Locomotor activity rhythms in dogs vary with age and cognitive status

Persistence of clock gene expression in peripheral blood in dogs maintained under different photoperiod schedules

Dogs are the common pets adopted by humans, and their circadian behavior and physiology are influenced by human habits. In many families, there is a change of lifestyle with respect to the natural daylight (NDL) cycle. Exposure to constant light disrupts some central and peripheral circadian rhythms. The aim of the present study was to improve the knowledge about the circadian changes of clock components in the peripheral blood in dogs housed under NDL and constant light (LL) conditions. Blood samples were collected on five female Beagle dogs (2 years old, 14 ± 0.5 kg) every 4 hours for a 24-hour period during an NDL (Sunrise 05:05 h - Sunset 20:55  h) and 24-hour period of constant light (LL). Blood samples were stored in a PAX gene Blood RNA Tube, real-time RT-quantitative polymerase chain reaction was performed to determine Clock, Per1-3, and Cry1-2 gene expression. During the NDL, all genes investigated showed robust diurnal daily rhythmicity. During the constant light, only Clock maintained its daily rhythmicity. Clock acrophase was observed close to sunrise (ZT 0) and was statistically different from the other clock genes except for Per3. Per3 daily oscillations were not statistically significant. No differences were observed among the clock genes tested in the amplitude and robustness values. Our results can be considered preliminary data to provide new insights into the adaptation mechanism of the canine peripheral circadian clock. The persistence of Clock gene expression during the LL indicated the presence of an endogenously generated signal in blood. Because peripheral blood is an easily accessible sample in dogs, the analysis of clock gene expression in this tissue could be useful to investigate the adaptive capacity of this species housed in different environmental conditions linked to the owner's lifestyle.

Where did my dog go? A pilot study exploring the movement ecology of farm dogs

Movement ecology is important for advancing our comprehension of animal behavior, but its application is yet to be applied to farm dogs. This pilot study uses combined GPS and accelerometer technology to explore the spatial patterns and activity levels of free roaming farm dogs, Canis familiaris (n = 3). Space-use distributions and range sizes were determined to compare locations visited across days and between individuals, as well as in relation to specific areas of interest. Individual activity levels were analyzed and compared within and between dogs. Space-use patterns and range sizes showed variation among the dogs, although substantial similarity in overall spatial distributions were observed between each pair. Among the dogs, the extent of spatial distribution overlap between days varied, with some individuals exhibiting more overlap than others. The dogs allocated different amounts of their time close to landscape features, and to slow-, medium-, and fast movements. This study demonstrates the potential of using automated tracking technology to monitor space-use and interactions between dogs, livestock, and wildlife. By understanding and managing the free ranging behavior of their farm dogs, farmers could potentially take steps to improve the health and wellbeing of both their dogs and their livestock, limiting disease spread, and reducing the possibility of related economic losses.

Scientific and technical assistance on welfare aspects related to housing and health of cats and dogs in commercial breeding establishments

This Scientific Report addresses a mandate from the European Commission according to Article 31 of Regulation (EC) No 178/2002 on the welfare of cats and dogs in commercial breeding establishments kept for sport, hunting and companion purposes. The aim was to scrutinise recent recommendations made by the EU Platform on Animal Welfare Voluntary Initiative on measures to assist the preparation of policy options for the legal framework of commercial breeding of cats and dogs. Specifically, the main question addressed was if there is scientific evidence to support the measures for protection of cats and dogs in commercial breeding related to housing, health considerations and painful procedures. Three judgements were carried out based on scientific literature reviews and, where possible a review of national regulations. The first judgement addressed housing and included: type of accommodation, outdoor access, exercise, social behaviour, housing temperature and light requirements. The second judgement addressed health and included: age at first and last breeding, and breeding frequency. Judgement 3 addressed painful procedures (mutilations or convenience surgeries) and included: ear cropping, tail docking and vocal cord resections in dogs and declawing in cats. For each of these judgements, considerations were provided indicating where scientific literature is available to support recommendations on providing or avoiding specific housing, health or painful surgical interventions. Areas where evidence is lacking are indicated.

A review of frailty instruments in human medicine and proposal of a frailty instrument for dogs

Over the last few decades, frailty has become a pillar of research and clinical assessment in human gerontology. This complex syndrome, characterized by loss of physiologic reserves leading to decreased resilience to stressors, is of critical importance because it predicts higher risks of poor health outcomes, including mortality. Thus, identifying frailty among the elderly human population has become a key focus of gerontology. This narrative review presents current scientific literature on frailty in both humans and animals. The authors discuss the need for an accessible frailty instrument for companion dogs suitable for general use in veterinary medicine and the advances that would be facilitated by this instrument. A phenotypic frailty instrument for companion dogs, utilizing components that are easily collected by owners, or in the general practice setting, is proposed. The authors elaborate on the domains (physical condition, physical activity, mobility, strength, cognitive task performance, and social behavior), factors that will be included, and the data from the Dog Aging Project that inform each domain.

Activity patterns are associated with fractional lifespan, memory, and gait speed in aged dogs

Maintaining an active lifestyle is considered a hallmark of successful aging. Physical activity significantly reduces the risk of cognitive decline and Alzheimer's disease in humans. However, pain and lack of motivation are important barriers to exercise. Dogs are a remarkable model for translational studies in aging and cognition as they are prone to Canine Cognitive Dysfunction syndrome, which has many similarities with Alzheimer's disease. According to owner reports, changes in activity levels are characteristic of this syndrome, with decreased daytime activity, but also excessive pacing, especially at sleep time. We used physical activity monitors to record the activity of 27 senior dogs and evaluated the association between activity level and age, fractional lifespan, cognitive status measured by an owner questionnaire and cognitive tests. We also assessed the relationship between activity and joint/spinal pain, and the off/on leash gait speed ratio (a potential marker of gait speed reserve and motivation). We found that activity patterns in dogs are associated with fractional lifespan and working memory. Additionally, dogs with higher on/off leash gait speed are more active in the afternoon of weekdays. These results encourage future studies evaluating how physical activity can improve or delay cognitive impairment in senior dogs.

