The base values of some proteins taken before horses enter training may later prove beneficial in assessing the horse’s readiness to race, according to researchers.
Jowita Grzędzicka and her fellow researchers said inadequate conditioning or sudden increases in workload can strain the musculoskeletal system of horses, resulting in the weakening of locomotor structures or overtraining.
This may contribute to the production of fatigue fractures.
Injuries in horses, such as fractures or tendon and ligament injuries, can have severe consequences, including euthanasia due to the inability to recover.
Musculoskeletal injuries in horses often result from a combination of several factors. Proper management, regular veterinary care, appropriate conditioning, and a balanced approach to training can help minimize the risk of musculoskeletal fatigue injuries in horses.
“Also, detecting the point of balance between inflammatory processes and repair mechanisms that may represent an appropriate or an inappropriate adaptive response is beneficial for horses’ health and welfare management.
“It should be recognized that this point is likely to be different for each horse,” they said, “and not only because there will be differences in training strategies.”
Clinical monitoring of fitness and performance in horses can be supported by the analysis of various blood parameters, they said. These biomarkers provide vital information about physiological status, training adaptability, and overall health.
“However, there is no single suitable biomarker that would allow for the detection of fatigue disorders at the early stage of their formation.”
The researchers, writing in the journal Agriculture, noted the findings of a recent study in which more than 1000 racehorses were evaluated, with three potential blood markers selected.
It was suggested that the insulin-like growth factor 1 (IGF1), interleukin-1 receptor antagonist (IL-1ra), and matrix metalloproteinase 2 (MMP2) mRNA expression may enable the early detection of horses at risk of injuries.
However, in other studies, it was suggested that cytokine concentrations indicate the athlete’s status better than mRNA expression in blood cells.
There is, they noted, a lack of studies connected with the evaluation of IGF1, MMP2, and IL-1ra changes in protein levels during different types of exercise load in racehorses.
The study team, all with the veterinary institute at the Warsaw University of Life Sciences, set out to evaluate changes in IGF1 and MMP-2, as well as novel markers such as interleukin-13 (IL-13) after exercise in horses at different fitness levels, as well as after different intensities of exercise.
The research centered on 23 Arabian horses and eight Thoroughbreds. They were divided into an inexperienced (beginner) group and an experienced (advanced) group, based on their level of training.
Differences between racing and training sessions were evaluated to see the influence of different intensities of exercise.
Blood samples were taken before and after exercise.
The researchers found that basal IGF1 and IL-13 concentrations were lower in the inexperienced group when compared to the experienced group.
There were no differences found between pre- and post-exercise samples, nor between training and racing effort.
Changes in these proteins do not occur shortly after exercise, they said. Thus, basal values may appear to be more beneficial in forecasting horse fitness levels.
The researchers said further investigation into the mechanisms underlying IGF1’s effects on exercise and optimizing exercise protocols to maximize IGF1 responses is needed not only in horses but also in humans. Its primary role, they said, is the stimulation of muscle growth by muscle protein synthesis promotion or the activation of satellite cells
MMP2, also known as gelatinase A, is an enzyme that plays a crucial role in tissue remodeling and repair. The balance between MMP2 activation and inhibition is crucial for maintaining tissue integrity during exercise.
Previous research has shown that MMP2 expression in injured horses was significantly elevated. “In our study, we did not observe any changes in the MMP2 serum concentration.”
However, the study involved only healthy horses. Thus, the increased activity of MMP2 may occur only in animals with injuries or overtraining syndrome.
“In this context, an evaluation of the MMP2 changes in overtrained horses may be useful for the prevention of fatigue injuries.”
IL-1ra is considered an anti-inflammatory cytokine, and its elevated levels can be a response to counteract the pro-inflammatory effects of other cytokines. Thus, there is a potential use of IL-1ra in preventing injury, especially in endurance horses.
The authors said the importance of understanding the factors that contribute to overtraining and musculoskeletal injuries in horses should be highlighted.
“However, comparing all studies investigating various blood biomarkers’ responses to exercise seems to be difficult due to the differences in the experimental design and examined animals.
“Thus, more studies are required to determine the exact effect of proposed blood biomarkers, since there are still numerous differences among the published data.”
The study team comprised Grzędzicka, Izabela Dąbrowska, Paula Kiełbik, Maciej Perzyna and Olga Witkowska-Piłaszewicz.
Grzędzicka, J.; Dąbrowska, I.; Kiełbik, P.; Perzyna, M.; Witkowska-Piłaszewicz, O. Are Proteins Such as MMP2, IGF1, IL-13, and IL-1ra Valuable as Markers of Fitness Status in Racehorses? A Pilot Study. Agriculture 2023, 13, 2134. https://doi.org/10.3390/agriculture13112134
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