H. C. Manso Filho

Metabolic changes in four beat gaited horses after field marcha simulation

REASONS FOR PERFORMING STUDY Mangalarga-Marchador is a popular 4-gaited Brazilian horse breed; however, there is little information about their metabolic and physiological response to exercise. OBJECTIVES To measure physiological and metabolic responses of the Mangalarga-Marchador to a simulated marcha field test and to compare these responses between 2 types of marcha gaits (picada and batida). METHODS Thirteen horses were used in the study and randomly assigned to either the picada or batida gait for the simulated marcha field test (speed ∼ 3.2 m/s; 30 min; load ∼ 80 kg). MEASUREMENTS Included body composition, heart rate (HR), respiratory rate (RR), glucose (GLUC), lactate (LACT), packed cell volume (PCV), total plasma protein (TPP), albumin, urea, creatinine, total and HDL cholesterol, triglycerides, creatine kinase, alanine, glutamate and glutamine (GLN). Measurements were obtained pretest (control/fasting), immediately after simulation (T(0)), and 15 (T(15)), 30 (T(30)) and 240 (T(240)) min after the simulation. Lactate (LACT) was measured at T(0), T(15) and T(30). Data were analysed using ANOVA, Tukeys test and t tests with significance set at P < 0.05. RESULTS Significant acute changes were observed in HR, RR, [GLUC], [LACT], [TPP], PCV and [GLN] (P<0.05) relative to control. Heart rate fell below 60 beats/min at T(15) and RR recovered to pretest values by T(240). Significant increases in [GLUC], [LACT], PCV and [TPP] and a decrease in [GLN] were observed at T(0). Treatment and interaction effects were also observed between marcha types and time of sampling for HR, RF, PCV, and [LACT] (P < 0.05). These parameters were large in picada. CONCLUSION The simulation of field-test produced changes in some physiological and blood parameters in marcha horses, with some degree of dehydration during recovery period. Also, it was demonstrated that picada horses spend more energy when compared with batida horses at the the same speed. POTENTIAL RELEVANCE Batida horses spend less energy when compared with picada horses, which will need special attention in their training and nutritional management.

Developmental changes in the concentrations of glutamine and other amino acids in plasma and skeletal muscle of the Standardbred foal

Glutamine is concentrated within skeletal muscle, where it has been proposed to play a regulatory role in maintaining protein homeostasis. The work presented here addressed the hypothesis that glutamine would be the most abundant free alpha-AA in plasma and skeletal muscle in the foal during the first year of life. Glycine, however, was the most abundant free alpha-AA in plasma at birth and between 3 and 12 mo of age. The concentration of glutamine, the second most abundant AA at birth, increased through the first 7 d (P < 0.05) and then returned to values similar to those at birth. This resulted in glutamine being the most abundant free alpha-AA in plasma from 1 d through 1 mo of age. The most abundant free alpha-AA in skeletal muscle at birth was glutamine, but the concentration fell by more than 50% by d 15 and continued to decrease, reaching about one-third of the original values by 1 yr of age (P < 0.05). Glutamine synthetase was barely detectable in skeletal muscle at birth, but the abundance increased rapidly within 15 d of birth. The concentration of glycine, the second most abundant alpha AA in muscle at birth, decreased by about 40% by d 15 (P < 0.05) and then stabilized at this value throughout the year. In contrast, glutamate, alanine, and serine concentrations, the third, fourth, and fifth most abundant free alpha-AA in muscle at birth, respectively, increased to new stable concentrations between 3 and 6 mo of age (P < 0.05). This resulted in alanine being the most abundant free alpha-AA in skeletal muscle at 12 mo of age, followed by glutamate, glutamine, and glycine. The decrease in intramuscular glutamine content, particularly during the first 2 wk after birth, is not compatible with a regulatory role for glutamine in muscle protein synthesis because it occurred at the time of maximum growth in these animals. The findings that, at certain times of development, glutamine was not the most abundant free alpha-AA in the foal is novel and signifies that intramuscular glutamine may have functions specific to muscle type and mammalian species.