The activity patterns of nonworking and working sled dogs

There are limited studies investigating the combined effects of biological, environmental, and human factors on the activity of the domestic dog. Sled dogs offer a unique opportunity to examine these factors due to their close relationship with handlers and exposure to the outdoors. Here, we used accelerometers to measure the activity of 52 sled dogs over 30 days from two locations in Canada. The two locations differ in the working demands of dogs, therefore we used linear mixed effects models to assess how different factors impact daytime and nighttime activity of working versus nonworking dogs. During the daytime, we found that males were more active than females among nonworking dogs and younger dogs were more active than older dogs among working dogs. Alaskan huskies had higher activity levels than non-Alaskan husky breeds in working sled dogs during the day. Nonworking dogs were slightly more active during colder weather, but temperature had no effect on working dogs’ activity. The strongest predictor of daytime activity in working dogs was work schedule. These results indicate that the influence of biological factors on activity varied depending on dogs’ physical demands and human activity was the most powerful driver of activity in working dogs.

Age and Physical Activity Levels in Companion Dogs: Results From the Dog Aging Project

While there has been an abundance of studies on the important relationship between physical activity and age in both dogs and humans, studies on dogs have primarily focused on how a dog's biological characteristics, such as their weight, affect the age-activity relationship. To date, there is little knowledge about how this relationship may be associated with contextual- and owner-level characteristics. We leveraged a large and novel data set from the Dog Aging Project (DAP) to investigate the extent to which the age-activity relationship is associated with certain dog and owner characteristics, namely dog size, owner age, and the environment in which they live. Dogs are a unique model for aging research as they are exposed to similar social and environmental elements as humans but have a shorter life span, allowing researchers to observe their entire life course. We find that older dogs are less active than younger dogs; rural dogs are more active than suburban and urban dogs, especially at younger ages; and larger dogs are more active than smaller dogs. These findings are generally consistent with previous studies. However, a surprising finding is that older owners have more active dogs than younger owners. As one of the first studies to utilize the large survey data from the DAP, this study lays the foundation for future investigations to further understand and identify the biological, social, and environmental causes, as well as consequences, of aging.

Canine Geriatric Syndrome: A Framework for Advancing Research in Veterinary Geroscience

Biological aging is the single most important risk factor for disease, disability, and ultimately death in geriatric dogs. The effects of aging in companion dogs also impose significant financial and psychological burdens on their human caregivers. The underlying physiologic processes of canine aging may be occult, or early signs of aging may be ignored because of the misconception that biological aging is natural and therefore inevitable. The ability to detect, quantify, and mitigate the deleterious processes of canine aging would greatly enhance veterinary preventative medicine and animal welfare. In this paper we propose a new conceptual framework for aging in dogs, the Canine Geriatric Syndrome (CGS). CGS consists of the multiple, interrelated physical, functional, behavioral, and metabolic changes that characterize canine aging as well as the resulting clinical manifestations, including frailty, diminished quality of life, and age-associated disease. We also identify potential key components of a CGS assessment tool, a clinical instrument that would enable veterinarians to diagnose CGS and would facilitate the development and testing of interventions to prolong healthspan and lifespan in dogs by directly targeting the biological mechanisms of aging. There are many gaps in our knowledge of the mechanisms and phenotype of aging in dogs that must be bridged before a CGS assessment tool can be deployed. The conceptual framework of CGS should facilitate identifying these gaps and should stimulate research to better characterize the processes and effects of aging in dogs and to identify the most promising preventative strategies to target these.

Development of infrastructure for a systemic multidisciplinary approach to study aging in retired sled dogs

Canines represent a valuable model for mammalian aging studies as large animals with short lifespans, allowing longitudinal analyses within a reasonable time frame. Moreover, they develop a spectrum of aging-related diseases resembling that of humans, are exposed to similar environments, and have been reasonably well studied in terms of physiology and genetics. To overcome substantial variables that complicate studies of privately-owned household dogs, we have focused on a more uniform population composed of retired Alaskan sled dogs that shared similar lifestyles, including exposure to natural stresses, and are less prone to breed-specific biases than a pure breed population. To reduce variability even further, we have collected a population of 103 retired (8-11 years-old) sled dogs from multiple North American kennels in a specialized research facility named Vaika. Vaika dogs are maintained under standardized conditions with professional veterinary care and participate in a multidisciplinary program to assess the longitudinal dynamics of aging. The established Vaika infrastructure enables periodic gathering of quantitative data reflecting physical, physiological, immunological, neurological, and cognitive decline, as well as monitoring of aging-associated genetic and epigenetic alterations occurring in somatic cells. In addition, we assess the development of age-related diseases such as arthritis and cancer. In-depth data analysis, including artificial intelligence-based approaches, will build a comprehensive, integrated model of canine aging and potentially identify aging biomarkers that will allow use of this model for future testing of antiaging therapies.

Owner reported breathing scores, accelerometry and sleep disturbances in brachycephalic and control dogs: A pilot study

OBJECTIVES

To compare physical activity and length and quality of sleep between brachycephalic dogs and a control population.

METHODS

Brachycephalic and control dogs were prospectively enrolled. Length of activity and sleep were determined via accelerometer use. Owners completed a questionnaire regarding typical daily activity, sleep patterns and an 'owner reported breathing score (ORBS)'. One hour of normal home sleep was recorded for each dog, and a veterinary observer subjectively scored the dogs' sleep quality.

RESULTS

Twenty brachycephalic and 15 control dogs were included. There were no differences between age and weight. Owners reported brachycephalic dogs to be less active (p = 0.022) and have higher ORBS (p < 0.001) compared to control dogs. Brachycephalic dogs had increased sleep disturbances compared to control dogs (p = 0.001), and video sleep score was positively correlated with increased sleep disturbances (r² = 0.47, p = 0.007). There were no differences in active and sleep times based on accelerometry between groups.

CONCLUSION

Brachycephalic dogs have more disturbed sleep, which may have negative implications on welfare, but there were no differences in activity or length of sleep between groups. There is evidence that signs suggestive of brachycephalic obstructive airway syndrome (BOAS) as assessed by ORBS is correlated with poorer sleep quality, indicating that reduced sleep quality is part of BOAS. Owners may underestimate disturbed sleep or may perceive disturbed sleep to be normal.

