CA.UKY.EDU/EQUINE ❙ THEHORSE.COM ❙ JUNE 2017 Researchers Review Muzzled Horse Behavior n owner’s No. 1 goal when outfitting their horse with a muzzle is usually related to A weight management—either keeping them from gaining weight or helping them shed some pounds. While study results have shown that muz- zles are, indeed, effective for weight control, they can also have other effects. For instance, they can alter horse behavior. However, few studies have docu- three for six hours) ITH LARSON E mented exactly how muzzling impacts for one hour, two K behavior. So, Ashley Fowler, MS, days per week, for five Studies have shown that horses appear to adjust to wearing and colleagues at the University of weeks. The researchers grazing muzzles in two to three weeks. Kentucky, in Lexington, conducted a watched their unmuz- study to compare the behavior of 12 zled behavior for the first week, then horses was not recorded, so the differ- horses when they were muzzled and monitored their muzzled behavior for ence in total movement is unknown.” unmuzzled. She presented the results Weeks 2 through 5. The team tested She said additional studies using pe- at the 2017 Equine Science Society closed-bottom muzzles that prevented dometers could help shed light on the Symposium, held May 30-June 2, in feed ingestion, but allowed water con- total movement and energy expendi- Minneapolis, Minnesota. sumption. ture between muzzled and unmuzzled Fowler and colleagues observed “We used total exclusion muzzles horses. the horses (turned out in groups of because some horses become really Additionally, the team observed that adept at grazing through muzzles that muzzled horses rubbed their grazing contain a hole,” Fowler explained, “so muzzles and pawed more frequently much so that they can continue to gain during the first two weeks of muzzling weight even while wearing a muzzle. compared to the last two weeks. Fowl- For these horses, exclusion muzzles er said this suggests it took the horses are a good option to still allow horses about two weeks to acclimate to wear- access to turnout, for exercise—which ing the muzzles. Unmuzzled horses did could encourage further weight loss— not have muzzles to rub, she added, and socialization.” and pawed very infrequently. The team found that: She also noted that the team ob- ■ When unmuzzled, horses foraged served altered drinking behavior when 52% of the time, stood 41% of the time, and walked 6% of the time; and In This Issue ■ When muzzled, horses stood 81% of the time and walked 16% of the time. Parasite Control: An Update 02 Although horses spent more time Nocardioform Placentitis 04 walking around their paddocks when muzzled, they also more than doubled ERICA LARSON Equine Summit Recap 05 the time they spent standing, Fowler When wearing muzzles, horses spent 81% of their time standing and 16% of their said. She cautioned that “movement Farm and Facilities time walking. during grazing bouts in unmuzzled Expo Recap 09 1 Bluegrass Equine Digest ❙ ca.uky.edu/equine ❙ TheHorse.com ❙ June 2017 Muzzled Horse Behavior Fowler cautioned that “these horses wore total exclusion muzzles; muzzles Masthead that allow reduced foraging might have horses wore muzzles. different effects on behavior.” ■ University of Kentucky Ag Equine “During the first week of muzzling, Muzzle use remains an effective Programs horses increased the number of times equine weight-management strategy Jenny Evans, MFA, co-managing editor and they visited the water trough,” she that many owners employ daily. senior veterinary science marketing and said. “While we didn’t measure water “Make sure that muzzles are well- promotion specialist, jenny.evans@uky. consumption, we suspect that instead fitting and sufficiently padded,” Fowler edu of drinking, horses were playing in the advised. “Ill-fitting muzzles can cause Holly Wiemers, MA, APR, co-managing edi- water or attempting to remove their sores (especially when the horses are tor and communications director of UK muzzles in the trough because we didn’t trying to rub their grazing muzzles off) Ag Equine Programs, holly.wiemers@ see an increase in the frequency of uri- and could also make it easier for the uky.edu nation with the increase in visits to the horse to remove the grazing muzzle.” ■ Bluegrass Equine Digest water trough.” She also encouraged owners to wait Advisory Board Finally, Fowler said the team ob- out the horse’s acclimatization period, served more social interactions when even if he develops new behaviors. Bob Coleman, PhD, PAS, associate profes- sor, director of undergraduate studies horses were muzzled than when they “Horses appear to adjust to muzzling for equine science and management were unmuzzled. within two to three weeks,” she said. and extension horse