Do Female Dogs Age Differently Than Male Dogs?

The influence of sex-specific factors on biological transformations and health outcomes in aging processes

The aging process demonstrates notable differences between males and females, which are key factors in disease susceptibility and lifespan. The differences in sex chromosomes are fundamental to the presence of sex bias in organisms. Moreover, sex-specific epigenetic modifications and changes in sex hormone levels impact the development of immunity differently during embryonic development and beyond. Mitochondria, telomeres, homeodynamic space, and intestinal flora are intricately connected to sex differences in aging. These elements can have diverse effects on men and women, resulting in unique biological transformations and health outcomes as they grow older. This review explores how sex interacts with these elements and shapes the aging process.

Specific differences and novel key regulatory genes of sex in influencing exceptional longevity phenotypes

BACKGROUND AND AIMS

Although the life expectancy of women systematically and robustly exceeds that of men, specific differences and molecular mechanisms of sex in influencing longevity phenotypes remain largely unknown. Therefore, we performed transcriptome sequencing of peripheral blood samples to explore regulatory mechanisms of healthy longevity by incorporating sex data.

METHODS

We selected 34 exceptional longevity (age: 98.26 ± 2.45 years) and 16 controls (age: 52.81 ± 9.78) without advanced outcomes from 1363 longevity and 692 controls recruited from Nanning of Guangxi for RNA sequencing 1. The transcriptome sequencing 1 data of 50 samples were compared by longevity and sex to screen differentially expressed genes (DEGs). Then, 121 aging samples (40-110 years old) without advanced outcomes from 355 longevity and 294 controls recruited from Dongxing of Guangxi were selected for RNA sequencing 2. The genes associated with aging from the transcriptome sequencing 2 of 121 aging samples were filtered out. Finally, the gender-related longevity candidate genes and their possible metabolic pathways were verified by cell model of aging and a real-time polymerase chain reaction (RT-PCR).

RESULTS

Metabolism differs between male and female and plays a key role in longevity. Moreover, the principal findings of this study revealed a novel key gene, UGT2B11, that plays an important role in regulating lipid metabolism through the peroxisome proliferator activated receptor gamma (PPARG) signalling pathway and ultimately improving lifespan, particularly in females.

CONCLUSION

The findings suggest specific differences in metabolism affecting exceptional longevity phenotypes between the sexes and offer novel therapeutic targets to extend lifespan by regulating lipid homeostasis.

Factors related to longevity and mortality of dogs in Italy

Besides its translational value, an improved understanding of dog longevity and mortality is necessary to guide health management decisions, breed selection, and improve dog welfare. In order to analyse the lifespan of dogs in Italy, identify the most common causes of death, and evaluate possible risk factors, anonymised medical records were collected from 9 veterinary teaching hospitals and 2 public health institutions. Data regarding breed, sex, neuter status, age, diagnosis, and mechanism of death were retrieved. Cause of death (COD) was classified by pathophysiologic process (PP) and organ system (OS). Of the 4957 dogs that died between 2004 and 2020 included in the study, 2920 (59.0%) were purebred, 2293 (46.2%) were female, 3005 (60.6%) were intact, 2883 (58.2%) were euthanised. Overall median longevity was 10.0 years. Median longevity was significantly longer for crossbreds, females, neutered dogs, and small-sized breeds. The breeds with the highest median age at death were the Yorkshire terrier, English cocker spaniel, West Highland white terrier, Italian volpino, and Shih Tzu, whilst the American bulldog, English bulldog, American pit bull terrier, Bernese mountain dog and the Maremma and the Abruzzes sheepdog had the lowest median age at death. The most frequent COD by PP was neoplasia (34.0%), which occurred more frequently in large breeds, namely German shepherd, Labrador retriever and Boxer. Degenerative diseases mostly affected small-sized dogs like Miniature pinscher and Dachshund. Regarding the OS involved, diseases of the renal/urinary system were most frequently responsible for COD (15.0%), prevalently degenerative and inflammatory/infectious. Substantial variation in median longevity according to causes of death by PP and OS was observed. These data are relevant for breeders, veterinary practitioners, and owners, to assist breed selection, facilitate early diagnosis, guide choice when purchasing a purebred dog and making health management decisions, and ultimately improve dog welfare.

Longevity of companion dog breeds: those at risk from early death

The companion dog is one of the most phenotypically diverse species. Variability between breeds extends not only to morphology and aspects of behaviour, but also to longevity. Despite this fact, little research has been devoted to assessing variation in life expectancy between breeds or evaluating the potential for phylogenetic characterisation of longevity. Using a dataset of 584,734 unique dogs located within the UK, including 284,734 deceased, we present variation in longevity estimates within the following: parental lineage (purebred = 1 breed, crossbred ≥ 2 breeds), breed (n = 155), body size (large, medium, small), sex (male, female) and cephalic index (brachycephalic, mesocephalic, dolichocephalic). Survival estimates were then partitioned amongst phylogenetic clades: providing evidence that canine evolutionary history (via domestication and associated artificial selection) is associated with breed lifespan. This information provides evidence to inform discussions regarding pedigree health, whilst helping current/prospective owners, breeders, policy makers, funding bodies and welfare organisations improve decision making regarding canine welfare.

