Chapter IX ~ DOGS
The dog exhibits a greater variance and range of physical and behavioral types (breeds) than any other domesticated animal. Several hundred true breeding varieties have been developed through centuries of domestication and fanciful selection, in various parts of the world.
Differences in size and conformation between breeds range from the Newfoundland to the Chihuahua (70 kg vs. 2 kg) and those of temperament are almost as divergent. Correlated with size differences will be variances in such physiological parameters as pulse rate (60-80 in large breeds; 90-130 in small) and respiratory rates (ranging from 16 in large to 30 in small animals). Of course, such parameters may also be markedly influenced by physiological (excitement), physical (exertion) and environmental factors.
The domestic dog (Canis familiaris) is capable of hybridization with wolf, coyote and jackal (Fox and Bekoff, 1975).
Territorial marking by leg cocking and urination is characteristic of all male canidae and is believed to also serve as a means of communication.
Numerous behavioral studies on dogs have been undertaken over the past 25 years and there are many comprehensive general reviews of this topic (Fox and Bekoff, 1975; Solarz, 1970; Fox, 1971; Campbell, 1975; Brunner, 1968), as well as analyses of the development of genetic and social behavior in several breeds (Brunner, 1968; Scott and Fuller, 1965).
Socialization is particularly
important in the early weeks of the dog's life. It is generally concluded
that this period, which extends from approximately the fourth to the twelfth
week, is the optimum time for the dog to develop social attachments. If
pups are raised in kennels with little human contact during the period
of socialization, subsequent training for specialized tasks is generally
quite difficult (Fox and Bekoff, 1975; Campbell, 1975).
Random Source Dogs
All dogs should be legally procured from reputable and, where required by legislation, licensed suppliers.
Most research dogs are acquired from random sources, usually municipal pounds. Such dogs have completely unknown genotypes, behavioral experiences and disease exposure profiles. Their use should be limited to those studies in which a defined animal is not a requirement.
Dogs from random sources (pounds) have often been discarded by their owners and turned loose to fend for themselves; thus, nutritional and disease problems will be frequently encountered in these animals.
Some few of the random source (pound) dogs that are legally acquired by a research institution will, nonetheless, inevitably be "lost" pets. The research institution, should, if requested, ensure that owners have the opportunity and, in fact, are encouraged to examine random dogs suspected of being lost. Identifications and retrievals of this sort should be done during the quarantine and conditioning period. If the owner is not interested in retrieving the pet, it should be utilized for an acute, non-survival study. Similarly, a pet dog donated for research should always be placed on an acute, non-survival study, unless the donor specifically states a wish for it to be used for chronic studies. In the latter situation, the nature of the study should be explained, and a written statement describing the animal and donating it to research should be signed by the donor.
Dogs Bred for Research
Dogs specifically bred for research
should be the models of choice for those types of studies in which defined
genetic, environmental and health statuses are necessary. The beagle is
by far the most commonly used breed for this purpose, while the Labrador
Retriever is often utilized when experimental objectives demand a larger
animal. Dogs bred for research are obtainable commercially from several
North American establishments (U.S. NRC, 1977).
Only properly conditioned dogs should be used for survival experiments. In addition to its value in safeguarding the health of other dogs in the colony, conditioning will result in less variability in both the normal and pathological values obtained from either mongrels or purebred dogs (Secord and Russell, 1973; Pick and Eubank, 1965).
The use of a conditioned dog is also recommended for many non-survival, acute studies. The pathophysiological changes that may be associated with the chronic, low grade infections and poor nutritional status frequently encountered in the unconditioned dog, constitute a totally uncontrolled experimental variable. This may be expected, in many situations, to distort the results obtained and affect repeatability and interpretation.
Regardless of whether the dog is destined for a chronic study or an acute, non-survival experiment, it should always be subjected to a complete and thorough health examination when delivered to the facility.
The Initial Examination
Conditioning commences with a thorough examination by a veterinarian or a person competent to recognize the presence of canine infectious or debilitating diseases, including dermatoses and the more obvious physical and behavioral abnormalities. Dogs showing signs of any of the above should be rejected or, if conditions dictate their acceptance, adequate steps should be taken to isolate sick animals and immediately initiate appropriate treatment. A general assessment of the dog's condition and nutritional status should be made and recorded at this time.
