The equine gastrointestinal microbiome: impacts of weight-loss

BACKGROUND: Obesity is an important equine welfare issue. Whilst dietary restriction is the most effective weight-loss tool, individual animals range in their weight-loss propensity. Gastrointestinal-derived bacteria play a fundamental role in host-health and have been associated with obesity and weight-loss in other species. This study evaluated the faecal microbiome (next-generation sequencing of 16S rRNA genes) of 15 obese Welsh Mountain pony mares, in the same 11-week period across 2 years (n = 8 Year 1; n = 7 Year 2). Following a 4-week acclimation period (pre-diet phase) during which time individuals were fed the same hay to maintenance (2% body mass (BM) as daily dry matter (DM) intake), animals underwent a 7-week period of dietary restriction (1% BM hay as daily DM intake). Faeces were sampled on the final 3 days of the pre-diet phase and the final 3 days of the dietary restriction phase. Bacterial communities were determined using Next Generation Sequencing of amplified V1-V2 hypervariable regions of bacterial 16S rRNA.RESULTS: Losses in body mass ranged from 7.11 to 11.59%. Changes in the faecal microbiome composition following weight-loss included a reduction in the relative abundance of Firmicutes and Tenericutes and a reduction in indices of bacterial diversity. Pre-diet diversity was negatively associated with weight-loss. Pre-diet faecal acetate concentration was a strong predictor of subsequent weight-loss and negatively associated with Sphaerochaeta (Spirochaetes phylum) abundance. When animals were divided into 3 groups (high, mid, low) based overall weight loss, pre-diet bacterial community structure was found to have the greatest divergence between the high and low weight-loss groups (R = 0.67, p &lt;  0.01), following PERMANOVA and ANOSIM analysis.CONCLUSIONS: Weight-loss in this group of ponies was associated with lower pre-diet faecal bacterial diversity and greater pre-diet acetate concentration. Overall, these data support a role for the faecal microbiome in weight-loss propensity in ponies and provide a baseline for research evaluating elements of the faecal microbiome in predicting weight-loss success in larger cohorts.</p

The equine gastrointestinal microbiome: impacts of weight-loss

Context. The formation of water on the dust grains in the interstellar medium may proceed with hydrogen peroxide (H2O2) as an intermediate. Recently gas-phase H2O2 has been detected in {\rho} Oph A with an abundance of ~1E-10 relative to H2. Aims. We aim to reproduce the observed abundance of H2O2 and other species detected in {\rho} Oph A quantitatively. Methods. We make use of a chemical network which includes gas phase reactions as well as processes on the grains; desorption from the grain surface through chemical reaction is also included. We run the model for a range of physical parameters. Results. The abundance of H2O2 can be best reproduced at ~6E5 yr, which is close to the dynamical age of {\rho} Oph A. The abundances of other species such as H2CO, CH3OH, and O2 can be reasonably reproduced also at this time. In the early time the gas-phase abundance of H2O2 can be much higher than the current detected value. We predict a gas phase abundance of O2H at the same order of magnitude as H2O2, and an abundance of the order 1E-8 for gas phase water in {\rho} Oph A. A few other species of interest are also discussed. Conclusions. We demonstrate that H2O2 can be produced on the dust grains and released into the gas phase through non-thermal desorption via surface exothermic reactions. The H2O2 molecule on the grain is an important intermediate in the formation of water. The fact that H2O2 is over-produced in the gas phase for a range of physical conditions suggests that its destruction channel in the current gas phase network may be incomplete.Comment: Accepted for publication in A&

Equine obesity: current perspectives

Foreword Equine obesity is now so common that is has become accepted by many as the norm ( Owers and Chubbock, 2012 ). Rates of obesity may be as high as 70% in some populations and obesity is often associated with morbidities that may ultimately result in mortality. Obesity is a common feature in animals diagnosed with equine metabolic syndrome, a conflation of metabolic disturbances including insulin dysregulation, which may lead to laminitis. Obesity is a risk factor for insulin dysregulation and is therefore implicated in laminitis risk. In addition to laminitis, adverse consequences of obesity include orthopaedic disease, hyperlipaemia, hyperthermia, infertility and poor performance. Over time, perception of what constitutes a healthy body condition in horses has shifted, with the result that potentially harmful excess adiposity may not be recognised by owners or those working in the equine industry ( Owers and Chubbock, 2012 ). In addition, increasing numbers of equines are kept as companions rather than athletes and live relatively inactive lifestyles favouring the development of obesity. Finally, owners of leisure horses often think their horses are working hard when, in reality, their exertions have minimal impact on their energy requirements. Despite increasing awareness within the veterinary profession and equine industry of the impact of obesity on equine welfare, little progress seems to have been made in tackling it. This document was commissioned in order to provide veterinary surgeons with up-to-date information on equine obesity and to equip them to tackle it within their own practices. Recommendations were developed using an informal two-round Delphi process, considering published and unpublished research relating to equine obesity using a round table forum and online discussion. Where research evidence was conflicting or absent, collective expert opinion based on the clinical experience of the group was applied. The opinions expressed are the consensus of views expressed by the authors. Where agreement was not reached, opposing views are presented such that readers can understand the arguments fully. The document is focused on the management of horses and ponies; while much of the information herein is applicable to donkeys it is important to recognise that the metabolism and management of donkeys are different and further research is required before specific recommendations can be made. The expert group was organised by UK-Vet Equine with sponsorship from Baileys Horse Feeds. </jats:sec