Dog size and patterns of disease history across the canine age spectrum: Results from the Dog Aging Project

Age in dogs is associated with the risk of many diseases, and canine size is a major factor in that risk. However, the size patterns are complex. While small size dogs tend to live longer, some diseases are more prevalent among small dogs. In this study we seek to quantify how the pattern of disease history varies across the spectrum of dog size, dog age, and their interaction. Utilizing owner-reported data on disease history from a substantial number of companion dogs enrolled in the Dog Aging Project, we investigate how body size, as measured by weight, associates with the lifetime prevalence of a reported condition and its pattern across age for various disease categories. We found significant positive associations between dog size and the lifetime prevalence of skin, bone/orthopedic, gastrointestinal, ear/nose/throat, cancer/tumor, brain/neurologic, endocrine, and infectious diseases. Similarly, dog size was negatively associated with lifetime prevalence of ocular, cardiac, liver/pancreas, and respiratory disease categories. Kidney/urinary disease prevalence did not vary by size. We also found that the association between age and lifetime disease prevalence varied by dog size for many conditions including ocular, cardiac, orthopedic, ear/nose/throat, and cancer. Controlling for sex, purebred vs. mixed-breed status, and geographic region made little difference in all disease categories we studied. Our results align with the reduced lifespan in larger dogs for most of the disease categories and suggest potential avenues for further examination.

RETROSPECTIVE STUDY OF MORBIDITY AND MORTALITY OF CAPTIVE AFRICAN WILD DOGS (LYCAON PICTUS) HELD WITHIN UNITED KINGDOM ZOOLOGICAL INSTITUTIONS BETWEEN 2000 AND 2020

The African wild dog (Lycaon pictus) is listed as Endangered by the International Union for Conservation of Nature and is part of captive breeding programs designed to support free-living populations and genetic diversity. This study's aim was to identify common causes of morbidity and mortality objectively in United Kingdom captive African wild dogs to inform management recommendations that will improve health and welfare and reduce disease prevalence. Data were gathered from 140 individual dogs housed in 10 institutions, with morbidity records for 122 individuals and 70 postmortem reports. Descriptive statistics including the Mann-Whitney U test and odds ratios were used to analyze morbidity and mortality across age and sex. The most common cause of death for African wild dogs, excluding those,< 7 d old, was trauma (23%), followed by geriatric (18%), degenerative (15%), and neoplastic (14%) conditions. The most common morbidity was also trauma (62%), of which 76% was caused by intraspecific aggression. Integumentary disease secondary to trauma was the most common morbidity by body system. Eight independent incidents of barbiturate toxicosis from consumption of contaminated carcasses, affecting 18 animals, were identified. Records for neonatal deaths were incomplete and conclusions limited; neonatal loss was estimated at 20.5%. Recommendations include research into factors affecting intraspecific aggression in captivity, operant conditioning for hand injection, provision of dietary carcasses from reputable sources, and improved record-keeping.

Comparison of clinical outcomes in cases of blunt, penetrating, and combination trauma in dogs: A VetCOT registry study

OBJECTIVE

To evaluate outcome (survival to discharge) among trauma types (blunt, penetrating, both) in dogs. The secondary objective was to evaluate if other trauma registry parameters differ between trauma types and influence survival.

DESIGN

Retrospective evaluation of veterinary trauma registry data.

SETTING

Veterinary Committee on Trauma (VetCOT) identified Veterinary Trauma Centers (VTCs).

ANIMALS

A total of 20,289 canine trauma patients with data entered in the VetCOT trauma registry from April 1, 2017 to December 31, 2019 INTERVENTIONS: None.

MEASUREMENTS AND MAIN RESULTS

Data were obtained from the VetCOT database and included patient demographics, trauma type (blunt, penetrating, both), Animal Trauma Triage (ATT) score, modified Glasgow Coma Scale (mGCS), abdominal fluid score (AFS), loss of glide sign on thoracic focused assessment with sonography for trauma (TFAST), pleural effusion on TFAST, surgical procedure performed and in what location (emergency room vs operating room), and outcome. Data from 20,289 dogs were collected over a 30-month period. The most common type of trauma was penetrating (10,816, 53.3%), followed by blunt (8360, 41.2%) and then combined blunt and penetrating trauma (1113, 5.5%). Dogs suffering only penetrating trauma had a 96.5% survival rate, blunt trauma had an 89.5% survival rate, and combined trauma had an 86.3% survival rate. Dogs suffering from both types of trauma had higher ATT scores, lower mGCS scores, and were more likely to be admitted to the ICU. Trauma type, mGCS, and ATT score were found to be associated with survival.

CONCLUSIONS

The present study highlights that dogs suffering from a combination of blunt and penetrating trauma are more likely to suffer moderate to severe injuries, have lower survival rates, and are more likely to be admitted to the ICU compared to dogs suffering from only blunt or penetrating trauma. Trauma type, mGCS, and ATT scores were found to be associated with survival in all groups.

MicroRNA Expression Variation in Female Dog (Canis familiaris) Reproductive Organs with Age and Presence of Uteropathy

While aging is associated with microRNA (miRNA) expression, little is known about its role in the aging of dog reproductive organs. We examined miRNA expression in ovaries, oviducts, and uteri from young and old dogs and dogs with uteropathy to elucidate miRNA's role in aging. The ovaries, oviducts, and uteri of 18 dogs (Canis familiaris)-young (8.5 ± 1.9 months old), old (78.2 ± 29.0 months old), and those with uteropathy (104.4 ± 15.1 months old)-were collected for miRNA expression examination. Total RNA samples were extracted, reverse-transcribed to cDNA, and real-time PCR analysis was also performed. In ovaries, miR-708 and miR-151 levels were significantly higher in old dogs than in young dogs, and only let-7a, let-7b, let-7c, miR125b, and miR26a were significantly upregulated in dogs with uteropathy. In the oviducts and uteri of old dogs, miR-140, miR-30d, miR-23a, miR-10a, miR-125a, miR-221, and miR-29a were upregulated. Realtime quantitative PCR revealed that targeted mRNA was similarly regulated to miRNA. These results suggest that miRNAs of reproductive organs in dogs may be biological markers for aging and reproductive diseases and could be used for mediating aging.

