Prevalence of obesity in riding horses in Scotland

Nutritional ecology of obesity: from humans to companion animals

We apply nutritional geometry, a framework for modelling the interactive effects of nutrients on animals, to help understand the role of modern environments in the obesity pandemic. Evidence suggests that humans regulate the intake of protein energy (PE) more strongly than non-protein energy (nPE), and consequently will over- and under-ingest nPE on diets with low or high PE, respectively. This pattern of macronutrient regulation has led to the protein leverage hypothesis, which proposes that the rise in obesity has been caused partly by a shift towards diets with reduced PE:nPE ratios relative to the set point for protein regulation. We discuss potential causes of this mismatch, including environmentally induced reductions in the protein density of the human diet and factors that might increase the regulatory set point for protein and hence exacerbate protein leverage. Economics--the high price of protein compared with fats and carbohydrates--is one factor that might contribute to the reduction of dietary protein concentrations. The possibility that rising atmospheric CO₂ levels could also play a role through reducing the PE:nPE ratios in plants and animals in the human food chain is discussed. Factors that reduce protein efficiency, for example by increasing the use of ingested amino acids in energy metabolism (hepatic gluconeogenesis), are highlighted as potential drivers of increased set points for protein regulation. We recommend that a similar approach is taken to understand the rise of obesity in other species, and identify some key gaps in the understanding of nutrient regulation in companion animals.

The production and distribution of IL-6 and TNF-a in subcutaneous adipose tissue and their correlation with serum concentrations in Welsh ponies with equine metabolic syndrome

A main symptom of equine metabolic syndrome (EMS) in ponies is pathological obesity characterized by abnormal accumulation of fat deposits and inflammation. In this study, we analyzed the expression of two pro-inflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), in subcutaneous adipose tissue and the correlation with serum concentrations in peripheral blood of Welsh ponies. Based on clinical examination findings, the animals were divided into two groups: ponies affected with EMS (n = 8) and obese ponies (n = 8). The adipose tissue was examined using immunohistochemical analysis while concentrations IL-6 and TNF-α were measured using enzyme-linked immunosorbent assays (ELISAs). Additionally, histological characterization of the adipose tissue was performed. The results obtained showed that IL-6 expression in adipose tissue biopsies derived from animals with EMS was enhanced while TNF-α levels of both groups were comparable. Compared to the obese ponies, EMS animals also had significantly elevated levels of serum IL-6 and TNF-α. Histological analysis revealed macrophage infiltration and fibrosis in adipose tissue preparations from the EMS group. These data suggest that IL-6 may play a key role in the course of EMS in Welsh ponies. Our findings also demonstrated that analysis of pro-inflammatory cytokines levels in serum may serve as an additional tool for diagnosing EMS.

Changes in oxidative stress in response to different levels of energy restriction in obese ponies

The present study evaluated the effect of different levels of energy restriction on metabolic parameters in obese ponies. Relative weight changes, markers of lipid metabolism and oxidant/antioxidant balance were monitored. A total of eighteen obese (body condition score ≥ 7/9) Shetland ponies were studied over a 23·5-week trial, which was divided into three periods. The first period involved a 4-week adaptation period in which each animal was fed 100% of their maintenance energy requirements needed to maintain a stable obese body weight (MERob). This was followed by a 16·5-week weight-loss period in which ponies were assigned to receive either 100% (control group, CONTROL), 80% (slow weight-loss (SLOW) group) or 60% (rapid weight-loss (RAPID) group) of their MERob. During the 3-week end-phase period, all ponies were again fed 100% of their MERob. Relative weight loss was higher in the RAPID group (P< 0·001) compared with the SLOW group. No linear relationship was found as a doubling of the percentage of energy restriction was accompanied by a tripling of the percentage of weight loss. Relative weight gain afterwards in the end-phase period was higher in the RAPID group (P< 0·001) compared with the SLOW and CONTROL groups. During the weight-loss period, TAG and NEFA concentrations were highest in the RAPID group, as were α-tocopherol and ferric-reducing ability of plasma concentrations. After 8 weeks of weight loss, the concentrations of advanced oxidation protein products were higher in the RAPID group compared with the SLOW and CONTROL groups (P< 0·001). In conclusion, the level of energy restriction influences the extent of changes in oxidant/antioxidant balance. Practically, more severe energy restriction regimens may be associated with a greater regain of weight after the restriction period.

