The Postural and Body Surface Temperature Response of Leisure Horses to Lunging with Selected Lunging Aids

Incorporating lunging into a horse's daily routine aims to enhance fitness, physical condition, and specific skills or exercises when using lunging aids (LAs). To assess the effectiveness of lunging, non-contact technologies like geometric morphometrics and infrared thermography can be employed. This study seeks to evaluate lunging efficiency based on the horse's posture and surface temperature when lunging with different head and neck positions. The study aims to determine if changes in a horse's posture correspond to increased metabolic activity, as indicated by body surface temperature. Thirteen horses included in the study were lunged with chambon (CH), rubber band (RB), and triangle side reins (TRs) as well as with a freely moving head (FMH). Images were taken in visible light and infrared. Principal Component Analysis (PCA) was used to analyze horse posture changes and a Pixel-Counting Protocol (PCP) was used to quantify surface temperature patterns. The horses' posture exhibited contrasting changes, reflected by a changing centroid shape (p < 0.0001) but not size (p > 0.05) when lunged with RB and TRs, but not CH. Different (p < 0.0001) surface temperature patterns were observed during lunging. FMH lunging resulted in lower temperatures over a larger surface, CH induced moderate temperatures on a smaller area, RB caused moderate to high temperatures across a broader surface, and TRs led to higher temperatures over a smaller region. The studied lunging cases returned different (p < 0.0001) surface temperature patterns. Lunging with FMH returned lower temperatures over a larger surface, CH moderate temperatures on a smaller area, RB moderate to high temperatures across a broader surface, and TRs higher temperatures over a smaller region. The proposed methods can be applied to evaluate the efficiency of lunging in horses.

Longitudinal Training and Workload Assessment in Young Friesian Stallions in Relation to Fitness: Part 1

Friesian stallions have to complete a 10-week studbook approval test (70-day test) consisting of dressage and driving training for acceptance as a breeding stallion. Training response of the horses to this approval program was evaluated. External workload (EW) of 16 stallions (3.2 ± 0.4 years old) was registered during the 9 weeks preceding the 70-day test (preparation period) and during 70-day test. Ridden indoor standardized exercise tests (SET), measuring heart rate (HR) and plasma lactate concentration (LA) at walk, trot and canter, were performed in week 1 (SET-I), 6 (SET-II) and 10 (SET-III) of the 70-day test. Linear mixed effect models were used to analyze HR and LA related to SETs and EW related to the phase of the study, using Akaike's information criterion for model reduction. EW was higher in the 70-day test compared to the preparation period, with longer duration of training sessions. Compared to SET-I, horses showed increased HR and LA after canter in SET-II and SET-III, indicating that they were more fatigued. The fact that the fitness of these Friesian stallions decreased during the 70-day test suggests overtraining. To optimize training effects and welfare of these horses, the workload of the training program needs to be adjusted.

Longitudinal Training and Workload Assessment in Young Friesian Stallions in Relation to Fitness, Part 2-An Adapted Training Program

Young Friesian stallions have to complete a 10-week training program (70-day test) for acceptance as a breeding stallion. Part one of this study showed that the 70-day test was too intense and led to reduced fitness. In the present (part two) study, the effects of an adapted training program were studied. Training frequency and minutes of cantering per week were lowered compared with part one. The external workload (EW) of sixteen stallions (3.4 ± 0.8 years) was monitored during the 6-weeks before testing (preparation period) as well as during the 70-day test. Standardized exercise tests (SETs) were performed in week 1 (SET-I), 6 (SET-II), and 10 (SET-III) of the 70-day test, measuring heart rate (HR) and plasma lactate concentration (LA). Linear mixed effect models were used to analyze the EW, and the HR and LA related to the SETs. The EW increased from the preparation period to the 70-day test; this increase in the EW was lower compared with the original training program. The horses showed lower HR and LA levels in SET-III compared with SET-I. The young Friesian horses were at risk to be overtrained in part one, but the adapted training program resulted in increased fitness. This study shows that a carefully chosen program is necessary to improve the performance and welfare of (young) horses.

A one-health approach to identifying and mitigating the impact of endocrine disorders on human and equine athletes

Endocrinopathies affect multiple species in ever-increasing percentages of their populations, creating an opportunity to apply one-health approaches to determining creative preventative measures and therapies in athletes. Obesity and alterations in insulin and glucose dynamics are medical concerns that play a role in whole-body health and homeostasis in both horses and humans. The role and impact of endocrine disorders on the musculoskeletal, cardiovascular, and reproductive systems are of particular interest to the athlete. Elucidation of both physiologic and pathophysiologic mechanisms involved in disease processes, starting in utero, is important for development of prevention and treatment strategies for the health and well-being of all species. This review focuses on the unrecognized effects of endocrine disorders associated with the origins of metabolic disease; inflammation at the intersection of endocrine disease and related diseases in the musculoskeletal, cardiovascular, and reproductive systems; novel interventions; and diagnostics that are informed via multiomic and one-health approaches. Readers interested in further details on specific equine performance conditions associated with endocrine disease are invited to read the companion Currents in One Health by Manfredi et al, JAVMA, February 2023.