Sex Differences in Molecular Mechanisms of Cardiovascular Aging

Cardiovascular disease (CVD) is still the leading cause of illness and death in the Western world. Cardiovascular aging is a progressive modification occurring in cardiac and vascular morphology and physiology where increased endothelial dysfunction and arterial stiffness are observed, generally accompanied by increased systolic blood pressure and augmented pulse pressure. The effects of biological sex on cardiovascular pathophysiology have long been known. The incidence of hypertension is higher in men, and it increases in postmenopausal women. Premenopausal women are protected from CVD compared with age-matched men and this protective effect is lost with menopause, suggesting that sex-hormones influence blood pressure regulation. In parallel, the heart progressively remodels over the course of life and the pattern of cardiac remodeling also differs between the sexes. Lower autonomic tone, reduced baroreceptor response, and greater vascular function are observed in premenopausal women than men of similar age. However, postmenopausal women have stiffer arteries than their male counterparts. The biological mechanisms responsible for sex-related differences observed in cardiovascular aging are being unraveled over the last several decades. This review focuses on molecular mechanisms underlying the sex-differences of CVD in aging.

Life tables of annual life expectancy and mortality for companion dogs in the United Kingdom

A life table is a tabulated expression of life expectancy and mortality-related information at specified ages in a given population. This study utilised VetCompass data to develop life tables for the UK companion dog population and broken down by sex, Kennel Club breed group, and common breeds. Among 30,563 dogs that died between 1st January 2016 and 31st July 2020, life expectancy at age 0 was 11.23 [95% confidence interval (CI): 11.19-11.27] years. Female dogs (11.41 years; 95% CI: 11.35-11.47) had a greater life expectancy than males (11.07 years; 95% CI: 11.01-11.13) at age 0. Life tables varied widely between breeds. Jack Russell Terrier (12.72 years; 95% CI: 12.53-12.90) and French Bulldog (4.53 years; 95% CI: 4.14-5.01) had the longest and shortest life expectancy at age 0, respectively. Life tables generated by the current study allow a deeper understanding of the varied life trajectory across many types of dogs and offer novel insights and applications to improve canine health and welfare. The current study helps promote further understanding of life expectancy, which will benefit pet owners and the veterinary profession, along with many other sectors.

Dynamic modeling of female neutering interventions for free-roaming dog population management in an urban setting of southeastern Iran

Understanding dynamics of free-roaming dog (FRD) population is critical for planning and implementation of dog population management programs. FRD population size estimation as well as dynamic modeling of dog population under different female dog neutering interventions were investigated in order to determine the most appropriate animal birth control approach. We performed population size estimate of dogs using sight-resight surveys by photography in a randomly selected 25 blocks of the city and all the suburbs of greater Kerman area. Main demographic features were characterized and the dog density distribution was mapped. A dynamic model was developed to predict free-roaming dog population variations after 5 and 10 years. Different scenarios based on 10, 30, 50, 60 and 70% female dog sterilization were considered to predict the effects of animal birth control measures. Free roaming dog population was estimated at 6781 dogs (65.3% males) in Kerman and suburbs with several major population hotspots. Analysis of the dog locations within the city showed that the largest proportion of the dogs were observed in the vacant lots (46.2%). Modeling predictions indicated that, in the absence of management, the free-roaming dog population could increase from a baseline of 6781 to 13,665 dogs (2.02 fold increase) in 5 years and to 19,376 dogs in 10 years (2.86 fold increase). Using a population dynamics model, we simulated five neutering coverages to explore the impact of female neutering on free-roaming dog population size. The 5-year projections of the model have shown that 50% annual female dog sterilization significantly reduced free-roaming dog population by 0.44 comparing to the baseline population. Findings of the present study improve our knowledge on the nature and extent of dog population dynamics in Iran. Effective population control and selection of the most appropriate neutering interventions require a comprehensive knowledge of the characteristics and dynamics of FRD population.

Ageing: Not only an age-related issue

Developments in the last century have led to an unprecedented increase in life expectancy. These changes open opportunities for humans to grow and develop in healthy and adaptive ways, adding life to years as well as years to life. There are also challenges, however - as we live longer, a greater number of people will experience chronic illness and disability, often linked to lifestyle factors. The current paper advances an argument that there are fundamental biological sex differences which, sometimes directly and sometime mediated by lifestyle factors, underpin the marked differences in morbidity and mortality that we find between the sexes. Furthermore, we argue that it is necessary to consider sex as a key factor in research on healthy ageing, allowing for the possibility that different patterns exist between males and females, and that therefore different approaches and interventions are required to optimise healthy ageing in both sexes.

Mastiff breed mortality: A study of owner experience, dog age and longevity

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Mastiffs are a group of large and giant powerful dogs consisting of 19 breeds worldwide.

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The median age of death for the Mastiff group was 8 years with European and North American dogs also dying at this age.

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A higher percentage of dogs died over 8 years when classed as senior within breed standards.

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Cancer was the most common cause of death in the Mastiff group with osteosarcoma the most common specifically in neutered animals.