Fibre digestibility, abundance of faecal bacteria and plasma acetate concentrations in overweight adult mares

The purpose of the present study was to compare digestibility of grass hay, faecal and plasma volatile fatty acid (VFA) concentrations, and faecal bacterial abundance in overweight and moderate-condition mares. Five overweight adult mixed-breed mares and five adult mixed-breed mares in moderate condition were housed individually and limit-fed orchard grass (Dactylis glomerata) hay at 20 g/kg body weight (as fed) daily for 14 d. Forage DM and fibre digestibility were determined using AOAC methods; digestible energy was measured using bomb calorimetry; plasma and faecal VFA concentrations were determined by use of GC and MS; faecal Firmicutes, Bacteroidetes, Fibrobacter succinogenes, Ruminococcus flavefaciens and total bacteria abundance was determined by quantitative real-time PCR using previously designed phylum-specific 16S ribosomal RNA gene primers. No differences in hay digestibility, faecal VFA concentrations or faecal bacterial abundance were detected between overweight and moderate-condition mares. Mean plasma acetate concentrations were higher (P = 0·03) in overweight (1·55 (range 1·43-1·65) mmol/l) v. moderate-condition (1·39 (range 1·22-1·47) mmol/l) mares. We conclude that the higher plasma acetate in overweight mares should be further investigated as a potential link between gut microbes and obesity in horses.

Obesity prevalence and associated risk factors in outdoor living domestic horses and ponies

Reasons for performing study. The prevalence of obesity in companion animals, including horses and ponies has risen drastically in recent years and risk factors have been little investigated. Horses are unique amongst companion animals in that many are outdoor-living and forage independently on pasture; they also have a dual utility and companionship role. The body condition of wild and free-living equines is known to vary seasonally, yet previous estimates of the prevalence of obesity and associated risk factors in domestic animals do not consider this. Most previous studies were conducted during the summer months when pasture quality is greater and obesity prevalence is likely to be highest. In addition, many previous estimates do not use validated body condition scoring methods and rely on owner reporting.

Objectives. To examine the prevalence and risk factors predictive of equine obesity at both the end of winter and the end of summer, in a domestic population of leisure horses with daily access to pasture. Using validated body condition scoring methods and a single, trained observer.

Methods. Body condition and belly girth measurements were taken at the end of winter and during the summer in a population of leisure horses (n = 96) with outdoor pasture access for ≥6 h per day. Risk factor information was obtained by two owner questionnaires and analysed statistically using a mixed effects logistic regression model. The dependent variable was obese (BCS ≥ 7/9) or non-obese (BCS < 7/9). Risk factors associated with seasonal change in belly girth were also explored using a mixed effects linear regression model.

Results. Obesity prevalence rose significantly from 27.08% at the end of winter to 35.41% during summer (p < 0.001). Breed was the risk factor most strongly associated with obesity (p < 0.001). Supplementary feed was not a strong predictor and there was no association with low intensity structured exercise. As winter BCS increased, the percentage seasonal change in belly girth decreased.

Conclusions. Obesity prevalence differed between winter and summer in domestic equines. Supplementary feed and low intensity structured exercise in equines living outdoors for ≥6 h per day had limited or no effect on obesity levels. Seasonal variation in body condition was lower in obese equines.

Potential relevance. It is important to consider season when studying equine obesity and obesity-associated disorders. Risk factor analysis suggests preventative measures may need to be breed specific. The metabolic implications of a lessened seasonal change in body condition in obese animals, warrants investigation.

