Ultrasonographic measurements of localized fat accumulation in Shetland pony mares fed a normal v. a high energy diet for 2 years

Metabolic and Endocrine Insights in Donkeys

Donkey medicine is gaining attention due to their increased use as companion animals, in shows, asinotherapy, etc. The increasing demand and unique aspects call for specialized care, requiring new information (physiology, infectious disorders, pharmacology, etc.). Since obesity is common in this species, hyperlipemia, metabolic syndrome and insulin dysregulation (ID) are common disorders in donkeys, in some cases with high mortality, either directly (multiorgan dysfunction) or indirectly due to poor quality of life (chronic laminitis). Donkeys have long-life expectancy and are often afflicted with pituitary pars intermedia dysfunction (PPID), a neurodegenerative and endocrine disease. Hyperlipemia is diagnosed based on high plasma triglyceride concentration in association with clinical findings and laboratory abnormalities from affected tissues (liver, kidney and pancreas). The measurement of resting serum insulin and plasma ACTH concentrations is the first step in ID and PPID diagnosis. In donkeys with clinical signs of ID (obesity or recurrent laminitis) or PPID (hypertrichosis, regional adiposity, laminitis and weight loss), where these hormones are in the normal or non-diagnostic range (donkey-specific cut-off values and reference ranges need to be established), dynamic tests are recommended (oral sugar test or thyrotropin-releasing hormone, respectively). Equine treatment protocols apply to donkeys, although pharmacological studies for most drugs, except pergolide, are lacking.

Rate of obesity within a mixed-breed group of horses in Ireland and their owners' perceptions of body condition and useability of an equine body condition scoring scale

BACKGROUND

Equine obesity is a significant health and welfare concern. The proportion of domestic horse populations that are overweight are as high as 45%. As the primary decision-makers for their horses' care, owners are theoretically ideally placed to identify whether their horses are appropriately conditioned, however, research in other countries has shown that many owners are unable to accurately judge their horse's body condition. In this study, through the comparison of body condition scoring (BCS) performed by an expert and the horse owners and interviews with owners, we aimed to identify the proportion of horses that were overweight or obese, to assess the accuracy of horse owners' BCS assessment both prior to and after receiving information and instructions on body condition scoring, and to identify common themes amongst owners' views regarding BCS assessment and the Henneke BCS system.

RESULTS

Forty-five percent of the horses in this study were overweight or obese. The agreement between the owners and an equine veterinarian regarding the horses' BCS was fair to good both prior to (κ = .311, P < 0.001; ICC = .502, P < 0.001) and after (κ = .381, P < 0.001; ICC = .561, P < 0.001) receiving information and instructions on scoring. Three quarters of the owners who took part in the study did not use any method of monitoring their horse's body condition. Thematic analysis of owner responses was varied, with the most common theme being an awareness of the need to monitor or make changes to their horse's condition with responses in this theme split between owners who felt in control and those who did not. Owner feedback on the utility and useability of the scorning system was that it was useful however parts are too technical or need improvement.

CONCLUSIONS

Equine obesity is a significant problem in this population in Ireland. Horse owners' ability to accurately judge their horse's condition does not improve with provision of instructions on body condition scoring. These results combined with owners' feedback on the Henneke BCS system indicate that it is not a tool that can be reliably used by owners.

Effect of a long-term high-energy diet on cardiovascular parameters in Shetland pony mares

BACKGROUND

Changes in cardiovascular parameters, including blood pressure (BP) and cardiac anatomical dimensions, are an inconsistent feature of the equine metabolic syndrome. The order in which these changes arise is unknown.

OBJECTIVES

Determine the order in which EMS-associated changes in cardiovascular parameters arise.

ANIMALS

Twenty Shetland pony mares.

METHODS

High-energy (HE) diet mares were fed 200% of net energy requirements for 1 (n = 3) or 2 (n = 7) consecutive diet-years, with 17 weeks of hay-only between years. Noninvasive BP measurements and echocardiograms were performed during both years. Resting 24-hour ECGs and measurements of autonomic tone (splenic volume and packed cell volume [PCV]) were performed at the end of diet-year 1. Results were compared to control mares receiving a maintenance diet for 1 (n = 7) or 2 (n = 3) consecutive years.