Despite being ranked 33 in Americas most popular breeds (American Kennel Club, 2020), there is a lack of research addressing longevity and death related health problems of Mastiff dog breeds and specifically commonly kept Bull Mastiffs and English Mastiffs. Likely a result of small founder populations and minimal breeding geographical locations, limited genetic variation is found making it important to determine key health concerns which may reduce longevity. The purpose of this study was to report findings from an online global survey of owners of deceased Mastiffs detailing breed, age at death, and if known, cause of death. Owner information was also collected including location by continent and country and the owners breeding or hobbyist experience. A closed-question survey was used via an online network of global Mastiff clubs and associations totalling a useable sample of 1036 dogs across a range of breeds. Notably, it is reported that age and cause of death varied dependant on breed. Results indicate that the median age of death for all dogs was 8 years with mean age of death in Europe as 7.72 years and 8.17 years in North America. The most common cause of death identified for all dogs was cancer (47%), old age (16%), cardiac problems (8%) and gastric problems including GDV and bloat (7%). The mean age of death for cancer dogs was 7.85 years with 23 types of cancer stated with Osteosarcoma being the most commonly recorded and specifically for neutered animals. As the survey was aimed at hobbyist and registered breeders, study findings contribute to knowledge of Mastiff mortality with the aim of promoting welfare of the breed.

Reproductive Suicide: Similar Mechanisms of Aging in C. elegans and Pacific Salmon

In some species of salmon, reproductive maturity triggers the development of massive pathology resulting from reproductive effort, leading to rapid post-reproductive death. Such reproductive death, which occurs in many semelparous organisms (with a single bout of reproduction), can be prevented by blocking reproductive maturation, and this can increase lifespan dramatically. Reproductive death is often viewed as distinct from senescence in iteroparous organisms (with multiple bouts of reproduction) such as humans. Here we review the evidence that reproductive death occurs in C. elegans and discuss what this means for its use as a model organism to study aging. Inhibiting insulin/IGF-1 signaling and germline removal suppresses reproductive death and greatly extends lifespan in C. elegans, but can also extend lifespan to a small extent in iteroparous organisms. We argue that mechanisms of senescence operative in reproductive death exist in a less catastrophic form in iteroparous organisms, particularly those that involve costly resource reallocation, and exhibit endocrine-regulated plasticity. Thus, mechanisms of senescence in semelparous organisms (including plants) and iteroparous ones form an etiological continuum. Therefore understanding mechanisms of reproductive death in C. elegans can teach us about some mechanisms of senescence that are operative in iteroparous organisms.

Alterations of Lipid Metabolism With Age and Weight in Companion Dogs

The companion dog has recently been promoted as powerful translational model of aging. However, while dogs share environments with their human owners and develop many of the same age-related morbidities, little is known about the underlying mechanisms that drive their health and longevity. In addition, dogs have a well described phenotypic pattern in which small dogs live significantly longer than large dogs, such that weight can be used as a crude proxy for longevity. To investigate this pattern, we completed a small lipidomics study on 41 dogs in the Birmingham, Alabama, United States, area to determine individual circulating lipids that were associated with age and body weight. We discovered that sphingomyelins were significantly higher in large, short-lived dogs, independent of age, and triglycerides were higher in older dogs of all sizes. Our results point towards physiological differences that may explain a portion of the variation in longevity seen in companion dogs.

The effect of age and sex on selected hematologic and serum biochemical analytes in 4,804 elite endurance-trained sled dogs participating in the Iditarod Trail Sled Dog Race pre-race examination program

Endurance-trained sled dogs provide a unique translational model to characterize changes in hematologic and serum biochemical analytes due to the aging process. The primary objective of this study was to determine the effect of age and sex on specific hematologic and serum biochemical parameters in the endurance trained sled dog. Longitudinal and cross-sectional data were analyzed from 9,746 blood and serum samples from 4,804 dogs collected over 7 years as part of the Iditarod Trail Sled Dog Race pre-race examination program. Mixed models analysis was used for statistical analysis and P < 0.01 was considered significant. Dogs ranged from 1–12 years of age and 39% were female. Serum total calcium and phosphorus concentrations and white blood cell count decreased nonlinearly to asymptotic values by 6.6, 3.1, and 6.9 years of age, respectively, equivalent to estimated physiologic ages in human years of 44, 27, and 46 years. Serum glucose concentrations reached their lowest value at 7.8 years of age, equivalent to an estimated human physiologic age of 50 years, after which time the concentration increased. Serum globulin concentrations increased with age, but nonlinearly for females and linearly for males. Most sex-related differences were <5%; however, females had lower serum urea nitrogen (14.7%) and creatinine (7.3%) concentrations, lower serum alanine aminotransferase activity (16.6%), and higher serum total bilirubin concentration (12.8%) and platelet count (6.0%). The endurance-trained sled dog provides an excellent model to separate the physiologic effects of age from those of a sedentary lifestyle on hematologic and serum biochemical analytes.

Frailty: A cost incurred by reproduction?

Evolutionary theories of senescence, such as the ‘disposable soma’ theory, propose that natural selection trades late survival for early fecundity. ‘Frailty’, a multidimensional measure of health status, may help to better define the long-term consequences of reproduction. We examined the relationship between parity and later life frailty (as measured by the Frailty Index) in a sample of 3,534 adults aged 65 years and older who participated in the English Longitudinal Study of Ageing. We found that the most parous adults were the most frail and that the parity-frailty relationship was similar for both sexes. Whilst this study provided some evidence for a ‘parity-frailty trade-off’, there was little support for our hypothesis that the physiological costs of childbearing influence later life frailty. Rather, behavioural and social factors associated with rearing many children may have contributed to the development of frailty in both sexes.

Lifespan of companion dogs seen in three independent primary care veterinary clinics in the United States

Background

The privately owned companion dog is an emerging model in comparative medicine, notably because it shares the human environment including its risk factors, is affected by many analogous age-related diseases, receives comparable medical care, and has excellent veterinary medical data available.

