Alfalfa and escape protein supplements for grazed corn residues
Gutierrez-Ornelas, E. | Klopfenstein, T.J.
Two calf corn-residue grazing trials were conducted to evaluate the effect of supplementing with two alfalfa hays (Medicago sativa), varying in their amount of CP and ADF, with and without escape protein (EP). In Trial 1, heifers (204 kg) grazed (1.36 heifers/ha) non-irrigated fields for 92 d. No difference (P > .05) in ADG was found when medium-protein (16.3% CP) and high-protein (18.0% CP) alfalfa hays were provided at 2.7 kg of DM-heifer-1.d-1. In Trial 2, 60 steers (257 kg) were supplemented individually with medium-protein (17.6% CP) alfalfa hay, 1.86 (MPL) and 2.27 kg DM (MPH), and one level of high-protein (18.7% CP) alfalfa hay, 1.86 kg DM (HPL). In a 2 X 3 factorial arrangement of treatments, steers were fed with or without EP (113 g.steer-1.d-1 from blood meal and corn gluten meal). Steers grazed a non-irrigated corn residue field (2.58 steers/ha) for 57 d and were watered and individually supplemented overnight. Diet quality and composition was estimated by collecting extrusa samples twice each week using four esophageally fistulated steers. No effects of alfalfa protein content or level (P > .05) were reflected in gain: 357, 309, and 326 g.steer-1.d-1 for steers receiving MPL, MPH, or HPL alfalfa treatments, respectively. Daily gains of steers receiving alfalfa plus EP were higher (P < .05) than those of steers receiving alfalfa plus an energy supplement (401 vs 260 g). Extrusa samples had a linear (P < .05) decrease in EP content throughout the grazing season that was associated (r2 = .87) with grain content of the corn residue. Alfalfa hay did not meet the metabolizable protein needs of cattle.
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