RESULTS

In year 1, HE mares had significantly higher values than control mares for mean relative left ventricular wall thickness (P = .001). After 2 diet-years, mean systolic (P = .003), diastolic (P < .001) and mean arterial BP (P = .001), heart rate (HR; P < .001), and mean left ventricular wall thickness (P = .001) also were significantly increased in HE compared to control mares. No pathological arrhythmias or differences in splenic volume or PCV were detected.

CONCLUSIONS AND CLINICAL IMPORTANCE

Ingesting a HE diet first induced minor changes in BP, and progressed to left-sided cardiac hypertrophy in Shetland pony mares. These findings are of interest given the increasing incidence of obesity in horses.

A Multiomic Approach to Investigate the Effects of a Weight Loss Program on the Intestinal Health of Overweight Horses

Obesity is endemic in human populations in the western society, and with mounting evidence that the intestinal ecological environment plays a major role in its pathogenesis, identification of therapies based on intestinal microbiota modulation are gaining attention. Obesity in companion animals is also a common clinical problem. We set out using a multidimensional approach, to determine the effectiveness and safety of a weight loss program for horses incorporating diet restriction and exercise. In addition, we aimed to investigate the effect of this program on the overall intestinal health of overweight sedentary horses. The investigation comprised of a randomized, controlled, 6-week study of 14 overweight sedentary horses and ponies who were blocked for age, gender, and breed (controls n = 7, treatment n = 7). The treatment group were fed a restricted diet (1.4% of body weight dry matter intake) and the control group a maintenance diet (2% of body weight as dry matter intake) over the study period. The treatment group were subjected to a prescribed exercise regime, while the control group were exercised to mimic foraging conditions. Several clinical measurements were taken at the start and end of the study, including morphological parameters, ultrasound measurements of subcutaneous fat, and blood pressure. Fecal microbiota analysis was performed using 16S rRNA gene sequence analysis, and fecal metabolome was analyzed using NMR spectroscopy, on samples taken at weeks 1, 3, and 6 of the study. All horses completed the study period successfully. However, two of the treatment group had to have modified exercise regimes. The treatment group showed significant weight loss (p < 0.00001) and an associated decrease in waste circumference (p < 0.0001) when compared with the control group. The alpha-diversity of the fecal microbiota in the treatment group showed a significant increase from the start to the end of the study period (p < 0.05); however, there was no significant difference between groups at any sampling point. There were significant changes (p < 0.05) in the metabolome in both groups between the start and end of the study, but not between groups at any sampling point. Finally, the resting blood pressure of all horses was significantly lower by the end of the study.

Nutritional Considerations When Dealing with an Obese Adult Equine

Equine obesity is common, reducing quality of life and requiring dietary energy restriction. Equine obesity is identified using subjective body condition scoring. Considerations are given for life stage and health status when managing obese equines. Every effort should be made to maximize feeding duration, and minimize time spent without feed while meeting all essential nutrient requirements. Limiting total daily dry matter intake to 2% of current bodyweight per day of a low caloric, forage-based diet may result in adequate body weight loss. Weight loss and weight management plans should be monitored for success and potential gastrointestinal, metabolic, and/or behavioral complications.

Alterations of serum vitamin E and vitamin A concentrations of ponies and horses during experimentally induced obesity

Vitamin A, vitamin E and retinol-binding protein 4 (RBP4) are a focus of current obesity research in humans. The impact of body weight (BW) gain on fat-soluble vitamins and its associated parameters in equines has not been previously reported. Ten Shetland ponies and 9 Warmblood horses, all adult geldings, non-obese and healthy, were fed an excessive energy diet for 20 months to induce BW gain. Serum α-tocopherol (vitamin E), retinol (vitamin A), retinol-binding protein 4 (RBP4) and retinol/RBP4 ratio were analysed before BW gain induction and at six timepoints during the BW gaining period. The mean (±SD) % BW gain achieved during two years of excess energy intake was 29.9 ± 19.4% for ponies and 17 ± 6.74% for horses. Serum α-tocopherol increased significantly in ponies and horses during excess energy intake and circulating α-tocopherol levels correlated positively with α-tocopherol intake (r = .6; p < .001). Serum retinol concentrations showed variations during the study but without relation to intake. Serum RBP4 decreased at the end of the study. The retinol/RBP4 ratio increased with BW gain without differences between ponies and horses. In comparison with human research, the increase in the retinol/RBP4 ratio was unexpected and needs further elucidation.

