Increase of fat-free mass and low percentage of body fat in Brazilian sport horses training under tropical climate

This study aimed to determine the subcutaneous fat layer thickness, percentage of body fat, fat mass, and fat-free mass of Brazilian sport horses at different levels of training for and competing in eventing and the effects of a tropical climate in the body composition of athletic horses. The study included 17 Brazilian sport horses aged between 4 and 10 years. Group 1 included young horses aged from 4 to 6 years training for Fédération Equestre Internationale (FEI) one-star events, and group 2 comprised adult horses aged from 7 to 10 years in training for FEI two-star events. The training protocol comprised exercise for 5 days a week for 60 min, including flatwork, aerobic conditioning, and jumping, both track and natural obstacles. The equines were weighted, and rump fat layer was determined by measuring the thickness of subcutaneous adipose tissue at the region of the gluteus medius muscle using ultrasound. The ultrasound evaluation was performed at the end of the equestrian season, which lasted 9 months. An increase in the body weight, fat layer, percentage of body fat, fat mass, and fat-free mass was observed in group 2 compared with the overall group and group 1, although the difference was not statistically significant (p>0.05). Despite the important increase in the percentage of body fat between young and adult horses, 4.87±1.22% and 5.64±1.90% found in group 1 and 2, respectively, it did not differ statistically (p=0.3775). This fact may contribute to a decline in their performance because fat can be a key source of energy. Lower mean values of all parameters were observed in group 1 than in group 2. In conclusion, Brazilian sport horses training for and competing in eventing under tropical conditions have the body composition accustomed for this equestrian discipline. Brazilian sport horses training for and competing in eventing have high values of fat-free mass and low percentage of body fat and fat mass, demonstrating the athletic capability of these horses. There were no significant changes in the body condition of young and adult Brazilian sport horses. A hot, humid environment led to an increase of weight and body condition.