specialist “Because horses aren’t able to graze “If an owner sees a horse rubbing their David Horohov, MS, PhD, chair of UK's anymore, they must fill their day up muzzle or pawing a lot during the first Department of Veterinary Science with other behaviors, and increasing couple weeks of daily muzzling, they and director of the UK Gluck Equine social interactions is one way to do shouldn’t give up. It is likely that the Research Center so,” she said. “So even though horses horse will reduce these behaviors in a Michael “Mick” Peterson, PhD, director of do spend more time standing around couple weeks.” UK Ag Equine Programs and professor outside when they are muzzled, at least in the department of biosystems and agricultural engineering they are able to have social interaction.” >Erica Larson is the news editor for The Horse. Ray Smith, PhD, professor and forage extension specialist in the department of plant and soil sciences Jill Stowe, PhD, associate professor in the Parasite Control: department of agricultural economics An Update ■ Bluegrass Equine Digest nternal parasites of horses Editorial Committee Ihave been recognized for Craig Carter, DVM, PhD, Dipl. ACVPM, centuries. But until the early director and professor of the UK 1900s, methods for the control Veterinary Diagnostic Laboratory Laurie Lawrence, PhD, professor in of equine endoparasites lacked the department of animal and food a scientific basis. For example, sciences in the 1600s one recommenda- Krista Lea, MS, coordinator of UK’s Horse tion was to incise (cut with a Pasture Evaluation Program in the de- surgical instrument) the horse’s partment of plant and soil sciences palate with the intent that the Martin Nielsen, DVM, PhD, Dipl. EVPC, ingested blood would kill any ACVM, associated professor at the UK internal parasites. Beginning Gluck Equine Research Center I K in the 1940s and extending ■ The Horse: Your Guide To to the 1980s, new classes of Equine Health Care N M. JANIC N M. antiparasitic compounds were E Erica Larson, News Editor developed approximately every KRIST Brian Turner, Layout and Design 10 years. There are only three classes of dewormers—benzimidazoles, Currently in the United tetrahydropyrimidines, and macrocyclic lactones—available States, only benzimidazoles in the United States for controlling equine parasites. The Bluegrass Equine Digest is a registered trademark of the University of Kentucky Ag Equine Programs (fenbendazole and oxibenda- and Gluck Equine Research Center. The Bluegrass zole), tetrahydropyrimidines (pyrantel pamoate and pyrantel tartrate), and macro- Equine Digest is produced by the University of cyclic lactones (ivermectin and moxidectin alone or combined with praziquantel) Kentucky in partnership with TheHorse.com and sponsor Zoetis. It is published monthly to provide are commercially available for parasite control in horses. up-to-date information on equine research from The major endoparasites of horses include bots, large strongyles, small stron- the University of Kentucky’s College of Agriculture, gyles or cyathostomes, ascarids, and tapeworms. Large strongyles (Strongylus spp) Food and Environment. Research material is meant are one of the most significant equine parasites. The larval stages can cause dis- to be shared. However, materials are copyrighted and require reprint permission from UK Ag Equine ease due to migration in blood vessels and abdominal organs. Drug resistance is Programs. Past issues of the Bluegrass Equine Digest not evident in the case of large strongyles. are available at www2.ca.uky.edu/equine/bed. 2 Bluegrass Equine Digest ❙ ca.uky.edu/equine ❙ TheHorse.com ❙ June 2017 Parasite Control Update Commentary The Future of Parasite Control? Cyathostome larvae do not Dr. Gene Lyons (PhD) provides a brief review of the history and current status of anthel- migrate parenterally like Strongy- mintic treatment of important equine gastrointestinal parasites. No new anthelmintics with lus spp, but encyst in the mucosa newer modes of action have been introduced since the early 1980s, and levels of anthel- and submucosa of the horse’s large mintic resistance are ever increasing in cyathostomin and Parascaris spp parasites. While intestine. Intestinal disease can resistance is slow to develop, work by Lyons has clearly illustrated that once it appears in a be induced by cyathostomes when given parasite, it is there to stay. large numbers of larvae excyst Today, we can expect resistance to at least one drug class to be present in every equine from (exit) the lining of the large operation across the world, and an overwhelming majority will feature multi-drug resistance. intestine, a condition called “larval With only three classes to choose between, we are running out of treatment options. A perti-