USDA mandates the documentation of euthanasia and retention of the dog’s unique identification tag for one year after disposition, and each unique identification number cannot be reused for 5 years. Carcass disposal should be according to the facility's guidelines.