Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2006
Publication Date: 3/19/2007
Citation: Coffey, W.K., Coblentz, W.K., Ogden, R.K., Caldwell, J.D., Hubbell, D.S., Hess, T.W., Martin, L.J., West, C.P., Akins, M.S., Johnson, Z.B. 2007. Performance by Spring-Calving Cows Grazing Tall Fescue Pastures with Either the Wild-Type Toxic Endophyte or a Non-Toxic Novel Endophyte. Journal of Animal Science. 85(suppl. 2):133.
Technical Abstract: Cows grazing 'Kentucky-31' tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] infected with its wild-type endophyte (Neotyphodium coenophialum; E+) generally display suboptimal performance. Recently, endophyte strains that do not produce compounds toxic to cattle have been incorporated into tall fescue varieties to reduce tall fescue toxicosis and maintain the positive benefits the endophyte imparts to the plant. Our objectives were to compare performance by spring-calving cows grazing E+ tall fescue with that by cows grazing a non-toxic endophyte-tall fescue association developed at the Univ. of Arkansas (HM4). Gelbvieh x Angus crossbred cows (n=156; 492±19.2 kg initial BW) were allocated randomly by weight and age to one of four 10-ha pastures in 2005 and to one of eight 10-ha pastures in 2006. Pastures consisted predominantly of E+ or HM4. Cows confirmed as pregnant began grazing the pastures October 15, 2004 and November 30, 2005. Cows remained on their assigned pastures until weaning in 2006, but were removed from HM4 in the summer of 2005 because of low forage availability from extremely dry summer conditions. Cow BW were greater (P<0.05) and hair scores were lower (P<0.05) at weaning from HM4 than E+, and cow BW at the end of the breeding season tended (P=0.07) to be greater from HM4 than E+. A greater percentage (P<0.01) of cows grazing HM4 were pregnant at the time of weaning in 2005. Calf birth date and birth weight were not different (P>0.48) between forages, but actual and adjusted weaning weight, and calf gain from birth to weaning were greater (P<0.05) from HM4 compared with E+ (240, 229, and 193 kg respectively from HM4 vs. 209, 199, and 169 kg respectively from E+). Therefore, replacing toxic tall fescue pastures with non-toxic, novel endophyte-infected tall fescue may improve calf growth and cow reproductive performance.