At the time of acceptance and initial examination of the random source dog, it is essential to establish a proper record for each animal. This should include all details that may be available on its previous history, date of delivery, general condition, findings of the initial examination, immunization and other procedures as implemented, etc.
This record must stay with the dog and be fully maintained up to date, throughout the animal's stay at the research institution, terminating with entries on its disposition (euthanasia).
A quarantine period of at least two to three weeks is recommended, except for animals to be used immediately for acute, non-survival, experiments. Quarantine may be considered as the initial phase of the dog's period of conditioning, permitting a more accurate assessment of the dog's health status and the implementation of an appropriate vaccination program. Quarantine will also allow time for the proper identification and treatment of all parasites, including the necessary follow-up treatments to cope with all stages of their life cycles (see parasites, under Health Care).
Certain infectious diseases, such as canine distemper, can be insidious in their onset due to very variable incubation periods and differences in the resistance of individuals. The quarantine period should provide time for such latent infections to become manifest.
The quarantine area should be completely separated from the colony area and, insofar as possible, should be self-sustained.
Cages for the quarantine area should be designed to minimize cross-contamination and nose-to-nose contact.
Observations on each animal should be carried out on a daily basis during quarantine, with a complete examination being carried out again at the end of this period.
Regardless of whether a formal quarantine procedure is followed or not, all dogs that are to be conditioned for chronic studies should receive preventive inoculations against canine distemper and infectious canine hepatitis. Vaccination against canine leptospirosis should be undertaken if this disease is endemic and, in some situations it may also be advantageous to vaccinate against canine parainfluenza virus.
Parvovirus vaccines for canine use have been developed (Pollock, 1983; Povey, 1982) and if the disease is prevalent in the area, may, following consultation with a veterinary clinician, be incorporated into the immunization routine (CVMA, 1981). This is particularly advisable where a breeding colony is being maintained.
Anti-rabies vaccination is of benefit in institutionalized and confined dogs, when colony replacements are from randomly acquired animals.
Vaccines specific for each of the above mentioned diseases are available singly or in combination. The vaccination program should be developed in consultation with a veterinary clinician.
Further benefits from a conditioning program are that it permits the animal to adjust to laboratory routines, feeding, watering (particularly to automatic watering systems) and handling. The conditioning period will also provide an opportunity to bring the animal's nutritional state to a satisfactory level. This may require vitamin and mineral supplements in addition to good quality food. The need for this is a clinical decision, which should be made by the examining veterinarian.
Ventriculocordectomy (partial devocalization) is another procedure that may need to be carried out during the conditioning period, particularly where noise levels are extremely disturbing to humans (as in some hospital research facilities) and to other animals in the facility.
The barking that usually occurs
in dog rooms and kennels appears to have no significant communication function.
Partial devocalization is considered to merely alter the pitch and volume
of the bark and not to interfere with a dog's normal behavioral pattern.
Social Interactions and Exercise
The dog is a highly social animal which, if permitted, will spend most of its time with other dogs, is generally well-adapted for running, and has a strong sense of territory. Dogs have come, through domestication, to accept humans as an integral part of their social order, usually occupying the top or alpha position (Beaver, 1981).
The above characteristics are probably the most important among the basic factors to be considered in providing satisfactory housing and caging for dogs in scientific institutions (Beaver, 1981; AWI, 1979). Certainly, they should be taken into consideration in the initial design of facilities whenever possible, and in the organization and type of accommodation provided for the research animal.
A simple way of adapting existing facilities so that they cater to the nature of the canine, is by releasing compatible groups of dogs into rooms with non-porous floors. Corridors can sometimes be used as indoor runs and, if an outdoor runway can also be provided, these will provide further opportunities for socializing and activity beneficial to the dogs.
Generally, group housing of compatible animals is the least stressful type of confinement for random source animals and, therefore, should be provided wherever possible. On the other hand, purebred dogs, bred for research, have for the most part known only caging. Group housing of these animals, which are usually unfamiliar even with restricted floor pens, will likely prove overly stressful.
Restricted Floor Pens
Floor pens will provide an adequate opportunity for exercise, particularly where they are divided into a holding zone and run. The latter may be either indoor or outdoor. Dogs individually confined for long periods should be housed in these pens, preferably with access, through a hatch, to individual outdoor exercise runs. Runs will, in addition to providing for exercise, permit the dog to defecate outside and, in the case of males, to mark out territory.