Heart rate responses of two breeds of four-gaited horses to a standardised field gaited test

In order to understand how gaited horses use their energy during exercise, a standardised field gaited test (SFGT) was developed to assess energy expenditure of four beat gaited horses independently of size, sex or breed. This work aimed at developing such an SFGT, using as main measurement parameter the heart rate (HR) of horses during the SFGT performance. Thirty-one four beat gaited horses were evaluated and divided into two groups: FIT (conditioned) and UNFIT (not conditioned). Horses were submitted to the SFGT and their heart rates were measured with a heart rate monitor as follows: right after being mounted, at the beginning of pre-test (HRSADDLE); at 5, 10, 15, 20, 25 and 30 minutes of four beat gait dislocation; and at 15 minutes after the recovery period (T+15). Maximum HR (HRMAX); HR percentage over 150 beats per minute (HR%≯150), HR percentage over 170 beats per minute (HR%≯170), and average HR during the four beat gait stage (HRM@M) of SFGT were calculated. Results were analysed by ANOVA for r...

Heart rate and blood biomarkers in Brazilian gaited horses during a standardised field gaited test

There is little information about biochemical and physiological parameters in Brazilian gaited horses that could be used to develop training and performance evaluation programs. The aims of the current study were to evaluate heart rate (HR) and blood biomarkers in gaited horses during a standardised field gaited test (SGT). Sixteen horses were used to develop an SGT (10 min of warming up, 30 min of marcha gait and 15 min of recovery). Blood samples and HR were collected at rest, after warming up, after 15 (F+15) and 30 (F+30) min of marcha, and after the recovery period. The following blood parameters were measured: glucose, lactate, total plasma protein, haematocrit, urea, creatinine, glutamine, glutamate, triglycerides, total cholesterol, Ca, P, Mg, Na, Cl and K. HR measurement was carried out using an HR monitor. The results were analysed using one- and two-way ANOVA tests, and post-hoc Holm-Sidak tests. Students t-tests were used to compare means, and the Pearsons test was utilised for correlation a...

Acute vascular occlusion in horses: effects on skeletal muscle size and blood flow

The purpose of this study was to demonstrate whether acute vascular occlusion was safe and if it would result in changes to limb muscle size in horses. Six healthy, unfit Standardbred mares were used. Horses (standing at rest) wore an occlusion cuff at the most proximal position of the left forelimb. The right forelimb was used as control. An occlusion pressure of 200 mmHg was set for 5 min followed by a 2 min recovery. Three sets of occlusions were given to each horse. Muscle thickness was measured using B-mode ultrasound. The circumference of the forelimb and first phalanx was measured using a flexible tape measure. Pulsed-wave Doppler was performed on the radialis artery with a 5–10 MHz mechanical transducer at baseline and at each occlusion. Peak flow velocity (PFV) and the flow velocity integral (FVI) were measured each time. Midforelimb, but not first phalanx, girth was increased (P 0.05) in PFV or FVI at any measurement time point. Acute vascular occlusion may be a suitable and safe model for studying muscle hypertrophy in horses.

Effect of training on intrinsic and resting heart rate and plasma volume in young and old horses

The chronic bradycardia seen in several species after intense exercise training may be due to autonomic mechanisms, non-autonomic mechanisms, such as increased pre-load, or a combination of the two. Thirteen, healthy, unfit Standardbred mares were split into two groups: young (age 12±1 yr; mean ± standard error, n=8) and old (age 22±1 yr, n=5) to test the hypothesis that there would be age and training related differences in resting heart rate (RHR), intrinsic heart rate (IHR), maximal heart rate (HRmax) and plasma volume (PV). Mares were trained 3 d/wk at 60% HRmax for 20 min and gradually increased to exercising 5 d/wk at 70% HRmax for 30 min and RHR, IHR, HRmax, and PV were measured prior to and after the 8 wk training period. There were no age related differences (P≯0.05) between young and old mares before (41±2 vs. 42±2 beats per minute (bpm); 86±5 vs. 80±4 bpm) or after training (35±1 vs. 34±1 bpm; 81±6 vs. 78±2 bpm) for RHR and IHR respectively. RHR was decreased (P<0.05) following training in both...