Investigating the pathogenesis of high-serum gamma-glutamyl transferase activity in Thoroughbred racehorses: A series of case-control studies

BACKGROUND

High-serum γ-Glutamyl Transferase (GGT) activity has been associated with and thought to be a marker of maladaptation to training and possibly poor performance in racehorses, but the cause is unknown.

OBJECTIVES

To investigate possible metabolic and infectious causes for the high GGT syndrome.

STUDY DESIGN

Pilot case-control study and nested case-control study.

METHODS

The case-control study in 2017 included 16 horses (8 cases and 8 controls with median [range] serum GGT 82 [74-148] and 22 [19-28] IU/L, respectively) from the same stable. In 2018, similar testing was performed in a nested case-control study that identified 27 case (serum GGT 50 ≥ IU/L)-control pairs from three stables for further testing. Serum liver chemistries, selenium measurements, viral PCR and metabolomics were performed.

RESULTS

No differences were found in frequency of detection of viral RNA/DNA or copy numbers for equine hepacivirus (EqHV) and parvovirus-hepatitis (EqPV-H) between cases and controls. Mild increases in hepatocellular injury and cholestatic markers in case vs control horses suggested a degree of liver disease in a subset of cases. Metabolomic and individual bile acid testing showed differences in cases compared with controls, including increased abundance of pyroglutamic acid and taurine-conjugated bile acids, and reduced abundance of Vitamin B6. Selenium concentrations, although within or above the reference intervals, were also lower in case horses in both studies.

MAIN LIMITATIONS

Observational study design did not allow us to make causal inferences.

CONCLUSIONS

We conclude that high GGT syndrome is likely a complex metabolic disorder and that viral hepatitis was not identified as a cause for this syndrome in this cohort of racehorses. Our results support a contribution of oxidative stress and cholestasis in its pathophysiology.

Gallop Racing Shifts Mature mRNA towards Introns: Does Exercise-Induced Stress Enhance Genome Plasticity?

Physical exercise is universally recognized as stressful. Among the "sport species", the horse is probably the most appropriate model for investigating the genomic response to stress due to the homogeneity of its genetic background. The aim of this work is to dissect the whole transcription modulation in Peripheral Blood Mononuclear Cells (PBMCs) after exercise with a time course framework focusing on unexplored regions related to introns and intergenic portions. PBMCs NGS from five 3 year old Sardinian Anglo-Arab racehorses collected at rest and after a 2000 m race was performed. Apart from differential gene expression ascertainment between the two time points the complexity of transcription for alternative transcripts was identified. Interestingly, we noted a transcription shift from the coding to the non-coding regions. We further investigated the possible causes of this phenomenon focusing on genomic repeats, using a differential expression approach and finding a strong general up-regulation of repetitive elements such as LINE. Since their modulation is also associated with the "exonization", the recruitment of repeats that act with regulatory functions, suggesting that there might be an active regulation of this transcriptional shift. Thanks to an innovative bioinformatic approach, our study could represent a model for the transcriptomic investigation of stress.

Young Friesian horses show familial aggregation in fitness response to a 7-week performance test

The aim of this study was to monitor the fitness level of young Friesian horses and to assess whether fitness data are predictive for final performance score and whether familial aggregation of response to training could be detected. Sixty-six young Friesian horses, the offspring of six different stallions (A, B, C, D, E and F), underwent a 7-week performance test. The horses were given a performance score for their ability for dressage (in weeks 5 and 7; 0-110 points) and were evaluated for fitness using standardised exercise tests (SETs) at the beginning (week 2, SET-I) and the end (week 6, SET-II) of the period. Heart rate (HR, beats/min) was measured in both SETs, and plasma lactate concentration (LA, mmol/L) was measured only in SET-II. Fitness of the horses improved moderately but significantly between SET-I and SET-II (P=0.015). There was a large heterogeneity in responsiveness to training; some horses were high responders, whereas others were non- or low responders. There was a familial aggregation of HR canter-1 response to training (P=0.039), while the HR of stallion C's offspring decreased significantly more than those of stallions A (P=0.09), D (P=0.013) and F (P=0.009). Horses that were reluctant to exercise did not differ in HR or LA concentrations compared to those that completed the SET, which may have been a sign of overreaching. HR had no predictive value for the performance score, but horses that did not reach the anaerobic threshold in SET-II scored significantly better (73.8 ± 5.6 points) than horses that did not (69.9 ± 5.9 points, P=0.025). The findings demonstrate for the first time in the horse a familial aggregation of HR response to training, as has been reported previously in humans. Familial aggregation suggests a genetic influence on the effect of training on fitness in horses. HR could not predict final performance score, but LA concentrations during SET-II were predictive.

