Beef cattle performance, forage productivity and quality from a mixed small-grain/ryegrass and warm-season annuals grazing system
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A two-phase grazing experiment was conducted to evaluate the feasibility and productivity of a cool-season/warm-season annuals grazing system for growing-finishing beef cattle. Eighteen Angus × Simmental steers grazed replicate 1.42-ha mixed pastures (3 steers/paddock) of oats (O; Avena sativa), rye (R; Secale cereale) and ryegrass (RG; Lolium perenne) as winter pasture from Jan 8 to May 28, 2009. Steers then rotationally grazed replicate 2.02-ha pastures of cowpea (Vigna unguiculata), lablab (Lablab purpureus) and pearl millet (Pennisetum glaucum) during a summer finishing phase. Data were analyzed as a completely randomized design by the PROC GLM procedure of SAS. Average daily gain was greater (P < 0.10) for O-RG (1.39 kg/d) than R-RG (1.13 kg/d), but was not different from O-R-RG (1.26 kg/d). Number of steer-grazing days was 547 d, 655 d and 625 d for R-RG, O-RG and O-R-RG, respectively. No differences in ADG were observed among summer-annual forage treatments. Forage concentrations of CP, NDF, ADF and ADL, and percentage IVDMD decreased with increasing plant maturity after the first 28 d of the summer grazing trial, all of which negatively impacted ADG. Results indicate that cool-season forage mixtures containing oats were superior to R + RG for supporting beef cattle production from winter grazing. Summer annuals supported satisfactory ADG of finishing cattle early in the summer grazing phase, but were unable to sustain satisfactory ADG for the remainder of the season because of rapidly advancing maturity.