Phlebitis

Fifty-two horses (8 males, 22 mares and 22 geldings; mean ± SEM age: 9 ± 1.75 years) were recruited on a volunteer basis from a cohort of 248 participants. We obtained informed consent from horse owners or riders. For successful participation in the study, we required the following criteria: (i) written informed consent; (ii) blood sample collection before and after the race; (iii) feces collection before the race; (iv) absence of gastrointestinal disorders during the four months prior to enrollment; (v) absence of antibiotic treatment during the four months prior to enrollment and absence of anthelmintic medication within 60 days before the race, and (vi) a complete questionnaire about diet composition and intake. Prior to completing the questionnaires, owners and riders were provided with a written description of the procedures. The number of volunteers enrolled in the study was limited because a high percentage of potential volunteers declined to participate due to they worried about the mechanical phlebitis or chemical phlebitis after blood sampling (specially before the endurance race).
We categorized participants based on the race distance: 90 km, 120 km and 160 km (Supplementary Fig. S1). Out of the 91 horses ascribed to the 90 km race, 19 horses met all inclusion criteria. For the 120 km category, we enrolled only 17 horses out of 101, whereas a total of 16 out of 56 horses that raced over 160 km met all inclusion criteria.
For each horse included in this study, we detailed the age, sex, breed, distance covered during the race, whether the horse completed the race and reason for elimination if any (metabolic, lameness, tiredness or other), pulse rate on arrival at the veterinary check point, the average speed during the race, and the race ranking over all animals racing the same distance. The athletic performance ranking of the horse was calculated by taking into account the average speed, recovery time, riding time and the horse and rider’s ability to finish the race. We also recorded environmental factors such as the hours traveled to arrive at the competition site, the stable from where they were coming, the trainer and the breeding establishment where they were born and kept together with their mothers until they were weaned. Lastly, the estimated macronutrient intakes per horse were also detailed (see the section Nutrient intake estimation for further details).
Since it has been previously established that gut microbiota profiles might be shaped by host genetics^{45 (link)}, we used the “kinship2” R package to create the numerator relationship matrix, which estimates the genetic parameters and predicts breeding values between animals. Both pedigree tree and correlation structure matrix are depicted in Supplementary Figs S10 and S11, respectively.
The weather conditions, terrain difficulty and altitude were the same for all participants enrolled in the study as all races (90, 120 and 160 km) took place during the second weekend of October 2015 in Fontainebleau (France). The average air temperature was 15 °C, with a maximum of 20 °C and a minimum of 11 °C. The average air humidity was 88%. No rain was recorded.
All individuals passed the International Equestrian Federation (FEI)’s compulsory examination before the start. During the endurance competition, all animals underwent veterinary checks every 30- to 40-km during the race, followed by recovery periods of 40 to 50 minutes, which is in accordance with the FEI rules on endurance riding. The veterinarians ensured that horses were not suffering from lameness, metabolic troubles or dehydration, and that their heart rate was low enough to start racing another 30 to 40 km. Horses that failed to complete the race were considered as non-finishers or eliminated.
The local animal care and use committee reviewed and approved the study protocol (ComEth EnvA-Upec-ANSES; reference: 11-0041, dated July 12^th 2011). All the protocols were conducted in accordance with EEC regulation (n^o 2010/63/UE) governing the care and use of laboratory animals, which has been effective in France since the 1^st of January 2013. In all cases, the owners and riders provided their informed consent prior to the start of study procedures with the animals.

Given the potential risks described below, trained medical personnel will be present during the administration and for the entire duration of the 2-hour monitoring period.
Ketamine is classified as a schedule I controlled substance due to its potential for abuse and addiction and can be abused in a number of ways, including via injection, snorting, or orally. Ketamine can produce vivid dreams and a feeling that the mind is separated from the body, referred to as “dissociation.” Regular users of ketamine can become tolerant to the dissociative effects of the drug, meaning an increasing amount is needed to achieve the same effect. Drug-related risks include (1) psychiatric symptoms such as fatigue, dizziness, anxiety, visual and auditory disturbances, panic attacks, increased irritability, and changes in mood and behavior; (2) medical symptoms such as transient increases in blood pressure and heart rate, an increase in the need to urinate, headaches, vision changes, chest pain, shortness of breath, confusion, memory impairment, anaphylaxis; and (3) a rare risk of dependency. To address these risks, in this trial, ketamine will be dispensed by the research pharmacy and administered by a trained medical professional, and the patient will receive close supervision and monitoring. Doses are individually calculated, and treatment sessions are structured to prevent tolerance building. Patients will be strongly discouraged from using ketamine outside of the context of this trial and will be informed that they can be discussed with the study physician if they have questions.
IV route–associated risks are infiltration, hematoma, air embolism, phlebitis, extravascular drug administration, and intraarterial injection. Most of these complications are transient and resolve with conservative monitoring. An intraarterial injection is rare but as threatening. An anesthesiologist is present on-site for the IV infusion and will attend if needed, per site rules and regulations.