Comparison of activity levels derived from two accelerometers in dogs with osteoarthritis: Implications for clinical trials

Accelerometer measurements are frequently reported as total weekly activity counts (AC). Methods of utilizing activity parameters to allow differentiation of activity intensities (i.e., manually derived cut-points) have been described. While this information may provide valuable data for researchers, only few investigators have utilized these methods. This may, in part, be due to the challenge associated with data processing. Some devices, however, generate activity intensity data automatically. This study was conducted to evaluate a novel accelerometer that allows for remote download of data via Wi-Fi (Heyrex), to compare automatically generated parameters quantifying activity levels to previously established cut-points (Actical) and to describe the variability of accelerometer data in dogs with osteoarthritis. Twelve client-owned dogs with osteoarthritis were fitted with a collar with two accelerometers (Heyrex and Actical). Accelerometer data were recorded for 28 days. Pearson bivariate correlations and coefficient of variation (CV%) were calculated for accelerometer data. There was a strong correlation between the AC reported by Heyrex and Actical devices. Several automatically generated parameters showed strong correlations to previously validated cut-points and displayed lower CV% than weekly AC. The activity intensity derived from the Heyrex was associated with the lowest CV% of all parameters from both accelerometers. Automatically generated activity intensity parameters should be considered as potential outcome measures in clinical trials for dogs with osteoarthritis. This novel technology may allow for convenient acquisition of activity intensity data in companion animals. However, technical difficulties (e.g., lack of Wi-Fi connectivity) may pose challenges when using this novel device.

Efficacy of a Therapeutic Diet on Dogs With Signs of Cognitive Dysfunction Syndrome (CDS): A Prospective Double Blinded Placebo Controlled Clinical Study

Cognitive dysfunction syndrome (CDS) is a common condition in senior dogs, which may be analogous to dementia such as Alzheimer's disease (AD) in people. In humans, AD has been associated with many risk factors such as reduced cerebral glucose metabolism, docosahexaenoic acid (DHA) deficiency, chronic oxidative stress, and chronic inflammation. By targeting some of these risk factors, we have developed two nutritional solutions (medium chain triglyceride, MCT and Brain Protection Blend, BPB) to enhance cognitive function and slow aging-induced cognitive decline. These have been positively evaluated in colony housed senior dogs and cats. The objective of this clinical study was to evaluate the effects of diets with MCTs and the BPB on client-owned dogs with CDS. Participating veterinary clinics screened senior dogs for signs of CDS as determined by a Senior Canine Behavior Questionnaire and a Canine Medical Health Questionnaire. Eighty-seven dogs were randomly enrolled into one of three diet groups with 29 dogs per group: Control, 6.5% MCT oil + BPB (6.5% MCT diet), 9% MCT oil + BPB (9% MCT diet). Diets were fed for a period of 90 days, and each dog's CDS signs were re-evaluated at day 30 and day 90. All 6 categories of the CDS signs were significantly improved (p <0.05) in the dogs given the 6.5% MCT diet at the end of the 90-day study. Control only improved in 4 out 6 categories. The 9% MCT diet only improved in dogs that accepted the diet. The results from this dog study confirm the benefits of MCT and BPB in managing clinical signs of CDS in dogs. The results support our hypothesis that targeting known risk factors associated with brain aging and AD is able to improve symptoms of CDS in dogs. These data may facilitate the development of similar nutrient blends to manage MCI and AD.

Avaliação diagnóstica na síndrome disfunção cognitiva canina

RESUMO O objetivo do presente estudo foi avaliar o questionário observacional e os testes de reatividade como forma de triagem e diagnóstico da disfunção cognitiva em cães idosos. Foram estudados 10 cães acima de sete anos, que apresentavam queixas comportamentais. Foi utilizado questionário que abordava questões comportamentais, como desorientação, atividade, interação socioambiental, alterações no padrão do sono e casa-sujidade. As respostas foram convertidas em pontuações, cujo somatório classificou o cão com disfunção cognitiva canina (DCC), ou borderline (BL), ou sem alterações comportamentais (SAC). Logo depois, foram realizados, em todos os cães, os seguintes testes cognitivos: open field, curiosidade, interação com humano e com espelho. Pela avaliação do questionário, foi determinado que dois cães tinham DCC, três eram BL, cinco eram SAC. Os cães classificados com DCC tinham idade superior aos demais e apresentaram alterações em todos os testes de reatividade, enquanto os cães BL apresentaram alterações em dois testes de reatividade e os SAC não apresentaram alterações. Conclui-se que, com o aumento da expectativa de vida canina, o questionário observacional foi um instrumento de triagem para a identificação dos cães classificados com DCC, BL e SAC, e os testes de reatividade como um método inovador para identificar o verdadeiro estado cognitivo dos pacientes idosos.

Diurnal changes in core body temperature, day/night locomotor activity patterns, and actigraphy-generated behavioral sleep in aged canines with varying levels of cognitive dysfunction

Core body temperature (CBT) rhythm, locomotor activity, and actigraphy-sleep were evaluated in geriatric dogs with cognitive dysfunction. Dogs (n=33; 9-16 yrs) performed a spatial working memory task and divided into three memory groups: Low, Moderate, and High, with subsequent evaluation of learning and attention. Rectal CBT was recorded 6 times over a 17.5 h period and Actiwatch® activity monitoring system for 5 days while housed indoors with 12 h light/dark schedule. Rhythm of daily activity data was evaluated using the traditional cosinor analysis and generation of non-parametric measures of interdaily stability, intradaily variability, and relative amplitude. CBT differed with time (F (5, 130)=11.36, p<0.001), and was the highest at 19:00C. CBT at 19:00 was positively related (p<0.01) to memory (r(31)=0.50) and 3-domain cognitive performance index (memory, learning, attention; r(31)=0.39). Total daytime or night-time activity did not differ between memory groups, but hourly counts at 8:00 were positively related (p<0.05) to memory (r(31)=0.52), learning (r(31)=0.36), and 3-domain cognitive performance index (r(31)=0.53). There were no significant differences between age or memory groups for any circadian rhythm measures. Daytime naps were inversely related to memory accuracy (r(31)=-0.39; p<0.05) and BT at 15:00 (r(30)=-0.51; p<0.01). Lower peak BT and increased napping may predict some aspects of cognitive performance of working memory, learning, and/or attention processes in these geriatric dogs, but minimal diurnal rhythm disruption of locomotor activity is observed when these cognitive processes decline.

