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11 September 2015 THE HORSE TheHorse.com For additional news items, see TheHorse.com/News Social Status in Horse Herds They might not be on Facebook yet, but horses do have their own sort of "social network," says one French equine behavior researcher. And the resulting relationships, which are highly dependent on the particular characteristics of individuals in the group, are solidly structured. Dominant horses, for example, are typically older, larger, and less fearful than other horses, said Mathilde Valenchon, PhD, of the French National Centre for Scientific Research, in Strasbourg. "Central" horses—those that tend to create multiple friendly relationships within the herd— tend to be more gregarious and sociable, she said. She also determined that central individuals are not necessarily the dominant ones, such as in other mammalian groups (primates, for example). "These data … show that equine groups are structured with complex social networks based on stable relationships of dominance and affinity," Valenchon added. The results also highlight the importance of respecting a group's stability in a practical sense, she said. This means not adding or removing horses to or from a herd frequently. Learn more at TheHorse. com/35991. —Christa Lesté-Lasserre, MA Equine grass sickness (EGS) affects horses' central and peripheral nervous systems and results in an array of char- acteristic clinical signs (including weight loss and a "tucked up" abdomen). It almost exclusively affects grazing horses. The disease takes three forms, based on the duration of clinical signs: acute (one to two days), subacute (two to seven days), and chronic (more than seven days). Extensive neuronal degeneration in the acute and subacute forms causes intesti- nal dysmotility, which is often deadly. But some horses with the chronic form, hav- ing less severe neuronal degeneration, can survive. First reported in 1909 in Scotland, EGS has been re- ported throughout the U.K. and Northern Europe. Suspected cases have also been reported in the Falkland Islands and Australia, and it was recently described in a mule in the U.S. (largely considered EGS-free). A clinically and pathologically identical disease, called mal seco, occurs in South America. Learn more about the clinical signs, treatment methods, and prognoses at TheHorse.com/36149. —Anne Couroucé-Malblanc, DVM, PhD, Dipl. ECEIM, WEVA Secretary Assessing Learning Abilities of Little Ones Researchers have developed various tests for evaluating a horse's ability to learn, but until now they hadn't looked at whether those same tests are effective in determining a foal's learning abilities. Such tests would allow scientists to predict a horse's potential, from an early age, to become a good learner in his or her future career. Line Peerstrup Ahrendt, PhD, of Aarhus University, in Denmark, and col- leagues recently tested 21 weaned foals (aged 30 to 50 weeks) in four learning tasks: a pressure-response test, a clicker test, and two food-based tests. Learn more about the tests at TheHorse.com/36016. Overall, foals responded well to the pressure-response test, learning over time that they should move away with less pressure, Ahrendt said. The clicker test produced fairly effective results, with wide variation among foals. But most of the foals lost interest in the first of the treat-related tests, which she said could be because they were not motivated by food rewards. Ahrendt said her team is revising the food-based tests in response to the lack of motivation for food rewards and investigating an additional 45 foals using the revised tests. While preliminary results suggest the pressure-response test and the clicker test worked well in foals, there was no real correlation between the two tests. In other words, foals that did well in one test did not necessarily do well in the other, she said. This could be discouraging, but Ahrendt remains optimistic that she'll find a way to test learning ability. "I may just be finding different learning abilities in these tests," she said. —Christa Lesté-Lasserre, MA ISTOCK.COM ISTOCK.COM Researchers recently examined whether unshod dressage horses are at a competitive disadvantage to those wearing shoes. Richard Mott, BSc, of Warwickshire College, in England, and colleagues investigated 20 adult Irish Sport Horses as they trotted in a fber/ sand arena. Half the horses were shod—and had been shod for at least the past year—and the other half had been barefoot for just as long. The researchers captured the movements on video and analyzed the gaits via a commercial gait analysis software program. Mott and colleagues found no signifcant differences between shod and barefoot horses when looking at four of the fve kinematic variables that affect dressage scores—stride duration, fetlock extension, scapular rotation, and elbow fexion. He said the study only relates to horses at a novice level and below and that his results allow for many interpretations. "There are a lot of assumptions that can be made from my work," he said. "But the only proven statement I can make is that you'll be no worse off being unshod, but it doesn't necessarily follow that you'll be better off without shoes." More study fndings are available at TheHorse.com/36010. —Christa Lesté-Lasserre, MA SHOD OR NOT? SCIENTISTS LOOK AT DRESSAGE HORSE MOVEMENT Equine Grass Sickness: What You Need to Know COURTESY CISCO-ONIRIS Horses with EGS often have a "tucked up" abdomen. ISTOCK.COM