Bluegrass Equine DIGEST CA.UKY.EDU/EQUINE ❙ THEHORSE.COM ❙ APRIL 2013 Genetic Basis for Establish- Articles of Interest ment of EAV Carrier State Gluck Center Researchers ew research from the Univer- Results of previous studies by Yun Study Ways to Advance sity of Kentucky (UK) suggests Young Go, DVM, MSc, PhD, a for- Breeding Season that genetic factors play a role mer graduate student in Balasuriya’s N AAEP Launches Equine in determining stallion susceptibility to laboratory, identified that horses can Parasite Control Guidelines equine arteritis virus (EAV) infection. be divided into two groups based on Results from the laboratory of Udeni in vitro (in the lab) susceptibility of Graduate Student Spotlight: Balasuriya, BVSc, PhD, professor of their lymphocytes (white blood cells) Krista Cotten virology at the UK Gluck Center, dem- to EAV infection. One group of horses onstrated a correlation between horse had lymphocytes susceptible to in vi- Nielsen Receives Grayson- genetic factors and establishment of tro EAV infection and the other group Jockey Club Grant for EAV carrier state in stallions. Genome- had lymphocytes resistant to in vitro Parasite Study wide analysis shows that equine chro- EAV infection. Based on this finding, mosome 11 (ECA11) carries genes that the investigators hypothesized that Weed of the Month: Spiny Pigweed are likely involved in cellular suscepti- there must be a genetic basis for this bility to the virus. phenomenon. Coat Color Genetics 101 Trimming Feed Costs Video Kentucky Equine Youth Festival Recap Locust Trace Field Day Recap UK Ag Equine Store Upcoming Events tools, they analyzed DNA from each group’s cells to determine which genes might contain markers involved in viral infection of the cell. Of the 310 horses, 167 had the sus- ceptible lymphocytes and 143 had the resistant type. By breed, 95% of the Standardbreds and approximately 90% of the American Standardbreds had the COURTESY GLUCK EQUINE RESEARCH CENTER COURTESY susceptible type. Thoroughbreds and Based on Dr. Yun Young Go's studies, Dr. Udeni Balasuriya and other Gluck Center researchers hypothesized there must be a genetic basis for EAV infection. Quarter Horses had the lowest preva- lence of the susceptible type (23%). Equine viral arteritis (EVA) out- In their study, the researchers ran- Quarter Horses had evenly distributed breaks result in significant economic domly selected 310 horses representing resistant and susceptible cell types. losses to the equine industry due to four breeds (Thoroughbreds, American The genome-wide analysis of EAV high rates of abortions, death in young Standardbreds, Standardbreds, and susceptibility showed that Standard- foals, and establishment of the carrier Quarter Horses) from Kentucky farms. bred horses were most fixed for suscep- state in stallions. Persistently infected They collected blood samples and di- tibility markers, meaning that almost carrier stallions function as the natu- vided them into two groups according all Standardbreds have the genetic ral reservoir of EAV, and they dissemi- to the susceptible and resistant types of markers associated with cell suscepti- nate the virus to susceptible mares at lymphocytes to in vitro infection with bility to EAV. Of the four breeds, Thor- breeding. EAV. Then, using genome-wide analysis oughbreds had the lowest number of 1 Bluegrass Equine Digest ❙ ca.uky.edu/equine ❙ TheHorse.com ❙ April 2013 EAV Carrier State EAV might interact with some of these semen samples using the same tech- cellular proteins to evade the equine im- niques. To continue these studies, we mune response and establish persistent have recently been awarded a $2.9 mil- markers associated with the susceptible infection in some, but not all, stallions lion five-year grant by the United States type. infected with the virus, as only some Department of Agriculture- Agriculture Thoroughbreds have less diversity for stallions become persistently infected and Food Research Initiative to spe- genetic markers than other breeds. By carriers, according to the authors. Re- cifically identify the genetic factors analyzing this breed first, the researchers cently, the same researchers demon- responsible for establishment of the EAV were able to uncover a specific marker strated that stallions with lymphocytes carrier state in stallions.” for lymphocyte susceptibility indicating susceptible to EAV infection might have These papers are available at http://jvi. that EAV infection is highly associated a higher risk of becoming carriers. asm.org/content/85/24/13174 and http:// with the ECA11 chromosome. The genes “These studies can help us develop jvi.asm.org/content/86/22/12407. on this chromosome encode proteins working hypotheses about why horses that are involved in virus attachment become infected, and how persistent >Nancy Zacks is a horse lover and freelance and entry into the cells, the inflamma- infection is established in the stallion,” writer with an MS in Science Journalism from the tory response, and cellular immunity. said Balasuriya. “The next step is to test Boston University