Risk factors associated with health disorders in sport and leisure horses in the Netherlands

Horses are used for a wide variety of purposes from being used for recreational purposes to competing at an international level. With these different uses, horses have to adapt to numerous challenges and changes in their environment, which can be a challenge itself in continuously safeguarding their welfare. The objective of this study was to assess the prevalence of health disorders with clinical examination and identify possible risk factors of health disorders affecting horse welfare in professional husbandry systems in the Netherlands. With the use of fixed protocols for recording health aspects in horses, 150 horse farms voluntarily participating in the study were assessed by trained assessors. On each farm, 20 horses were clinically examined, in total almost 3,000 animals. This study recorded on the basis of the clinical examinations: the respiratory system (i.e., abnormal breathing [1%], coughing [1%], nasal discharge [1.9%]), body condition (i.e., 18.8% fat body condition and 6.4% poor body condition), locomotion (14.5% exhibited irregularity of locomotion and 4.8% were lame), back palpation (a light response [22.6%] and moderate to severe response [8.4%]), mouth (i.e., irregularities on mouth corners [3.4%] and bars [3.4%]), and ocular discharge (12%). Risk factor analysis, stepwise using mixed model regression, demonstrated several risk factors for health aspects. Horses used for instruction (riding lessons) were almost two times more at risk to develop moderate to severe back pain compared to horses used for recreation (odds ratios [OR] = 0.54) or for competition (OR = 0.61). Horses used for instruction (riding school lessons), breeding, or recreation all had a higher risk for irregular locomotion or lameness compared to competition horses (OR = 0.42, OR = 0.55, OR = 2.14, respectively). Horses used for recreation were more prone to have a higher BCS compared to horses used for breeding (OR = 3.07) and instruction (OR = 2.06). The prevalence of health problems and the identified risk factors are valid for the horses in the present study in which farms voluntarily participated. Furthermore, the results may provide the basis for horse welfare and health programs on farm and horse industry levels. With the development of a valid welfare monitoring system for the horse industry, the welfare of horses can be increased through improving awareness and stimulating changes in management.

Preventive health care and owner-reported disease prevalence of horses and ponies in Great Britain

This study aimed to describe the provision of preventive health care and owner-reported disease prevalence in horses and ponies within Great Britain (GB), and to assess geographical variations in health care provision. A cross-sectional survey was conducted, using a postal questionnaire administered to a random sample of veterinary-registered owners of horses and ponies in GB (n=797). The majority of animals received regular preventive health care: 95.6% had regular hoof care; 71.3% were vaccinated for both influenza and tetanus and median time since last anthelmintic administration was 8.7 weeks. Thirty-one percent of owners indicated their animal was overweight/obese. A new health problem within the previous 7 days was reported for 7.4% of animals, 59.3% of which were veterinary-diagnosed. Thirty-two percent of animals were reported to have a long-term/recurrent condition, of which osteoarthritis (13.9%) was the most prevalent. Obesity, musculoskeletal disorders, and dermatological conditions were the most prevalent conditions affecting veterinary-registered horses/ponies.

Effects of metformin hydrochloride on blood glucose and insulin responses to oral dextrose in horses

REASONS FOR PERFORMING STUDY

Metformin is a potential therapeutic agent for the treatment of insulin resistance (IR). In laboratory animals, orally administered metformin reduces intestinal glucose absorption and may therefore affect insulinaemic responses to oral carbohydrate ingestion.

OBJECTIVES

To determine whether pretreatment with metformin reduces plasma glucose concentration and insulin responses following consumption of dextrose in horses.

STUDY DESIGN

Therapeutic cross-over study.

METHODS

Seven healthy Standardbred and Thoroughbred geldings were subjected to an oral dextrose challenge test on 4 occasions: with and without metformin, before and after induction of IR with dexamethasone. Metformin was administered by nasogastric tube at 30 mg/kg bwt 1 h before administration of dextrose. Glucose and insulin concentrations in plasma/serum were measured at regular intervals during each test. Linear mixed models were specified for each predetermined outcome variable, and for each model the 'treatment' was included as a fixed effect with 4 categorical levels (none, metformin, dexamethasone and dexamethasone with metformin) and horse accounted for as a random effect.

RESULTS

In healthy horses, the administration of metformin resulted in a statistically significant reduction in peak glucose concentration (P = 0.002), area under the glucose curve (P<0.001) and insulin concentration 120 min after dextrose administration (P = 0.011). Following the induction of IR, administration of metformin was associated with significant differences in peak glucose concentration (P<0.001), the percentage increase in glucose concentration (P = 0.010), the area under the glucose curve (P<0.001) and insulin concentration at 120 min (P = 0.034) and 150 min after dextrose administration (P = 0.014).

CONCLUSIONS

Metformin resulted in reduced glycaemic and insulinaemic responses both in healthy horses and in horses with experimentally induced IR.

