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Ageing appears to affect immune and neuroendocirne function in horses and response to acute exercise. No studies have examined the combined effects of training and ageing on immune and neuroendocirne function in horses.To ascertain whether training and age would affect the plasma beta-endorphin (BE) and cortisol (C) as well as immune function responses to acute exercise in Standardbred mares.Graded exercise tests (GXT) and simulated race tests (SRT) were performed before and after 12 weeks training at 60 % HRmax. BE and C were measured at rest and at 5, 10, 20, 40, 60 and 120 min post GXT. Leucocyte cell number, CD4+ and CD8+ lymphocyte subsets, and mitogen stimulated lymphoproliferative response (LPR), were measured in jugular blood before and after the SRTs.Cortisol rose by 5 min post GXT in young (Y) and middle-age (MA) mares (P0.05) and remained elevated until 40 and 60 min post GXT, respectively during both pre- and post training GXT. There was no rise in C in old (0) mares after either GXT (P0.05). Pretraining BE rose (P0.05) by 5 min post GXT in all mares. After training, BE was higher in Y and O vs. MA (P0.05) at 5 min post GXT. Post training BE was higher at 5 min post GXT in Y and O vs. pretraining (P0.05). After SRT, lymphocyte number rose in all mares (P0.05); however, lower lymphocyte numbers (P0.05) were seen in MA vs. Y and O vs. MA (P0.05). The O had reduced LPR to Con A and PHA stimulation (P0.05) compared to Y and MA after the SRT after both pre- and post training SRT. LPR to PWM was lower (P0.05) in O vs. Y and MA after the pretraining SRT. Training caused an increase in resting LPR to PWM in MA only (P0.05).Both age and training altered the plasma beta-endorphin and cortisol responses as well as and immune responses to acute exercise.This study provides important information on the effects of ageing and training that will aid in the management and care of an increasing number of active older horses.

Summary Reasons for performing study:A large percentage of performance horses develop gastric ulcers and many of those horses are treated with omeprazole. Unfortunately, no data have been published on the effects of the drug on markers of performance in animals without ulcers. Hypothesis:Omeprazole would alter markers of aerobic and anaerobic performance. Methods: Ten unfit, healthy, ulcer free, Standardbred mares were administered either control (CON; oral apple sauce, 20 ml) or omeprazole (OP; oral paste, 4 mg/kg bwt s.i.d.) in a random crossover fashion with the investigators blind to the treatment. Treatments were administered for 7 days prior to performing an incremental exercise test (GXT) on a high-speed treadmill. Endoscopic examinations were performed just prior to the trial to verify that the mares were ulcer-free. During the GXT, the mares ran on a treadmill up a 6% grade to measure maximal oxygen consumption (VO2max), run time (RT), velocity at VO2max, maximal velocity (Vmax), packed cell volume (PCV), plasma lactate concentration (LA) and plasma protein concentration (TP). Measurements were recorded at rest, at the end of each 1 min step of the GXT and at 2 and 5 min post GXT. Data were analysed using ANOVA for repeated measures and t tests for paired comparisons. Results: There was no effect (P>0.05) of omeprazole on VO2max; velocity at VO2max; RT; Vmax; 2 min recovery plasma LA. Nor were there any changes (P>0.05) in the relationship between treadmill speed and VO2, PCV, TP, or plasma LA. Conclusions:Omeprazole does not appear to improve physiological markers of performance in healthy, ulcer free horses. Potential relevance:These data may benefit various authorities responsible for deciding administration and timing policies of omeprazole as well as clinicians and horse owners.

Summary Reasons for performing study: Recombinant human erythropoietin (rhuEPO) causes an increase in red blood cell production and aerobic capacity in other species; however, data are lacking on effects in the horse. Hypothesis: This study tested the hypothesis that rhuEPO administration would alter red cell volume (RCV), aerobic capacity (VO2max) and indices of anaerobic power. Methods: Eight healthy, unfit mares accustomed to the laboratory and experimental protocols were randomly assigned to either a control (CON, n=4; 3 ml saline 3 times/week for 3 weeks) or EPO group (EPO, n = 4, 50 iu/kg bwt rhuEPO/3 ml saline 3 times/week for 3 weeks). Exercise tests (GXT) were performed on a treadmill (6% incline), 1 week before and 1 week after treatment. The GXT started at 4 m/sec, with a 1 m/sec increase every 60 sec until the horse reached fatigue. Oxygen uptake was measured via an open flow indirect calorimeter. Blood samples were collected before, during (each step) and 2 and 15 min post GXT to measure packed cell volume (PCV), haemoglobin concentration (Hb), blood lactate concentration (LA) and plasma protein concentration (TP). Plasma volume (PV) was measured using Evans Blue dye. Blood volume (BV) and RCV were calculated using PCV from the 8 m/sec step of the GXT. Results: There were no alterations (P>0.05) in any parameters in CON horses. By week 3, EPO produced increases (P 0.05) due to decreased PV (-11%, P

