The University of Kentucky College of Agriculture last week released the results of a recently completed experiment conducted by the Departments of Veterinary Science (Karen McDowell, MS, PhD) and Entomology (Bruce Webb, MS, PhD, and Walter Barney) and the Livestock Disease Diagnostic Center (Neil Williams, DVM, PhD, and Mike Donahue, PhD). This is the fourth in a series of ongoing experiments designed to identify the factor or agent responsible for fetal losses due to MRLS (see MRLS reports of June 12, 2002 and October 25, 2002, at this web site: https://www.uky.edu/Ag/VetScience/mrls/index.htm).

Eastern tent caterpillars (ETC) were collected in Central Kentucky in the Spring of 2003 and stored at -80°C until use. Thirty-five early pregnant mares were divided into seven groups of five mares each, with individual treatments added to each mare’s feed for a 10-day period. Mares in Group 1 were fed Eastern tent caterpillars, and served as positive controls. Mares in Group 2 were fed saline, and served as negative controls. Three additional groups of mares were fed ETC that had been carefully dissected into three portions, the exoskeleton (skin and associated structures; Group 3), the gut (Group 4), or the remainder of the internal insect tissues (Group 5). The final two groups of mares were fed ETC that had been homogenized in saline and then separated by size (greater than 0.45 microns, Group 6; or smaller than 0.45 microns, Group 7). Each treatment fed to each mare represented the equivalent of 50 grams of ETC larvae