Loss of Cdk5 function in the nucleus accumbens decreases wheel running and may mediate age-related declines in voluntary physical activity

KEY POINTS

Physical inactivity, which drastically increases with advancing age, is associated with numerous chronic diseases. The nucleus accumbens (the pleasure and reward 'hub' in the brain) influences wheel running behaviour in rodents. RNA-sequencing and subsequent bioinformatics analysis led us to hypothesize a potential relationship between the regulation of dendritic spine density, the molecules involved in synaptic transmission, and age-related reductions in wheel running. Upon completion of follow-up studies, we developed the working model that synaptic plasticity in the nucleus accumbens is central to age-related changes in voluntary running. Testing this hypothesis, inhibition of Cdk5 (comprising a molecule central to the processes described above) in the nucleus accumbens reduced wheel running. The results of the present study show that reductions in synaptic transmission and Cdk5 function are related to decreases in voluntary running behaviour and provide guidance for understanding the neural mechanisms that underlie age-dependent reductions in the motivation to be physically active.

ABSTRACT

Increases in age are often associated with reduced levels of physical activity, which, in turn, associates with the development of numerous chronic diseases. We aimed to assess molecular differences in the nucleus accumbens (NAc) (a specific brain nucleus postulated to influence rewarding behaviour) with respect to wheel running and sedentary female Wistar rats at 8 and 14 weeks of age. RNA-sequencing was used to interrogate transcriptomic changes between 8- and 14-week-old wheel running rats, and select transcripts were later analysed by quantitative RT-PCR in age-matched sedentary rats. Voluntary wheel running was greatest at 8 weeks and had significantly decreased by 12 weeks. From 619 differentially expressed mRNAs, bioinformatics suggested that cAMP-mediated signalling, dopamine- and cAMP-regulated neuronal phosphoprotein of 32 kDa feedback, and synaptic plasticity were greater in 8- vs. 14-week-old rats. In depth analysis of these networks showed significant (∼20-30%; P < 0.05) decreases in cell adhesion molecule (Cadm)4 and p39 mRNAs, as well as their proteins from 8 to 14 weeks of age in running and sedentary rats. Furthermore, Cadm4, cyclin-dependent kinase 5 (Cdk5) and p39 mRNAs were significantly correlated with voluntary running distance. Analysis of dendritic spine density in the NAc showed that wheel access increased spine density (P < 0.001), whereas spine density was lower in 14- vs. 8-week-old sedentary rats (P = 0.03). Intriguingly, intra-NAc injection of the Cdk5 inhibitor roscovitine, dose-dependently decreased wheel running. Collectively, these experiments suggest that an age-dependent loss in synaptic function and Cdk5/p39 activity in the NAc may be partially responsible for age-related declines in voluntary running behaviour.

Dietary Mannoheptulose Does Not Significantly Alter Daily Energy Expenditure in Adult Labrador Retrievers

Mannoheptulose (MH), a sugar found in avocados that inhibits glycolysis in vitro, has been preliminarily investigated as a novel food ingredient for dogs. This study aimed to determine the effects of dietary MH, delivered as an extract of un-ripened avocado, on energy expenditure (EE) in healthy adult Labrador Retriever dogs (total of 12 dogs, 26.99 ± 0.634 kg, 4.9 ± 0.2 y). The study was a double-blind, cross-over with each dog receiving both dietary treatments, control (CON) and MH (400 mg/kg of diet; 6 mg/kg BW), in random order. Resting and post-prandial (10 h) EE and respiratory quotient (RQ) were determined by indirect calorimetry (d 42). The following day, body composition was assessed using dual X-ray absorptiometry. Continuous activity monitoring was conducted using an Atical® accelerometer (d 43–47). A vastus lateralis muscle biopsy was obtained prior to the morning meal (d 49) and 4 h after consumption of their meal (d 56) to determine the protein content and phosphorylation of 5' adenosine monophosphate-activated protein kinase (AMPK). Diet did not affect body weight, resting EE or skeletal muscle AMPK phosphorylation. Dogs fed MH had significantly lower post-prandial RQ (p = 0.02) and ratio of fat to lean body mass (p = 0.02). Physical activity during light time periods (but not dark) was lower in dogs fed MH (p < 0.05) during weekends, but not on weekdays. These results suggest that MH affects energy balance of adult dogs, but that these effects are not dose dependent and not due to physical activity.

The Use of an Open Field Model to Assess Sound-Induced Fear and Anxiety Associated Behaviors in Labrador Retrievers

Previous studies have shown that the playing of thunderstorm recordings during an open-field task elicits fearful or anxious responses in adult beagles. The goal of our study was to apply this open field test to assess sound-induced behaviors in Labrador retrievers drawn from a pool of candidate improvised explosive devices (IED)-detection dogs. Being robust to fear-inducing sounds and recovering quickly is a critical requirement of these military working dogs. This study presented male and female dogs, with 3 minutes of either ambient noise (Days 1, 3 and 5), recorded thunderstorm (Day 2), or gunfire (Day 4) sounds in an open field arena. Behavioral and physiological responses were assessed and compared to control (ambient noise) periods. An observer blinded to sound treatment analyzed video records of the 9-minute daily test sessions. Additional assessments included measurement of distance traveled (activity), heart rate, body temperature, and salivary cortisol concentrations. Overall, there was a decline in distance traveled and heart rate within each day and over the five-day test period, suggesting that dogs habituated to the open field arena. Behavioral postures and expressions were assessed using a standardized rubric to score behaviors linked to canine fear and anxiety. These fear/anxiety scores were used to evaluate changes in behaviors following exposure to a sound stressor. Compared to control periods, there was an overall increase in fear/anxiety scores during thunderstorm and gunfire sound stimuli treatment periods. Fear/anxiety scores were correlated with distance traveled, and heart rate. Fear/anxiety scores in response to thunderstorm and gunfire were correlated. Dogs showed higher fear/anxiety scores during periods after the sound stimuli compared to control periods. In general, candidate IED-detection Labrador retrievers responded to sound stimuli and recovered quickly, although dogs stratified in their response to sound stimuli. Some dogs were robust to fear/anxiety responses. The results suggest that the open field sound test may be a useful method to evaluate the suitability of dogs for IED-detection training.