Past studies of dog lifespan have used academic, corporate or insurance data. While independent primary care data exist for the UK, none have as of yet been published for the US. This study analyzed data from three independent primary care US veterinary hospitals and identified factors that influence lifespan and mortality in a cohort of n = 20,970 privately owned dogs using Kaplan-Meier survival estimators and Cox Proportional Hazards modelling, including body size as a covariate.

Results

As previously reported, body size was negatively correlated with lifespan. Gonadectomy was associated with a longer lifespan, with the effect being stronger in females than in males. This lifespan advantage was conserved in gonadectomized female dogs that lived to at least ages 5 and 8 years. We did not find significant differences in lifespan between purebred and mixed breed dogs; however, breeds with larger effective population sizes and/or lower inbreeding coefficients had median survival times 3–6 months longer than breeds with smaller effective population sizes or higher inbreeding coefficients, indicating that these measures of genetic diversity may be affecting breed lifespans. We also found that dog breeds belonging to the “Mountain” ancestral group had median survival times that were 3.5–4.6 years shorter than other purebred dog groups, which remained significant even when correcting for body size.

Conclusions

Our findings show that it is possible to obtain and analyze data from independent veterinary clinics in the US, an approach that could be useful for studies of comparative epidemiology under the One Health and One Welfare paradigms. We also show that the lifespan effects of gonadectomy are not identical between the sexes and should be investigated separately by sex in future analyses. More research is needed to further clarify the influence of age at gonadectomy, as well as the factors leading to the observed differences in lifespan in the “Mountain” ancestral group and in dog breeds of varying inbreeding coefficients and effective population sizes.

A short life on the farm: aging and longevity in agricultural, large-bodied mammals

As average human lifespans increase across the globe, companion animals, specifically dogs and cats, are also living longer with more age-related morbidities. However, a similar trend is not seen in mammalian livestock species. Cows, pigs, goats, and sheep, as well as more niche mammalian species raised across the world, have been primarily raised for their economic benefit to humans and are culled from the population once their production declines. To this end, we lack clear knowledge about the age-related morbidities and causes of death that afflict livestock animals due to natural aging, as well as detailed age-specific survival rates. Here, we review the current state of the field of agricultural mammal aging, as well as provide specific questions and directions that may provide novel resources for veterinarians and aging biologists. By raising awareness of the overall quality of life and ongoing health of individual livestock animals, we can potentially increase production into older life stages, leading to decreased costs to farmers and improved welfare for the animals themselves.

Demography and commonly recorded clinical conditions of Chihuahuas under primary veterinary care in the UK in 2016

BACKGROUND

The Chihuahua, the world's smallest dog breed, is a popular breed in the UK today. The VetCompass™ Programme collates de-identified clinical records from primary-care veterinary practices in the UK for epidemiological research. This study aimed to characterise the demography, age at death and common disorders of Chihuahuas under primary veterinary care during 2016 in the UK.

RESULTS

Chihuahuas comprised 11,647/336,865 (3.46%) dogs under veterinary care during 2016. The annual proportional birth rate for Chihuahuas rose from 1.01% in 2005 to 5.35% in 2016. Median adult bodyweight was 3.4 kg (interquartile range [IQR]: 2.7-4.3, range 0.8-9.8).). Median age was 2.8 years (interquartile range [IQR] 1.6-4.9). Median age at death from this young expanding population was 8.2 years (IQR 3.5-12.1). Females (10.2 years) outlived males (6.9 years) (Mann-Whitney U test: P = 0.005). The most common grouped causes of death were heart disease (18.8%, 95% CI: 10.9-29.0), lower respiratory tract disorder (16.3%, 95% CI: 8.9-26.2) and traumatic injury (13.8%, 95% CI: 7.1-23.3). The most common specific disorders were periodontal disease (13.5%, 95% CI: 12.6-14.4), obesity (5.9%, 95% CI: 5.3-6.5), retained deciduous dentition (5.7%, 95% CI: 5.1-6.4), anal sac impaction (4.9%, 95% CI: 4.4-5.5) and aggression (4.2%, 95% CI: 3.7-4.8). Among the 28 most common fine-level disorders, males had statistically (P <  0.005) higher probability than females for 5 disorders (aggression, heart murmur, otitis externa, conjunctivitis and upper respiratory tract infection). There were no disorders with statistically (P <  0.005) higher prevalence in females.

CONCLUSIONS

This study documented rising ownership and a currently youthful population of Chihuahuas in the UK. These results suggest that the Chihuahua is currently undergoing a popularity boom but veterinarians need to be watchful for welfare issues related to impulse purchase of Chihuahua puppies by owners with limited experience of dog care. Periodontal disease, obesity, retained deciduous dentition, anal sac impaction and aggression were identified as common health issues within the breed. The unique veterinary care needs of this popular miniature breed suggest that veterinarians should consider the value of advanced training in anesthesia and dentistry in small-sized dogs.

