There is a great need for objective external training load prescription and performance capacity evaluation in equestrian disciplines. Therefore, reliable standardised exercise tests (SETs) are needed. Classic SETs require maximum intensities with associated risks to deduce training loads from pre-described cut-off values. The lactate minimum speed (LMS) test could be a valuable alternative. Our aim was to compare new performance parameters of a modified LMS-test with those of an incremental SET, to assess the effect of training on LMS-test parameters and curve-shape, and to identify the optimal mathematical approach for LMS-curve parameters. Six untrained standardbred mares (3–4 years) performed a SET and LMS-test at the start and end of the 8-week harness training. The SET-protocol contains 5 increments (4 km/h; 3 min/step). The LMS-test started with a 3-min trot at 36–40 km/h [until blood lactate (BL) > 5 mmol/L] followed by 8 incremental steps (2 km/h; 3 min/step). The maximum lactate steady state estimation (MLSS) entailed >10 km run at the LMS and 110% LMS. The GPS, heartrate (Polar®), and blood lactate (BL) were monitored and plotted. Curve-parameters (R core team, 3.6.0) were (SET) VLa1.5/2/4 and (LMS-test) area under the curve (AUC>/<LMS), LMS and Aerobic Window (AW) via angular vs. threshold method. Statistics for comparison: a paired t-test was applied, except for LMS: paired Wilcoxon test; (p < 0.05). The Pearson correlation (r > 0.80), Bland-Altman method, and ordinary least products (OLP) regression analyses were determined for test-correlation and concordance. Training induced a significant increase in VLa1.5/2/4. The width of the AW increased significantly while the AUC</>LMS and LMS decreased post-training (flattening U-curve). The LMS BL steady-state is reached earlier and maintained longer after training. BLmax was significantly lower for LMS vs. SET. The 40° angular method is the optimal approach. The correlation between LMS and VMLSS was significantly better compared to the SET. The VLa4 is unreliable for equine aerobic capacity assessment. The LMS-test allows more reliable individual performance capacity assessment at lower speed and BL compared to SETs. The LMS-test protocol can be further adapted, especially post-training; however, inducing modest hyperlactatemia prior to the incremental LMS-stages and omitting inclusion of a per-test recovery contributes to its robustness. This LMS-test is a promising tool for the development of tailored training programmes based on the AW, respecting animal welfare.

Aleurone, a layer of the bran fraction, is deemed to be responsible for the positive health effects associated with the consumption of whole-grain products. Studies on rodents, pigs, and humans report beneficial effects of aleurone in five main areas: the reduction of oxidative stress, immunomodulatory effects, modulation of energy management, digestive health, and the storage of vitamins and minerals. Our study is the first aleurone supplementation study performed in horses. The aim of this study was to investigate the effect of an increase in the dose levels of aleurone on the postprandial glucose-insulin metabolism and the gut microbiome in untrained healthy horses. Seven adult Standardbred horses were supplemented with four different dose levels of aleurone (50, 100, 200, and 400 g/day for 1 week) by using a Latin square model with a 1-week wash out in between doses. On day 7 of each supplementation week, postprandial blood glucose-insulin was measured and fecal samples were collected. 16S ribosomal RNA (rRNA) gene sequencing was performed and QIIME2 software was used for microbiome analysis. Microbial community function was assessed by using the predictive metagenome analysis tool Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) and using the Metacyc database of metabolic pathways. The relative abundancies of a pathway were analyzed by using analysis of composition of microbiomes (ANCOM) in R. There was a significant dose-dependent increase in the postprandial time to peak of glucose (p = 0.030), a significant delay in the time to peak of insulin (p = 0.025), and a significant decrease in both the insulin peak level (p = 0.049) and insulin area under the curve (AUC) (p = 0.019) with increasing dose levels of aleurone, with a consideration of 200 g being the lowest significant dose. Alpha diversity and beta diversity of the fecal microbiome showed no significant changes. Aleurone significantly decreased the relative abundance of the genera Roseburia, Shuttleworthia, Anaerostipes, Faecalibacter, and Succinovibrionaceae. The most pronounced changes in the relative abundance at phyla level were seen in Firmicutes and Verrucomicrobia (downregulation) and Bacteroidetes and Spirochaetes (upregulation). The PICRUSt analysis shows that aleurone induces a downregulation of the degradation of L-glutamate and taurine and an upregulation of the three consecutive pathways of the phospholipid membrane synthesis of the Archaea domain. The results of this study suggest a multimodal effect of aleurone on glucose-insulin metabolism, which is most likely to be caused by its effect on feed texture and subsequent digestive processing; and a synergistic effect of individual aleurone components on the glucose-insulin metabolism and microbiome composition and function.

The purpose of this literature review is to clarify how exercise capacity can be measured in horses and which standardized exercise tests (SETs) exist. In this review, the measurement of the exercise capacity of horses is discussed and the standardized exercise tests (SET) are described. Two main types of SETs are used. Laboratory or treadmill tests are easy to standardize and provide more options to use all kinds of measuring devices, since the horse stays on the treadmill. On the other hand, field tests are conducted under the natural conditions associated with the specific sports discipline, and are easier to implement in the training schedule. However, field tests encompass interfering variables, such as weather conditions, ground surface conditions and the rider or jockey. Several variables are measured in order to calculate the fitness level which may be expressed by different parameters, such as V200 (speed at a heart rate of 200 beats per minute), Vla4 (speed at a blood lactic acid level of 4 mmol/L) and VO2max (maximum oxygen uptake).

It is well known that exercise induces chemical, metabolic and structural changes in muscles. However, the effect of the type of exercise on these changes has not been thoroughly studied in horses yet, because of a lack of standardized study methods. In this review, the effect of three different types of exercise on muscle adaptation and metabolic responses is investigated. The requirements for power exercise are not the same as for low intensity exercise. Each type of training induces its own shift in muscle fiber typing, as well as in enzyme concentrations and (an) aerobic capacity. These physiological adaptations in response to training facilitate more efficient exercise and therefore increase performance. Hence, it is important to know the adaptations that muscles undergo in response to each type of exercise to optimize training management of sport horses in function of the needs of the discipline in which they compete.

Training in the fasted state has beneficial effects on performance in the human athlete. In the horse, training in the fasted state is associated with an increased mobilization of non-esterified fatty acids (NEFA) as an energy source. This is in contrast with postprandial (grain-fed) training, during which lipolysis is suppressed. A higher NEFA availability is thought to reduce muscle glycogen depletion and muscle acidification. This could aid in delaying muscle fatigue. The equine gastrointestinal tract and roughage rich diet do not allow a real ‘fasted’ state. Luckily, roughage does not induce high plasma insulin peaks, and therefore does not have the same negative effects as grain feeding. Furthermore, the roughage-containing hindgut serves as a fluid and electrolyte buffer and continuously provides the liver with propionic acid, a precursor used in gluconeogenesis. In horses, unlike in human athletes, there is still a lot to discover when it comes to optimal pre-exercise feeding management throughout competition and training. However, whatever approach is chosen, high quality roughage needs to be the key ingredient of the equine diet. In sport horses with high energy demands, feeding good quality roughage may be combined with fibre rich concentrates, pelleted roughages sources or vegetal oil instead of starch rich concentrates to reach the energy requirements for intensive work. Last but not least, feeding multiple small meals throughout the day is preferred over feeding a larger meal twice a day.