Effects of intensified training and subsequent reduced training on glucose metabolism rate and peripheral insulin sensitivity in Standardbreds

OBJECTIVE

To determine the influence of intensified training and subsequent reduced training on glucose metabolism rate and peripheral insulin sensitivity in horses and identify potential markers indicative of early overtraining.

ANIMALS

12 Standardbred geldings.

PROCEDURES

Horses underwent 4 phases of treadmill-based training. In phase 1, horses were habituated to the treadmill. In phase 2, endurance training was alternated with high-intensity exercise training. In phase 3, horses were divided into control and intensified training groups. In the intensified training group, training intensity, duration, and frequency were further increased via a protocol to induce overtraining; in the control group, these factors remained unaltered. In phase 4, training intensity was reduced. Standardized exercise tests were performed after each phase and hyperinsulinemic euglycemic clamp (HEC) tests were performed after phases 2, 3, and 4.

RESULTS

10 of 12 horses completed the study. Dissociation between mean glucose metabolism rate and mean glucose metabolism rate-to-plasma insulin concentration ratio (M:I) was evident in the intensified training group during steady state of HEC testing after phases 3 and 4. After phase 4, mean glucose metabolism rate was significantly decreased (from 31.1 ± 6.8 μmol/kg/min to 18.1 ± 3.4 μmol/kg/min), as was M:I (from 1.05 ± 0.31 to 0.62 ± 0.17) during steady state in the intensified training group, compared with phase 3 values for the same horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Dissociation between the glucose metabolism rate and M:I in horses that underwent intensified training may reflect non-insulin-dependent increases in glucose metabolism.

Variations of plasma leptin in show horses during a work season

Leptin is an adipocytokine mainly expressed by adipose tissue. Secretion of leptin in healthy animals is closely related to fat mass and metabolic activity. The aim of this study was to investigate plasma leptin variations, in relation to nutritional and exercise parameters in adult show horses during a work season. EDTA-blood samples were taken at rest from 37 Iberian horses. Body weight, body condition score and fat percentage determined by ultrasonic measurement of rump fat thickness were measured. Plasma leptin was determined with a multi-species RIA kit. Linear mixed effects model was used to assess relationship between plasma leptin and other biological parameters. Plasma leptin concentration was <12.6 ng/ml (mean = 2.8 ± 1.6 ng/ml) and was significantly higher during training periods (p < 0.0001) (4.5 ± 1.7 ng/ml) than in show periods (2.0 ± 1.1 ng/ml), despite a significant increase (p < 0.0001) in energy intake. The body weight remained almost constant. The plasma leptin concentrations were significantly affected by exercise (p < 0.0001), body weight (p = 0.04) and BCS (p < 0.0001), but were not affected by percentage of fat. In conclusion, the marked decrease in leptin values observed during a period of intense (i.e. excessive) exercise could result from an adaptation to cumulative alterations in energy balance, to exercise per se or to a combination of both.

Effect of conditioning horses every third day at v10 on measures of fitness

This study examined the effect of exercising horses five times per fortnight with two bouts of 5 min duration at their v(10) with 2 days between consecutive exercise sessions. Five Anglo-Arabian horses were treadmill-conditioned for 6 weeks. A standardized exercise test (SET) was performed at the beginning of the conditioning period (CP) to determine the blood lactate-running speed (BLRS) and the heart rate-running speed (HRRS) relationship and the SET was repeated every 2 weeks. After each SET, the BLRS relation was used to calculate the horse's speed (v = velocity), which produced a blood lactate concentration (LA) of 10 mmol/l (v(10) ) and 4 mmol/l (v(4) ). From the HRRS was calculated the speed at which the horses had a heart rate of 180 b/min (v(180) ). Each horse was then conditioned for the next 2 weeks five times at its individual v(10) for two 5-min bouts. Exercise speed was individually adapted to the new v(10) every 2 weeks. In addition, horses were submitted to another SET prescription to determine the peak oxygen consumption (VO(2 peak) ) before, after 3 weeks and at the end of CP. The v(4) of horses increased during the CP (p < 0.05). v(180) did not change (p > 0.05). VO(2 peak) increased in the first 3 weeks of CP (p < 0.05) and levelled off afterwards (p > 0.05). The conclusion drawn was that exercising horses five times per fortnight at their v(10) for two 5-min bouts with 2 days between consecutive exercise sessions improved v(4) and VO(2 peak) but not v(180).