Heart rate and velocity in Vaquejada horses during field tests

The use of heart rate (HR) monitors for horse training assessment under field conditions has been expanded because its use facilitates the understanding of horse fitness levels. Work has been carried out to determine the HR, velocity (V) and exercise time for pull and helper horses submitted to the Vaquejada simulation test (VST). The test was used on 70 Quarter Horses that had trained and competed for more than 6 months. The VST consists of two horses, a puller and a helper, and a bull, all running on a soft sand track. A race cycle consists of three runs with the bull. Pull horses run one cycle and helper horses run two cycles. A Polar V800-GPS HR monitor for equines was used to measure several parameters: time, V and HR. The results were analysed by ANOVA and a Tukey test with P set at 5%. It was shown that pull horses developed an HRmax of ~200 bpm and an HRmin ~110 bpm, both higher than the helper horses (P<0.05). However, the HRmed of pull horses (~150 bpm) and helper horses (~139 bpm) in C-2 trials...

Aerobic exercise produces changes in plasma IL-6 but not IL-1b in four-beat gaited horses

Exercise is an important stressor and is correlated with cytokine production in several tissues. There is little information about changes in interleukin (IL)-6 and IL-1b in four-beat gaited horses during a typical aerobic exercise challenge. The objective of this research was to characterise changes in plasma IL-6, IL-1b, cortisol and other blood biomarkers in four-beat gaited horses after a marcha simulation test. We subjected 12 fit horses (approximately 5 years old and 390 kg) to the marcha simulation test (MST) (i.e. a 10 min warm-up, 30 min at marcha and 15 min cool down). Blood samples were collected before the MST, immediately after the MST and 15 and 120 min after the MST (i.e. recovery). Results were analysed with One Way Repeated Measures ANOVA and a Tukey tests with P≤0.05 and Pearson correlation test. The highest value of plasma IL-6 was observed immediately after MST (6.85 pg/ml) (P≥0.05). IL-1 and cortisol did not change (P≥0.05). However, creatine kinase (CK) and aspartate aminotransferase...

Exercise training, Glut-4 protein abundance and glutamine in skeletal muscle of mature and very old horses

Two groups of unfit Standardbred mares (adult: 9-14 years, 540 kg, n=7) and old (20-25 years, 530 kg, n=5) were used to test two hypotheses, first, that aging and training would alter plasma and muscle glutamine [Gln] and glutamate [Glu] and second, that aging and training would alter Glut-4 expression in skeletal muscle. All animals were housed on pasture with free access to grass and all received hay and supplementation with a commercially prepared supplement (15% crude protein and 3.00 Mcal/kg dry matter) in individual stalls. Mares were fed to meet or exceed NRC (2007) nutrient recommendations for moderate to heavy exercise. The mares were exercise trained in a free-stall motorised circular exercise machine for 30 min/d, 5 d/week, for 8 weeks. Work intensity during training was set at a relative intensity of ~60% of the maximum heart rate, previously determined during an incremental exercise test (GXT). Blood samples and muscle biopsies (gluteus) obtained before and after 8 weeks of training were used...

The effect of repeated barrel racing on blood biomarkers and physiological parameters in Quarter Horses

The objective of this study was to evaluate barrel horses undergoing a field test with one repetition. Quarter-Horses were used (14 males and females; average age: 6.5 years old), and they ran two times for 5 min in the same field. Six different periods were evaluated: rest (T-0), immediately after the first (T-1) and second races (T-2), and after 15 (T-15), 30 (T-30) and 240 min (T-240) of recovery. Heart rate (HR), speed, distance and duration were measured using a HR monitor with GPS during the races. Blood was collected to determinate glucose, lactate, total proteins (TP), albumin, globulin, urea, creatinine, uric acid (UA), triglycerides, cholesterol, non-esterified fatty acids (NEFA), gammaglutamyltransferase (GGT), creatine kinase (CK), and cortisol concentrations, as well as to perform a haemogram. The results were analysed using ANOVA and Tukey’s tests using a P-value of 5%, and they showed a maximum HR>200 bpm after both races. The largest %HR>>170 bpm occurred in the second race (P<0.05). Gluco...