Desexing Dogs: A Review of the Current Literature

Background: Desexing dogs is promoted for population control, preventative healthcare, and behavior modification. Common methods are orchiectomy and ovariectomy/ovariohysterectomy. GnRH superagonist implants are available in some areas. Alternative methods like vasectomy and salpingectomy/hysterectomy are uncommon. The terminology used to describe desexing is inconsistent and contradictory, showing a need for the adaption of standardized terminology. Population Control: Surprisingly, empirical studies show no effects of desexing on population control in companion and shelter dogs despite desexing being consistently recommended in the literature. There is evidence for a population control effect in free-roaming dogs, where desexing also has benefits on zoonotic disease and bite risk. Population control in free-roaming dogs is mostly correlated with female, not male desexing. Health and Lifespan: Desexing affects numerous disease risks, but studies commonly neglect age at diagnosis and overall lifespan, age being by far the most important risk factor for most diseases. We argue that lifespan is a more important outcome than ultimate cause of death. A beneficial effect of desexing on lifespan is consistently demonstrated in females, while evidence for a beneficial effect in males is inconsistent. Studies are likely biased in desexing being a proxy for better care and desexed dogs having already lived to the age of desexing. Desexing reduces or eliminates common life-limiting diseases of the female reproductive system such as pyometra and mammary tumors, while no analogous effect exists in males. Disease risks increases across sexes and breeds include cruciate ligament rupture, various cancers, and obesity. Urinary incontinence risk is increased in females only. Various other disease risk changes show considerable variability between breeds and sexes. Behavioral Effects: Desexed males show reduced libido, roaming, conspecific mounting, and urinary marking frequency, as well as reduced male dog-directed aggression in a majority of males desexed for behavioral reasons. There is a detrimental effect on the risk and progression of age-related cognitive dysfunction. Desexed dogs may be less likely to cause bite injuries across sexes. The evidence for other effects such as human-directed aggression, human or object mounting, resource guarding, or shyness and anxiety is inconsistent and contradictory. There are few studies specific to females or individual breeds. Conclusions: The evidence for a beneficial effect of desexing is stronger in female than in male dogs; however, there is significant variation between breeds and sexes, and more research is needed to further elucidate these differences and to arrive at individualized evidence-based recommendations for clinical practice.

Tryptophan metabolism is differently regulated between large and small dogs

Companion dogs have recently been promoted as an animal model for the study of aging due to their similar disease profile to humans, the sophistication of health assessment and disease diagnosis, and the shared environments with their owners. In addition, dogs show an interesting life history trait pattern where smaller individuals are up to two-fold longer lived than their larger counterparts. While some of the mechanisms underlying this size and longevity trade-off are strongly suspected (i.e., growth hormone/IGF-I), there are likely a number of undiscovered mechanisms as well. Accordingly, we have completed a large-scale global metabolomic profiling of dogs encompassing a range of sizes and ages from three cities across the USA. We found a surprisingly strong location signal in the metabolome, stronger in fact than any signal related to age, breed, or sex. However, after controlling for the effects of location, tryptophan metabolism emerged as significantly associated with weight of the dogs, with small dogs having significantly higher levels of tryptophan pathway metabolites. Overall, our results point toward novel, testable hypotheses about the underlying physiological mechanisms that influence size and longevity in the companion dog and suggest that dogs may be useful in sorting out the complexities of the tryptophan metabolic network.

West Highland White Terriers under primary veterinary care in the UK in 2016: demography, mortality and disorders

Background

The West Highland White Terrier (WHWT) is a relatively common breed in the UK, although Kennel Club registrations have declined in recent years. The VetCompass™ Programme collates de-identified clinical data from primary-care veterinary practices in the UK for epidemiological research. Using VetCompass clinical data, this study aimed to characterise the demography, longevity and common disorders of WHWTs under primary veterinary care in the UK.

Results

WHWTs comprised 6605/905,544 (0.7%) dogs under veterinary care during 2016 from 886 clinics. Mean adult bodyweight was 9.6 kg (standard deviation [SD] 1.8 kg). Males (10.1 kg, SD 1.8 kg) were heavier than females (9.0 kg, SD 1.6 kg) (P < 0.001). Median age was 7.8 years (interquartile range [IQR] 4.3–11.1). Median longevity was 13.4 years (IQR 11.0–15.0). Males (13.8 years) outlived females (12.9 years) (P = 0.045). The most common grouped causes of death were lower respiratory tract (10.2, 95% CI: 5.5–16.7), neoplastic (10.2, 95% CI: 5.5–16.7) and spinal cord disorder (7.8, 95% CI: 3.8–13.9). Overall, 71.5% WHWTs had > 1 disorder recorded during 2016. The most prevalent specific disorders were periodontal disease (15.7, 95% CI: 14.1–17.3), otitis externa (10.6, 95% CI: 9.3–12.0), overgrown nails (7.2, 95% CI: 6.2–8.4), allergic skin disorder (6.5, 95% CI: 5.5–7.7) and obesity (6.1, 95% CI: 5.1–7.2). The most prevalent grouped disorders were cutaneous (22.7, 95% CI: 20.9–24.6), dental (17.8, 95% CI: 16.2–19.6) and aural (12.3, 95% CI: 11.0–13.8). The median age of dogs affected with the 27 most common disorders varied from 6.7 (pododermatitis) to 13.9 years for cataracts.

Conclusions

These findings highlight that, despite a recent decline in popularity, WHWTs are still relatively common in the UK. Dental disease, ear disease, overgrown nails, allergic skin disorder and obesity were identified as common health issues within the breed. Cutaneous disorders were the most common disorder group in the breed but showed a lower prevalence than might be expected. These results can be used by breeders, veterinary practitioners and owners as an evidence base to predict, prevent and manage key health and welfare issues for WHWTs.

Associations between neutering and idiopathic epilepsy in Labrador retrievers and Border collies under primary veterinary care in the UK

There are sparse published scientific data on associations between neutering and the severity and survival of dogs with idiopathic epilepsy. This study aimed to explore the timing of neutering with respect to onset of seizures in dogs with idiopathic epilepsy. Associations between neutering and both age of onset of seizures and the occurrence of cluster seizures or status epilepticus were examined. Survival analysis investigated the effects of sex-neuter categories. The median survival time of Border collies was compared with data previously reported in literature. The study included veterinary primary-care clinical data on 117 Labrador retrievers and 57 Border collies diagnosed with idiopathic epilepsy from the VetCompass project in the UK. The majority (74.2%; P≤0.001) of neutered cases were neutered before the onset of seizures. Age (years) at onset of seizures did not differ between dogs intact at time of onset and dogs neutered before onset of seizures (males 3.6 vs. 3.7; P=0.468 and females 3.4 vs. 4.1; P=0.154). Neuter status was not associated with the occurrence of cluster seizures (males P=0.947 and females P=0.844). Dogs intact at onset of seizures had longer median survival times than dogs neutered before onset of seizures (males, 1436 days vs. 1234 days; P=0.019; females, 1778.5 days vs. 1261 days; P=0.027). Median survival time of 1393 days for Border collies was longer than previously reported (P≤0.001). These results do not support recommendations to neuter dogs with idiopathic epilepsy within an evidence-based treatment plan.