Effect of long-term overfeeding of a high-energy diet on glucose tolerance in Shetland pony mares

Background

Overfeeding is associated with obesity and insulin dysregulation (ID), which are both risk factors for equine metabolic syndrome. How chronic overfeeding affects development of these factors is poorly understood.

Objectives

To examine the influence of long‐term high‐energy diet provision on body condition and ID.

Animals

Eleven Shetland pony mares.

Methods

In a 3‐phase study, the high‐energy group (n = 7) was fed 200% of net energy (NE) requirements (hay; concentrate: 36% sugar and starch, 13% fat) for 24 weeks, followed by 17 weeks hay‐only feeding before resuming the high‐energy diet (n = 4) for an additional 29 weeks. Mares were weighed weekly. Oral glucose tolerance tests were performed 3 to 4 times per dietary period. Results were compared with those of a control group (phase 1, n = 4; phases 2 and 3, n = 6) that received 100% NE requirements, using a general linear mixed model with post hoc Bonferroni testing.

Results

The mean body weight of the high‐energy group increased by 27% per high‐energy feeding period. During both feeding periods, area under the curve (AUC) for plasma glucose concentration decreased (P < .01), whereas AUC for plasma insulin concentration increased. Mean basal plasma glucose concentration and peak plasma insulin concentrations were higher (P < .05) in the high‐energy group than in the control group.

Conclusion and Clinical Importance

Feeding a high‐energy diet to healthy nonobese Shetland pony mares led to more efficient glucose metabolism within 5 weeks, followed by significant hyperinsulinemia and obesity. Hyperinsulinemic status was reversed during 17 weeks of hay‐only feeding, regardless of body condition, but returned rapidly after restarting the high‐energy diet.

The influence of equine body weight gain on inflammatory cytokine expressions of adipose tissue in response to endotoxin challenge

Background

Human obesity is linked with systemic inflammation. However, it is still controversial if equines produce more inflammatory cytokines with increasing body weight and if the production of those show breed type specific patterns. The main objective of this study was to determine if diet induced obesity is associated with increased inflammatory signatures in adipose tissue of equines and if a breed predisposition exists between ponies and horses. Additionally, we aimed to identify adipose tissue depot differences in inflammatory cytokine expression. Nineteen healthy, non-overweight and metabolically healthy equines received a hypercaloric diet for 2 years. Body weight, body condition score and cresty neck score were assessed weekly throughout the study. At three time points, insulin sensitivity was determined by a combined glucose-insulin test. Adipose tissue samples were collected from two intra-abdominal and two subcutaneous depots under general anesthesia at each time point after an endotoxin trigger. In the adipose tissue samples levels of CD68 mRNA (a marker of macrophage infiltration) and pro-inflammatory cytokine mRNA (IL-1β, IL-6 and TNFα) were analyzed with RT-qPCR. As markers of lipid metabolism mRNA levels of lipoprotein lipase (LPL) and fatty acid binding protein 4 (FABP4) were determined with RT-qPCR.

Results

CD68 mRNA levels increased with body weight gain in several adipose tissue (AT) depots (Wilcoxon signed rank test with Bonferroni correction; retroperitoneal AT horses: P = 0.023, mesocolonial AT horses: P = 0.023, subcutaneous tail head AT ponies: P = 0.015). In both abdominal depots CD68 mRNA levels were higher than in subcutaneous adipose tissue depots (Kruskal–Wallis-ANOVA with Bonferroni correction: P < 0.05). No breed related differences were found. Pro-inflammatory cytokine mRNA IL-1β, IL-6 and TNFα levels were higher in subcutaneous depots compared to abdominal depots after body weight gain. IL-1β, IL-6 and TNFα mRNA levels of mesocolon adipose tissue were higher in obese horses compared to obese ponies (Mann–Whitney-U test; IL-1β: P = 0.006; IL-6: P = 0.003; TNFα: P = 0.049). In general, horses had higher FABP4 and LPL mRNA levels compared to ponies in neck AT and tail AT at all time points.

Conclusion

Our findings suggest an increased invasion of macrophages in intra-abdominal adipose tissue with increasing body weight gain in equines in combination with a low dose endotoxin stimulus. This might predispose equines to obesity related comorbidities. In obese horses mesocolon adipose tissue showed higher inflammatory cytokine expression compared to obese ponies. Additionally, subcutaneous adipose tissue expressed more pro-inflammatory cytokines compared to intra-abdominal adipose tissue. Horses had higher FABP4 and LPL mRNA levels in selected AT depots which may indicate a higher fat storage capacity than in ponies. The differences in lipid storage might be associated with a higher susceptibility to obesity-related comorbidities in ponies in comparison to horses.