POTENTIAL RELEVANCE

Metformin may benefit horses with naturally acquired IR by reducing glycaemic and insulinaemic responses to dietary nonstructural carbohydrates. Further investigations into the mechanisms of action of metformin in horses and controlled clinical trials are warranted.

Adaption of horses to a novel dynamic feeding system: movement and behavioural responses

REASONS FOR PERFORMING STUDY

Many domestic horses and ponies are sedentary and obese due to confinement to small paddocks and stables and a diet of infrequent, high-energy rations. Severe health consequences can be associated with this altered lifestyle.

OBJECTIVES

The aims of this study were to investigate the ability of horses to learn to use a dynamic feeder system and determine the movement and behavioural responses of horses to the novel system.

METHODS

A dynamic feed station was developed to encourage horses to exercise in order to access ad libitum hay. Five pairs of horses (n = 10) were studied using a randomised crossover design with each pair studied in a control paddock containing a standard hay feeder and an experimental paddock containing the novel hay feeder. Horse movement was monitored by a global positioning system (GPS) and horses observed and their ability to learn to use the system and the behavioural responses to its use assessed.

RESULTS

With initial human intervention all horses used the novel feeder within 1 h. Some aggressive behaviour was observed between horses not well matched in dominance behaviour. The median distance walked by the horses was less (P = 0.002) during a 4 h period (117 [57-185] m) in the control paddock than in the experimental paddock (630 [509-719] m).

CONCLUSIONS

The use of an automated feeding system promotes increased activity levels in horses housed in small paddocks, compared with a stationary feeder.

POTENTIAL RELEVANCE

The novel feeder system may have application in the husbandry of horses and ponies kept in small paddocks by encouraging a natural pattern of exercise without human intervention and an ad libitum diet of hay. This may improve the health and welfare of horses.

Weight loss resistance: a further consideration for the nutritional management of obese Equidae

Evidence-based, weight loss management advice is required to address equine obesity. Changes in body mass (BM), body condition score (BCS), heart (HG) and belly circumference (BG), direct (ultrasonographic) and indirect (D(2)O dilution, bioelectrical impedance analysis [BIA]) measures of body fat as well as indices of insulin resistance (IR) were monitored in 12 overweight (BCS ≥ 7/9) horses and ponies of mixed breed and gender for 16 weeks. Animals were randomly assigned to two groups (Group 1, n=6, BCS 7.6/9 ± 0.6, 489 ± 184.6 kg; Group 2, n=6, BCS 8.1/9 ± 0.6, 479 ± 191.5 kg). Daily dry matter intake (DMI) was restricted to 1.25% BM as one of two, near-isocaloric (DE ∼0.115 MJ/kg BM/day), forage-based diets (Group 1, 0.8% BM chaff-based feed: 0.45% BM hay; Group 2, 1.15% BM hay: 0.1% BM nutrient-balancer). Statistical modelling revealed considerable between-animal heterogeneity in proportional weight losses (0.16-0.55% of Week 1 BM weekly). The magnitude of weight loss resistance (WLR) or sensitivity to dietary restriction was independent of diet or any measured outset variable and was largely (65%) attributed to animal identity. Predicted rates of weight loss decreased over time. BCS and BIA were poor estimates of D(2)O-derived body fat%. Reciprocal changes in depths of retroperitoneal and subcutaneous adipose tissues were evident. Changes in BG were associated with losses in retroperitoneal fat and BM (r(2), 0.67 and 0.79). Indices of IR improved for 9/12 animals by Week 16. For obese animals, weight loss should be initiated by restricting forage DMI to 1.25% BM. Subsequent restriction to 1% BM may be warranted for WLR animals.

Prevalence of overconditioning in mature horses in southwest Virginia during the summer

BACKGROUND

The prevalence of obesity in horses in the eastern United States is not well documented.

OBJECTIVE

To determine body condition and risk factors for obesity in horses in Southwest Virginia during summer.

ANIMALS

A sample of 300 mature (4-20 years old), light breed horses (140 mares, 151 geldings, and 9 stallions) from the VMRCVM Equine Field Service practice equine database. The horses were from 114 farms and 138 owners.