Dietary Mannoheptulose Increases Fasting Serum Glucagon Like Peptide-1 and Post-Prandial Serum Ghrelin Concentrations in Adult Beagle Dogs

Simple Summary

There is increased interest in the use of nutraceuticals for weight management in companion animals. A nutraceutical can broadly be considered a food (or a part of) that provides a health benefit. Mannoheptulose (MH), a sugar found in avocados, is being investigated as a nutraceutical for dogs. In this study, dogs fed a diet containing MH had increased concentrations of blood biomarkers related to energy intake. In addition, dogs fed MH were less physically active than dogs fed a control diet. These findings suggest that dietary MH has the ability to alter energy intake and lower daily energy expenditure.

Abstract

There is a growing interest in the use of nutraceuticals for weight management in companion animals. The purpose of this study was to determine the effects of mannoheptulose (MH), a sugar in avocados that inhibits glycolysis, on energy metabolism in adult Beagle dogs. The study was a double-blind, randomized controlled trial where dogs were allocated to a control (CON, n = 10, 10.1 ± 0.4 kg) or MH containing diet (168 mg/kg, n = 10, 10.3 ± 0.4 kg). Blood was collected after an overnight fast and 1 h post-feeding (week 12) to determine serum satiety related hormones and biochemistry. Resting and post-prandial energy expenditure and respiratory quotient were determined by indirect calorimetry (weeks 4 and 8). Physical activity was measured using an accelerometer (weeks 3, 7, 11). Body composition was assessed using dual X-ray absorptiometry (week 12). MH significantly (p < 0.05) increased fasting serum glucagon-like peptide-1 and post-prandial serum ghrelin. MH tended (p < 0.1) to increase fasting serum gastric inhibitory peptide and decrease physical activity. Together, these findings suggest that dietary MH has the ability to promote satiation and lowers daily energy expenditure.

Association between energy availability and physical activity in older adults

OBJECTIVE

Age-related declines in physical activity are commonly observed in human and animal populations, but their physiologic bases are not fully understood. The authors hypothesize that a lack of available energy contributes to low levels of activity in older persons.

DESIGN

Cross-sectional analyses of relationships between physical activity level and energy availability were performed in 602 community-dwelling volunteers aged 45-91 yrs from the Baltimore Longitudinal Study of Aging. Energy expenditure was measured at rest and during a maximal 400-m walk for calculation of "available energy." Overall and vigorous physical activity levels were assessed using standardized questionnaires. General linear regression models were used to assess the relationships between available energy and general and vigorous physical activity, and stratified analyses were used to analyze the possible differential association between available energy and physical activity across high and low (peak sustained walking oxygen consumption per unit time, <18.3 ml of oxygen per kilogram per minute) levels of aerobic fitness.

RESULTS

Low available energy was associated with low levels of total physical activity (β = 64.678, P = 0.015) and vigorous activity (β = 9.123, P < 0.0001). The direct relationship between available energy and physical activity was particularly strong in persons categorized as having low aerobic fitness between available energy and physical activity with both total (β = 119.783, P = 0.022) and vigorous activity (β = 10.246, P = 0.015) and was independent of body composition and age.

CONCLUSIONS

The findings from this study support the hypothesis that available energy promotes the maintenance of physical activity in older persons. The findings also run counter to the perception that age-related declines in physical activity are primarily societally or behaviorally driven.

Association of signalment parameters with activity of pet dogs

Activity monitors are increasingly being used to quantify the activity of pet dogs. The aim of the present study was to investigate associations between signalment and activity of free-living pet dogs. Healthy pet dogs were recruited to wear an Actical activity monitor on their collars continuously for 2 weeks in their home environment. At least fifteen dogs were enrolled in each of the following weight ranges: <10, 10–20, 21–30, 31–40, >40 kg and their age, sex and reproductive status recorded. Each dog's intensity of activity for each minute of recording was classified using the total counts for that minute and our pre-established cut-points. The percentage of time dogs spent in sedentary, light or moderate/vigorous activity each day was calculated. Median total daily activity counts and median percentages of time dogs spent in activities of differing intensity were used for the analysis. Associations between signalment characteristics and activity parameters were evaluated with the Mann–Whitney test, the Kruskal–Wallis test and Spearman rank correlations. Ninety-eight dogs were enrolled with ≥17 dogs in each weight category. Time that dogs were sedentary correlated positively with age (r 0·50, uncorrected P < 0·001), while the median total daily activity count (r −0·47, uncorrected P < 0·001), time spent in light (r −0·46, uncorrected P < 0·001) and more vigorous activity (r −0·50, uncorrected P < 0·001) were negatively associated with age. No other significant associations between signalment and activity parameters were found. The lack of differences in activity across weight categories may reflect the impact of lifestyle negating any potential behavioural differences across breeds.

Effect of age and severity of cognitive dysfunction on spontaneous activity in pet dogs - part 1: locomotor and exploratory behaviour

Age-related cognitive dysfunction syndrome (CDS) has been reported in dogs and it is considered a natural model for Alzheimer's disease in humans. Changes in spontaneous activity (including locomotor and exploratory behaviour) and social responsiveness have been related to the age and cognitive status of kennel-reared Beagle dogs. The aim of this study was to assess the influence of age and severity of CDS on locomotor and exploratory behaviour of privately owned dogs. This is the first part of a two-part report on spontaneous activity in pet dogs. An open-field (OF) test and a curiosity test were administered at baseline and 6 months later to young (1-4 years, n=9), middle-aged (5-8 years, n=9), cognitively unimpaired aged (≥ 9 years, n=31), and cognitively impaired aged ( ≥ 9 years, n=36) animals. Classification of cognitive status was carried out using an owner-based observational questionnaire, and in the cognitively impaired group, the dogs were categorised as having either mild or severe cognitive impairment. Dogs were recorded during sessions in the testing room and the video-recordings were subsequently analysed. The severity of CDS (but not age) influenced locomotion and exploratory behaviour so that the more severe the impairment, the higher the locomotor activity and frequency of corner-directed (aimless) behaviours, and the lower the frequency of door-aimed activities. Curiosity directed toward novel stimuli exhibited an age-dependent decline although severely affected animals displayed more sniffing episodes directed towards the objects. OF activity did not change after 6 months. Testing aged pet dogs for spontaneous behaviour might help to better characterise cognitively affected individuals.

