Asymmetry of movement was triggered in Icelandic horses which became heavier and put on weight, the researchers report.
The animals in the study, all geldings, also showed signs of reduced fitness, and their performance was rated worse in a breed assessment test by the judges.
The study by Anna Jansson and her fellow researchers, reported in the journal Physiological reports, set out to examine the effect of changes in body weight and body fat content on physical performance and recovery.
Nine Icelandic horses were divided into two groups, and changes in body weight and fat content were induced by feeding high or restricted energy intake for 36 days in a cross design.
During the last week of each treatment, body weight and body condition score were recorded, and their body fat percentage was estimated using ultrasound. Each horse was then put through a standardized treadmill exercise test and a competition-type field test, which was scored by the judges.
Blood samples were taken and heart rate (HR), rectal temperature (RT) and respiratory rate (RR) were also recorded.
Objective locomotion analyzes were performed before and after the field test.
Researchers, from the Swedish University of Agricultural Sciences and HÃ³lar University in Iceland, found that the higher energy diet served its purpose: body weights, body fat percentages and body condition scores were higher. from 5 to 8% in horses on the more energetic diet.
In the standardized treadmill test, horses that gained weight and body fat showed a higher heart rate, as well as increases in plasma lactate concentration, respiratory rate, and rectal temperature than horses. restricted diet horses.
The overall results of the blood tests of the heaviest horses were indicative of poorer physiological fitness.
The authors also found that the objective asymmetry of locomotion was higher in the heavier group of horses, based on the sensor measurements.
The second exercise assessment involved a field test simulating a breed assessment field test for Icelandic horses, in which riding skills and gaits are scored by judges. Two certified judges were used in the study.
The judges’ scores for gallop, form under a rider and the total score for riding ability were lower for the heavier horses. Scores for tÃ¶lt and pace showed a tendency to be lower in the heavier horses.
The researchers, discussing their findings, said they believed their study was the first to examine the effect of increased body fat content and body weight on the response to metabolic and physiological exercise and performance in horses in a controlled crossover study.
The results clearly show that an increase in the percentage of body fat, body weight and body condition of 5-8% decreases physiological and metabolic form, based on the parameters evaluated.
“It also impairs actual performance as assessed by treatment blind judges and appears to induce asymmetry of locomotion, measured objectively using a sensor technique.”
They noted that the asymmetry of locomotion seen in the heaviest horses was more pronounced in the forelimbs one day after their performance in the field test.
“This indicates that weight gain may have a negative impact on the locomotive apparatus and that the effect may be magnified after acute exercise.”
The authors stated that higher body fat content and body weight in horses altered metabolic and physiological responses to exercise more than one would expect from increased weight load alone.
“Higher body fat content and body weight in horses also reduced actual performance, caused asymmetry in locomotion, and delayed recovery after exercise.”
The study team consisted of Jansson, Sara Ringmark, Einar Ãsgeirsson, Tanja JÃ³hannsdÃ³ttir and Charlotta Liedberg, all from the Swedish University of Agricultural Sciences; and Vikingur Gunnarsson, Sveinn Ragnarsson, Denise SÃ¶derroos and GuÃ°rÃºn StefÃ¡nsdÃ³ttir, all with HÃ³lar University.
Increased body fat content in horses alters the metabolic and physiological response to exercise, decreases performance and increases asymmetry of locomotion
Anna Jansson, Vikingur Ã Gunnarsson, Sara Ringmark, Sveinn Ragnarsson, Denise SÃ¶derroos, Einar Ãsgeirsson, Tanja R. JÃ³hannsdÃ³ttir, Charlotta Liedberg, GuÃ°rÃºn J. StefÃ¡nsdÃ³ttir
Physiological reports, June 10, 2021, https://doi.org/10.14814/phy2.14824