Equine metabolic syndrome

Laminitis is one of the most common and frustrating clinical presentations in equine practice. While the principles of treatment for laminitis have not changed for several decades, there have been some important paradigm shifts in our understanding of laminitis. Most importantly, it is essential to consider laminitis as a clinical sign of disease and not as a disease in its own right. Once this shift in thinking has occurred, it is logical to then question what disease caused the laminitis. More than 90 per cent of horses presented with laminitis as their primary clinical sign will have developed it as a consequence of endocrine disease; most commonly equine metabolic syndrome (EMS). Given the fact that many horses will have painful protracted and/or chronic recurrent disease, a good understanding of the predisposing factors and how to diagnose and manage them is crucial. Current evidence suggests that early diagnosis and effective management of EMS should be a key aim for practising veterinary surgeons to prevent the devastating consequences of laminitis. This review will focus on EMS, its diagnosis and management

The impact of early life nutrition and housing on growth and reproduction in dairy cattle

Contentious issues in calf rearing include milk feeding practices and single versus group housing. The current study was performed on a high producing 170 Holstein cow dairy farm, to investigate the impact of nutrition and housing on growth and reproduction. Heifer calves (n = 100) were allocated in birth order to one of two commonly used management strategies. All calves received 3-4 litres of dam specific colostrum within 6 hours of birth. Group A calves were group housed from birth and fed milk replacer (MR) ad libitum via a computerised machine utilising a single teat, with weaning commencing at 63 days of age. Group R calves were initially housed in individual pens and received 2.5 litres of MR twice daily via a bucket until 21 days of age when they were group housed and fed 3 litres of MR twice daily via a group trough with weaning commencing at 56 days. From 12 weeks of age onwards, calves in both dietary groups were subject to common nutritional and husbandry protocols. All breeding of heifers was via artificial insemination with no hormonal intervention. Calves were weighed, body condition scored and morphometric measures recorded weekly up till 12 weeks of age then monthly until conception. Pre-weaning growth rates (kg/day) were significantly higher in Group A calves compared to Group R (0.89, 95% CI 0.86-0.93 vs 0.57, 95% CI 0.54-0.6 kg/day P 0.050) in any of the mean values of measured reproductive parameters, multivariable Cox regression suggested that there was a weak trend (P = 0.072) for Group A animals to achieve first service earlier than their Group R counterparts (62.6 weeks versus 65.3 weeks). Irrespective of dietary group, the hazard for achievement of all measured reproductive parameters, apart from time to puberty, was 20-40% less for heifers borne from multiparous dams compared to heifers from primiparous dams

Glucose concentration during equine in vitro maturation alters mitochondrial function

The use of in vitro embryo production in the horse is increasing in clinical and research settings, however, protocols are yet to be optimised. Notably, the two most commonly used base media for in vitro maturation (IVM) supply glucose at markedly different concentrations: physiological (5.6 mM, M199) or supraphysiological (17 mM, DMEM/F-12). Exposure to high glucose has detrimental effects on oocytes and early embryos in many mammalian species, but the impact has not yet been examined in the horse. To address this, we compared the energy metabolism of equine COCs matured in M199-based maturation medium containing either 5.6 or 17 mM glucose, as well as expression of key genes in oocytes and cumulus cells. Oocytes were fertilised by ICSI and cultured. Analysis of spent medium revealed that COC glucose consumption and production of lactate and pyruvate were similar between treatments. However, the glycolytic index was decreased at 17 mM and analysis of mitochondrial function of COCs revealed that IVM in 17 mM glucose was associated with decreased ATP-coupled respiration and increased non-mitochondrial respiration compared to that for 5.6 mM glucose. We also found that the metabolic enzyme lactate dehydrogenase-A (LDHA) was downregulated in cumulus cells of oocytes that completed IVM in 17 mM glucose. There was no difference in maturation or blastocyst rates. These data indicate that COC mitochondrial function and gene expression are altered by high glucose concentration during IVM. Further work is needed to determine if these changes are associated with developmental changes in the resulting offspring