Cholinesterase inhibitors improve both memory and complex learning in aged beagle dogs

Similar to patients with Alzheimer's disease (AD), dogs exhibit age-dependent cognitive decline, amyloid-β (Aβ) pathology, and evidence of cholinergic hypofunction. The present study sought to further investigate the role of cholinergic hypofunction in the canine model by examining the effect of the cholinesterase inhibitors phenserine and donepezil on performance of two tasks, a delayed non-matching-to-position task (DNMP) designed to assess working memory, and an oddity discrimination learning task designed to assess complex learning, in aged dogs. Phenserine (0.5 mg/kg; PO) significantly improved performance on the DNMP at the longest delay compared to wash-out and partially attenuated scopolamine-induced deficits (15 μg/kg; SC). Phenserine also improved learning on a difficult version of an oddity discrimination task compared to placebo, but had no effect on an easier version. We also examined the effects of three doses of donepezil (0.75, 1.5, and 6 mg/kg; PO) on performance of the DNMP. Similar to the results with phenserine, 1.5 mg/kg of donepezil improved performance at the longest delay compared to baseline and wash-out, indicative of memory enhancement. These results further extend the findings of cholinergic hypofunction in aged dogs and provide pharmacological validation of the canine model with a cholinesterase inhibitor approved for use in AD. Collectively, these studies support utilizing the aged dog in future screening of therapeutics for AD, as well as for investigating the links among cholinergic function, Aβ pathology, and cognitive decline.

Use of an activity monitor to detect response to treatment in dogs with osteoarthritis

OBJECTIVE

To determine whether an activity monitor (AM) could be used to detect changes in activity in dogs with osteoarthritis treated with carprofen or a placebo.

DESIGN

Randomized controlled trial.

ANIMALS

70 dogs with no clinically important abnormalities other than osteoarthritis for which they were not currently being treated.

PROCEDURES

Dogs wore an AM continuously for 21 days. On days 8 through 21, the dogs were treated with carprofen (n = 35) or a placebo (35). Total activity counts for days 1 through 7 (baseline) were compared with total activity counts for days 15 through 21 (endpoint). The change in total activity count from baseline to endpoint was assessed within each treatment group as well as between groups. Linear regression analysis was performed to test for an association between treatment and percentage change in activity counts while controlling for other variables.

RESULTS

For placebo-treated dogs, median baseline total activity count was not significantly different from median endpoint total activity count (1,378,408 vs 1,310,112, respectively). For dogs receiving carprofen, there was a significant increase in median activity count from baseline to endpoint (1,276,427 vs 1,374,133). When age and baseline activity counts were controlled for, dogs in the carpofen-treated group had a 20% increase in activity counts, compared with placebo-treated dogs (95% confidence interval, 10% to 26%).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that the AM used in the present study may be a valid outcome assessment tool for documenting improved activity associated with treatment in dogs with osteoarthritis.

Evaluation of the effect of signalment and body conformation on activity monitoring in companion dogs

OBJECTIVE

To evaluate the effect of signalment and body conformation on activity monitoring in companion dogs.

ANIMALS

104 companion dogs.

PROCEDURES

While wearing an activity monitor, each dog was led through a series of standard activities: lying down, walking laps, trotting laps, and trotting up and down stairs. Linear regression analysis was used to determine which signalment and body conformation factors were associated with activity counts.

RESULTS

There was no significant effect of signalment or body conformation on activity counts when dogs were lying down, walking laps, and trotting laps. However, when dogs were trotting up and down stairs, there was a significant effect of age and body weight such that, for every 1-kg increase in body weight, there was a 1.7% (95% confidence interval, 1.1% to 2.4%) decrease in activity counts and for every 1-year increase in age, there was a 4.2% (95% confidence interval, 1.4% to 6.9%) decrease in activity counts.

CONCLUSIONS AND CLINICAL RELEVANCE

When activity was well controlled, there was no significant effect of signalment or body conformation on activity counts recorded by the activity monitor. However, when activity was less controlled, older dogs and larger dogs had lower activity counts than younger and smaller dogs. The wide range in body conformation (eg, limb or body length) among dogs did not appear to significantly impact the activity counts recorded by the monitor, but age and body weight did and must be considered in analysis of data collected from the monitors.

The effect of laparoscopic versus open ovariectomy on postsurgical activity in small dogs

OBJECTIVE

To describe a technique for laparoscopic ovariectomy (LapOVE) in small dogs, and compare the surgical time, complications, and postoperative activity of dogs undergoing LapOVE to those undergoing conventional traditional open ovariectomy (OOVE).

STUDY DESIGN

A randomized, controlled clinical trial.

ANIMALS

Intact small breed (<10 kg) female dogs (n=20).

METHODS

Ventral median celiotomy was performed for OOVE. A 2-midline portal technique using a 3.5 mm laparoscope port and a 6 mm instrument portal was used for LapOVE. An accelerometer was attached to the collar of each dog to record 24-hour preoperative and 48-hour postoperative activity. Total activity counts recorded before surgery were compared with total counts recorded after surgery. The percent change in counts after surgery was compared between OOVE- and LapOVE-treated dogs.

RESULTS

No major complications occurred and surgical time for LapOVE was significantly longer than for OOVE cases (P=.005). Dogs in the LapOVE group had a 25% decrease in total activity counts after surgery (95% confidence interval [CI]: 11-38%), whereas dogs in the OOVE group had a 62% decrease in total activity counts after surgery (95% CI: 48-76%).

CONCLUSIONS

Both procedures were performed with reasonable surgical times and without major complication. Postoperative activity, as measured by accelerometry, was significantly different between the 2 groups.

CLINICAL RELEVANCE

Laparoscopy is a safe method for ovariectomy in small dogs and results in increased postoperative activity counts when compared with an open technique.