Disorders of Bulldogs under primary veterinary care in the UK in 2013

The Bulldog is a popular companion breed in the UK despite widely reported disease predispositions. This study aimed to characterise the demography, mortality and common disorders of Bulldogs under veterinary care in the UK during 2013. VetCompass collates anonymised clinical data from UK primary-care veterinary practices for epidemiological research. The clinical records of all Bulldogs available in the VetCompass study dataset were reviewed manually in detail to extract the most definitive diagnoses recorded for all disorders that existed during 2013 and for all deaths. Bulldogs comprised 1621 (0.36%) of 445,557 study dogs. Bulldogs increased from 0.35% of the 2009 birth cohort to 0.60% in 2013. Median longevity was 7.2 years, which was lower in males (6.7 years) than females (7.9 years) (P = 0.021). The most prevalent fine-level precision disorders recorded were otitis externa (n = 206, prevalence 12.7%, 95% CI: 11.1–14.4), pyoderma (142, 8.8%, 95% CI: 7.4–10.2) and overweight/obesity (141, 8.7%, 95% CI: 7.4–10.2). The most prevalent disorder groups were cutaneous (n = 463, prevalence: 28.6%, 95% CI: 26.4–30.8), ophthalmological (292, 18.0%, 95% CI: 16.2–20.0), aural (211, 13.0%, 95% CI: 11.4–14.8), enteropathy (188, 11.6%, 95% CI: 10.1–13.3) and upper respiratory tract (171, 10.5%, 95% CI: 9.1–12.1). Provision of an evidence base on the most common disorders and causes of mortality within breeds can support owners, breeders and the veterinary profession to improve health and welfare within these breed.

Greyhounds under general veterinary care in the UK during 2016: demography and common disorders

Background

The greyhound is a sighthound known for its speed and agility. Greyhounds were selectively bred as functional racing animals but increasingly are kept as pets in the UK, often after their racing careers are over. The VetCompass™ Programme collates de-identified clinical data from primary-care veterinary practices in the UK for epidemiological research. Using VetCompass™ clinical data, this study aimed to characterise the demography, mortality and common disorders of the general population of pet greyhounds under veterinary care in the UK.

Results

Greyhounds comprised 5419/ 905,544 (0.60%) dogs under veterinary care during 2016 from 626 clinics. Mean adult bodyweight was 29.7 kg (standard deviation [SD] 4.5 kg). Males (32.3 kg, SD 4.1 kg) were heavier than females (27.2 kg, SD 3.3 kg) (P < 0.001). Mean age was 7.6 years (SD 3.4). The most common colours were black (39.2%), black and white (20.8%), brindle (12.0%). Based on 474 deaths, median longevity was 11.4 years (range 0.2–16.5). Females (11.8 years) outlived males (11.2 years) (P = 0.002). The most common grouped causes of death were neoplasia (21.5%, 95% CI: 17.4–26.0), collapse (14.3%, 95% CI: 10.9–18.2) and musculoskeletal disorder (7.8%, 95% CI: 5.3–11.0). Based on a random subset of 2715/5419 (50.1%) greyhounds, 77.5% had > 1 disorder recorded during 2016. The most prevalent specific disorders were periodontal disease (39.0%, 95% CI: 37.2–40.9), overgrown nails (11.1%, 95% CI 10.0–12.4), wound (6.2%, 95% CI: 5.3–7.1), osteoarthritis (4.6%, 95% CI: 3.8–5.4) and claw injury (4.2%, 95% CI: 3.4–5.0).

Conclusions

These findings highlight the greyhound as a relatively common pet dog breed in the UK, accounting for 0.6% of dogs under primary veterinary care. Dental disease, trauma and osteoarthritis were identified as common health issues within the breed. Knowledge of common disorders can help greyhound breeders and regulators to prioritise breeding, rearing and racing management to mitigate some of the most prevalent issues. Greyhound rehoming organizations can also better inform adopters about prophylactic care.

Sex differences in health and aging: a dialog between the brain and gonad?

Women live longer than men in virtually all circumstances. However, a more common pattern among animals is that one sex lives longer under some conditions, the other lives longer under other conditions. In laboratory mice, interventions that extend longevity are surprisingly often sex-specific in their effects. Understanding these conditional sex differences could provide mechanistic insight into how longevity could be modulated in humans. One way that longevity can be consistently enhanced is by inhibiting reproduction or eliminating the capacity to reproduce. Thus, there appears to be a mechanistic link between gonadal activity and longevity. There also appears to be a mechanistic link between some types of neuroendocrine signaling and longevity. Combining these two observations suggest that communication between the brain and gonad is a ripe avenue for further exploring longevity-assurance mechanisms. Also, because the timing and activity of specific brain-gonad endocrine differs between the sexes, neuroendocrine linkages between the brain and gonad, particularly among the less obvious hormones such as activin and inhibin, could provide additional insight into mechanisms of sex differences in aging.

