Original Research
Improved Ability to Maintain Fitness in Horses During Large Pasture Turnout

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Abstract

The objective was to compare horses' maintenance of fitness during extended periods of no forced exercise with that after stall confinement. Horses were divided into three groups: pasture turnout (P), stalled and exercised (E), or stalled with no exercise (S). Pre- and post-study body fat and bone mineral content were estimated, and horses performed a standardized exercise test (SET). Horses wore global positioning units to estimate distance traveled. The P group traveled a greater distance daily compared with the E and S groups (P < .01). Lateral bone density was greater for the P group after the study (P = .05). Comparing first and second SETs, the P group had lower heart rates at the trot (P < .01) and hand-gallop (P = .028), the E group had lower heart rates at the hand-gallop (P < .01), and the S group had higher 1-minute recovery heart rates (P < .01). Plasma lactate concentrations were higher at the peak of exercise (P < .01) and 10-minute recovery (P = .015) for the S group, whereas the P and E groups had lower rectal temperature at the peak of exercise (P = .029) and 10-minute recovery (P = .031 and P = .041, respectively). These data suggest that the S group lost fitness, whereas the P group remained as fit as the E group. The improvement for the P group compared with the E or S group was greater bone mineral content. Access to pasture appears to help maintain bone strength and exercise fitness ability.

Introduction

Maintenance of fitness can be problematic during periods of no forced exercise owing to weather or injury. Horses often lose muscle mass and bone density [1] during these detraining periods. Horses confined to stalls have limited movement, and this may exacerbate the problem. Serrano et al. [2] observed that previous improvements in conditioning adaptations such as hypertrophy of type IIA muscle fibers, increases in aerobic muscle enzymes, and increases in capillary density were reverted with 3 months of detraining. McGowan et al. [3] observed a decrease in the time to fatigue, a decrease in the VO2 max, and a decrease in buffering capacity in horses during detraining.

These detraining effects could delay the return to previous fitness levels and interfere with training progress [4]. The objective of this study was to compare the horse's ability to maintain fitness levels during an extended period of pasture turnout with no forced exercise with that after stall confinement with either no forced exercise or daily forced exercise.

Section snippets

Horses and Exercise

Sixteen horses of light horse type averaging 591.1 ± 10.4 kg and 16.4 ± 1.2 years of age were randomly divided into three groups: pasture turnout (P; n = 6), stalled and exercised (E; n = 5), and stalled with no exercise (S; n = 5). All of the horses had previously participated in 12 weeks of 1-2 hours of light-to-moderate exercise per day in the college's riding program. Following this period, the P group was turned out into an approximately 100-acre pasture, which could be described as

Results

Horses maintained body weight and body condition score during the study. Horses averaged 591.1 ± 10.4 kg at the start of the study and 594.9 ± 11.2 kg at the end of the study. Not surprisingly, the P group horses traveled a greater voluntary distance (10.76 ± 0.4 km) on a daily basis during their turnout compared with either the E group (5.09 ± 0.4 km) or S group (4.51 ± 0.4 km) (P < .01). It should be noted that the E group would have also have had forced exercise, which would increase the

Discussion

It appears from the data that the horses in the S group lost fitness over the course of the 14-week period. This is supported by the increase in recovery heart rate during the second SET as well as elevated plasma lactate concentrations at peak and recovery times in the second SET compared with the first. The P horses remained just as fit as the E horses with the amount of voluntary movement in the pasture compared with the amount of forced exercise in the E group between SETs. Lower heart

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