By Judy O'Brien Van Put
SULLIVAN COUNTY January 7, 2003 Ah, those annoying vices that horses sometimes "develop". Wood chewing, cribbing, stall weaving and the like can become a bothersome problem, and frustrating to try to overcome.
However, a recent study in England may shed new light on stable vices, and even suggests that these irritating habits appear with surprising frequency among foals sometimes as young as two months of age! An article in the January issue of Equus magazine provides interesting information on this study, which was conducted at the University of Bristol.
Research was based on 225 young thoroughbreds and part-thoroughbreds, from the time they were foals through the age of four years. The researchers observed the young horses for a total of 20 hours, before, during and just after weaning, documenting each subject's behavior as well as its diet, stable routine and herd interactions. After weaning, their caretakers were asked to answer questionnaires about each horse's behavior and care and were requested to report immediately the onset of any stable vices, also known as "stereotypes." If an abnormal behavior was reported, the researchers visited the farm to confirm it, and to collect further data. In addition, the researchers visited farms randomly to observe the study horses.
It was found that approximately 35 percent of the study horses developed at least one stable vice, according to Christine Nicol, MA DPhil., who conducted the study with PhD student Amanda Waters. Nicol says that most interesting was what the data seemed to reveal about the "roots" of the most common stable vices, cribbing, wood-chewing, weaving and stall-walking.
Cribbing, which involves grabbing onto a surface and "gulping" air, appeared relatively early in approximately 10 percent of the study horses. When first noticed, the median age (the age found in the middle of all the ages noted at the onset of the habit) was 20 weeks. Nicol relates, "The crib-biting data are amazing. No one can believe that half the foals that started to crib-bite did so before they were 20 weeks old. And the youngest foals were only two months old when they began to crib. I think this means that breeders need to look out for the earliest signs of crib-biting foals even before they are weaned."
She added that the data indicated a strong link between cribbing and feeding concentrates: young horses who received sweet feed, oats and other high-energy rations were four times more likely to start cribbing.
Wood-chewing was reported in 30 percent of the study horses, beginning at a median age of 30 weeks. In the development of this vice, confinement seemed to play a greater role than diet. "Feeding haylage (hay that is specially processed and baled soon after cutting) rather than hay increased the risk of wood-chewing nearly threefold, but keeping foals in barns rather than at pasture increased the risk of wood-chewing even more nearly fivefold," according to Dr. Nicol.
Weaving, which is the side-to-side shifting of weight while standing still, was observed in 4.6 percent of the horses, with the median age of onset at 60 weeks, and stall-walking was seen in slightly more than two percent of the horses at a median age of 64 weeks.
"Weaving and box-walking tended to develop when horses were sold to new yards or kept confined for long periods over their first winter," Dr. Nicol said. "The foals tend to be older when this happens. The particular trigger appears to be social isolation."
The coincidence of vices was also influenced by social interaction. The foals of dominant mares were much more likely to crib or chew wood than foals of low- or middle-ranking mares. Dr. Nicol believes this may reflect the tendency of these mares to limit the suckling time of their foals. "We have separate data that show that mares vary in how long they allow their foals to suckle, and this may be linked to mare rank," she stated. "Suckling may be a protective behavior its benefits are not just nutritive gain, but comfort and security." When not allowed to comfort themselves through suckling, the foals may turn to other oral behaviors, such as cribbing.
To try to prevent these vices from occurring, the researchers recommend that foals be turned out as much as possible, even during the weaning process. They also recommend the gradual introduction of hay replacers and concentrates to a young horse's diet, along with free-choice hay.