Ultrasonographic measures of body fatness and their relationship with plasma levels and adipose tissue expression of four adipokines in Welsh pony mares

Obesity is responsible for metabolic dysregulations that alter fertility and induce pathologies. The objectives of the present study were to validate a reliable method for the evaluation of body fatness in mares and to associate the body fat estimation data to metabolic changes, including adipokines at the plasma and adipose tissue levels. To reach this purpose, animals were subjected to two extreme breeding conditions to study the variation of morphological, ultrasound, and physiological parameters. Twenty Welsh mares were followed up monthly from April to October before and after animals were moved outdoors to grasslands. Body weight (BW), body length (BL), height at the withers (HW), thoracic perimeter (TP), 5-point body condition score (BCS), and subcutaneous fat thickness (SFT) at the level of the shoulder, the lumbar region, and the rump, measured by ultrasonography, and plasma and adipose tissue metabolic indicators were assessed in parallel. Statistical analysis was performed using a linear mixed-effects model, whereas Pearson tests were used for the analysis of the correlations between the different parameters. Although mean BW did not increase significantly (P = 0.0940), TP (P = 0.0002) and BCS (P < 0.0001) increased during the study period. Ultrasonographic examination of subcutaneous adipose tissue showed an increase in SFT at the level of the shoulder (P < 0.0001), lumbar region (P < 0.0001), and rump (P < 0.0001). Plasma concentrations of nonesterified fatty acids (P < 0.0001), phospholipids (P < 0.0001), and cholesterol (P < 0.0001) increased significantly, whereas triglycerides (P < 0.0001) decreased significantly during the study period. Although both plasma concentrations and adipose tissue expression of leptin (P < 0.0001) and resistin (P < 0.0001) increased significantly, adiponectin (P < 0.0001) significantly decreased and visfatin remained unchanged (P = 0.8401). Expression of adipokine receptors studied showed the opposite pattern compared with their ligand. Ultrasonographic measurements of subcutaneous adipose tissue thickness at the shoulder, lumbar region, and rump are relevant indicators of fatness related with adipokine plasma concentrations and expression of adipokine-related receptors in adipose tissue, and particularly highlight seasonal effects.

Impact of body weight gain on hepatic metabolism and hepatic inflammatory cytokines in comparison of Shetland pony geldings and Warmblood horse geldings

Background

Non-alcoholic fatty liver disease is known as determining part of human obesity. The impact of body weight (BW) gain on liver metabolism has not been extensively investigated yet.

Objectives

To investigate hepatic alterations caused by increasing BW in ponies and horses.

Animals

A total of 19 non-obese equines (10 Shetland ponies, geldings; nine Warmblood horses, geldings).

Methods

Animals received 200% of their metabolizable maintenance energy requirements for 2 years. Serum alkaline phosphatase, glutamate dehydrogenase (GLDH), aspartate aminotransferase (AST), and gamma-glutamyl transferase activities and bile acids were analyzed several times during 2 years of hypercaloric diet. Hepatic lipid content and hepatic levels of the interleukin (IL)-6, tumor necrosis factor α (TNFα), cluster of differentiation (CD) 68, IL-1β, lipoprotein lipase (LPL), fatty acid-binding protein 1, chemerin and nuclear factor-κB mRNAs were assessed at the start of the study and after 1 and 2 years of excess energy intake.

Results

The mean (±SD) BW gain recorded during 2 years of excess energy intake was 29.9 ± 19.4% for ponies and 17 ± 6.74% for horses. The hepatic lipid content was not profoundly affected by increasing BW. Levels of the IL-6, TNFα, CD68 and IL-1β mRNAs did not change during BW gain. Levels of the chemerin mRNA increased significantly in both breeds (ponies: P = 0.02; horses: P = 0.02) in response to BW gain. Significant differences in serum GLDH and AST activities, serum bile acid concentrations and hepatic levels of the LPL mRNA were observed between ponies and horses at the end of the study.

Conclusions

Chemerin might represent an interesting marker for future equine obesity research. Interestingly, steatosis caused by increasing BW may occur later in the development of obesity in equines than in humans. Additionally, the hepatic metabolism exhibits differences between ponies and horses, which may explain in part the greater susceptibility of ponies to obesity-associated metabolic dysregulations.