College of Communication. Gluck Center Researchers The facemask consists of a leather headpiece Study Ways to Advance with a single blue LED fitted on the inside of a semi-rigid rubber eye cup over the right eye. Breeding Season The mask is equipped with adjustable Velcro down the center of the head piece. Equine Recombinant Fol- A mare’s transition from licle Stimulating Hormone reproductive inactivity dur- University of Kentucky ing the winter to the breeding Veterinarians have devel- and administered either 0.65 Gluck Equine Research Cen- season can be lengthy and oped various management mg of reFSH or a placebo by ter scientists recently stud- complicated. Increased day- and therapeutic strategies random selection. They moni- ied the use of recombinant light suppresses melatonin (a to shift a mare’s first ovula- tored the mares by ultrasound hormones to induce mares’ hormone preventing mares tion of the year from April to until a 35 mm or larger fol- reproductive cyclicity and from cycling in winter) and February. The most common licle developed, discontinued advance the breeding season. allows secretion of reproduc- management is light treat- reFSH treatment, and admin- The study, done in collabora- tive hormones necessary to ment, which should begin in istered human chorionic go- tion with the University of induce ovulation and repro- December for mares to begin nadotropin (hCG) to induce California and Colorado State ductive cycles. Mares under their reproductive cycles in ovulation. All mares treated University, aimed to deter- natural light do not enter the mid-February. with reFSH developed folli- mine the efficacy of an equine breeding season until late “Even housed under artifi- cles after a week, and 23 of 30 recombinant follicle stimulat- April. Their transition pe- cial barn light, the mares may mares in this group ovulated ing hormone (reFSH) in non- riod is characterized by an still experience normal length within 72 hours after receiv- cycling mares housed under increase in follicle develop- of transition period lasting 50 ing hCG. The control group natural light conditions. ment and uterine edema. to 70 days or more, prior to did not develop follicles dur- the first ovulation of the sea- ing the period. son,” said Mats Troedsson, While reFSH proved suc- DVM, PhD, director of the cessful stimulating early UK Gluck Equine Research dominant follicles and ovu- Center and chair of the de- lation in the seasonally an- partment of veterinary sci- estrous mares, a continued ence. Therefore, there might cyclicity failed to appear. be a need for alternative treat- “However, the treated mares ments of shorter duration. returned to anestrus follow- In their study, the re- ing the induced ovulation searchers employed 60 deep and followed the calendar of anestrous (wintertime, non- the control group,” Troeds- cycling) mares in California, son said. He suggested that Colorado, and Kentucky from continuous treatment might the end of January until one be necessary in mares that or more pre-ovulatory fol- fail to become pregnant fol- ANNE M. EBERHARDT ANNE M. Mares are often housed under artificial barn light to hasten their licles developed. They divided lowing breeding on induced transition period for breeding season. the mares into two groups ovulation. 2 Bluegrass Equine Digest ❙ ca.uky.edu/equine ❙ TheHorse.com ❙ April 2013 Breeding Season Studies MASTHEAD Mobile Light Therapy Efficacy Using artificial indoor light to speed up ■ University of Kentucky Ag Equine Programs mares’ transition to breeding season can Jenny Evans, Managing Editor, [email protected] be time-consuming and costly in electric- Holly Wiemers, Managing Editor, [email protected] ity, bedding, and labor. Researchers at the Gluck Center col- ■ Bluegrass Equine Digest Advisory Board laborated with Barbara Murphy, BSc, Nancy Cox, PhD, associate dean for research in UK’s College of Agriculture, Kentucky Agricultural PhD, a researcher at the University Col- Experiment Station director lege Dublin, Ireland, who recently devel- Ed Squires, PhD, Dipl. ACT (hon.), director of UK Ag Equine Programs and executive director of the UK Gluck oped a facemask with blue light directed Equine Research Foundation at a single eye to suppress melatonin Mats Troedsson, DVM, PhD, Dipl. ACT, director of the UK Gluck Equine Research Center and chair of the production in mares under natural light. department of veterinary science The team set out to determine if the facemask was as effective in advancing ■ Bluegrass Equine Digest Editorial Committee breeding season as traditional indoor Craig Carter, DVM, PhD, Dipl. ACVPM, director of the UK Veterinary Diagnostic Laboratory barn light. Bob Coleman, PhD, PAS, associate director for undergraduate education in equine science and management From mid-December to mid-February and extension horse specialist 2013, the researchers studied 59 Thor- Laurie Lawrence, PhD, professor in the department of animal and food sciences oughbred mares, ages 4 to 17, from Ray Smith, PhD, professor and forage extension specialist farms in Lexington, Ky.