METHODS

Horses were evaluated over a 60-day period in this cross-sectional, prospective study. A questionnaire was completed for each horse. Body condition score (BCS) was assigned using a scale of 1 (emaciated) to 9 (obese) by 2 independent scorers. Morphometric measurements included average neck circumference (ANC), girth, body length, and height at the withers. Horses were categorized based on BCS as underconditioned (BCS < 4), optimal condition (BCS 4-6), overconditioned (BCS 7), and obese condition (BCS 8-9).

RESULTS

Five horses (1.7%) were underconditioned, 142 horses (47.3%) were optimally conditioned, 97 horses (32.3%) were overconditioned, and 56 (18.7%) were obese. Estimated body weight (EBW) (r = 0.14, P = .015), body mass index (BMI) (r = 0.46, P < .001), and neck circumference to height ratio (NCHR) (r = 0.50, P = .001) increased with increasing BCS.

CONCLUSIONS AND CLINICAL IMPORTANCE

The prevalence of overconditioned and obese horses in this population was higher than reported in previous studies and indicates that obesity might be an emerging problem in horses.

Adipose tissue-derived adiponectin expression is significantly associated with increased post operative mortality in horses undergoing emergency abdominal surgery

REASONS FOR PERFORMING STUDY

Adipose tissue is an important source of inflammatory cytokines (adipokines) and adiposity has been identified as having a significant effect on human morbidity and mortality. Obesity is also an emerging welfare problem in the UK horse population, but the role that it plays in secondary diseases is unclear.

OBJECTIVES

To examine the expression of inflammation-related adipokine genes in retroperitoneal adipose tissue of horses undergoing emergency abdominal surgery and to explore associations with adiposity and post operative survival.

METHODS

Retroperitoneal adipose tissue samples were obtained from 76 horses undergoing emergency abdominal surgery. Real-time PCR was used to measure gene expression for leptin, adiponectin, tumour necrosis factor-alpha, macrophage chemoattractant protein-1, macrophage inhibitory factor, serum amyloid A, haptoglobin and interleukin-1. Multivariate patterns of adipokine expression were explored with principal component analysis (PCA), whilst univariable associations with post operative survival were tested in a Cox proportional hazards model.

RESULTS

Leptin gene expression was higher in overweight and obese horses than in lean animals. Expression of mRNA encoding adiponectin mRNA in visceral adipose tissue was positively associated with increased post operative mortality (hazard ratio 1.31, 95% CI 1.05-1.65). However, PCA did not demonstrate multivariable patterns of adipokine gene expression from visceral adipose tissue associated with body mass index or with survival.

CONCLUSIONS

In horses presented with acute intestinal disease, increased adiponectin gene expression from retroperitoneal adipose tissue is associated with an increased risk of mortality. Obesity assessed by BMI had no association with increased post operative mortality in horses with primary gastrointestinal disease.

POTENTIAL RELEVANCE

Further study is warranted on the expression and effects of adipokines, particularly adiponectin, and correlation with postoperative outcome.

Voluntary ingestion of wood shavings by obese horses under dietary restriction

Dietary restriction for the weight-loss management of obese horses limits the natural trickle-feeding behaviour. During feed restriction, wood shavings are often advised as bedding to prevent dietary supplementation from non-feed sources. Data from twelve overweight/obese horses and ponies of mixed breed and sex, bedded on wood shavings during 16 weeks of feed restriction, were retrospectively evaluated. DM intake (DMI) was restricted to 1·25 % of body mass (BM) daily. Animals were randomly assigned to one of two diets (hay/chaff, n 6; hay/balancer meal, n 6). BM was recorded weekly. Feeding behaviour was recorded by continual observation over 24 h during week 15. The apparent digestibility (gross energy (GE), acid-detergent fibre (ADF) and DM) of feed was determined for all animals by total faecal collection (72 h, week 16). Rates of weight loss were independent of diet type, DM (R2 0·15), GE (R2 0·20) and ADF digestibilities (R2 0·18). Despite similar DMI, faecal DM ranged between 0·52 and 1·16 % of BM daily and was associated with wide ranges in apparent digestibility (GE − 11·34 to 53·08 %; ADF − 50·37 to 42·83 % and DM 2·14 to 57·32 %), which were improbably low for some animals. Apparent digestibilities were associated with DM output (GE R2 0·96; ADF R2 0·99 and DM R2 0·99) and time spent feeding (GE R2 0·62; DM R2 0·61 and ADF R2 0·59), indicating that feed intake was supplemented with wood shavings in at least five of the twelve animals. Quantities of wood shavings ingested (negligible to >3·0 kg/d) were back-calculated from predicted feed digestibilities. All animals remained healthy. Implications of ‘feed-bulking/energy dilution’ for feed-restricted animals need further consideration.

