Hyperthyroidism is the most common endocrine disease of cats, and clinical signs reflect the overall increase in metabolism. These cats are often restless and have been described as hyperactive, polyphagic, irritable, and even aggressive. They may be more vocal, appear anxious, and urine mark.
4.7 Medical Conditions That Have Breed Tendencies and Their Associated Behavior Changes
Diseases that have a breed tendency can be due to morphologic extremes or to an inherited condition (Rooney 2009). Examples of morphologic extremes include characteristics like dome‐shaped heads in Cavalier King Charles spaniels and corkscrew tails in bulldogs. Inherited conditions are numerous, and, at last count, 312 non‐conformation‐linked inherited disorders had been identified in the top 50 breeds of registered dogs (Summers et al. 2010).
Selecting for breed standards and specific characteristics leads to inbreeding, reducing variation and causing an increased likelihood of concentrating genes that may have undesired effects. In addition, the incidence of these diseases in mixed‐breed and shelter dog populations has never been studied and is, therefore, unknown.
Recent research has attempted to divide diseases with breed tendencies into (i) disorders related to breed standards and (ii) inherited defects (Asher et al. 2009; Summers et al. 2010). In addition, a Genetic Illness Severity Index for Dogs (GISID) was developed to rank these conditions in terms of their impact on the welfare of the dog (Asher et al. 2009). In general, these diseases affect welfare by compromising a particular body system, often causing pain and discomfort (Yeates 2012). In addition, some of these conditions may further impact welfare by preventing normal expressions of behavior, either due to pain or associated with anatomical alterations such as ear, tail, and body conformation (Rooney 2009).
Although the cat genome has been mapped, not as much progress has been made in identifying genetic diseases in cats. Purebred cats make up only a small portion of the overall cat population (estimates show that about 8% of cats are purebred) (American Pet Products Association 2013). Compared to the multitude of genetic tests available for dogs, there are only 20 that have been developed for cats (Slutsky et al. 2013).
A database developed by the University of Pennsylvania allows users to search for available genetic tests in both cats and dogs (Slutsky et al. 2013):
4.8 Behavior and/or Medical Conditions Seen in Intact versus Neutered Dogs
4.8.1 Female Canine
The normal reproductive cycle of the bitch consists of four phases that include proestrus, estrus, diestrus, and anestrus. Most breeds reach puberty and begin to cycle between 4 and 15 months of age. Generally, smaller breeds will come into heat sooner than larger breeds, although there is variation both within and among breeds. The domestic dog is a non‐seasonal breeder and typically has two estrus cycles per year.
The female undergoes several changes during the estrus cycle. During the proestrus stage, the bitch’s vulva becomes swollen and firm. There may be a slight discharge that ranges in color from clear to bloody. At this stage, males will be interested in her, although she will not be interested in them. The behavior at this time mimics play, including play bows, running together, and playful chasing. The female may briefly stand for the male and then move away. The bitch may also quickly turn and growl, snap, or bite an unwelcome suitor. Generally, her ears are held back, and her tail is tucked between her legs. While tail tucking is typically associated with fear, in this instance, it is an evasive behavior preventing intromission should a male become too insistent.
Behaviorally, estrus is the stage in which the female is receptive (allows copulatory mounting) to the male. During this time, her vulva is still enlarged, although it may be somewhat softer. The discharge may still be present and ranges from a clear to slightly serosanguinous fluid. The initial courtship behavior may still mimic play. The behavior may progress to more intense sniffing of genitalia. Instead of the female moving away, she will stand in a braced position with her back feet base wide and deviate her tail to the side if touched near her vulva. If the male is inexperienced, the female may mount him, or she may actively solicit the male by backing into him with her tail flagged to the side. An estrus bitch will urinate a small amount frequently, similar to a dog with a UTI. Dogs have a tremendous sense of smell, and the hormonal changes in the female’s urine attract males over a large area (Bradshaw and Nott 1995). This results in the intact male roaming in search of the female.
The proestrus and estrus stages can last anywhere from a couple of days to four weeks. Behaviorally, diestrus is the first day the female is no longer receptive to the male. The vulva decreases in size, and the female may display aggressive threats as she defends herself from males. The diestrus period is the time from ovulation to either parturition or anestrus.
Initially, there are very few behavioral changes between a gravid and non‐pregnant female. During the last two weeks of gestation, the pregnant bitch’s abdomen starts to enlarge, her nipples and mammary glands continue to develop, and, at times, milk may even leak from her glands. She may prefer to eat smaller portions and may also be polydipsic and polyphagic. The enlarged uterus filled with growing feti places increasingly greater pressure on the stomach. Small frequent meals allow the bitch to ingest enough nutrients to support herself and the growing feti and to produce milk. Milk production also requires an increase in water consumption. The enlarging mammary glands may cause discomfort, resulting in increased licking of the uncomfortable area. Depending on the size of her litter and her body condition, she may also move more slowly. The change in hormones that occur during impending parturition may result in some bitches becoming anorectic and having looser feces. This may result in an evacuated gastrointestinal