Evaluation of optimal sampling interval for activity monitoring in companion dogs

OBJECTIVE-To determine by use of an accelerometer the sampling interval that has the least variable total activity counts from one week to the next in companion (ie, nonlaboratory) dogs. ANIMALS-80 dogs. PROCEDURES-Dogs wore an accelerometer continuously for 2 weeks. Between-dog and within-dog day-to-day variability in total activity counts were evaluated. The changes in counts between week 1 and week 2 were compared for weekdays, weekends, and full weeks. RESULTS-Significant between-dog variability in total activity counts was detected. Within dogs, there was significant day-to-day variability, with highest counts recorded on weekends. In comparison of data from the first week with data from the second week, the greatest differences were in weekend counts (median difference, 21%; range, 0% to 154%) and the smallest differences were in full 7-day counts (median difference, 10%; range, 0% to 74%). Comparison of weekday counts revealed a median change of 12% (range, 0% to 104%). CONCLUSIONS AND CLINICAL RELEVANCE-Significant between-dog variability in total daily activity counts was detected. Within dogs, a full 7-day comparison of total activity counts from one week to the next provided the least variable estimate of the dogs' activity. For dogs in their home environment, the activity monitor may be most useful in following changes in activity over time. For dogs that have no change in routine according to the owner's report, the least variable estimates of activity can be collected by comparing activity in 7-day intervals.

Implications of age and diet on canine cerebral cortex transcription

Mechanisms contributing to age-related cognitive decline are poorly defined. Thus, we used canine microarrays to compare gene expression profiles of brain tissue from geriatric and young adult dogs. Cerebral cortex samples were collected from six geriatric (12-year old) and six young adult (1-year old) female beagles after being fed one of two diets (animal protein-based versus plant-protein based) for 12 months. RNA samples were hybridized to Affymetrix GeneChip Canine Genome Arrays. Statistical analyses indicated that the age had the greatest impact on gene expression, with 963 transcripts differentially expressed in geriatric dogs. Although not as robust as age, diet affected mRNA abundance of 140 transcripts. As demonstrated in aged rodents and humans, geriatric dogs had increased expression of genes associated with inflammation, stress response, and calcium homeostasis and decreased expression of genes associated with neuropeptide signaling and synaptic transmission. In addition to its existing strengths, availability of gene sequence information and commercial microarrays make the canine a powerful model for studying the effects of aging on cognitive function.

Nonexercise movement in elderly compared with young people

The association between free-living daily activity and aging is unclear because nonexercise movement and its energetic equivalent, nonexercise activity thermogenesis, have not been exhaustively studied in the elderly. We wanted to address the hypothesis that free-living nonexercise movement is lower in older individuals compared with younger controls matched for lean body mass. Ten lean, healthy, sedentary elderly and 10 young subjects matched for lean body mass underwent measurements of nonexercise movement and body posture over 10 days using sensitive, validated technology. In addition, energy expenditure was assessed using doubly labeled water and indirect calorimetry. Total nonexercise movement (acceleration arbitrary units), standing time, and standing acceleration were significantly lower in the elderly subjects; this was specifically because the elderly walked less distance per day despite having a similar number of walking bouts per day compared with the young individuals. The energetic cost of basal metabolic rate, thermic effect of food, total daily energy expenditure, and nonexercise activity thermogenesis were not different between the elderly and young groups. Thus, the energetic cost of walking in the elderly may be greater than in the young. Lean, healthy elderly individuals may have a biological drive to be less active than the young.

Region specific neuron loss in the aged canine hippocampus is reduced by enrichment

Neuron loss within the hippocampus and entorhinal cortex occurs as a function of age in humans. We first tested the hypothesis that neuron loss occurs in the aged dog. The total unilateral number of neurons in the canine entorhinal cortex and subdivisions of the hippocampus from the left hemisphere were estimated using the optical fractionator. The brains from 5 old (13.0-15.0 years old) and 5 young (3.4-4.5 years old) beagle dogs were analyzed. The hilus of the hippocampus showed a significant loss of neurons (approximately 30%) in the aged dog brain compared to young. Differences were not detected in the remaining hippocampal subfields and entorhinal cortex. We further tested the hypothesis that an antioxidant fortified food or behavioral enrichment would reduce the age-related loss of hilar neurons. Behaviorally enriched aged dogs had more neurons in the hilus (approximately 18%) compared to aged controls. These results suggest that the aged canine hippocampus in the left hemisphere shows selective neuron loss and that behavioral enrichment may reduce this loss.

Aging on the job

The older population is growing faster than the population as a whole. Paid work is the main mechanism for physical activity in humans. We, therefore, wanted to ascertain whether work practices (such as employment status and the types of tasks workers perform) follow the biological decline in physical activity that occurs with aging in humans and many other species. We recorded work practices in 3352 adults in the Ivory Coast to establish how work burdens are distributed across different age groups in a community that is minimally fettered by legal constraints. We found a decrease in the amount of work performed with increasing age, and we found that elderly persons performed more skilled, less exothermic tasks than younger workers. These data mirror global workforce distribution trends expressed by age. If the trend continues, a major portion of the population will be unlikely to contribute to the labor force in the near future, producing potentially adverse economic consequences in some populations. Although the problem might be averted or at least minimized by implementing different employment policies, biological factors could overlay and supervene any economic planning.

Application of an automated voxel-based morphometry technique to assess regional gray and white matter brain atrophy in a canine model of aging

In recent years, voxel-based morphometry (VBM) has emerged as a technique to examine regional brain changes associated with normal and pathological aging. Despite its popularity in studies of human aging, application of VBM to animal models of brain aging is rare. In the present study, VBM techniques were developed to validate earlier region of interest (ROI) measures of brain aging in the dog and to provide a more comprehensive analysis of local changes in a canine model of brain aging. Consistent with previous findings, frontal lobe atrophy increased with age, most notably in aged male dogs. Age-related gray matter reductions were also observed in parietal and temporal lobes, thalamus, cerebellum, and brainstem. Temporal lobe atrophy was particularly prominent in old females. A number of age-related changes in white matter not previously explored in the dog were also identified with VBM. Specifically, aged males exhibited greater decreases in the internal capsula and cranial nerve bundles compared to decreased volumes in the alveus of the hippocampus in old female dogs. Together, the present results indicate that application of VBM techniques in a canine model of aging yields more comprehensive information regarding topographical patterns of brain aging in male and female dogs than previously reported using traditional manual ROI methods.