Circadian desynchrony and metabolic dysfunction; did light pollution make us fat?

Circadian rhythms are daily oscillations in physiology and behaviour that recur with a period of 24h, and that are entrained by the daily photoperiod. The cycle of sunrise and sunset provided a reliable time cue for many thousands of years, until the advent of artificial lighting disrupted the entrainment of human circadian rhythms to the solar photoperiod. Circadian desynchrony (CD) occurs when endogenous rhythms become misaligned with daily photoperiodic cycles, and this condition is facilitated by artificial lighting. This review examines the hypothesis that chronic CD that has accompanied the availability of electric lighting in the developed world induces a metabolic and behavioural phenotype that is predisposed to the development of obesity. The evidence to support this hypothesis is based on epidemiological data showing coincidence between the appearance of obesity and the availability of artificial light, both geographically, and historically. This association links CD to obesity in humans, and is corroborated by experimental studies that demonstrate that CD can induce obesity and metabolic dysfunction in humans and in rodents. This association between CD and obesity has far reaching implications for human health, lifestyle and work practices. Attention to the rhythmicity of daily sleep, exercise, work and feeding schedules could be beneficial in targeting or reversing the modern human predisposition to obesity.

A cross sectional study of the prevalence and risk factors for owner misperception of canine body shape in first opinion practice in Glasgow

The objectives of the study were to investigate whether owners were able to assign the correct body shape to their dog and to assess the dog and owner level factors associated with incorrect owner assessment of dog body shape. Six hundred and eighty questionnaires were administered to dog owners in 5 first opinion practices around Glasgow during July 2007. At the same time, the interviewer and owner assessed the body shape of each dog. The interviewer assessment of body shape was taken as the gold standard. Incorrect owner assessment of dog body shape (misperception) was divided into two groups: underestimation and overestimation. Multinomial logistic regression and classification and regression trees (CART) were used to assess risk factors associated with each type of misperception. Misperception of dog body shape was present in 44.1% of owners with underestimation (i.e. the owner considered the animal to have a leaner body shape from the gold standard assessment) being the most common form of misperception. Risk factors identified by both multinomial logistic regression and CART were gender of owner, age of the dog and dog body shape. The classification tree appeared to have improved predictive ability when compared to the multinomial model.

Comparison of owner-reported health problems with veterinary assessment of geriatric horses in the United Kingdom

REASONS FOR PERFORMING STUDY

Previous studies suggest that owners underestimate or incorrectly recognise or report health problems in geriatric horses. However, few studies have directly compared owner-reported and veterinary assessed disease.

OBJECTIVES

To compare the findings of veterinary clinical examination of geriatric horses with owner-reported clinical signs and disease.

METHODS

A total of 200 horses aged ≥ 15 years were randomly selected to receive a veterinary examination, from responses to a cross-sectional postal questionnaire survey. Veterinary examinations were performed within 2 months of questionnaire return, and agreement between owner-reported data and veterinary clinical findings was assessed.

RESULTS

Owners under-reported many clinical signs and disease conditions detected on veterinary clinical examination. For example, dental abnormalities (detected in 95.4% of horses, reported by 24.5% of owners); cardiac murmurs (detected in 20% of horses, reported by 0.5% of owners); lameness (present in 50% of horses, reported by 23% of owners) and hoof abnormalities (detected in 80% of horses, reported by 27% of owners). Agreement between owner-reported and veterinary assessed respiratory disease (Kappa 0.02-0.2), body condition score (Kappa 0.24) and coat abnormalities (Kappa 0.42) was poor, fair and moderate, respectively. Range of motion (ROM) of the tarsal and metacarpophalangeal joints was lower in horses with owner-reported osteoarthritis (P = 0.005 and <0.001, respectively).

