Voluntary intake and digestibility of reed canarygrass and timothy hay fed to horses 1 A. L. Ordakowski-Burk,* 2 R. W. Quinn,* T. A. Shellem,* and L. R. Vough† Departments of *Animal and Avian Sciences and †Natural Resource Sciences and Landscape Architecture, University of Maryland, College Park 20742 ABSTRACT: Thousands of hectares of timothy (Phleum pretense L.) grown in the Mid-Atlantic region are infected by cereal rust mite (Abacarus hysterix) that causes discoloration and curling of leaves, decreased nutritional quality, and substantial decreases in yield. A decline in production of timothy hay can lower income for hay producers and cause horse owners to search for alternative hays. Low alkaloid reed canarygrass (Pha- laris arundinacea L.) hay has potential as an alterna- tive to timothy hay because it grows well in the Mid- Atlantic region, is believed to have a similar nutrient quality to timothy, and is not as susceptible to cereal rust mite. Eleven mature, stalled Thoroughbred geld- ings (549 ± 12.1 kg) that were exercised daily were used to compare voluntary DMI and apparent nutrient DM digestibility of timothy and low-alkaloid Chiefton vari- ety reed canarygrass hay. Horses were paired by age and BW and randomly assigned to timothy or reed ca- narygrass hay during a 14-d period to measure volun- tary DMI followed by a 4-d period to measure apparent DM digestibility. Both hays met the minimum require- Key words: digestibility, hay, horse, reed canarygrass, timothy, voluntary intake ©2006 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2006. 84:3104–3109 doi:10.2527/jas.2005-607 INTRODUCTION Timothy hay is produced on an estimated 34,400 ha in Maryland and is one of the most popular hay species fed to horses in the Mid-Atlantic region of the United States. However, since the late 1980s, cereal rust mite has been infecting timothy in the Mid-Atlantic region, causing discoloration and curling of leaves, decreased nutritional quality, decreased yields up to 70% (Cham- 1 This research was supported in part by a grant from the Maryland Horse Industry Board. The authors thank the staff at the Central Maryland Research and Education Center for their assistance during the study and Larry Douglass for assistance with statistical analysis. 2 Corresponding author: amyburk@umd.edu Received October 20, 2005. Accepted May 10, 2006. 3104 ments for DE, CP, Ca, P, K, Fe, and Mn, but they did not meet the minimum requirements for Cu, Zn, and Na for horses at maintenance and averaging 550 kg of BW. Timothy hay seemed to have a lower CP concentra- tion (14.4%) compared with reed canarygrass hay (17.1%) and a more desirable Ca:P ratio at 1.6:1 com- pared with 0.8:1 for reed canarygrass hay. Horses fed timothy consumed more hay (P < 0.001) during the voluntary DMI period compared with horses fed reed canarygrass. Greater voluntary DMI of timothy oc- curred on d 1, 3, and 5 (P < 0.05), but DMI was similar for other days. Apparent DM digestibility was greater in horses fed timothy hay by 9.6% compared with horses fed reed canarygrass hay (P < 0.05). Horses fed timothy had greater DM digestibility of ADF (P = 0.001), NDF (P = 0.001), sugar (P = 0.05), and Ca (P = 0.001) but lower apparent DM digestibility of CP (P = 0.012) and crude fat (P = 0.004). Timothy hay was superior in voluntary DMI and apparent DM digestibility com- pared with low-alkaloid reed canarygrass hay fed to horses. berlain et al., 2003), and a decrease in the income of timothy hay producers. Use of pesticides (e.g., carbaryl) and management techniques including late-fall harvest have decreased the impact of the cereal rust mite; how- ever, resistance to carbaryl is expected to eventually develop. A decline in the production of timothy hay may cause hay producers to grow other forages adapted to the climate of the Mid-Atlantic region, forcing horse owners to find other suitable forage alternatives. Reed canarygrass shows potential as an alternative hay to timothy hay because it is a tall, leafy, high yield- ing cool-season perennial grass that grows well in the moist temperate climate and soils of the Mid-Atlantic region, is tolerant to flooding and drought, and has the potential for more summer regrowth (Balasko and Nelson, 2003). Also, newer varieties of reed canarygrass were shown to have equivalent or greater nutrient di- Published December 8, 2014