Where restricted pens are used for housing or conditioning, the provision of resting platforms (jump boards) is recommended. A heated area of a floor pen, with appropriate drainage away from it, serves the same purpose. It is preferable that jump boards be hinged or removable to facilitate proper kennel cleaning. Proper jump board construction, maintenance and sanitation are important factors in minimizing their possible role in parasite and disease transmission.
It is often possible to hold more than one dog in a restricted floor pen; where size and compatibility permit, this practice is recommended. Dogs are claimed to be happier, less noisy and less destructive if housed in pairs or groups (Hime, 1976).
Dog cages of a variety of designs, sizes, combinations and construction are readily available commercially. Stainless steel is the material of choice for cage construction; however, fibreglass and formica-arborite are satisfactory.
Floors of cages should be sloped forward to facilitate cleaning and drainage. The use of a removable floor grid of plastic coated expanded metal facilitates cleaning and appears to lessen the risk of foot problems, particularly for animals that are caged for long periods of time. If a grid floor is not used and no resting board is available, then newspaper bedding (preferably shredded) should be provided. Extra bedding should be given to the chronic subject to prevent or at least retard the development of "capped" hocks and elbows.
The sides or walls of pens and runs should be so designed and constructed as to assure that animals cannot climb or jump from pen to pen, or get over dividers. The pen sides or walls should be "nose and paw proof", to prevent the potential of having the animal bitten by an adjacent dog.
Cage dimensions will vary greatly with the breed, but should always be sufficient to readily permit the animal to stand, stretch fully (both horizontally and vertically), turn around and lie down fully extended.
There is evidence that the provision
of cages with floor space in excess of this minimum, at least for purebred
laboratory beagles, does not result in altered behavioral patterns, the
taking of more exercise, or in improved health (Hite, Hanson, Bohidar et
al. 1977; Newton, 1972). Nevertheless, where individual dog cages are in
use, it is strongly recommended that the animals be released for exercise,
at least once and preferably twice daily, into the largest available space
(USHEW, 1974; AWI, 1970).
The recommended nutritional standards for research dogs generally accepted in Canada are those given in the (U.S.) National Research Council's "Nutrient Requirements of Dogs" (U.S. NRC, 1972). Standards for pet foods have recently been prepared and published by a committee of the Canadian General Standards Board (CGSB) and, will also serve as a useful guide (CGSB, 1983). The Gaines Dog Research Center regularly publishes up-to-date information on this subject (GDRC, 1977).
Numerous dried and semi-dried dog foods in the form of meal, kibble and patties, are available commercially, as are a variety of canned dog foods. Any of these types of feed, if they are of good quality, may serve as a complete ration.
Combinations may be used to give variety. Most large commercial producers of dog foods prepare products that constitute complete and balanced rations in themselves which, if fed in an appropriate way, are not likely to give rise to nutritional disorders (Kronfeld, 1975). Adding supplements in the way of scraps, etc., will not usually improve the nutritional value of the feed; however, it may increase palatability.
Dietary problems are more often attributable to improper feeding practices than to nutritional inadequacies per se in commercial dog feeds (Kronfeld, 1975; Morris, 1977). Nutrient requirements of dogs have recently been reviewed in terms of the varying requirements of different phases of the life cycle, and the variability associated with activity levels, environmental changes and physiological state (Sokolowski, 1982).
Mature dogs normally require feeding only once per day. Puppies from weaning to four months of age should be fed three times daily, then twice daily until mature. Recommendations on daily amount of feed per kilogram of body weight have been published more recently than those in the NRC Nutrient Requirements (U.S. NRC, 1972) and should be followed for laboratory housed dogs to reduce the likelihood of overfeeding (Kronfeld, 1975; Morris, 1977). The time of feeding should be regular and water should always be available ad lib.
During pregnancy and lactation, bitches should be fed twice daily and consideration should be given to supplementation, particularly if the quality of the ration is in doubt. It is important to provide a ration with a high net protein availability during gestation.
Special diets for use in the management of gastrointestinal, renal and cardiovascular diseases are available commercially. Useful information has been published on the formulation of such diets (Kronfeld, 1975; Morris, 1977).
Many research institutions need to raise puppies. It is essential that a good quality diet be fed both to the lactating bitch and to the weanling puppy. Occasionally, puppies may have to be raised separately from their mother. Procedures to follow in such an eventuality have recently been reviewed (Morris, 1977; Sokolowski, 1982; Degraff, 1980).
