New research from Europe suggests that castration can be performed on colts without adverse effects far earlier than previously thought—even at 3 days of age.
Colts are generally castrated at 12 to 18 months old. But, says Stefan Deleuze, DVM, PhD, of the Université de Liège in Belgium and the INRAE of Nouzilly, France, the reasons behind this custom are unclear: “I presume it is based on the belief the body needs the hormones of puberty to achieve full development.”
In addition, he says, some owners believe delaying castration until puberty is crucial to a horse’s mental development. “They believe colts need to be at least pubertal at the time of castration if you don’t want to have a horse who is slow and sluggish.”
Physical and mental development
To study the effects of castration, Deleuze and his team selected 22 male Welsh ponies. The researcher gelded half of the youngsters at 3 days old, and the rest at 18 months old. All the ponies underwent similar castration procedures under general anesthesia.
The researchers weighed and measured the youngsters monthly from birth until 8 months of age, then every three months until they turned 2 and every six months until age 3.
They also performed temperament tests—including responses to novel objects and reactivity to humans—on the study horses when they were 1 and 3 years old.
The resulting data challenges the notion that the influx of hormones at puberty is necessary for normal growth and maturation. The researchers found no differences— at any age—between the two groups in terms of physical development or temperament.
“Temporary exposure to steroids at puberty doesn’t seem to be necessary to have a better gelding,” says Deleuze. He adds that early castration did not appear to affect the mare-foal bond.
Monitored for three years
The researchers monitored the study horses for only their first three years but, says Deleuze “I would guess that their health thereafter would depend more on their management and training than age at castration.”
What’s more, early castration has potential benefits, he says. “Although routinely performed, castration is not without risk. Bleeding, eventration [herniation] and fracture when the animals recover from general anesthesia are possible,” he says. “Performing castration at a very early age lessens these risks.”
Deleuze says he doesn’t expect a widespread interest in castrating horses earlier, but this study can help veterinarians advise owners in situations where it may be beneficial.
A previously overlooked option
“Popular beliefs are strong and live long, so I don’t expect a rapid change in horse farm management,” he says. “However, our study now gives us scientific ground to say that early castration does not adversely impact the horses. It is easier and somewhat safer to perform.”
Reference: “Early castration in foals: Consequences on physical and behavioural development,” Equine Veterinary Journal, April 2022