ARS | Publication request: Effects of grazing stockpilied endophyte-infected tall fescue pastures on growth and physiological indices of dairy heifers

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: January 3, 2011
Publication Date: February 8, 2012
Citation: Henry, R., Huff, J., Reiter, S., Coblentz, W.K., Looper, M.L., Rosenkrans, C.F. 2012. Effects of grazing stockpilied endophyte-infected tall fescue pastures on growth and physiological indices of dairy heifers. Journal of Animal Science. February 5-8, 2011.

Technical Abstract: Tall fescue (Lolium arundinaceum [Schreb.] S. J. Darbyshire) is a cool-season grass grown on over 20 million acres of pasture land and hayfields in the Midwestern and Southeastern United States. A grazing trial was conducted to determine the effects of stockpiled tall fescue on the physiological and growth indices of dairy heifers. Our study utilized two cultivars of tall fescue, Kentucky 31 (KY31; wild-type endophyte-infected; 4 paddocks) and HiMag 4 (HiMag; non-toxic endophyte-infected; 4 paddocks). Both cultivars were fertilized with ammonium nitrate (N = 35%) in September and allowed to grow in the fall before the start of the grazing trial in December. Crossbred dairy heifers (Holstein x Jersey; n = 32) were stratified by weight and randomly allotted to forage on December 6. All heifers were given a daily corn-based grain supplement (~0.8% BW) and ad libitum access to water. Forage availability and protein content varied during the trial, but were not limiting. Forage fiber content (NDF and ADF percent) increased, and forage protein content decreased in both cultivars during the trial. Tall fescue cultivar did not affect (P > 0.2) heifer body weights; however, heifers grazing HiMag had faster (P = 0.06) ADG during the first 28 d than heifers grazing KY31 (1.1 vs. 0.9 kg). Blood characteristics were not affected (P > 0.17) by tall fescue cultivar. White blood cells were elevated (P < 0.01) at d 28 and 56; while, red blood cell numbers increased (P < 0.01) at each 28 d interval. Serum metabolite and enzyme activities showed inconsistent variation over the duration of the trial. The results of this trial indicate that stockpiled tall fescue can be used to develop dairy heifers without detrimental effects on growth or blood cell profiles.