Not all commercial dog and puppy
foods are of equal quality and there is little doubt, but that some health
problems, particularly vitamin and mineral deficiencies such as rickets,
may be associated with the feeding of inferior quality foods (Lowe, 1976).
Food Related Problems
Dogs may sustain food deprivation for about a week without serious effects. They will, however, become significantly less resistant to stress if their body weight falls to more than 15% below normal.
Coprophagy is a frequent occurrence
in kennelled dogs, the actual causes for which are not well-established.
A simple means of overcoming the problem is to daily sprinkle a small amount
of an unseasoned commercial meat tenderizer over the food (Morris, 1977).
Breeding stock should be penned separately, as the multiple housing of breeding females is frequently accompanied by pseudopregnancies. Males should be held separately from the females, as housing in the same area usually decreases their libido. The female should be brought to the male's pen (territory) for mating (Fox, 1965).
Bitches should always be allowed to whelp in isolated pens and their whelping cage should be kept at temperatures of 27o to 30oC (80-85o F) (Harrop, 1960). Disposable whelping cages are available commercially and may prove convenient.
Artificial insemination (AI) may be carried out successfully in dogs, and its use should be considered in special situations, as for example in dogs with bleeding disorders, where its use will avoid hematoma of the penis. AI also facilitates the using of selected males from remote sources (Sweeny, 1977; Kirk, 1970).
The excretion of urine and feces in puppies up until two or three weeks of age usually requires stimulation through maternal licking of the anal and external genital regions. Hand reared puppies will need to be stimulated by periodic stroking over these areas with moist, warm gauze, to facilitate elimination (Degraff, 1980).
The bitch has a modified monestrous cycle, with heat occurring twice yearly, most often in early spring and late summer. The estrous cycle consists of four active phases (proestrus, estrus, metestrus, diestrus) and a period of inactivity or rest. The reproductive tract changes that characterize these phases are synchronized with the cyclic secretions of gonadotropic and ovarian hormones.
Proestrus has a duration of eight to ten days, during which the vulva swells and a hemorrhagic discharge occurs. During this stage, males are attracted, but the bitch will not permit coitus.
Estrus, which averages about six days (range four to eight days), is the phase during which the bitch will accept the male and permit coitus. Ovulation normally occurs at about 48 hours into the estrous phase. The hemorrhagic discharge of proestrus will cease and be replaced by a clear, straw coloured exudate as the bitch enters the estrous phase. That a bitch is in estrus and, therefore, ready to accept the male can usually be determined by the fact that she will flip her tail to one side when touched by hand on the back of the pelvis or over the sacrum.
A short metestrous phase occurs at the termination of estrus, lasting for two or three days. During this phase, the vulva returns to normal and after a few days the bitch ceases to attract the male. Diestrus is of approximately two months' duration and, if conception has occurred, will be the period of pregnancy. Anestrus begins at the termination of either diestrus or pregnancy, and lasts for approximately three months, during which time the bitch's reproductive system is comparatively quiescent.
Microscopical examination of vaginal smears may be used to accurately differentiate between the various phases of the estrous cycle, for experimental purposes and in the occasional bitch in which the macroscopical and behavioral signs of heat are unclear. The cytological features that characterize the state of estrus and the stages of the cycle are easily visualized microscopically (Fowler, Felman and Loeb, 1974; Banks, 1981).
It is important that the signs of pending parturition be recognized, in order to provide the bitch with the privacy she requires, and for assistance in whelping should it become necessary.
One of the earliest signs of parturition in the bitch is the onset of lactation, as milk can usually be expressed from the teats several days prior to whelping.
As parturition approaches, a bitch will usually start to prepare a bed by tearing up paper, or scratching at the floor in a specific area. She will appear restless and may show signs of anxiety such as panting and looking rather apprehensively at her hind quarters.
Immediately prior to the onset
of birth, relaxation of the sacrosciatic and sacroiliac ligaments and musculature
occurs, giving the hind quarters a sunken appearance. This should be followed
shortly by involuntary uterine contractions at decreasing intervals, which
will later be assisted by voluntary contractions of the abdominal muscles
and diaphragm (Harrop, 1960; Sweeny, 1977; Kirk, 1970).