Daily Rhythms of Blood Pressure, Heart Rate, and Body Temperature in Fed and Fasted Male Dogs

Daily or circadian rhythmicity in physiological processes has been described in a large number of species of birds and mammals. However, in dogs, most studies have either failed to detect rhythmicity or have found that rhythmicity reflects merely an acute exogenous effect of feeding rather than an autonomous rhythmic process. In the present study, we investigated the rhythmicity of body temperature, blood pressure, and heart rate in dogs fed daily as well as in dogs deprived of food for 60 h. Our results document clear rhythmicity in all three parameters and demonstrate that the rhythmicity is independent of the feeding schedule. The failure of various previous investigations to document daily rhythmicity in dogs is probably due to lack of experimental rigour rather than to weakness of daily rhythmicity in dogs.

Aging muscle

Age causes structural and functional changes in skeletal muscle in a wide range of species, including humans. Muscle changes in humans start in the fourth decade of life and cause frailty and disabilities. Associated changes in body composition form the basis of many metabolic disorders, such as insulin resistance, type 2 diabetes, hypertension, and hyperlipidemia, which result in an increased incidence of cardiovascular death. Decreases in the synthesis rates of many muscle proteins, specifically of myosin heavy chain and mitochondrial proteins, occur with age. The underlying causes of the reduction in mitochondrial biogenesis and ATP production seem to be decreases in mitochondrial DNA and messenger RNA. Reduced ATP production could be the basis of reduced muscle protein turnover, which requires energy. Both aerobic exercise and resistance exercise enhance muscle protein synthesis and mitochondrial biogenesis. Insulin and amino acids have also been shown to enhance muscle mitochondrial biogenesis and mitochondrial protein synthesis. However, the insulin-induced increase in muscle mitochondrial ATP production is defective in type 2 diabetic patients with insulin resistance. Moreover, a dissociation between increases in muscle mitochondrial biogenesis and insulin sensitivity after exercise has been noted in older persons. It remains to be determined whether muscle mitochondrial dysfunction causes or results from insulin resistance. Exercise seems to enhance the efficiency of muscle mitochondrial DNA in rodents. Reduced physical activity as a contributor of age-related mitochondrial dysfunction remains to be determined. It is proposed that a reduction in tissue mitochondrial ATP production signals the hypothalamic centers to reduce spontaneous physical activities. Voluntary physical activity is regulated by cognitive centers and could attenuate the progressive decline in mitochondrial functions that occurs with age.

Chronic antioxidant and mitochondrial cofactor administration improves discrimination learning in aged but not young dogs

The present experiment was part of a 3-year longitudinal study examining the effects of age and antioxidant treatment on cognitive decline in beagles. Two size-concept tasks were administered following pretraining on a series of two-choice (six subtests) and three-choice size discrimination tasks. Thirty-nine young and aged dogs were matched for age and cognitive ability then divided into four treatment groups. A combined antioxidant-mitochondrial cofactor treatment led to significantly improved performance in aged dogs on the first subtest of the two-choice size discrimination series. Treated aged dogs did not significantly differ from the young. Aged dogs on the antioxidant diet continued to perform better than aged controls on the second and third subtests, but these effects did not achieve significance. Young dogs performed significantly better than the aged dogs on the second and third subtests. The remaining two-choice tasks of the discrimination series were comparatively easy, leading to a floor effect. The antioxidant animals performed better on the three-choice size discrimination, but not on the two size-concept tasks. Antioxidants improved the performance of aged dogs on the initial learning tests, suggesting a selective improvement of factors related to the aging process and specific cognitive processes rather than general cognitive enhancement.

A longitudinal study of brain morphometrics using serial magnetic resonance imaging analysis in a canine model of aging

Longitudinal changes in cortical atrophy, ventricular enlargement, and lesion development in serial MRI scans collected from 47 healthy dogs from 1999 (8-11 years old) to 2002 (11-14 years old) were studied. The first method involved manual region of interest volumetric analysis to examine changes in cerebral and ventricular volume during the three years. No change in cerebral volume was detected but ventricular volume increased significantly each year in 2000, 2001, and 2002. Increased ventricular volume parallels early studies of age-dependent ventricular enlargement in the brain of aging beagle dogs. The second method involved a visual analysis of co-registered serial MRIs for each subject. Consistent with the volumetric results, there was no visible change in cortical thickness indicating no cerebral atrophy, but a significant increase in ventricular size was noted. Visual examination also revealed a significant increase in number of dogs who developed aging lesions over the last 2 years in 2001 and 2002. Additionally, a disproportionate number of lesions were recorded in the frontal cortex and caudate nucleus compared to other brain regions. These lesion findings are consistent with other studies in the aging dog that suggest that the frontal lobes may be particularly vulnerable to age-related changes.

Effects of scopolamine challenge on regional cerebral blood volume. A pharmacological model to validate the use of contrast enhanced magnetic resonance imaging to assess cerebral blood volume in a canine model of aging

Cognitive impairment resulting from disruption of cholinergic function may occur through modulation of cerebrovascular volume (CBV). In the present study, dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) was used to examine cerebrovascular volume in young and old dogs during baseline and after administration of a cholinergic antagonist (scopolamine). In the first study, 24 animals (2-15 years of age) were given a baseline scan followed by a second scan after scopolamine administration (30 microg/kg). Gray matter rCBV was significantly higher than white matter rCBV during baseline and scopolamine administration. In the second study a subset of 7 dogs (4 young and 3 old) received scopolamine before anesthesia was induced for a second DSC-MRI scan. Consistent with the first study, gray matter rCBV was significantly higher than white matter rCBV. Scopolamine administered before anesthesia however, resulted in higher rCBV values compared to baseline in cerebral gray matter. Additionally, rCBVs were higher in young dogs at baseline in gray and white matter and marginally higher in gray matter when scopolamine was administered before anesthesia. These results indicate that in the dog, rCBV varies with brain compartment, decreases with age, and that DSC-MRI provides a measure of cerebrovascular function which may be related to age-dependent changes in cognition, brain structure, and neuropathology.