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Effect of long-term oral administration of a low dosage of clenbuterol on body fat percentage in working and nonworking adult horses

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  • 1 Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.
  • | 2 Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.
  • | 3 Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.
  • | 4 Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.
  • | 5 Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.
  • | 6 Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348.

Abstract

OBJECTIVE To determine the anabolic and lipolytic effects of a low dosage of clenbuterol administered orally in working and nonworking equids.

ANIMALS 8 nonworking horses and 47 polo ponies in active training.

PROCEDURES Each polo pony continued training and received either clenbuterol (0.8 μg/kg) or an equal volume of corn syrup (placebo) orally twice daily for 21 days, and then was evaluated for another 21-day period. Nonworking horses received clenbuterol or placebo at the same dosage for 21 days in a crossover trial (2 treatments/horse). For working and nonworking horses, percentage body fat (PBF) was estimated before treatment and then 2 and 3 times/wk, respectively. Body weight was measured at intervals.

RESULTS Full data sets were not available for 8 working horses. For working horses, a significant treatment effect of clenbuterol was detected by day 3 and continued through the last day of treatment; at day 21, the mean change in PBF from baseline following clenbuterol or placebo treatment was −0.80% (representing a 12% decrease in PBF) and −0.32%, respectively. By day 32 through 42 (without treatment), PBF change did not differ between groups. When treated with clenbuterol, the nonworking horses had a similar mean change in PBF from baseline from day 6 onward, which peaked at −0.75% on day 18 (an 8% decrease in PBF). Time and treatment had no significant effect on body weight in either experiment.

CONCLUSIONS AND CLINICAL RELEVANCE Among the study equids, long-term low-dose clenbuterol administration resulted in significant decreases in body fat with no loss in body weight.

Contributor Notes

Address correspondence to Dr. Nolen-Walston (rnolenw@vet.upenn.edu).