CONCLUSIONS AND POTENTIAL RELEVANCE

The low prevalence and relatively poor agreement of owner-reported disease compared to that detected on veterinary examination suggests inaccurate or under-recognition, or inaccurate reporting of health problems by owners of geriatric horses, which could lead to a delay in presentation for veterinary treatment. Increased veterinary involvement and improved owner education in the care of geriatric horses should facilitate earlier identification of disease, particularly that which is not readily detectable by owners, and aid management of health and welfare problems.

A survey of health care and disease in geriatric horses aged 30 years or older

This study reports on aspects of preventive health care and on the prevalence of disease in geriatric (≥30 years old) horses and ponies in North-West England and North Wales. Of 128 questionnaires mailed to horse owners, 87 useable responses were received and 69 horses were subject to veterinary examination. Of the animals examined, 16% were underweight with body condition scores (BCS)<2/5, and 10% were overweight (BCS>3/5). This contrasted with the owner responses that reported 23% of the animals surveyed to be underweight and only 3% to be overweight. When assessed at trot, 77% of the horses were lame on at least one limb, with 97% having a reduced range of motion in at least one joint. Only 16% of these animals were reported by owners to have been lame within the previous 12 months. Owner-reported changes to hair coat were significantly associated with hirsutism or abnormal moulting detected at clinical examination (39%). At least one ophthalmic lesion was identified in all of the horses and ponies examined and 17% of owners reported that their animal had experienced visual problems within the previous year. Although dental abnormalities were detected in all animals where an oral examination was performed, only 42% of owners reported that their horse suffered from a known dental disorder. In general, despite a high prevalence of disease detected in these geriatric animals and with the majority having multiple abnormalities at clinical examination, there was under-reporting/under-recognition of these health problems by owners.

Assessment of body fat in the pony: part I. Relationships between the anatomical distribution of adipose tissue, body composition and body condition

REASONS FOR PERFORMING STUDY

Evaluation of equine body fat content is important for nutritional and clinical purposes. However, our understanding of total body fat and its regional distribution in the body is sparse. Currently, body fat evaluation relies on the subjective assessment of body condition score (BCS), which has never been validated against 'gold standard' chemical analysis or dissection measurements in ponies.

OBJECTIVES

To define the relationships between subjective (BCS), objective (morphometric) indices of body fat and 'gold standard' measurements of actual body composition.

HYPOTHESES

BCS and morphometry offer valid, noninvasive methods for determination of body fat in equids.

METHODS

Seven mature (mean ± s.e. 13 ± 3 years, 212 ± 14 kg, BCS 1.25-7/9), Welsh Mountain pony mares, destined for euthanasia (for nonresearch purposes), were used. For all ponies, body mass (BM), BCS and various morphometric measurements were recorded. Following euthanasia, all ponies were systematically dissected. Discrete white adipose tissue (WAT) depots were independently described. Gross, body chemical composition was determined by proximate analyses.

RESULTS

Total somatic soft tissues increased linearly (r(2) = 1.00), whereas body WAT content (1-26% live BM) increased exponentially (r(2) = 0.96), with BCS. WAT was equally distributed between internal and external sites in all animals irrespective of BCS. Nuchal fat was a poor predictor of total WAT (r(2) = 0.66). Periorbital WAT did not alter with BCS (r(2) = 0.01). Heart girth:withers height and ultrasonic retroperitoneal fat depth were closely associated with total, chemically-extracted lipid which comprised 1-29% live BM (r(2) = 0.91 and 0.88, respectively).

CONCLUSIONS AND POTENTIAL RELEVANCE

The exponential relationship between BCS and total body WAT/lipid suggests that BCS is unlikely to be a sensitive index of body fat for animals in moderate-obese states. Morphometric measurements (body girths and retroperitonel fat depth) may be useful to augment subjective BCS systems.