The purpose of this study was to test the hypotheses that ageing would result in a decline in maximal heart rate (HRmax) and maximal aerobic capacity (VO2max) and, secondarily, that those effects would be reversible with training. Eighteen, healthy, unfit Standardbred mares representing 3 age groups: young (Y = mean +/- s.e. 6.8 +/- 0.4 years, n = 6); middle-aged (MA = 15.2 +/- 0.4 years, n = 6); and old (O = 27.0 +/- 0.2 years, n = 6) were used. HRmax, VO2max and oxygen pulse at VO2max (OPmax) and the velocities producing HRmax (VHRmax) and VO2max (VVO2max) were measured during pretraining and post-training incremental exercise tests (GXT). During training, mares exercised 3 days/week (Weeks 1-8) and 4 days/week (Weeks 9-12) at a submaximal intensity (approximately 60% HRmax) for approximately 30 min/day. There were no differences (P0.05) between Y and MA, before (218 +/- 2 vs. 213 +/- 3 beats/min; 116 +/- 3 vs. 109 +/- 3 ml/kg bwt/min; 0.55 +/- 0.01 vs. 0.52 +/- 0.02 ml/kg/beat; 9.0 +/- 0.3 vs. 9.3 +/- 0.2 ms; 8.8 +/- 0.2 vs. 8.8 +/- 0.2 m/s) or after training (224 +/- 2 vs. 218 +/- 2 beats/min; 131 +/- 3 vs. 120 +/- 2 ml/kg bwt/min; 0.58 +/- 0.01 vs. 0.55 +/- 0.01 ml/kg/beat; 10.5 +/- 0.2 vs. 9.5 +/- 0.1 ms; 10.6 +/- 0.2 vs. 9.5 +/- 0.1 m/s) for HRmax, VO2max, OPmax, VHRmax or VVO2max, respectively. Old horses had lower HRmax, VO2max and OPmax and reached them at lower velocities compared to Y and MA (P0.05), both before (193 +/- 3 beats/min; 83.2 +/- 2.0 ml/kg bwt/min; 0.43 +/- 0.01 ml/kg/beat; 7.8 +/- 0.1 m/s; 7.2 +/- 0.1 m/s) and after training (198 +/- 2 beats/min; 95 +/- 2 ml/kg bwt/min; 0.48 +/- 0.01 ml/kg/beat; 8.2 +/- 0.2 m/s; 8.0 +/-0.2 m/s). Training did not alter HRmax in any age group (P0.05) but did cause increases in VO2max, OPmax and VVO2max for all groups (P0.05). Interestingly, training increased VHRmax only in Y (P0.05). These data demonstrate that there is a reduction in HRmax, VO2max, OPmax, VHRmax and VVO2max in old horses, and that training can partially reverse some effects of ageing.

Six young (mean + s.e., 5.3 +/- 0.8 years, 445 +/- 13 kg bwt) and 6 old (22.0 +/- 0.4 years, 473 +/- 18 kg bwt) Standardbred and Thoroughbred mares were used to test the hypothesis that age would alter the endocrine response to exercise. All of the mares were unconditioned but accustomed to the laboratory, to standing quietly and running on a treadmill, and to the standardised incremental exercise test (SET) used in the experiment. Two weeks prior to the experiment, each horse underwent a SET to determine maximal oxygen uptake (VO2max) and the speeds to be used in the actual experiment. A second graded exercise test (GXT) was performed without instrumentation for the measurement of plasma renin activity (PRA) and the plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), aldosterone (ALDO), and endothelin-1 (ET-1). Blood samples (30 ml) were collected at rest and at the end of each one minute step of the exercise test. Plasma concentrations of hormones were measured using radioimmunoassay kits. There were no differences (P > 0.05) between old vs. young mares for resting PRA (2.2 +/- 0.3 vs. 1.5 +/- 0.3 ng/ml/h), or the plasma concentrations of ANP (10.0 +/- 0.9 vs. 10.7 +/- 0.6 pg/ml); AVP (0.7 + 0.7 vs. 1.4 +/- 0.4 pg/ml); ALDO (39.2 +/- 10.3 vs. 22.7 +/- 4.6 pg/ml); or ET-1 (0.23 +/- 0.04 vs. 0.18 +/- 0.03 pg/ml). Exercise significantly increased PRA and the concentrations of ANP, AVP, and ALDO in both groups of horses; however, ET-1 was not altered (P > 0.05) by exercise in either group. There were differences (P < 0.05) between means obtained from the old and young groups for PRA (5.4 +/- 0.6 vs. 3.9 +/- 0.8 ng/ml/h and the concentrations of ANP (14.5 +/- 2.3 vs. 26.5 +/- 9.0 pg/ml), AVP (13.6 +/- 0.3 vs. 26.1 +/- 13.9 pg/ml, and ALDO (76.8 +/- 22.0 vs. 41.5 +/- 4.9 pg/ml) measured in samples obtained at the speed eliciting VO2max. These data suggest that older horses have an age-altered endocrine response to exercise.