Table 1.
Characteristics of female Rottweilers in study population
| Usual longevity1N = 100 dogs | Exceptional longevity2N = 83 dogs | |
|---|---|---|
| Age at death3 (years), median (IQR) | 9.6 (9.0–10.0) | 13.6 (13.3–14.3) |
| Year of birth (range) | 1984–2000 | 1980–1995 |
| Residence | ||
| Geographic distribution | 29 states, Canada | 27 states, Canada |
| Number of households4 | 93 | 79 |
| Lifetime ovary exposure5 (years), median (IQR) | 2.5 (0.7–6.0) | 5.5 (2.0–7.5) |
| Reproductive history6 | ||
| Nulliparity in dogs with intact ovaries for ≥ 12 months (%) | 26/62 (42) | 24/70 (34) |
| Body weight7 (lbs), median (IQR) | 90.0 (85.0–100.0) | 85.0 (79.2–90.0) |
| Height8 (in), median (IQR) | 24.0 (23.0–24.5) | 23.5 (22.6–24) |
| Mother achieved exceptional longevity, n (%)9 | ||
| Yes | 1 (3) | 11 (22) |
| No | 30 (97) | 40 (78) |
| Cause of death10, n (%) | ||
| Cancer – all types | 73 (73) | 25 (32) |
| Bone sarcoma11 | 38 (38) | 6 (8) |
| Other types | 35 (35) | 19 (24) |
| Non-cancer diseases12 | 27 (27) | 53 (68) |
| Gastrointestinal | 8 (8) | 4 (5) |
| Musculoskeletal | 6 (6) | 8 (10) |
| Cardiovascular | 4 (4) | 3 (4) |
| Neurologic | 2 (2) | 7 (9) |
| Urologic | 1 (1) | 2 (3) |
| Frailty13 | 1 (1) | 16 (21) |
| Other14 | 3 (3) | 7 (9) |
| Unknown | 2 (2) | 6 (8) |
IQR = interquartile range, which indicates the difference between the 1st and 3rd quartiles.
Usual longevity cohort represents dogs that died at 8.0–10.8 years, a range surrounding the breed-specific median age at death established in a population-based study of more than 700 Rottweilers (Cooley et al., 2003). The 100 females in the usual longevity group include 34 dogs previously reported by Cooley et al. The female:male ratio in the usual longevity cohort was 100:86 (1.26:1). Median (range) age at death for usual longevity males was 9.5 (8.0–10.7 years).
Exceptional longevity cohort represents dogs that died at ≥ 13.0 years, which is more than 30% longer than the breed-specific median longevity (9.4 years). The 83 females in the exceptional longevity group include nine exceptionally long-lived dogs reported by Cooley et al. (2003). The female:male ratio in the exceptional longevity cohort was 83:36 (2.30:1). Median (range) age at death for exceptional longevity males was 13.6 (13.0–15.5 years).
For each dog, age at death was validated using date of birth from American Kennel Club registration records or medical records. The vast majority (> 80%) of dogs underwent elective euthanasia when their quality of life was considered unacceptable by owner.
The 183 female dogs in the study population resided in 172 different households. Only 18 owners had more than one dog represented in the study population. Eleven owners had one dog in the usual longevity cohort and one dog in the exceptional longevity cohort.
For each dog, duration of ovary exposure is equivalent to age at ovariectomy established in the medical history provided by owners and veterinarians.
Thirty-eight usual longevity dogs and 13 exceptional longevity dogs underwent early ovariectomy prior to breeding age, i.e. ovariectomy during first 12 months of life. These dogs were not eligible for reproduction. After excluding these dogs, the table shows a similar percentage of dogs from both groups were not exposed to the ‘reproductive cost’ of offspring.
Body weight was obtained from owner questionnaire or medical record, representing when the dog was a healthy 5 to 7-year-old adult.
For each dog, height represents shoulder height, the distance measured from ground to shoulder, reported by owner.
Data reported here represents only those cases in which information on the longevity of the mother could be validated directly from the owner of the mother. Validated data were available for mothers of 82 of the 183 index females in the study population. A more detailed analysis of the apparent familial clustering of exceptional longevity in these dogs is in progress.
For each dog, cause of death was determined by reviewing medical records and medical histories provided by veterinarians and owners. Few causes of death were verified by necropsy and therefore the reliability of these data is likely comparable to that of human mortality studies based on death certificates. There is no reason to suspect that the cause of death was preferentially misclassified in dogs with usual longevity vs. dogs with exceptional longevity, or misclassified on the basis of ovarian hormone exposure as classification of cause of death was made by investigators (DJW, AHM) blinded to age at ovariectomy. In eight of 183 dogs (two usual longevity, six exceptional longevity), cause of death could not be ascertained from the clinical data.
Bone cancer (appendicular bone sarcoma) was diagnosed based upon physical examination and radiographs. In some cases, histologic confirmation was made by pathologic examination of tissues obtained at biopsy or necropsy.
Death caused by non-cancer diseases was subdivided into five major categories on the basis of frequency: gastrointestinal (e.g. intestinal perforation; inflammatory bowel disease); musculoskeletal (e.g. severe arthritis); cardiovascular (e.g. congestive heart failure); neurologic (e.g. compressive myelopathy due to intervertebral disk herniation; seizures); and urologic (e.g. chronic renal failure).
Death was attributed to frailty in those dogs whose owners and veterinarians reported death or euthanasia associated with a combination of age-related disabilities, including deficits in mobility, cognition, hearing, eyesight and inability to maintain body weight.
Dogs in this category included those whose cause of death was attributed to less common conditions: hematologic, endocrine, hepatobiliary, or respiratory diseases; environmental causes (e.g. heat stroke); and dogs that died in their sleep without recognized illness.