Canine hyperadrenocorticism associations with signalment, selected comorbidities and mortality within North American veterinary teaching hospitals

OBJECTIVE

To describe a large population of dogs with a diagnosis of hyperadrenocorticism at the time of death in North American veterinary teaching hospitals, and to identify comorbid conditions associated with hyperadrenocorticism.

MATERIALS AND METHODS

Retrospective cohort study of 1519 dogs with hyperadrenocorticism from a population of 70,574 dogs reported to the Veterinary Medical Database. Signalment, presence or absence of hyperadrenocorticism, aetiology of hyperadrenocorticism (if described), frequency of select comorbidities and causes of death were evaluated in dogs with and without hyperadrenocorticism.

RESULTS

Hyperadrenocorticism was more frequent in females. Neutering was associated with a minor, but significant, increase in the odds of hyperadrenocorticism. Hyperadrenocorticism was the presumed cause of death of 393 (25∙9%) of affected dogs. When aetiology was specified (527 dogs, corresponding to 34∙7% of the cases), pituitary-dependent hyperadrenocorticism [387 (73∙4%) out of 527 dogs] was more common than functional adrenocortical tumour [136 (25∙8%) out of 527 dogs). Hyperadrenocorticism was over-represented in certain expected (miniature poodle, dachshund) and unexpected (Irish setter, bassett hound) breeds compared with the population at large. Of the select comorbidities investigated, dogs with hyperadrenocorticism were at increased risk for concurrent diabetes mellitus, urinary tract infection, urolithiasis, hypertension, gall bladder mucocoele and thromboembolic disease compared with dogs without hyperadrenocorticism.

CLINICAL SIGNIFICANCE

Hyperadrenocorticism is significantly associated with certain comorbid conditions but is not a major cause of mortality in affected dogs. Documented patterns now provide targets for prospective clinical research.

Demographic Change Across the Lifespan of Pet Dogs and Their Impact on Health Status

Although dogs' life expectancies are six to twelve times shorter than that of humans, the demographics (e. g., living conditions) of dogs can still change considerably with aging, similarly to humans. Despite the fact that the dog is a particularly good model for human healthspan, and the number of aged dogs in the population is growing in parallel with aged humans, there has been few previous attempts to describe demographic changes statistically. We utilized an on-line questionnaire to examine the link between the age and health of the dog, and owner and dog demographics in a cross-sectional Hungarian sample. Results from univariate analyses revealed that 20 of the 27 demographic variables measured differed significantly between six dog age groups. Our results revealed that pure breed dogs suffered from health problems at a younger age, and may die at an earlier age than mixed breeds. The oldest dog group (>12 years) consisted of fewer pure breeds than mixed breeds and the mixed breeds sample was on average older than the pure breed sample. Old dogs were classified more frequently as unhealthy, less often had a “normal” body condition score, and more often received medication and supplements. They were also more often male, neutered, suffered health problems (such as sensory, joint, and/or tooth problems), received less activity/interaction/training with the owner, and were more likely to have experienced one or more traumatic events. Surprisingly, the youngest age group contained more pure breeds, were more often fed raw meat, and had owners aged under 29 years, reflecting new trends among younger owners. The high prevalence of dogs that had experienced one or more traumatic events in their lifetime (over 40% of the sample), indicates that welfare and health could be improved by informing owners of the greatest risk factors of trauma, and providing interventions to reduce their impact. Experiencing multiple life events such as spending time in a shelter, changing owners, traumatic injury/prolonged disease/surgery, getting lost, and changes in family structure increased the likelihood that owners reported that their dogs currently show behavioral signs that they attribute to the previous trauma.

Bacteria in the ageing gut: did the taming of fire promote a long human lifespan?

Unique among animals as they evolved towards Homo sapiens, hominins progressively cooked their food on a routine basis. Cooked products are characterized by singular chemical compounds, derived from the pervasive Maillard reaction. This same reaction is omnipresent in normal metabolism involving carbonyls and amines, and its products accumulate with age. The gut microbiota acts as a first line of defence against the toxicity of cooked Maillard compounds, that also selectively shape the microbial flora, letting specific metabolites to reach the blood stream. Positive selection of metabolic functions allowed the body of hominins who tamed fire to use and dispose of these age-related compounds. I propose here that, as a hopeful accidental consequence, this resulted in extending human lifespan far beyond that of our great ape cousins. The limited data exploring the role of taming fire on the human genetic setup and on its microbiota is discussed in relation with ageing.

The companion dog as a model for human aging and mortality

Around the world, human populations have experienced large increases in average lifespan over the last 150 years, and while individuals are living longer, they are spending more years of life with multiple chronic morbidities. Researchers have used numerous laboratory animal models to understand the biological and environmental factors that influence aging, morbidity, and longevity. However, the most commonly studied animal species, laboratory mice and rats, do not experience environmental conditions similar to those to which humans are exposed, nor do we often diagnose them with many of the naturally occurring pathologies seen in humans. Recently, the companion dog has been proposed as a powerful model to better understand the genetic and environmental determinants of morbidity and mortality in humans. However, it is not known to what extent the age‐related dynamics of morbidity, comorbidity, and mortality are shared between humans and dogs. Here, we present the first large‐scale comparison of human and canine patterns of age‐specific morbidity and mortality. We find that many chronic conditions that commonly occur in human populations (obesity, arthritis, hypothyroidism, and diabetes), and which are associated with comorbidities, are also associated with similarly high levels of comorbidity in companion dogs. We also find significant similarities in the effect of age on disease risk in humans and dogs, with neoplastic, congenital, and metabolic causes of death showing similar age trajectories between the two species. Overall, our study suggests that the companion dog may be an ideal translational model to study the many complex facets of human morbidity and mortality.