Effects of season and body condition on appetite, body mass and body composition in ad libitum fed pony mares

Changes in appetite, body mass (BM), body condition score (BCS), direct (ultrasonographic) and indirect (deuterium oxide dilution technique) measures of body fat were monitored in Welsh Mountain pony mares (n=11, 5-19 years of age) offered ad libitum access to a complete diet (gross energy 16.9±0.07 MJ/kg dry matter) for 12 weeks during summer (n=6; 246±20 kg) and winter (n=5; 219±21 kg). At the outset, each group comprised two thin (BCS 1-3/9), moderate (BCS 4-6/9) and obese (BCS 7-9/9) animals. For ponies that were non-obese at the outset, BM was gained more rapidly (P=0.001) in summer (0.8±0.1 kg/day) than winter (0.6±0.0 kg/day). This was associated with a seasonal increase in dry matter intake (DMI) which became maximal (summer, 4.6±0.3% BM as DMI/day; winter, 3.5±0.1% BM as DMI/day) during the second month. The appetite of the obese ponies was half that reported for non-obese animals in the summer and BM remained constant irrespective of season. Body 'fatness' increased progressively for non-obese but not obese ponies. Body fat content was exponentially associated with increasing BCS but BCSs >6 were not useful indicators of actual body fat. Endogenous circannual mechanisms to suppress winter weight gain were insufficient to prevent the development of obesity in ad libitum fed ponies.

Effect of dietary restriction on body condition, composition and welfare of overweight and obese pony mares

REASONS FOR PERFORMING STUDY

Increased prevalence of obesity among UK horses and ponies demands evidence-based advice to promote weight loss.

HYPOTHESIS

Restriction of dry matter intake (DMI) to 1% of body mass (BM, 67% [corrected] of predicted maintenance digestible energy [DE] requirements) would promote weight loss without compromise to health.

METHODS

Five mature (mean ± s.e. 10 ± 2 years), overweight/obese pony mares (BM, 257 ± 20 kg: body condition score [BCS] 6.8/9 ± 0.5) were studied over 12 weeks. Animals were individually housed. Daily provision of a chaff-based, complete diet (measured DE, 8.5 MJ/kg DM) was restricted to 1% of actual BM as DMI daily. BCS, girth measurements and ultrasound-derived measures of subcutaneous fat depth overlying the gluteal region and 12th intercostal space (rib-eye) were recorded weekly. Body fat content was estimated at the beginning and end of the study by deuterium oxide dilution methods. Clinical biochemistry was monitored weekly. Behaviour was observed (24 h, 3/5 ponies) on 3 occasions.

RESULTS

BM decreased by 4.3 ± 1.1% during the first week and thereafter by 0.7 ± 0.1% of BM at end of Week 1 each week. BCS remained constant. Heart and belly girths, rump width and subcutaneous fat depth at rib-eye decreased significantly with time and BM. Fat comprised 45 ± 19% of BM loss. Fatter animals lost relatively more fat. With decreased feeding activity, time spent in 'play' and rest increased by 36 ± 11% and 438 ± 95%, respectively.

CONCLUSIONS

This plane of nutrition resulted in an overall rate of weight loss of 1% of outset BM weekly. BCS was not a useful index of early weight loss but heart and belly girths and subcutaneous rib-eye fat were identified as alternative markers.

POTENTIAL RELEVANCE

This study provides an evidence-base for the management of weight loss in obese animals, especially those for which exercise may be contra-indicated.

Medical implications of obesity in horses--lessons for human obesity

There is growing recognition that obesity is common and represents a significant detriment to the health of companion animals in a manner similar to that by which it is affecting the human population. As is the case for other species, obesity appears to promote insulin resistance in horses and it is through this pathophysiological process that many of the adverse medical consequences of obesity are being characterized. Equine medical conditions that have been described in the context of obesity and insulin resistance differ from those in humans. Chronic human conditions that have been attributed to obesity and insulin resistance, such as atherosclerosis and diabetes mellitus, are rarely described in obese horses. Significant current interest is centered on the recognition that insulin resistance plays a role in the pathogenesis of laminitis, a potentially severe and debilitating cause of lameness in the equine species. Other equine medical conditions that are more likely in obese, insulin-resistant individuals include hyperlipemia (hepatic lipidosis) and developmental orthopedic disease (osteochondrosis). Pituitary pars intermedia dysfunction (equine Cushing's syndrome) represents another common endocrinopathic condition of older horses associated with insulin resistance. This review presents an introductory overview of the present understanding of obesity and insulin resistance and how these conditions may be associated with disease conditions in horses.