Wobbly legged foals might be able to walk within an hour of birth, but that doesn’t mean they’re experts at coordinated movement. In fact, a new study by Dutch and Belgian scientists suggests it can take several months for young horses to develop their gaits, with varying speed and impulse. And those gaits can show significant changes in peak force when the foal has osteochondral lesions.

“Although foals can stand and walk impressively fast, they do not move as ‘small adult horses,’” said Ben Gorissen, DVM, a PhD candidate in the Utrecht University Faculty of Veterinary Medicine Department of Pathobiology Division of Anatomy and Physiology, in the Netherlands. “In a very precocious animal such as the horse, gait development takes time.”

“Furthermore, our research shows that at the acute phase of the disease, osteochondrosis causes pain and, with that, a subclinical lameness, which can be diagnosed with objective gait analysis,” Gorissen said.

In their study, Gorissen and his fellow researchers measured the hoof pressures and forces applied by 11 Dutch Warmblood foals at the walk and the trot during their first 24 weeks of life. Handlers led the foals over pressure plates that detect peak vertical forces (the maximum downward force of the hoof when it strikes the ground), vertical impulses (vertical force related to the time the force lasts), and stance duration (how long the hoof stayed on the ground during each step). Because the foals were growing, the scientists “normalized” the measurements, meaning they used algorithms to adjust them according to the growing body mass.

They also took X rays of the tarsocrural (part of the hock) and femoropatellar (part of the stifle) joints when the foals were four and six weeks old and six months old to screen for osteochondrosis lesions.

They found that for both walking and trotting, the young horses’ speed and vertical impulse increased as they aged, Gorissen said. By contrast, however, normalized peak vertical forces remained essentially the same. While it might seem contradictory for vertical forces to remain constant while speed increases, the researchers explained this is probably due to the growing limbs—longer limbs increase speed mechanically through an increased stride length, without necessarily increasing the normalized vertical forces. Also, those forces can be somewhat fixed due to limb stiffness, they added, which resolves as the horse matures.

In foals with osteochondrosis lesions, however, those normalized peak vertical forces dropped somewhat in the affected limb, he said. None of the foals showed signs of lameness, but they did clearly reduce their unilateral weight-bearing, according to the pressure plate measurements. This finding could be useful as a screening measure for foals at a higher risk of developing osteochondrosis dissecans, said Gorissen.

“Objective gait analysis, in this case a pressure plate, is much more sensitive to detect subtle changes in limb loading than is the human eye,” he said. “As shown in my study, foals were not visually lame at walk and trot in a straight line on a hard surface. However, we were able to show a significant reduction in limb loading around the onset of osteochondrosis (which has been shown to be a very dynamic condition).

“This would mean that a pressure plate could be used as a first screening tool to check for subtle problems in the locomotor system,” he continued. “Foals showing a sudden reduction in limb loading could then be examined further and appropriate action, for example box rest, could be taken based on this presumptive, merely objective differential diagnosis.”

The study, “The development of locomotor kinetics in the foal and the effect of osteochondrosis,” was published in the Equine Veterinary Journal