Performance and Serum Metabolites of Fall-Weaned Beef Steers Strip-Grazing on Nonstockpiled Tall Fescue

Abstract

Limited information is available regarding the use of different tall fescue (Festuca arundinacea Schreb.) types during the fall to support the growth of calves after weaning. Seventy-two springborn beef calves were evaluated in 2 consecutive years (36 calves/yr) during a 42-d backgrounding period to determine the effects of weaning and endophyte infection of tall fescue on performance, apparent DMI, percent forage utilization, and serum metabolite concentrations. In each year, 4 calves were assigned to each pasture (n = 3 pastures/treatment) and grazed endophyte-free, toxic endophyte-infected, or non-ergot alkaloid-producing endophyte-infected tall fescue. No effect of tall fescue type (P > 0.10) was detected on apparent DMI, ADG, or serum concentrations of blood urea N, creatine kinase, glucose, and nonesterified fatty acids. Postgrazing forage mass tended (P = 0.07) to be greater for endophyte-infected pastures, and percent forage utilization differed (P = 0.006) between tall fescue types, being lowest for endophyte-infected tall fescue (31.2%). All 3 tall fescue types provided enough forage mass and nutritive value to support BW gains in excess of 1 kg/d in newly weaned beef calves. Creatine kinase peaked on d 1 (P < 0.05) as a result of weaning and transport of the calves. Nonesterified fatty acid and creatine kinase concentrations on d 1 reflected the effect of transport on tissue mobilization. Backgrounding calves during fall on any of the tall fescue types studied allows for acceptable ADG, with no detrimental effects before entering a stocker or finishing program.