Playtime Builds a Foal’s Bones
A playful foal hops, leaps, rears, attacks, threatens to bite and kick, and flees imaginary predators. But his behavior isn’t just a cute and charming show for his breeders (or seemingly a nuisance for his dam who gets caught in his line of fire every now and then). According to New Zealand researchers, foal play has a critical role in musculoskeletal development.
By building up strong, resistant tissues through natural play, horses have a better chance of becoming “sustainable” athletes later in life, said Chris Rogers, PhD, Associate Professor at the School of Veterinary Science at Massey University in Palmerston North, New Zealand.
“Modern [horse breeding] systems need to provide appropriate opportunities for foals to perform spontaneous locomotor play to optimise bone development and reduce the risk of future musculoskeletal injury later in life,” he stated in his recent publication in Animals.
“Early exercise (in the form of play) provides a positive platform for not just the musculoskeletal system, but also metabolic programming, as we’ve seen in studies in other mammalian species, and in humans it can reduce the risk of diabetes in later life,” Rogers told Horses and People. “So juvenile play really has far-reaching consequences.”
Rogers and his colleague Keren Dittmer, PhD, also of Massey University, carried out a review of scientific literature—including several of their own studies—on juvenile play in mammals, in particular horses. A common theme they noted was that the play activity had a direct relationship to a healthy “mechanostat”—the way mechanical loading on bone affects its structural mass and architecture, creating, essentially, more sustainable bone over the long term.
While general exercise, including walking long distances, trotting, and grazing, are important for proper musculoskeletal growth, play offers a different bodily challenge, said Rogers. In play, horses have bursts of “dramatic,” intense, high-energy movement with various bodily positions placing particular kinds of strain on the musculoskeletal system that they wouldn’t get from just normal locomotion.
In natural settings, this would allow them to be prepared for immediate needs to flee predators, but also to sustain the strains of physical activity related to reproduction, Rogers said. In a domestic setting, this same play activity could prepare the musculoskeletal system for the demands of equestrian sport, with both immediate effects as well as cellular-level effects that can last a lifetime.
While that need for play appears critical in early life, it seems that even adult horses could benefit from play, he added. “(Ongoing play throughout life) may be very important to maintain musculoskeletal health,” said Rogers. “Given that play appears to provide strain rates in the appropriate zone to stimulate bone, it may be that horses are inherently primed (part of evolutionary programming) to use play to maintain bone so it can tolerate the loads exposed to when the horse is required to flee from predators.”
Structured exercise is important for domestic horses—but it can’t replace the benefits of play, in both youngsters and adults, according to Rogers. “The advantage of play is that it permits the foal to provide its own feedback loop on strain and recovery,” he said. Furthermore, female horses often have different kinds of play compared to male horses, which could be nature’s way of preparing each sex for the unique challenges it will face throughout life.
Depriving horses from opportunities to play—by keeping them confined in small areas and/or separated from other horses their age—could hinder proper musculoskeletal development, he said. However, science has not yet uncovered to what extent foals can be immobilized without significant effects on their long-term health. It’s also not yet known how much they can “catch up” after periods of confinement (for example, after an illness or injury).
“For us this is still the big unknown,” he said. “It does appear from a developmental pathway perspective that some tissues in the horse remain receptive to stimuli up to puberty or even two year old, but for tissue such as cartilage it may be somewhere between birth and six months. At present we lack data on the long term effect that temporary restriction of activity has on the tissues’ developmental potential.”
In addition to musculoskeletal reinforcement, play allows horses—especially juveniles—to develop social skills (including with regard to their sexual development) and experience good welfare, Rogers explained.
“The differences in play activity and play type between colts and fillies implies that play is important for tissue but also for social skills and, in the long term, ‘fitness,’—meaning, the ability of the individual to be best prepared to function effectively and reproduce,” he said. “From a welfare point of view, play appears to be hard wired as a necessary activity, so inability to perform play activity may be a compromise of welfare.”